59 results on '"Susan L Ackerman"'
Search Results
2. Defects in translation-dependent quality control pathways lead to convergent molecular and neurodevelopmental pathology
- Author
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Markus Terrey, Scott I Adamson, Jeffrey H Chuang, and Susan L Ackerman
- Subjects
cerebellum ,neurogenesis ,translation ,ribosome ,n-Tr20 ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Translation-dependent quality control pathways such as no-go decay (NGD), non-stop decay (NSD), and nonsense-mediated decay (NMD) govern protein synthesis and proteostasis by resolving non-translating ribosomes and preventing the production of potentially toxic peptides derived from faulty and aberrant mRNAs. However, how translation is altered and the in vivo defects that arise in the absence of these pathways are poorly understood. Here, we show that the NGD/NSD factors Pelo and Hbs1l are critical in mice for cerebellar neurogenesis but expendable for survival of these neurons after development. Analysis of mutant mouse embryonic fibroblasts revealed translational pauses, alteration of signaling pathways, and translational reprogramming. Similar effects on signaling pathways, including mTOR activation, the translatome and mouse cerebellar development were observed upon deletion of the NMD factor Upf2. Our data reveal that these quality control pathways that function to mitigate errors at distinct steps in translation can evoke similar cellular responses.
- Published
- 2021
- Full Text
- View/download PDF
3. GTPBP1 resolves paused ribosomes to maintain neuronal homeostasis
- Author
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Markus Terrey, Scott I Adamson, Alana L Gibson, Tianda Deng, Ryuta Ishimura, Jeffrey H Chuang, and Susan L Ackerman
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tRNA-Arg-TCT-4-1 ,ribosome stalling ,cerebellum ,granule cells ,hippocampus ,retina ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Ribosome-associated quality control pathways respond to defects in translational elongation to recycle arrested ribosomes and degrade aberrant polypeptides and mRNAs. Loss of a tRNA gene leads to ribosomal pausing that is resolved by the translational GTPase GTPBP2, and in its absence causes neuron death. Here, we show that loss of the homologous protein GTPBP1 during tRNA deficiency in the mouse brain also leads to codon-specific ribosome pausing and neurodegeneration, suggesting that these non-redundant GTPases function in the same pathway to mitigate ribosome pausing. As observed in Gtpbp2-/- mice (Ishimura et al., 2016), GCN2-mediated activation of the integrated stress response (ISR) was apparent in the Gtpbp1-/- brain. We observed decreased mTORC1 signaling which increased neuronal death, whereas ISR activation was neuroprotective. Our data demonstrate that GTPBP1 functions as an important quality control mechanism during translation elongation and suggest that translational signaling pathways intricately interact to regulate neuronal homeostasis during defective elongation.
- Published
- 2020
- Full Text
- View/download PDF
4. Notch signaling regulates UNC5B to suppress endothelial proliferation, migration, junction activity, and retinal plexus branching
- Author
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Qanber Raza, Taliha Nadeem, Seock-Won Youn, Bhairavi Swaminathan, Ahana Gupta, Timothy Sargis, Jing Du, Henar Cuervo, Anne Eichmann, Susan L. Ackerman, L. A. Naiche, and Jan Kitajewski
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Retinal angiogenesis ,Notch effectors ,UNC5B ,Endothelial proliferation ,Endothelial migration ,Cell–cell adhesion ,Medicine ,Science - Abstract
Abstract Notch signaling guides vascular development and function by regulating diverse endothelial cell behaviors, including migration, proliferation, vascular density, endothelial junctions, and polarization in response to flow. Notch proteins form transcriptional activation complexes that regulate endothelial gene expression, but few of the downstream effectors that enable these phenotypic changes have been characterized in endothelial cells, limiting our understanding of vascular Notch activities. Using an unbiased screen of translated mRNA rapidly regulated by Notch signaling, we identified novel in vivo targets of Notch signaling in neonatal mouse brain endothelium, including UNC5B, a member of the netrin family of angiogenic-regulatory receptors. Endothelial Notch signaling rapidly upregulates UNC5B in multiple endothelial cell types. Loss or gain of UNC5B recapitulated specific Notch-regulated phenotypes. UNC5B expression inhibited endothelial migration and proliferation and was required for stabilization of endothelial junctions in response to shear stress. Loss of UNC5B partially or wholly blocked the ability of Notch activation to regulate these endothelial cell behaviors. In the developing mouse retina, endothelial-specific loss of UNC5B led to excessive vascularization, including increased vascular outgrowth, density, and branchpoint count. These data indicate that Notch signaling upregulates UNC5B as an effector protein to control specific endothelial cell behaviors and inhibit angiogenic growth.
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- 2024
- Full Text
- View/download PDF
5. Activation of GCN2 kinase by ribosome stalling links translation elongation with translation initiation
- Author
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Ryuta Ishimura, Gabor Nagy, Ivan Dotu, Jeffrey H Chuang, and Susan L Ackerman
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translation elongation ,neurodegeneration ,translation initiation ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Ribosome stalling during translation has recently been shown to cause neurodegeneration, yet the signaling pathways triggered by stalled elongation complexes are unknown. To investigate these pathways we analyzed the brain of C57BL/6J-Gtpbp2nmf205-/- mice in which neuronal elongation complexes are stalled at AGA codons due to deficiencies in a tRNAArgUCU tRNA and GTPBP2, a mammalian ribosome rescue factor. Increased levels of phosphorylation of eIF2α (Ser51) were detected prior to neurodegeneration in these mice and transcriptome analysis demonstrated activation of ATF4, a key transcription factor in the integrated stress response (ISR) pathway. Genetic experiments showed that this pathway was activated by the eIF2α kinase, GCN2, in an apparent deacylated tRNA-independent fashion. Further we found that the ISR attenuates neurodegeneration in C57BL/6J-Gtpbp2nmf205-/- mice, underscoring the importance of cellular and stress context on the outcome of activation of this pathway. These results demonstrate the critical interplay between translation elongation and initiation in regulating neuron survival during cellular stress.
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- 2016
- Full Text
- View/download PDF
6. Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons
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Sebastian Poliak, Daniel Morales, Louis-Philippe Croteau, Dayana Krawchuk, Elena Palmesino, Susan Morton, Jean-François Cloutier, Frederic Charron, Matthew B Dalva, Susan L Ackerman, Tzu-Jen Kao, and Artur Kania
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axon guidance ,motor neurons ,Netrin ,ephrin ,synergy ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin–ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways.
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- 2015
- Full Text
- View/download PDF
7. Correction: GTPBP1 resolves paused ribosomes to maintain neuronal homeostasis
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Jeffrey H. Chuang, Susan L. Ackerman, Alana L Gibson, Scott I Adamson, Tianda Deng, Markus Terrey, and Ryuta Ishimura
- Subjects
QH301-705.5 ,Science ,Biology ,Mechanistic Target of Rapamycin Complex 1 ,Ribosome ,General Biochemistry, Genetics and Molecular Biology ,Mice ,RNA, Transfer ,Gene expression ,Animals ,Biology (General) ,Monomeric GTP-Binding Proteins ,Mice, Knockout ,Neurons ,Sirolimus ,General Immunology and Microbiology ,General Neuroscience ,Correction ,Neurodegenerative Diseases ,General Medicine ,Chromosomes and Gene Expression ,Cell biology ,Anti-Bacterial Agents ,Neuronal homeostasis ,Gene Expression Regulation ,Medicine ,Ribosomes ,Neuroscience ,Signal Transduction - Abstract
Ribosome-associated quality control pathways respond to defects in translational elongation to recycle arrested ribosomes and degrade aberrant polypeptides and mRNAs. Loss of a tRNA gene leads to ribosomal pausing that is resolved by the translational GTPase GTPBP2, and in its absence causes neuron death. Here, we show that loss of the homologous protein GTPBP1 during tRNA deficiency in the mouse brain also leads to codon-specific ribosome pausing and neurodegeneration, suggesting that these non-redundant GTPases function in the same pathway to mitigate ribosome pausing. As observed in
- Published
- 2021
8. Endothelial Unc5B controls blood-brain barrier integrity
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Doyeun Kim, Jessica Furtado, Laurent Jacob, Laurence Pibouin-Fragner, Lena Claesson-Welsh, Nawal Maïssa, Dritan Agalliu, Y. Xu, Anne Eichmann, Kevin Boyé, Mathilde Poulet, Geraldo Lh, Bertrand Tavitian, Susan L. Ackerman, and Nelson B
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Chemistry ,Mutant ,Central nervous system ,Regulator ,Wnt signaling pathway ,LRP6 ,Blood–brain barrier ,Cell biology ,medicine.anatomical_structure ,nervous system ,cardiovascular system ,medicine ,Phosphorylation ,Receptor - Abstract
Blood-brain barrier (BBB) integrity is critical for proper function of the central nervous system (CNS). Here, we showed that the endothelial Netrin1 receptor Unc5B controls BBB integrity by maintaining Wnt/β–catenin signaling. Inducible endothelial-specific deletion of Unc5B in adult mice led to region and size-selective BBB opening. Loss of Unc5B decreased BBB Wnt/β–catenin signaling, and β–catenin overexpression rescued Unc5B mutant BBB defects. Mechanistically, Netrin1 enhanced Unc5B interaction with the Wnt co-receptor LRP6, induced its phosphorylation and activated Wnt/β–catenin downstream signaling. Intravenous delivery of antibodies blocking Netrin1 binding to Unc5B caused a transient disruption of Wnt signaling and BBB breakdown, followed by neurovascular barrier resealing. These data identify Netrin-Unc5B signaling as a novel regulator of BBB integrity with potential therapeutic utility for CNS diseases.
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- 2021
9. Lipid Metabolism and Axon Degeneration: An ACOX1 Balancing Act
- Author
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Susan L. Ackerman and Emily N. Griffin
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0301 basic medicine ,Biology ,medicine.disease_cause ,Article ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Gene ,Oxidase test ,Mutation ,General Neuroscience ,Neurodegeneration ,Lipid metabolism ,Peroxisome ,Lipid Metabolism ,medicine.disease ,Axons ,Cell biology ,030104 developmental biology ,medicine.anatomical_structure ,nervous system ,Gain of Function Mutation ,ACOX1 ,Acyl-CoA Oxidase ,Neuron ,030217 neurology & neurosurgery - Abstract
ACOX1 (acyl-CoA oxidase 1) encodes the first and rate-limiting enzyme of the very-long-chain fatty acid (VLCFA) β-oxidation pathway in peroxisomes and leads to H(2)O(2) production. Unexpectedly, dACOX1 is mostly expressed and required in glia, and loss of dACOX1 leads to developmental delay, pupal death, reduced lifespan, impaired synaptic transmission, and glial and axonal loss. Patients who carry a previously unidentified, de novo, dominant variant in ACOX1 (p.N237S) also exhibit glial loss. However, this mutation causes increased levels of ACOX1 protein and function resulting in elevated levels of reactive oxygen species in glia in flies and murine Schwann cells. ACOX1 (p.N237S) patients exhibit a severe loss of Schwann cells and neurons. However, treatment of flies and primary Schwann cells with an anti-oxidant suppressed the p.N237S induced neurodegeneration. In summary, both loss and gain of ACOX1 leads to glial and neuronal loss, but different mechanisms are at play and require different treatments.
- Published
- 2020
10. Defects in translation-dependent quality control pathways lead to convergent molecular and neurodevelopmental pathology
- Author
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Jeffrey H. Chuang, Markus Terrey, Scott I Adamson, and Susan L. Ackerman
- Subjects
Male ,Cerebellum ,Mouse ,translation ,Cell Cycle Proteins ,Mice ,Protein biosynthesis ,2.1 Biological and endogenous factors ,Aetiology ,Biology (General) ,Mice, Knockout ,Neurons ,General Neuroscience ,Translational ,Neurogenesis ,Translation (biology) ,General Medicine ,Chromosomes and Gene Expression ,Cell biology ,neurogenesis ,medicine.anatomical_structure ,ribosome ,Neurological ,Medicine ,Female ,Signal transduction ,Reprogramming ,Research Article ,chromosomes ,Peptide Chain Termination ,cerebellum ,QH301-705.5 ,Knockout ,Science ,n-Tr20 ,Biology ,General Biochemistry, Genetics and Molecular Biology ,GTP-Binding Proteins ,Genetics ,medicine ,Animals ,PI3K/AKT/mTOR pathway ,mouse ,General Immunology and Microbiology ,Neurosciences ,Peptide Chain Termination, Translational ,Endonucleases ,Proteostasis ,gene expression ,Biochemistry and Cell Biology - Abstract
Translation-dependent quality control pathways such as no-go decay (NGD), non-stop decay (NSD), and nonsense-mediated decay (NMD) govern protein synthesis and proteostasis by resolving non-translating ribosomes and preventing the production of potentially toxic peptides derived from faulty and aberrant mRNAs. However, how translation is altered and the in vivo defects that arise in the absence of these pathways are poorly understood. Here, we show that the NGD/NSD factorsPeloandHbs1lare critical in mice for cerebellar neurogenesis but expendable for survival of these neurons after development. Analysis of mutant mouse embryonic fibroblasts revealed translational pauses, alteration of signaling pathways, and translational reprogramming. Similar effects on signaling pathways, including mTOR activation, the translatome and mouse cerebellar development were observed upon deletion of the NMD factorUpf2. Our data reveal that these quality control pathways that function to mitigate errors at distinct steps in translation can evoke similar cellular responses.
- Published
- 2021
11. GTPBP1 resolves paused ribosomes to maintain neuronal homeostasis
- Author
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Tianda Deng, Jeffrey H. Chuang, Markus Terrey, Alana L Gibson, Ryuta Ishimura, Susan L. Ackerman, and Scott I Adamson
- Subjects
0301 basic medicine ,retina ,Mouse ,hippocampus ,GTPase ,Ribosome ,neuroscience ,Mice ,0302 clinical medicine ,Biology (General) ,Neurons ,Chemistry ,General Neuroscience ,Neurodegeneration ,Neurodegenerative Diseases ,General Medicine ,Chromosomes and Gene Expression ,Anti-Bacterial Agents ,Cell biology ,Neurological ,Transfer RNA ,Medicine ,Neuron death ,Signal Transduction ,chromosomes ,ribosome stalling ,cerebellum ,QH301-705.5 ,Knockout ,1.1 Normal biological development and functioning ,Science ,tRNA-Arg-TCT-4-1 ,Mechanistic Target of Rapamycin Complex 1 ,Neuroprotection ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Underpinning research ,Genetics ,medicine ,Animals ,Integrated stress response ,mouse ,Monomeric GTP-Binding Proteins ,Sirolimus ,General Immunology and Microbiology ,Neurosciences ,medicine.disease ,Transfer ,030104 developmental biology ,Gene Expression Regulation ,gene expression ,RNA ,Translational elongation ,Biochemistry and Cell Biology ,Research Advance ,Ribosomes ,030217 neurology & neurosurgery ,granule cells ,Neuroscience - Abstract
Ribosome-associated quality control pathways respond to defects in translational elongation to recycle arrested ribosomes and degrade aberrant polypeptides and mRNAs. Loss of a tRNA gene leads to ribosomal pausing that is resolved by the translational GTPase GTPBP2, and in its absence causes neuron death. Here, we show that loss of the homologous protein GTPBP1 during tRNA deficiency in the mouse brain also leads to codon-specific ribosome pausing and neurodegeneration, suggesting that these non-redundant GTPases function in the same pathway to mitigate ribosome pausing. As observed in Gtpbp2-/- mice (Ishimura et al., 2016), GCN2-mediated activation of the integrated stress response (ISR) was apparent in the Gtpbp1-/- brain. We observed decreased mTORC1 signaling which increased neuronal death, whereas ISR activation was neuroprotective. Our data demonstrate that GTPBP1 functions as an important quality control mechanism during translation elongation and suggest that translational signaling pathways intricately interact to regulate neuronal homeostasis during defective elongation.
- Published
- 2020
12. GTPBP1 resolves paused ribosomes to maintain neuronal homeostasis
- Author
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Susan L. Ackerman, Alana L Gibson, Scott I Adamson, Tianda Deng, Ryuta Ishimura, Jeffrey H. Chuang, and Markus Terrey
- Subjects
Chemistry ,Transfer RNA ,Neurodegeneration ,medicine ,Integrated stress response ,GTPase ,Translational elongation ,Signal transduction ,Neuron death ,medicine.disease ,Ribosome ,Cell biology - Abstract
Ribosome-associated quality control pathways respond to defects in translational elongation to recycle arrested ribosomes and degrade aberrant polypeptides and mRNAs. Loss of an individual tRNA gene leads to ribosomal pausing that is resolved by the translational GTPase GTPBP2, and in its absence causes neuron death. Here we show that loss of the homologous protein GTPBP1 during tRNA deficiency in the mouse brain also leads to codon-specific ribosome pausing and neurodegeneration, suggesting that these non-redundant translational GTPases function in the same pathway to mitigate ribosome pausing. Ribosome stalling in the mutant brain led to activation of the integrated stress response (ISR) mediated by GCN2 and decreased mTORC1 signaling. However, in contrast to the ISR, which enhanced neuron survival, reduced mTORC1 signaling increased neuronal death. Our data demonstrate that GTPBP1 functions as an important quality control mechanism during translation elongation and suggest that translational signaling pathways intricately interact to regulate neuronal homeostasis during defective translation elongation.
- Published
- 2020
13. Paranode stability requires UNC5B expression by oligodendrocytes
- Author
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Doyeun Kim, Samuel Clemot, Abbas F. Sadikot, Susan L. Ackerman, Edwin W. Wong, Omar de Faria, Diane S. Nakamura, Roland Pilgram, Timothy E. Kennedy, Mihai Victor Mocanu, Jenea M. Bin, and Amir Shmuel
- Subjects
Myelin ,medicine.anatomical_structure ,nervous system ,Compact myelin ,Axon extension ,Netrin ,medicine ,Cell migration ,Biology ,Axon ,Neural development ,Gene knockout ,Cell biology - Abstract
Netrins are secreted proteins that direct cell migration and axon extension in the developing CNS and are essential for normal neural development. In the mature CNS, netrin-1 is expressed by neurons and oligodendrocytes and implicated in the stability of axo-oligodendroglial paranodal junctions. Here we report that the netrin receptor UNC5B is highly expressed by mature oligodendrocytes and enriched at paranodes. We demonstrate that paranodes become disorganized following conditional deletion of UNC5B in oligodendrocytes, with disruption of the interface between glial loops and detachment of glial loops from the axon. Examining axoglial domain segregation, Caspr1 and Kv1.1 disperse along the axon, internodes shorten, and the periodicity of compact myelin is reduced, indicating significant breakdown of myelin organization in UNC5B cKOs. Paranodal disruption and axoglial domain disorganization progressively worsen with age and a delay in motor learning develops specifically in aged animals that lack oligodendroglial UNC5B. We detect reduced amounts of oligodendroglial Claudin-11 and JAM-C proteins in UNC5B knockouts, suggesting that disruption of the specialized autotypic junctions between glial loops may underlie paranodal disorganization. Our findings reveal an essential contribution of oligodendroglial UNC5B at axoglial junctions that is required for the stability of mature myelin.
- Published
- 2020
14. ANKRD16 prevents neuron loss caused by an editing-defective tRNA synthetase
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Thomas Weber, Susan L. Ackerman, Litao Sun, Bappaditya Roy, Qi Liu, Paul Schimmel, Markus Terrey, My-Nuong Vo, Hongjun Fu, John R. Yates, Jeong Woong Lee, Kurt Fredrick, and James J. Moresco
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0301 basic medicine ,Mutation ,Multidisciplinary ,Positional cloning ,Aminoacyl tRNA synthetase ,Mutant ,Protein aggregation ,medicine.disease_cause ,Cell biology ,Serine ,03 medical and health sciences ,chemistry.chemical_compound ,030104 developmental biology ,chemistry ,Transfer RNA ,medicine ,Ankyrin repeat - Abstract
Editing domains of aminoacyl tRNA synthetases correct tRNA charging errors to maintain translational fidelity. A mutation in the editing domain of alanyl tRNA synthetase (AlaRS) in Aars sti mutant mice results in an increase in the production of serine-mischarged tRNAAla and the degeneration of cerebellar Purkinje cells. Here, using positional cloning, we identified Ankrd16, a gene that acts epistatically with the Aars sti mutation to attenuate neurodegeneration. ANKRD16, a vertebrate-specific protein that contains ankyrin repeats, binds directly to the catalytic domain of AlaRS. Serine that is misactivated by AlaRS is captured by the lysine side chains of ANKRD16, which prevents the charging of serine adenylates to tRNAAla and precludes serine misincorporation in nascent peptides. The deletion of Ankrd16 in the brains of Aarssti/sti mice causes widespread protein aggregation and neuron loss. These results identify an amino-acid-accepting co-regulator of tRNA synthetase editing as a new layer of the machinery that is essential to the prevention of severe pathologies that arise from defects in editing.
- Published
- 2018
15. Regulation of mRNA Translation in Neurons—A Matter of Life and Death
- Author
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Susan L. Ackerman, Caitlin E. Monaghan, and Mridu Kapur
- Subjects
0301 basic medicine ,Cytoplasm ,Biology ,Ribosome ,Article ,03 medical and health sciences ,Eukaryotic translation ,Translational regulation ,medicine ,Animals ,Humans ,Integrated stress response ,Initiation factor ,RNA, Messenger ,Neurons ,Genetics ,Cell Death ,General Neuroscience ,Neurodegeneration ,Neurodegenerative Diseases ,medicine.disease ,Eukaryotic translation initiation factor 4 gamma ,Cell biology ,030104 developmental biology ,Protein Biosynthesis ,Neuron death - Abstract
Dynamic regulation of mRNA translation initiation and elongation is essential for the survival and function of neural cells. Global reductions in translation initiation resulting from mutations in the translational machinery or inappropriate activation of the integrated stress response may contribute to pathogenesis in a subset of neurodegenerative disorders. Aberrant proteins generated by non-canonical translation initiation may be a factor in the neuron death observed in the nucleotide repeat expansion diseases. Dysfunction of central components of the elongation machinery, such as the tRNAs and their associated enzymes, can cause translational infidelity and ribosome stalling, resulting in neurodegeneration. Taken together, dysregulation of mRNA translation is emerging as a unifying mechanism underlying the pathogenesis of many neurodegenerative disorders.
- Published
- 2017
16. Intraperitoneal Calcitriol for Treatment of Severe Hyperparathyroidism in Children with Chronic Kidney Disease: A Therapy Forgotten
- Author
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Elizabeth Piva, Elizabeth Harvey, Rahul Chanchlani, and Susan L. Ackerman
- Subjects
Male ,medicine.medical_specialty ,Calcitriol ,medicine.medical_treatment ,030232 urology & nephrology ,030204 cardiovascular system & hematology ,Severity of Illness Index ,Gastroenterology ,Drug Administration Schedule ,Sampling Studies ,Peritoneal dialysis ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Short Reports ,Refractory ,Internal medicine ,polycyclic compounds ,medicine ,Humans ,Child ,Hyperparathyroidism ,Dose-Response Relationship, Drug ,business.industry ,Infant ,Alfacalcidol ,General Medicine ,medicine.disease ,Kidney Transplantation ,Treatment Outcome ,Endocrinology ,chemistry ,Parathyroid Hormone ,Nephrology ,Kidney Failure, Chronic ,Female ,Hyperparathyroidism, Secondary ,lipids (amino acids, peptides, and proteins) ,Secondary hyperparathyroidism ,business ,Peritoneal Dialysis ,Injections, Intraperitoneal ,Mineral bone disease ,Follow-Up Studies ,medicine.drug ,Kidney disease - Abstract
Active Vitamin D sterols such as calcitriol and alfacalcidol are quite effective in the treatment of mineral bone disease secondary to chronic kidney disease. However, some children on peritoneal dialysis (PD) are resistant to oral formulations of active Vitamin D, and use of an intravenous formulation in such patients is inconvenient. In these children, intraperitoneal (IP) calcitriol has been shown to be effective in the treatment of secondary hyperparathyroidism. However, its use has declined. We report 2 children, aged 1 and 9.5 years, on chronic cycler PD with severe secondary hyperparathyroidism refractory to oral active Vitamin D who were successfully treated with IP calcitriol for a period of 12 and 4 months, respectively. We also discuss the published literature on the efficacy of IP calcitriol for treatment of secondary hyperparathyroidism and specific considerations for its use in PD patients.
- Published
- 2016
17. Loss ofClcc1Results in ER Stress, Misfolded Protein Accumulation, and Neurodegeneration
- Author
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Thomas J. Jucius, Susan A. Cook, Susan L. Ackerman, and Yichang Jia
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Protein Folding ,Positional cloning ,Mice, Transgenic ,Transfection ,Mice ,Chloride Channels ,Cerebellum ,medicine ,Animals ,Humans ,RNA, Messenger ,Muscle, Skeletal ,Endoplasmic Reticulum Chaperone BiP ,Heat-Shock Proteins ,CLCC1 ,Neurons ,Mice, Inbred C3H ,biology ,General Neuroscience ,Endoplasmic reticulum ,Neurodegeneration ,Peripheral Nervous System Diseases ,Neurodegenerative Diseases ,Articles ,Endoplasmic Reticulum Stress ,medicine.disease ,Molecular biology ,Mice, Inbred C57BL ,Disease Models, Animal ,HEK293 Cells ,Secretory protein ,Mutation ,Unfolded protein response ,biology.protein ,Signal transduction ,Neuron death - Abstract
Folding of transmembrane and secretory proteins occurs in the lumen of the endoplasmic reticulum (ER) before transportation to the cell surface and is monitored by the unfolded protein response (UPR) signaling pathway. The accumulation of unfolded proteins in the ER activates the UPR that restores ER homeostasis by regulating gene expression that leads to an increase in the protein-folding capacity of the ER and a decrease in the ER protein-folding load. However, prolonged UPR activity has been associated with cell death in multiple pathological conditions, including neurodegeneration. Here, we report a spontaneous recessive mouse mutation that causes progressive cerebellar granule cell death and peripheral motor axon degeneration. By positional cloning, we identify the mutation in this strain as a retrotransposon insertion in theClcc1gene, which encodes a putative chloride channel localized to the ER. Furthermore, we demonstrate that the C3H/HeSnJ inbred strain has late onset cerebellar degeneration due to this mutation. Interestingly, acute knockdown ofClcc1expression in cultured cells increases sensitivity to ER stress. In agreement, GRP78, the major HSP70 family chaperone in the ER, is upregulated inClcc1-deficient granule cellsin vivo, and ubiquitinated proteins accumulate in these neurons before their degeneration. These data suggest that disruption of chloride homeostasis in the ER disrupts the protein-folding capacity of the ER, leading to eventual neuron death.
- Published
- 2015
18. Deficiencies in tRNA synthetase editing activity cause cardioproteinopathy
- Author
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Leslie A. Nangle, My-Nuong Vo, Susan L. Ackerman, Ye Liu, Paul Schimmel, and Jakob S. Satz
- Subjects
Models, Molecular ,Protein Folding ,Heart Diseases ,Plasma protein binding ,Protein aggregation ,medicine.disease_cause ,Mice ,JUNQ and IPOD ,Bacterial Proteins ,Ubiquitin ,medicine ,Animals ,Homeostasis ,Humans ,Myocytes, Cardiac ,Proteostasis Deficiencies ,Alleles ,Genetics ,Mutation ,Multidisciplinary ,biology ,Hydrolysis ,Alanine-tRNA Ligase ,Biological Sciences ,Protein Structure, Tertiary ,Mice, Inbred C57BL ,Microscopy, Fluorescence ,Echocardiography ,Paraffin ,RNA editing ,Transfer RNA ,biology.protein ,Desmin ,RNA Editing ,Protein Binding - Abstract
Misfolded proteins are an emerging hallmark of cardiac diseases. Although some misfolded proteins, such as desmin, are associated with mutations in the genes encoding these disease-associated proteins, little is known regarding more general mechanisms that contribute to the generation of misfolded proteins in the heart. Reduced translational fidelity, caused by a hypomorphic mutation in the editing domain of alanyl-tRNA synthetase (AlaRS), resulted in accumulation of misfolded proteins in specific mouse neurons. By further genetic modulation of the editing activity of AlaRS, we generated mouse models with broader phenotypes, the severity of which was directly related to the degree of compromised editing. Severe disruption of the editing activity of AlaRS caused embryonic lethality, whereas an intermediate reduction in AlaRS editing efficacy resulted in ubiquitinated protein aggregates and mitochondrial defects in cardiomyocytes that were accompanied by progressive cardiac fibrosis and dysfunction. In addition, autophagic vacuoles accumulated in mutant cardiomyocytes, suggesting that autophagy is insufficient to eliminate misfolded proteins. These findings demonstrate that the pathological consequences of diminished tRNA synthetase editing activity, and thus translational infidelity, are dependent on the cell type and the extent of editing disruption, and provide a previously unidentified mechanism underlying cardiac proteinopathy.
- Published
- 2014
19. Ribosome stalling induced by mutation of a CNS-specific tRNA causes neurodegeneration
- Author
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Xiang-Lei Yang, Gabor Nagy, Susan L. Ackerman, Paul Schimmel, Ryuta Ishimura, Jeffrey H. Chuang, Yasuharu Nishimura, Huihao Zhou, Ivan Dotu, and Satoru Senju
- Subjects
Genetics ,Mutation ,Multidisciplinary ,Point mutation ,Transfer RNA ,medicine ,Protein biosynthesis ,RNA ,Cellular homeostasis ,Translation (biology) ,Biology ,medicine.disease_cause ,Ribosome - Abstract
Problems making proteins kills nerve cells Neurodegeneration is associated with a variety of different diseases, but its cellular roots are often obscure. Ishimura et al. find that mutant mice whose brain cells start to die rapidly soon after birth have lost the function of two vital cellular components (see the Perspective by Darnell). The first is a protein that releases stalled ribosomes stuck on messenger RNA (mRNA); the second is a transfer RNA (tRNA), which reads the code for arginine in the mRNA. This tRNA is expressed predominantly in the central nervous system. The lack of the tRNA leads to increased ribosomal stalling at arginine codons, which, when left uncorrected, blocks protein synthesis and proves fatal. Science , this issue p. 455 ; see also p. 378
- Published
- 2014
20. Activation of GCN2 kinase by ribosome stalling links translation elongation with translation initiation
- Author
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Ivan Dotu, Ryuta Ishimura, Jeffrey H. Chuang, Susan L. Ackerman, and Gabor Nagy
- Subjects
0301 basic medicine ,Mouse ,Eukaryotic Initiation Factor-2 ,Peptide Chain Elongation, Translational ,Inbred C57BL ,neuroscience ,Mice ,Biology (General) ,Phosphorylation ,Peptide Chain Initiation, Translational ,genes ,Neurons ,General Neuroscience ,EIF4E ,Translational ,neurodegeneration ,Translation (biology) ,Arg ,General Medicine ,Protein-Serine-Threonine Kinases ,Cell biology ,Peptide Chain Initiation ,Genes and Chromosomes ,Neurological ,Medicine ,T arm ,EF-Tu ,Research Article ,chromosomes ,QH301-705.5 ,Science ,RNA, Transfer, Arg ,Biology ,Protein Serine-Threonine Kinases ,translation initiation ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,GTP-Binding Proteins ,Prokaryotic translation ,Genetics ,Integrated stress response ,Initiation factor ,Animals ,Protein Processing ,mouse ,Peptide Chain Elongation ,General Immunology and Microbiology ,Gene Expression Profiling ,Post-Translational ,Neurosciences ,Molecular biology ,Activating Transcription Factor 4 ,translation elongation ,Mice, Inbred C57BL ,Transfer ,Internal ribosome entry site ,030104 developmental biology ,RNA ,Biochemistry and Cell Biology ,Protein Processing, Post-Translational ,Ribosomes ,Neuroscience - Abstract
Ribosome stalling during translation has recently been shown to cause neurodegeneration, yet the signaling pathways triggered by stalled elongation complexes are unknown. To investigate these pathways we analyzed the brain of C57BL/6J-Gtpbp2nmf205-/- mice in which neuronal elongation complexes are stalled at AGA codons due to deficiencies in a tRNAArgUCU tRNA and GTPBP2, a mammalian ribosome rescue factor. Increased levels of phosphorylation of eIF2α (Ser51) were detected prior to neurodegeneration in these mice and transcriptome analysis demonstrated activation of ATF4, a key transcription factor in the integrated stress response (ISR) pathway. Genetic experiments showed that this pathway was activated by the eIF2α kinase, GCN2, in an apparent deacylated tRNA-independent fashion. Further we found that the ISR attenuates neurodegeneration in C57BL/6J-Gtpbp2nmf205-/- mice, underscoring the importance of cellular and stress context on the outcome of activation of this pathway. These results demonstrate the critical interplay between translation elongation and initiation in regulating neuron survival during cellular stress. DOI: http://dx.doi.org/10.7554/eLife.14295.001, eLife digest Information stored in DNA is used to make proteins in a two-step process. First, the DNA is copied to make molecules of messenger ribonucleic acid (or messenger RNA for short). Next, machines called ribosomes use the messenger RNAs as templates to assemble chains of amino acids – the building blocks of proteins – in a process called translation. Another type of RNA molecule called transfer RNA carries each amino acid to the ribosomes. If a specific transfer RNA is not available for translation at the right time, the ribosome might stall as it moves along the messenger RNA. At this point, the ribosome needs to be restarted or it will fall off the mRNA without finishing the protein. In 2014, a group of researchers reported that certain types of brain cells are very sensitive to ribosome stalling, and tend to die if translation does not continue. A protein called GTPBP2 was shown to play an important role in restarting stalled ribosomes in these cells. Here, Ishimura, Nagy et al. – including some of the researchers from the earlier work – investigated the molecular pathways that ribosome stalling triggers in brain cells using mutant mice that lacked the GTPBP2 protein. The experiments show that ribosome stalling activates an enzyme known as GCN2, which was already known to sense other types of malfunctions in cellular processes. Ishimura, Nagy et al. also show that GCN2 triggers stress responses in the cells by activating a communication system called the ATF4 pathway. This pathway protects the cells from damage, and its absence results in more rapid cell deterioration and death. The next challenges are to understand the exact mechanism by which GCN2 senses stalled ribosomes, and to find out how ribosome stalling causes the death of brain cells. DOI: http://dx.doi.org/10.7554/eLife.14295.002
- Published
- 2016
21. Analysis of Expression Pattern and Genetic Deletion of Netrin5 in the Developing Mouse
- Author
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Andrew M Garrett, Thomas J Jucius, Liam P.R. Sigaud, Fu-Lei eTang, Wen-Cheng eXiong, Susan L. Ackerman, and Robert W. Burgess
- Subjects
0301 basic medicine ,animal structures ,chemorepulsion ,Biology ,lcsh:RC321-571 ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Netrin Receptor DCC ,Netrin ,medicine ,Molecular Biology ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,Original Research ,axon guidance ,fungi ,Neural crest ,motor exit point ,Motor neuron ,Spinal cord ,dorsal root entry zone ,030104 developmental biology ,medicine.anatomical_structure ,nervous system ,Neural Crest ,Peripheral nervous system ,Axon guidance ,Motor neuron migration ,Neuroscience - Abstract
Boundary cap cells are a transient, neural-crest-derived population found at the motor exit point and dorsal root entry zone of the embryonic spinal cord. These cells contribute to the central/peripheral nervous system boundary, and in their absence neurons and glia from the CNS migrate into the PNS. We found Netrin5 (Ntn5), a previously unstudied member of the netrin gene family, to be robustly expressed in boundary cap cells. We generated Ntn5 knockout mice and examined neurodevelopmental and boundary-cap-cell-related phenotypes. No abnormalities in cranial nerve guidance, dorsal root organization, or sensory projections were found. However, Ntn5 mutant embryos did have ectopic motor neurons that migrated out of the ventral horn and into the motor roots. Previous studies have implicated semaphorin6A (Sema6A) in boundary cap cells signaling to plexinA2 (PlxnA2)/neuropilin2 (Nrp2) in motor neurons in restricting motor neuron cell bodies to the ventral horn, particularly in the caudal spinal cord. In Ntn5 mutants, ectopic motor neurons are likely to be a different population, as more ectopias were found rostrally. Furthermore, ectopic motor neurons in Ntn5 mutants were not immunoreactive for NRP2. The netrin receptor DCC is a potential receptor for NTN5 in motor neurons, as similar ectopic neurons were found in Dcc mutant mice, but not in mice deficient for other netrin receptors. Thus, Ntn5 is a novel netrin family member that is expressed in boundary cap cells, functioning to prevent motor neuron migration out of the CNS.
- Published
- 2016
22. Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons
- Author
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Louis-Philippe Croteau, Dayana Krawchuk, Frédéric Charron, Daniel Morales, Jean-François Cloutier, Artur Kania, Sebastian Poliak, Susan L. Ackerman, Matthew B. Dalva, Elena Palmesino, Susan Morton, and Tzu-Jen Kao
- Subjects
animal structures ,Mouse ,QH301-705.5 ,Receptor, EphB2 ,Science ,Growth Cones ,synergy ,Ephrin-B2 ,Receptors, Nerve Growth Factor ,Biology ,General Biochemistry, Genetics and Molecular Biology ,Mice ,Netrin ,medicine ,Animals ,Ephrin ,Nerve Growth Factors ,Biology (General) ,Axon ,Growth cone ,Motor Neurons ,General Immunology and Microbiology ,axon guidance ,Tumor Suppressor Proteins ,General Neuroscience ,fungi ,Erythropoietin-producing hepatocellular (Eph) receptor ,General Medicine ,Anatomy ,Netrin-1 ,Motor neuron ,Spinal cord ,Chicken ,ephrin ,Developmental Biology and Stem Cells ,medicine.anatomical_structure ,nervous system ,embryonic structures ,Medicine ,Axon guidance ,Netrin Receptors ,Neuroscience ,Signal Transduction ,Research Article - Abstract
During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin–ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways. DOI: http://dx.doi.org/10.7554/eLife.10841.001, eLife digest The ability of animals to walk and perform skilled movements depends on particular groups of muscles contracting in a coordinated manner. Muscles are activated by nerve cells called motor neurons found in the spinal cord. The connections between the motor neurons and muscles are established in the developing embryo. Each motor neuron produces a long projection called an axon whose growth is guided towards the target muscle by signal proteins. The motor neurons are exposed to many such signal proteins at the same time and it is not clear how they integrate all this information so that their axons target the correct muscles. Poliak, Morales et al. used a variety of genetic and biochemical approaches to study the formation of motor neuron and muscle connections in the limbs of mice and chicks. The experiments show that a signal protein called Netrin-1 is produced in the limbs of developing embryos and attracts the axons of some types of motor neurons and repels others. This is due to the motor neurons producing different types of receptor proteins to detect Netrin-1. Further experiments show that individual axons can combine information from attractive or repulsive Netrin-1 signals together with repulsive signals from another family of proteins called ephrins in a 'synergistic' manner. That is, the combined effect of both cues is stronger than their individual effects added together. This synergy involves ligand-dependent interactions between the Netrin-1 and ephrin receptor proteins, and the activation of a common enzyme. Poliak, Morales et al.’s findings reveal a new role for Netrin-1 in guiding the development of motor neurons in the limb. Future work will focus on further understanding the mechanism of synergy between Netrin-1 and ephrins. Netrin-1 and ephrins are also involved in the formation of blood vessels and many other developmental processes, so understanding how they work together would have a wide-reaching impact on research into human health and disease. DOI: http://dx.doi.org/10.7554/eLife.10841.002
- Published
- 2015
23. The UNC5C Netrin Receptor Regulates Dorsal Guidance of Mouse Hindbrain Axons
- Author
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Doyeun Kim and Susan L. Ackerman
- Subjects
ATOH1 ,Dorsum ,Cerebellum ,Green Fluorescent Proteins ,Cell Count ,Hindbrain ,Receptors, Nerve Growth Factor ,UNC5C ,Article ,Mice ,Cell Movement ,Neural Pathways ,Basic Helix-Loop-Helix Transcription Factors ,Inferior olivary nucleus ,medicine ,Animals ,Amino Acids ,Mice, Knockout ,Neurons ,biology ,General Neuroscience ,Gene Expression Regulation, Developmental ,Embryo, Mammalian ,Axons ,Mice, Inbred C57BL ,Rhombencephalon ,medicine.anatomical_structure ,Animals, Newborn ,nervous system ,biology.protein ,Axon guidance ,Brainstem ,Netrin Receptors ,Neuroscience - Abstract
The cerebellum receives its input from multiple precerebellar nuclei located in the brainstem and sends processed information to other brain structures via the deep cerebellar neurons. Guidance molecules that regulate the complex migrations of precerebellar neurons and the initial guidance of their leading processes have been identified. However, the molecules necessary for dorsal guidance of precerebellar axons to the developing cerebellum or for guidance of decussating axons of the deep nuclei are not known. To determine whetherUnc5cplays a role in the dorsal guidance of precerebellar and deep cerebellar axons, we studied axonal trajectories of these neurons inUnc5c−/−mice. Our results show thatUnc5cis expressed broadly in the precerebellar and deep cerebellar neurons.Unc5cdeletion disrupted long-range dorsal guidance of inferior olivary and pontine axons after crossing the midline. In addition, dorsal guidance of the axons from the medial deep cerebellar and external cuneate neurons was affected inUnc5c−/−mice, as were anterior migrations of pontine neurons. Coincident with the guidance defects of their axons, degeneration of neurons in the external cuneate nucleus and subdivisions of the inferior olivary nucleus was observed inUnc5c−/−mice. Lastly, transgenic expression ofUnc5cin deep neurons and pontine neurons by theAtoh1promoter rescued defects of the medial deep cerebellar and pontine axons observed inUnc5c−/−embryos, demonstrating thatUnc5cacts cell autonomously in the guidance of these axons. Our results suggest thatUnc5cplays a broad role in dorsal guidance of axons in the developing hindbrain.
- Published
- 2011
24. Plexin-A2 and its ligand, Sema6A, control nucleus-centrosome coupling in migrating granule cells
- Author
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Géraldine Kerjan, Fumikazu Suto, Hajime Fujisawa, Doyeun Kim, Kazunori Suda, Julie Renaud, Susan L. Ackerman, Alain Chédotal, Coralie Fouquet, Makoto Sanbo, Itsuko Sumita, Yvrick Zagar, Kevin J. Mitchell, Virginie Georget, Neurobiologie des processus adaptatifs (NPA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Samsung Advanced Institute of Technology (SAIT), Samsung, Artificial Intelligence and Pattern Recognition Laboratory, Korea Advanced Institute of Science and Technology (KAIST), Korea Institute of Machinery and Materials, KIMM, Laboratory of Neurobiology and Behavioral Genetics, National Institute for Physiological Science, Division of Developmental Genetics, National Institute of Genetics (NIG), Core Research for Evolutional Science and Technology (CREST), and Japan Science and Technology Agency (JST)
- Subjects
Cerebellum ,animal structures ,[SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology ,Nerve Tissue Proteins ,Receptors, Cell Surface ,Semaphorins ,In Vitro Techniques ,Mice ,Cell Movement ,medicine ,Animals ,Cells, Cultured ,Cell Nucleus ,Centrosome ,Mice, Knockout ,Neurons ,biology ,General Neuroscience ,Plexin ,Granule (cell biology) ,Gene Expression Regulation, Developmental ,Oligodendrocyte ,Cell biology ,Mice, Inbred C57BL ,Cell nucleus ,medicine.anatomical_structure ,embryonic structures ,biology.protein ,Neuroscience ,Nucleus ,Astrocyte - Abstract
During their migration, cerebellar granule cells switch from a tangential to a radial mode of migration. We have previously demonstrated that this involves the transmembrane semaphorin Sema6A. We show here that plexin-A2 is the receptor that controls Sema6A function in migrating granule cells. In plexin-A2-deficient (Plxna2(-/-)) mice, which were generated by homologous recombination, many granule cells remained in the molecular layer, as we saw in Sema6a mutants. A similar phenotype was observed in mutant mice that were generated by mutagenesis with N-ethyl-N-nitrosourea and had a single amino-acid substitution in the semaphorin domain of plexin-A2. We found that this mutation abolished the ability of Sema6A to bind to plexin-A2. Mouse chimera studies further suggested that plexin-A2 acts in a cell-autonomous manner. We also provide genetic evidence for a ligand-receptor relationship between Sema6A and plexin-A2 in this system. Using time-lapse video microscopy, we found that centrosome-nucleus coupling and coordinated motility were strongly perturbed in Sema6a(-/-) and Plxna2(-/-) granule cells. This suggests that semaphorin-plexin signaling modulates cell migration by controlling centrosome positioning.
- Published
- 2008
25. UNC5C is required for spinal accessory motor neuron development
- Author
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Marc Tessier-Lavigne, Allison K. Dillon, Zaven Kaprielian, Susan L. Ackerman, Lindsay Hinck, Xiaowei Lu, and A.R. Jevince
- Subjects
Accessory nerve ,Receptors, Cell Surface ,Receptors, Nerve Growth Factor ,Biology ,UNC5C ,Gene Expression Regulation, Enzymologic ,Mice ,Cellular and Molecular Neuroscience ,Accessory Nerve ,Chemorepulsion ,Pregnancy ,Netrin ,medicine ,Animals ,Molecular Biology ,In Situ Hybridization ,Floor plate ,Mice, Knockout ,Motor Neurons ,Critical Period, Psychological ,Cell Biology ,Motor neuron ,Embryo, Mammalian ,Spinal cord ,Immunohistochemistry ,Embryonic stem cell ,medicine.anatomical_structure ,Spinal Cord ,Female ,Netrin Receptors ,Neuroscience - Abstract
In both invertebrates and vertebrates, UNC5 receptors facilitate chemorepulsion away from a Netrin source. Unlike most motor neurons in the embryonic vertebrate spinal cord, spinal accessory motor neuron (SACMN) cell bodies and their axons translocate along a dorsally directed trajectory away from the floor plate/ventral midline and toward the lateral exit point (LEP). We have recently shown that Netrin-1 and DCC are required for the migration of SACMN cell bodies, in vivo. These observations raised the possibility that vertebrate UNC5 proteins mediate the presumed repulsion of SACMN away from the Netrin-rich ventral midline. Here, we show that SACMN are likely to express UNC5A and UNC5C. Whereas SACMN development proceeds normally in UNC5A null mice, many SACMN cell bodies fail to migrate away from the ventral midline and inappropriately cluster in the ventrolateral spinal cord of mouse embryos lacking UNC5C. These results support an important role for UNC5C in SACMN development.
- Published
- 2007
26. Impact of fill volume on ultrafiltration with icodextrin in children on chronic peritoneal dialysis
- Author
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Elizabeth Piva, Sharon Rousso, Christoph Licht, Elizabeth A. Harvey, Tonny Banh, and Susan L. Ackerman
- Subjects
Chronic peritoneal dialysis ,Male ,medicine.medical_specialty ,Adolescent ,Body Surface Area ,medicine.medical_treatment ,030232 urology & nephrology ,Ultrafiltration ,Urology ,030204 cardiovascular system & hematology ,Icodextrin ,Peritoneal dialysis ,03 medical and health sciences ,0302 clinical medicine ,Dialysis Solutions ,Glucose polymers ,Medicine ,Humans ,Renal Insufficiency, Chronic ,Child ,Glucans ,Body surface area ,business.industry ,Infant ,Glucose ,Biochemistry ,Volume (thermodynamics) ,Nephrology ,Child, Preschool ,Pediatrics, Perinatology and Child Health ,Female ,Linear correlation ,business ,Peritoneal Dialysis - Abstract
Icodextrin is a solution of glucose polymers developed to provide sustained ultrafiltration over an extended dwell. Our aim was to determine whether or not fill volume with icodextrin contributes to the ability to achieve ultrafiltration in children.The charts of all children on chronic peritoneal dialysis between January 2000 and July 2014 were screened for the use of an icodextrin day dwell. Data were extracted from the electronic chart and the HomeChoice™ Pro card and corrected for body surface area (BSA).Fifty children had an icodextrin day dwell. A linear correlation was found between the daytime fill volume and net ultrafiltration (p 0.001). More ultrafiltration was achieved with a fill volume above 550 ml/m(2) BSA (107 ± 75 ml/m(2) BSA) than with smaller fill volumes (-8 ± 99 ml; p = 0.004). Ultrafiltration was achieved in 88 % of children with a fill volume above 550 ml/m(2) BSA versus only 44 % of patients with a smaller fill volume (p = 0.001). Icodextrin was well tolerated.Our observations reveal that the larger the fill volume the higher the likelihood of achieving ultrafiltration with icodextrin and suggest that a minimum day dwell volume of 550 ml/m(2) BSA seems to facilitate ultrafiltration in children. To our knowledge this is the largest study addressing ultrafiltration with icodextrin in children.
- Published
- 2015
27. Editing-defective tRNA synthetase causes protein misfolding and neurodegeneration
- Author
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Susan A. Cook, Muriel T. Davisson, Chantal M. Longo-Guess, John P. Sundberg, Paul Schimmel, Jeong Woong Lee, Jaeseon Jang, Kirk Beebe, Susan L. Ackerman, and Leslie A. Nangle
- Subjects
Models, Molecular ,Protein Folding ,Molecular Sequence Data ,RNA, Transfer, Ala ,Cerebellar Purkinje cell ,Biology ,medicine.disease_cause ,Catalysis ,Mice ,Purkinje Cells ,JUNQ and IPOD ,Escherichia coli ,Serine ,medicine ,Animals ,Humans ,Mutation ,Alanine ,Multidisciplinary ,Alanine-tRNA Ligase ,Neurodegeneration ,Acetylation ,Neurodegenerative Diseases ,Fibroblasts ,medicine.disease ,Mice, Mutant Strains ,Protein Structure, Tertiary ,Mice, Inbred C57BL ,Phenotype ,Aggresome ,Biochemistry ,Transfer RNA ,Unfolded protein response ,Protein folding - Abstract
Misfolded proteins are associated with several pathological conditions including neurodegeneration. Although some of these abnormally folded proteins result from mutations in genes encoding disease-associated proteins (for example, repeat-expansion diseases), more general mechanisms that lead to misfolded proteins in neurons remain largely unknown. Here we demonstrate that low levels of mischarged transfer RNAs (tRNAs) can lead to an intracellular accumulation of misfolded proteins in neurons. These accumulations are accompanied by upregulation of cytoplasmic protein chaperones and by induction of the unfolded protein response. We report that the mouse sticky mutation, which causes cerebellar Purkinje cell loss and ataxia, is a missense mutation in the editing domain of the alanyl-tRNA synthetase gene that compromises the proofreading activity of this enzyme during aminoacylation of tRNAs. These findings demonstrate that disruption of translational fidelity in terminally differentiated neurons leads to the accumulation of misfolded proteins and cell death, and provide a novel mechanism underlying neurodegeneration.
- Published
- 2006
28. Endoplasmic reticulum stress in health and disease
- Author
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Lihong Zhao and Susan L. Ackerman
- Subjects
Protein Folding ,Endoplasmic reticulum ,Cell ,Models, Immunological ,Neurodegenerative Diseases ,Translation (biology) ,Cell Biology ,Disease ,Biology ,Endoplasmic Reticulum ,Cell biology ,medicine.anatomical_structure ,Immune system ,Downregulation and upregulation ,Diabetes Mellitus ,Unfolded protein response ,medicine ,Animals ,Humans ,Homeostasis - Abstract
Unfolded proteins and other conditions affecting endoplasmic reticulum (ER) homeostasis cause ER stress. The cell reacts to ER stress by activation of the unfolded protein response (UPR), which induces profound changes in cellular metabolism including general translation attenuation, transcriptional upregulation of molecular chaperone genes, and activation of ER-associated degradation. However, prolonged or acute ER stress results in cell death. Recent progress suggests that ER stress and UPR play key roles in the immune response, diabetes, tumor growth under hypoxic conditions, and in some neurodegenerative diseases. Further research on ER stress and UPR will greatly enhance the understanding of these physiological and pathological processes, and provide novel avenues to potential therapies.
- Published
- 2006
29. In VivoMagnetic Resonance Imaging and Semiautomated Image Analysis Extend the Brain Phenotype forcdf/cdfMice
- Author
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Tatiana V. Lipina, John C. Roder, Susan L. Ackerman, R. Mark Henkelman, Natasa Kovacevic, and Nicholas A. Bock
- Subjects
Male ,Inferior colliculus ,Cerebellum ,Pathology ,medicine.medical_specialty ,Mutant ,Contrast Media ,Mice, Transgenic ,Biology ,Mice ,Mice, Neurologic Mutants ,Imaging, Three-Dimensional ,Chlorides ,In vivo ,Image Interpretation, Computer-Assisted ,medicine ,Animals ,medicine.diagnostic_test ,General Neuroscience ,Brain ,Magnetic resonance imaging ,Articles ,Magnetic Resonance Imaging ,Phenotype ,medicine.anatomical_structure ,Manganese Compounds ,Cytoarchitecture ,Female ,Neuroscience ,Neuroanatomy - Abstract
Magnetic resonance imaging and computer image analysis in human clinical studies effectively identify abnormal neuroanatomy in disease populations. As more mouse models of neurological disorders are discovered, such an approach may prove useful for translational studies. Here, we demonstrate the effectiveness of a similar strategy for mouse neuroscience studies by phenotyping mice with the cerebellar deficient folia (cdf) mutation. Usingin vivomultiple-mouse magnetic resonance imaging for increased throughput, we imaged groups ofcdfmutant, heterozygous, and wild-type mice and made an atlas-based segmentation of the structures in 15 individual brains. We then performed computer automated volume measurements on the structures. We found a reduced cerebellar volume in thecdfmutants, which was expected, but we also found a new phenotype in the inferior colliculus and the olfactory bulbs. Subsequent local histology revealed additional cytoarchitectural abnormalities in the olfactory bulbs. This demonstrates the utility of anatomical magnetic resonance imaging and semiautomated image analysis for detecting abnormal neuroarchitecture in mutant mice.
- Published
- 2006
30. Dorsally derived netrin 1 provides an inhibitory cue and elaborates the'waiting period' for primary sensory axons in the developing spinal cord
- Author
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Keisuke Watanabe, Susan L. Ackerman, Takahiro Furuta, Kazuhiro Ikenaka, Nobuaki Tamamaki, and Katsuhiko Ono
- Subjects
Indoles ,animal structures ,Sensory system ,Biology ,UNC5C ,Models, Biological ,Cell Line ,Mice ,Organ Culture Techniques ,Dorsal root ganglion ,Pregnancy ,Cricetinae ,Ganglia, Spinal ,Netrin ,medicine ,Animals ,Nerve Growth Factors ,Neurons, Afferent ,Mantle (mollusc) ,Molecular Biology ,In Situ Hybridization ,Floor plate ,Mice, Inbred ICR ,Epidermal Growth Factor ,Tumor Suppressor Proteins ,fungi ,Neural tube ,Galactosides ,Anatomy ,Netrin-1 ,Spinal cord ,Immunohistochemistry ,Axons ,medicine.anatomical_structure ,Spinal Cord ,nervous system ,Mutation ,embryonic structures ,Female ,Neuroscience ,Developmental Biology - Abstract
Dorsal root ganglion (DRG) neurons extend axons to specific targets in the gray matter of the spinal cord. During development, DRG axons grow into the dorsolateral margin of the spinal cord and projection into the dorsal mantle layer occurs after a `waiting period' of a few days. Netrin 1 is a long-range diffusible factor expressed in the ventral midline of the developing neural tube, and has chemoattractive and chemorepulsive effects on growing axons. Netrin 1 is also expressed in the dorsal spinal cord. However, the roles of dorsally derived netrin 1 remain totally unknown. Here, we show that dorsal netrin 1 controls the correct guidance of primary sensory axons. During the waiting period, netrin 1 is transiently expressed or upregulated in the dorsal spinal cord, and the absence of netrin 1 results in the aberrant projection of sensory axons, including both cutaneous and proprioceptive afferents, into the dorsal mantle layer. Netrin 1 derived from the dorsal spinal cord, but not the floor plate, is involved in the correct projection of DRG axons. Furthermore,netrin 1 suppresses axon outgrowth from DRG in vitro. Unc5crcm mutant shows abnormal invasion of DRG axons as observed in netrin 1 mutants. These results are the first direct evidence that netrin 1 in the dorsal spinal cord acts as an inhibitory cue for primary sensory axons and is a crucial signal for the formation of sensory afferent neural networks.
- Published
- 2006
31. Protein accumulation and neurodegeneration in the woozy mutant mouse is caused by disruption of SIL1, a cochaperone of BiP
- Author
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Jeong-Woong Lee, Belinda S. Harris, Susan L. Ackerman, Chantal M. Longo-Guess, and Lihong Zhao
- Subjects
Male ,Molecular Sequence Data ,Cerebellar Purkinje cell ,Biology ,Endoplasmic Reticulum ,Autoantigens ,Mice ,Purkinje Cells ,Downregulation and upregulation ,Adenine nucleotide ,Cerebellum ,Heat shock protein ,Genetics ,medicine ,Animals ,Guanine Nucleotide Exchange Factors ,Endoplasmic Reticulum Chaperone BiP ,Heat-Shock Proteins ,Cell Nucleus ,Mice, Knockout ,Endoplasmic reticulum ,Homozygote ,Neurodegeneration ,medicine.disease ,Molecular biology ,Mice, Inbred C57BL ,Mutation ,Nerve Degeneration ,Unfolded protein response ,Ataxia ,Female ,Neuron death ,Molecular Chaperones - Abstract
Endoplasmic reticulum (ER) chaperones and ER stress have been implicated in the pathogenesis of neurodegenerative disorders, such as Alzheimer and Parkinson diseases, but their contribution to neuron death remains uncertain1,2. In this study, we establish a direct in vivo link between ER dysfunction and neurodegeneration. Mice homozygous with respect to the woozy (wz) mutation develop adult-onset ataxia with cerebellar Purkinje cell loss. Affected cells have intracellular protein accumulations reminiscent of protein inclusions in both the ER and the nucleus. In addition, upregulation of the unfolded protein response, suggestive of ER stress, occurs in mutant Purkinje cells. We report that the wz mutation disrupts the gene Sil1 that encodes an adenine nucleotide exchange factor of BiP3, a crucial ER chaperone4. These findings provide evidence that perturbation of ER chaperone function in terminally differentiated neurons leads to protein accumulation, ER stress and subsequent neurodegeneration.
- Published
- 2005
32. Cholesterol metabolism and Rett syndrome pathogenesis
- Author
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Susan L. Ackerman and Gabor Nagy
- Subjects
Genetics ,congenital, hereditary, and neonatal diseases and abnormalities ,medicine.medical_specialty ,Mutant ,Rett syndrome ,Disease ,Biology ,medicine.disease ,nervous system diseases ,MECP2 ,Pathogenesis ,Endocrinology ,Internal medicine ,mental disorders ,Transcriptional regulation ,medicine ,Cholesterol metabolism ,Gene - Abstract
Rett syndrome is caused by mutations in the gene encoding the transcriptional regulator MECP2. A new study demonstrates that cholesterol homeostasis is disrupted in Mecp2 mutant mice and suggests new therapeutic options for this disease.
- Published
- 2013
33. The harlequin mouse mutation downregulates apoptosis-inducing factor
- Author
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Susan L. Ackerman, Chantal M. Longo-Guess, Kevin L. Seburn, Ronald E. Hurd, Jeff Klein, Roderick T. Bronson, Marlies P. Rossmann, and Wayne N. Frankel
- Subjects
Aging ,Cerebellum ,Programmed cell death ,AIFM1 ,Cell Survival ,Down-Regulation ,Apoptosis ,Biology ,medicine.disease_cause ,Polymerase Chain Reaction ,Retina ,Mice ,Purkinje Cells ,Genetic model ,medicine ,Animals ,cardiovascular diseases ,Cells, Cultured ,Neurons ,Genetics ,Multidisciplinary ,Flavoproteins ,Cell Cycle ,Neurodegeneration ,Apoptosis Inducing Factor ,Membrane Proteins ,Free Radical Scavengers ,Hydrogen Peroxide ,Catalase ,Free radical scavenger ,medicine.disease ,Glutathione ,Mice, Mutant Strains ,Cell biology ,Microscopy, Electron ,Oxidative Stress ,Phenotype ,medicine.anatomical_structure ,Mutation ,Apoptosis-inducing factor ,Lipid Peroxidation ,biological phenomena, cell phenomena, and immunity ,Oxidative stress - Abstract
Harlequin (Hq) mutant mice have progressive degeneration of terminally differentiated cerebellar and retinal neurons. We have identified the Hq mutation as a proviral insertion in the apoptosis-inducing factor (Aif) gene, causing about an 80% reduction in AIF expression. Mutant cerebellar granule cells are susceptible to exogenous and endogenous peroxide-mediated apoptosis, but can be rescued by AIF expression. Overexpression of AIF in wild-type granule cells further decreases peroxide-mediated cell death, suggesting that AIF serves as a free radical scavenger. In agreement, dying neurons in aged Hq mutant mice show oxidative stress. In addition, neurons damaged by oxidative stress in both the cerebellum and retina of Hq mutant mice re-enter the cell cycle before undergoing apoptosis. Our results provide a genetic model of oxidative stress-mediated neurodegeneration and demonstrate a direct connection between cell cycle re-entry and oxidative stress in the ageing central nervous system.
- Published
- 2002
34. Abstract IA13: Ribosome stalling and disease
- Author
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Susan L. Ackerman
- Subjects
chemistry.chemical_classification ,Cancer Research ,Nuclear gene ,Cancer ,Translation (biology) ,Biology ,medicine.disease ,Ribosome ,Amino acid ,Cell biology ,Oncology ,chemistry ,Transfer RNA ,medicine ,Protein biosynthesis ,Gene - Abstract
La Jolla, CA. Protein synthesis is vital for cell function and disturbances in translation are associated with cancer, neurological disorders and other diseases. Although regulation of translation is thought to largely occur at initiation, elongation, the reiterative addition of amino acids by the ribosome, is emerging as a translational phase that is also highly regulated. Transfer RNAs, the adaptor molecules essential for elongation are encoded by several hundreds of nuclear genes in higher eukaryotes suggesting great functional redundancy. Our work has defined epistatic interactions between mutations in a mammalian tRNA gene and a novel ribosome rescue factor, defining the importance of individual tRNA genes in translation and the pathologies that can arise from disruptions in this process. Citation Format: Susan L. Ackerman. Ribosome stalling and disease. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr IA13.
- Published
- 2017
35. Unc5C and DCC act downstream of Ctip2 and Satb2 and contribute to corpus callosum formation
- Author
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Amber-Lee S. Donahoo, Olga V. Britanova, Linda J. Richards, Swathi Srivatsa, Susan L. Ackerman, Ingo Bormuth, Victor Tarabykin, and Srinivas Parthasarathy
- Subjects
Chromatin Immunoprecipitation ,General Physics and Astronomy ,Receptors, Cell Surface ,Receptors, Nerve Growth Factor ,Biology ,Cell fate determination ,UNC5C ,Corpus callosum ,Article ,General Biochemistry, Genetics and Molecular Biology ,Corpus Callosum ,Mice ,Morphogenesis ,medicine ,Animals ,Luciferases ,Receptor ,Transcription factor ,In Situ Hybridization ,DNA Primers ,Regulation of gene expression ,Multidisciplinary ,Neocortex ,Tumor Suppressor Proteins ,Gene Expression Regulation, Developmental ,General Chemistry ,DCC Receptor ,Molecular biology ,Electroporation ,medicine.anatomical_structure ,nervous system ,Axon guidance ,Netrin Receptors ,Neuroscience ,Plasmids - Abstract
The pyramidal neurons of the mammalian neocortex form two major types of long-range connections—corticocortical and cortico-subcortical. The transcription factors Satb2 and Ctip2 are critical regulators of neuronal cell fate that control interhemispheric versus corticofugal connections respectively. Here, we investigate the axon guidance molecules downstream of Satb2 and Ctip2 that establish these connections. We show that the expression of two Netrin1 receptors- DCC and Unc5C is under direct negative regulation by Satb2 and Ctip2, respectively. Further, we show that the Netrin1–Unc5C/DCC interaction is involved in controlling the interhemispherical projection in a subset of early born, deep layer callosal neurons., The neocortex is responsible for higher level cognitive functions and long-range neural connections are critical for mediating these functions. Here, Srivatsa et al. show that axon guidance molecules downstream of transcription factors Stab2 and Ctip2 play a role in the establishment of cortical connections during mouse brain development.
- Published
- 2014
36. Abnormal dispersion of a purkinje cell subset in the mouse mutant cerebellar deficient folia (cdf)
- Author
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Susan L. Ackerman, Elaine Beierbach, Chankyu Park, Richard Hawkes, and Dan Goldowitz
- Subjects
Cerebellum ,Purkinje cell ,Cell ,Morphogenesis ,Cell Count ,Nerve Tissue Proteins ,Choristoma ,Biology ,Calbindin ,Mice ,Mice, Neurologic Mutants ,Purkinje Cells ,Cell Movement ,medicine ,Animals ,Aldolase C ,General Neuroscience ,Homozygote ,Embryonic stem cell ,Reelin Protein ,Phenotype ,medicine.anatomical_structure ,Cerebellar cortex ,Neuroscience - Abstract
Purkinje cells of different molecular phenotypes subdivide the cortex of the cerebellum both rostrocaudally into parasagittal bands and mediolaterally into transverse zones. Superimposed on the Purkinje cell compartmentation, the cerebellar cortex is pleated into a reproducible array of lobes and lobules. During cerebellar development, Purkinje cell bands are formed through the rostrocaudal dispersal of embryonic clusters, triggered primarily by a Reelin-dependent signaling pathway. In the naturally occurring mouse mutant cerebellar deficient folia (cdf), there is a failure of Purkinje cell dispersion that results in widespread Purkinje cell ectopia in the adult. The ectopia is restricted primarily to that subset of Purkinje cells that does not express zebrin II/aldolase C and that forms ectopic clusters in among the cerebellar nuclei. Most Purkinje cells that express zebrin II are located normally in a monolayer. Thus, the cerebellum of cdf mutants has a failure of Purkinje cell dispersion that is confined primarily to a zebrin II-negative (zebrin II−) subpopulation. Despite the Purkinje cell ectopia, the parasagittal band organization of the cerebellum is still clear. The shortening of the cortex is distributed evenly over all lobules, with the result that transverse expression boundaries are relocated with respect to the lobules and fissures. The number of Purkinje cells in the cdf/cdf cerebellum is similar to the number in littermate controls. Therefore, it appears that the lesion in cdf results in the failure of a zebrin II− Purkinje cell subset to disperse either due to a cell intrinsic defect or due to an abnormal interaction between the Purkinje cells and either granule cells or afferent inputs. J. Comp. Neurol. 436:42–51, 2001. © 2001 Wiley-Liss, Inc.
- Published
- 2001
37. Granule Cells and Cerebellar Boundaries: Analysis ofUnc5h3Mutant Chimeras
- Author
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Dan Goldowitz, Stefan Przyborski, Susan L. Ackerman, and Kristin M. Hamre
- Subjects
Cell type ,Cerebellum ,Genotype ,Recombinant Fusion Proteins ,Mitosis ,Mice, Inbred Strains ,Receptors, Cell Surface ,Biology ,Cytoplasmic Granules ,Ligands ,Mice ,Purkinje Cells ,Chimera (genetics) ,Cell Movement ,Netrin ,medicine ,Animals ,ARTICLE ,Coloring Agents ,Neurons ,General Neuroscience ,Granule cell ,Immunohistochemistry ,Cell biology ,Phenotype ,medicine.anatomical_structure ,nervous system ,Mutation ,Neuroglia ,Midbrain tegmentum ,Netrin Receptors ,Neuroscience - Abstract
Mutations in theUnc5h3gene, a receptor for the netrin 1 ligand, result in abnormal migrations of both Purkinje and granule cells to regions outside the cerebellum and of granule cells to regions within the cerebellum. Because both Purkinje and granule cells express this molecule, we sought to determine whether one or both of these cell types are the primary target of the mutation.Chimeric mice were made between wild-type ROSA26 transgenic mouse embryos (whose cells express β-galactosidase) andUnc5h3mutant embryos. The resulting chimeric brains exhibited a range of phenotypes. Chimeras that had a limited expression of the extracerebellar phenotype (movement of cerebellar cells into the colliculus and midbrain tegmentum) and the intracerebellar phenotype (migration of granule cells into white matter) had a normal-appearing cerebellum, whereas chimeras that had more ectopic cells had attenuated anterior cerebellar lobules. Furthermore, the colonization of colliculus and midbrain tegmentum by cerebellar cells was not equivalent in all chimeras, suggesting different origins for extracerebellar ectopias in these regions.The granule cells of the extracerebellar ectopias were almost entirely derived fromUnc5h3/Unc5h3mutant embryos, whereas the ectopic Purkinje cells were a mixture of both mutant and wild-type cells. Intracerebellar ectopias in the chimera were composed exclusively of mutant granule cells. These findings demonstrate that both inside and outside the cerebellum, the granule cell is the key cell type to demarcate the boundaries of the cerebellum.
- Published
- 2000
38. From ER to Eph Receptors: New Roles for VAP Fragments
- Author
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Susan L. Ackerman and Gregory A. Cox
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Biochemistry, Genetics and Molecular Biology(all) ,Endoplasmic reticulum ,Erythropoietin-producing hepatocellular (Eph) receptor ,Biology ,VAPB ,medicine.disease ,EPH receptor A2 ,General Biochemistry, Genetics and Molecular Biology ,Cell biology ,EPH receptor A3 ,Immunology ,medicine ,Amyotrophic lateral sclerosis ,Signal transduction ,Receptor - Abstract
Dominantly inherited mutations in an endoplasmic reticulum protein called VAPB have been found in a subset of patients with a rare familial form of amyotrophic lateral sclerosis (ALS). In this issue, Tsuda et al. (2008) identify a secreted form of VAPB that binds directly to Eph receptors inducing their activation and signaling, providing fresh insights into ALS pathogenesis, including non-neuronal aspects of this disorder.
- Published
- 2008
39. Cloning and Mapping of theUNC5CGene to Human Chromosome 4q21–q23
- Author
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Susan L. Ackerman and Barbara B. Knowles
- Subjects
Adult ,Cerebellum ,DNA, Complementary ,Molecular Sequence Data ,Gene Expression ,Receptors, Cell Surface ,Kidney ,UNC5C ,Homology (biology) ,Gene mapping ,Gene expression ,Netrin ,Genetics ,medicine ,Humans ,Receptors, Growth Factor ,Tissue Distribution ,Amino Acid Sequence ,RNA, Messenger ,Cloning, Molecular ,Caenorhabditis elegans Proteins ,Lung ,Gene ,Caenorhabditis elegans ,Sequence Homology, Amino Acid ,biology ,Brain ,Chromosome Mapping ,Membrane Proteins ,Helminth Proteins ,Sequence Analysis, DNA ,Blotting, Northern ,biology.organism_classification ,medicine.anatomical_structure ,Genes ,nervous system ,Chromosomes, Human, Pair 4 ,Netrin Receptors ,Sequence Alignment - Abstract
The vertebrate Unc5 genes, like their Caenorhabditis elegans counterpart, define a family of putative netrin receptors. One member of this family, Unc5h3, has been shown to have an important role during cell migration in the developing murine cerebellum. Mice homozygous for mutations in Unc5h3 are ataxic and have cerebellar hypoplasia and laminar structure defects. In addition, these mice have ectopic granule and Purkinje cells in the midbrain and brainstem. We have identified the human homologue of this gene, UNC5C, and shown it to have a restricted expression pattern in adult human tissues. By radiation hybrid analysis, we have determined that UNC5C localizes to chromosome 4q21-q23 between markers D4S1557 and D4S836 and is closely linked to the Parkinson disease gene.
- Published
- 1998
40. The mouse rostral cerebellar malformation gene encodes an UNC-5-like protein
- Author
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Leslie P. Kozak, Bert B. Boyer, Stefan Przyborski, Susan L. Ackerman, Barbara B. Knowles, and Laurie A. Rund
- Subjects
Cerebellum ,Molecular Sequence Data ,Gene Expression ,Mice, Transgenic ,Receptors, Cell Surface ,Receptors, Nerve Growth Factor ,In situ hybridization ,Biology ,UNC5C ,medicine.disease_cause ,Polymerase Chain Reaction ,Mice ,Cell Movement ,Netrin ,medicine ,Animals ,Receptors, Growth Factor ,Tissue Distribution ,Amino Acid Sequence ,Nerve Growth Factors ,Cloning, Molecular ,Caenorhabditis elegans Proteins ,In Situ Hybridization ,Neurons ,Mutation ,Multidisciplinary ,Sequence Homology, Amino Acid ,Tumor Suppressor Proteins ,Homozygote ,fungi ,Membrane Proteins ,Helminth Proteins ,Anatomy ,Netrin-1 ,Blotting, Northern ,Cell biology ,Mice, Inbred C57BL ,medicine.anatomical_structure ,nervous system ,Membrane protein ,Cerebellar cortex ,Immunoglobulin superfamily ,Netrin Receptors ,Cell Division - Abstract
Migration of neurons from proliferative zones to their functional sites is fundamental to the normal development of the central nervous system. Mice homozygous for the spontaneous rostral cerebellar malformation mutation (rcm(s)) or a newly identified transgenic insertion allele (rcm(tg)) exhibit cerebellar and midbrain defects, apparently as a result of abnormal neuronal migration. Laminar structure abnormalities in lateral regions of the rostral cerebellar cortex have been described in homozygous rcm(s) mice. We now demonstrate that the cerebellum of both rcm(s) and rcm(tg) homozygotes is smaller and has fewer folia than in the wild-type, ectopic cerebellar cells are present in midbrain regions by three days after birth, and there are abnormalities in postnatal cerebellar neuronal migration. We have cloned the rcm complementary DNA, which encodes a transmembrane receptor of the immunoglobulin superfamily. The sequence of the rcm protein (Rcm) is highly similar to that of UNC-5, a Caenorhabditis elegans protein that is essential for dorsal guidance of pioneer axons and for the movement of cells away from the netrin ligand, which is encoded by the unc-6 gene. As Rcm is a member of a newly described family of vertebrate homologues of UNC-5 which are netrin-binding proteins, our results indicate that UNC-5-like proteins may have a conserved function in mediating netrin-guided migration.
- Published
- 1997
41. Notch1-induced brain tumor models the sonic hedgehog subgroup of human medulloblastoma
- Author
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Sivaraman Natarajan, David Shih, Emily E. Miller, Kyuson Yun, Jeong Kyo Yoon, Michael D. Taylor, Roderick T. Bronson, Timothy M Stearns, Susan L. Ackerman, and Yaochen Li
- Subjects
Cancer Research ,Cellular differentiation ,Transgene ,Blotting, Western ,Brain tumor ,Notch signaling pathway ,Fluorescent Antibody Technique ,Apoptosis ,Mice, Transgenic ,medicine.disease_cause ,Real-Time Polymerase Chain Reaction ,Article ,Immunoenzyme Techniques ,Mice ,medicine ,Biomarkers, Tumor ,Animals ,Humans ,Hedgehog Proteins ,RNA, Messenger ,Sonic hedgehog ,Receptor, Notch1 ,Cerebellar Neoplasms ,Cell Proliferation ,Oligonucleotide Array Sequence Analysis ,Medulloblastoma ,biology ,Brain Neoplasms ,Reverse Transcriptase Polymerase Chain Reaction ,Gene Expression Profiling ,Cancer ,Cell Differentiation ,medicine.disease ,Molecular biology ,Oncology ,embryonic structures ,biology.protein ,Carcinogenesis - Abstract
While activation of the Notch pathway is observed in many human cancers, it is unknown whether elevated Notch1 expression is sufficient to initiate tumorigenesis in most tissues. To test the oncogenic potential of Notch1 in solid tumors, we expressed an activated form of Notch1 (N1ICD) in the developing mouse brain. N1ICD;hGFAP-cre mice were viable but developed severe ataxia and seizures, and died by weaning age. Analysis of transgenic embryo brains revealed that N1ICD expression induced p53-dependent apoptosis. When apoptosis was blocked by genetic deletion of p53, 30% to 40% of N1ICD;GFAP-cre;p53+/− and N1ICD;GFAP-cre;p53−/− mice developed spontaneous medulloblastomas. Interestingly, N1ICD-induced medulloblastomas most closely resembled the sonic hedgehog subgroup of human medulloblastoma at the molecular level. Surprisingly, N1ICD-induced tumors do not maintain high levels of the Notch pathway gene expression, except for Notch2, showing that initiating oncogenic events may not be decipherable by analyzing growing tumors in some cases. In summary, this study shows that Notch1 has an oncogenic potential in the brain when combined with other oncogenic hits, such as p53 loss, and provides a novel mouse model of medulloblastoma. Cancer Res; 73(17); 5381–90. ©2013 AACR.
- Published
- 2013
42. A deficiency of ceramide biosynthesis causes cerebellar purkinje cell neurodegeneration and lipofuscin accumulation
- Author
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Stefka D. Spassieva, Wendy B. Macklin, Susan L. Ackerman, H. Elizabeth Shick, Thomas J. Jucius, Lina M. Obeid, Lihong Zhao, Leonard D. Shultz, and Yusuf A. Hannun
- Subjects
Cancer Research ,Purkinje cell ,Biochemistry ,Mice ,Purkinje Cells ,0302 clinical medicine ,Neurobiology of Disease and Regeneration ,Chlorocebus aethiops ,Sphingosine N-Acyltransferase ,Sphingosine N-acyltransferase ,Homeostasis ,Genetics (clinical) ,0303 health sciences ,Mice, Inbred BALB C ,Neurodegeneration ,Ceramide synthase 1 ,Cell Differentiation ,Lipids ,3. Good health ,Cell biology ,medicine.anatomical_structure ,COS Cells ,lipids (amino acids, peptides, and proteins) ,Research Article ,Positional cloning ,lcsh:QH426-470 ,Cerebellar Purkinje cell ,Biology ,Ceramides ,Lipofuscin ,03 medical and health sciences ,medicine ,Genetics ,Animals ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,Sphingolipids ,Base Sequence ,Membrane Proteins ,medicine.disease ,Sphingolipid ,lcsh:Genetics ,Mutation ,Animal Genetics ,030217 neurology & neurosurgery ,Neuroscience - Abstract
Sphingolipids, lipids with a common sphingoid base (also termed long chain base) backbone, play essential cellular structural and signaling functions. Alterations of sphingolipid levels have been implicated in many diseases, including neurodegenerative disorders. However, it remains largely unclear whether sphingolipid changes in these diseases are pathological events or homeostatic responses. Furthermore, how changes in sphingolipid homeostasis shape the progression of aging and neurodegeneration remains to be clarified. We identified two mouse strains, flincher (fln) and toppler (to), with spontaneous recessive mutations that cause cerebellar ataxia and Purkinje cell degeneration. Positional cloning demonstrated that these mutations reside in the Lass1 gene. Lass1 encodes (dihydro)ceramide synthase 1 (CerS1), which is highly expressed in neurons. Both fln and to mutations caused complete loss of CerS1 catalytic activity, which resulted in a reduction in sphingolipid biosynthesis in the brain and dramatic changes in steady-state levels of sphingolipids and sphingoid bases. In addition to Purkinje cell death, deficiency of CerS1 function also induced accumulation of lipofuscin with ubiquitylated proteins in many brain regions. Our results demonstrate clearly that ceramide biosynthesis deficiency can cause neurodegeneration and suggest a novel mechanism of lipofuscin formation, a common phenomenon that occurs during normal aging and in some neurodegenerative diseases., Author Summary Lipids play many essential cellular roles as structural components of biological membranes or signaling molecules. Alterations of lipids have been observed in the brains of patients with neurodegenerative diseases. However, whether these changes can cause neurodegeneration or otherwise influence the pathology of these diseases is unclear. We identified mouse mutations in a gene encoding a neuronally expressed enzyme that generates ceramide, the basic structural component of many lipids known as sphingolipids. These mutations result in progressive ataxia and loss of cerebellar Purkinje cells. In addition, many neurons in these mutant mice harbor lipofuscin, a storage material containing both membranes and proteins, that is present in aging brains and in brains of patients with neurodegenerative disorders, suggesting that both membrane and protein homeostasis are impaired in mutant neurons. This study directly demonstrates that disruption of sphingolipid biosynthesis can lead to selective neuron death and the abnormal accumulation of lipofuscin, and it underscores the need for further study of the roles of lipids in neurodegenerative disorders.
- Published
- 2011
43. An assessment of mechanisms underlying peripheral axonal degeneration caused by aminoacyl-tRNA synthetase mutations
- Author
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Kathy E. Miers, Anthony Antonellis, Kevin L. Seburn, Heather M. McLaughlin, Erica L. Kleinbrink, Susan L. Ackerman, Morgane Stum, and Robert W. Burgess
- Subjects
Mutant ,Neuromuscular Junction ,Biology ,medicine.disease_cause ,Peripheral axonal degeneration ,Article ,Amino Acyl-tRNA Synthetases ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,Mice ,Purkinje Cells ,Charcot-Marie-Tooth Disease ,medicine ,Animals ,Molecular Biology ,Genetics ,Mutation ,Microscopy, Confocal ,Aminoacyl tRNA synthetase ,Wild type ,Peripheral Nervous System Diseases ,Translation (biology) ,Cell Biology ,Immunohistochemistry ,Axons ,Mice, Mutant Strains ,Complementation ,Mice, Inbred C57BL ,Disease Models, Animal ,Phenotype ,chemistry ,Protein Biosynthesis ,Transfer RNA ,Nerve Degeneration ,Femoral Nerve - Abstract
Mutations in glycyl-, tyrosyl-, and alanyl-tRNA synthetases (GARS, YARS and AARS respectively) cause autosomal dominant Charcot–Marie–Tooth disease, and mutations in Gars cause a similar peripheral neuropathy in mice. Aminoacyl-tRNA synthetases (ARSs) charge amino acids onto their cognate tRNAs during translation; however, the pathological mechanism(s) of ARS mutations remains unclear. To address this, we tested possible mechanisms using mouse models. First, amino acid mischarging was discounted by examining the recessive “sticky” mutation in alanyl-tRNA synthetase (Aarssti), which causes cerebellar neurodegeneration through a failure to efficiently correct mischarging of tRNAAla. Aarssti/sti mice do not have peripheral neuropathy, and they share no phenotypic features with the Gars mutant mice. Next, we determined that the Wallerian Degeneration Slow (Wlds) mutation did not alter the Gars phenotype. Therefore, no evidence for misfolding of GARS itself or other proteins was found. Similarly, there were no indications of general insufficiencies in protein synthesis caused by Gars mutations based on yeast complementation assays. Mutant GARS localized differently than wild type GARS in transfected cells, but a similar distribution was not observed in motor neurons derived from wild type mouse ES cells, and there was no evidence for abnormal GARS distribution in mouse tissue. Both GARS and YARS proteins were present in sciatic axons and Schwann cells from Gars mutant and control mice, consistent with a direct role for tRNA synthetases in peripheral nerves. Unless defects in translation are in some way restricted to peripheral axons, as suggested by the axonal localization of GARS and YARS, we conclude that mutations in tRNA synthetases are not causing peripheral neuropathy through amino acid mischarging or through a defect in their known function in translation.
- Published
- 2010
44. LOSS OF APOPTOSIS INDUCING FACTOR RESULTS IN CELL TYPE-PECIFIC NEUROGENESIS DEFECTS
- Author
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Ryuta Ishimura, Susan L. Ackerman, and Gail R. Martin
- Subjects
Cerebellum ,Time Factors ,Purkinje cell ,Embryonic Development ,Apoptosis ,Biology ,Article ,S Phase ,Mice ,Purkinje Cells ,Mesencephalon ,medicine ,Animals ,Neurons ,General Neuroscience ,Stem Cells ,Neurogenesis ,Neurodegeneration ,Cell Cycle ,G1 Phase ,Apoptosis Inducing Factor ,Nestin ,Cell cycle ,Granule cell ,medicine.disease ,Mice, Mutant Strains ,Cell biology ,medicine.anatomical_structure ,nervous system ,Apoptosis-inducing factor ,Neuroscience ,Gene Deletion - Abstract
Mitochondrial dysfunction is commonly associated with neurodegeneration in the aging brain. In addition, the importance of mitochondrial function during brain development is illustrated by the neurological deficits observed in infants with mitochondrial complex deficiencies. However, the extent to which abnormalities in mitochondrial function might impact neurogenesis during brain development is not well understood. Previously, we demonstrated that adult harlequin (Hq) mutant mice, which have an 80% reduction in the mitochondrial protein apoptosis-inducing factor (AIF), exhibited signs of oxidative stress and progressive loss of adult cerebellar and retinal neurons. To assess whether in addition to its role in postmitotic neuron survivalAifis also necessary for cerebellar development, we analyzed embryos in whichAifwas deleted in the prospective midbrain and cerebellum at a very early stage of development using anEn1(engrailed 1) promoter-drivencrerecombinase gene. These mutant mice, which died at birth, had midbrain defects and dramatic deficits in cerebellar Purkinje and granule cell precursors. Additional analysis revealed thatAif-null Purkinje cell precursors prematurely entered S-phase, but most failed to undergo mitosis and ultimately died via apoptosis. In contrast, proliferation of mutant granule cell precursors was blocked before S-phase. Mice in whichAifwas deleted later in embryogenesis using a nestin promoter-drivencregene survive for several days after birth, and postnatal granule cell precursors in these mice also failed to enter S-phase. Our results indicate that the loss ofAifresults in cell cycle abnormalities in a neuron-specific manner during cerebellar development.
- Published
- 2008
45. The RHOX5 homeodomain protein mediates transcriptional repression of the netrin-1 receptor gene Unc5c
- Author
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Miles F. Wilkinson, Zhiying Hu, James A. MacLean, Susan L. Ackerman, and Sreenath Shanker
- Subjects
Male ,Transcription, Genetic ,Molecular Sequence Data ,Receptors, Cell Surface ,Biology ,UNC5C ,Biochemistry ,Cell Line ,Gene cluster ,medicine ,Humans ,Molecular Biology ,Psychological repression ,Gene ,Regulation of gene expression ,Homeodomain Proteins ,Base Sequence ,Cell Biology ,Transfection ,Molecular biology ,medicine.anatomical_structure ,Gene Expression Regulation ,Homeobox ,Netrin Receptors ,Germ cell ,Transcription Factors - Abstract
The X-linked mouse Rhox gene cluster contains more than 30 homeobox genes that are candidates to regulate multiple steps in male and female gametogenesis. The founding member of the Rhox gene cluster, Rhox5, is an androgen-dependent gene expressed in Sertoli cells that promotes the survival and differentiation of the adjacent male germ cells. Here, we report the first identification and characterization of a Rhox5-regulated gene. This gene, Unc5c, encodes a pro-apoptotic receptor with tumor suppressor activity that we found is negatively regulated by Rhox5 in the testis in vivo. Transfection analyses in cell lines of different origin indicated that Rhox5-dependent down-regulation of Unc5c requires another Sertoli cell-specific cofactor. Examination of other mouse Rhox family members revealed that mouse RHOX2 and RHOX3 also have the ability to down-regulate Unc5c expression. The human RHOX protein PEPP2 (RHOXF2) also had this ability, indicating that Unc5c repression is a conserved RHOX-dependent response. Deletion analysis identified a Rhox5-responsive element in the Unc5c 5′-untranslated region. Although 5′-untranslated regions typically house post-transcriptional elements, several lines of evidence indicated that Rhox5 down-regulates Unc5c at the transcriptional level. The repression of Unc5c expression by Rhox5 may, in part, mediate the pro-survival function of Rhox5 in the testis, as we found that Unc5c mutant mice have decreased germ cell apoptosis in the testis. Along with our other data, these findings led us to propose a model in which Rhox5 is a negative regulator upstream of Unc5c in a Sertoli-cell pathway that promotes germ-cell survival.
- Published
- 2007
46. Motor axon guidance of the mammalian trochlear and phrenic nerves: dependence on the netrin receptor Unc5c and modifier loci
- Author
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Robert W. Burgess, Susan L. Ackerman, and Thomas J. Jucius
- Subjects
Cell signaling ,animal structures ,Quantitative Trait Loci ,Receptors, Cell Surface ,Trochlear Nerve ,Receptors, Nerve Growth Factor ,Biology ,UNC5C ,Mice ,Netrin ,medicine ,Animals ,Axon ,Phrenic nerve ,Motor Neurons ,General Neuroscience ,Trochlear nerve ,fungi ,Articles ,Commissure ,Axons ,Mice, Inbred C57BL ,Phrenic Nerve ,medicine.anatomical_structure ,Phenotype ,nervous system ,Axon guidance ,Netrin Receptors ,Neuroscience - Abstract
Netrin signaling is important to guide migrating neurons and axons in many systems. Experiments with vertebrate CNS explants suggested netrin is bifunctional, attracting some axons and repelling others. Netrin1-expressing cells attracted spinal commissural axons and repelled trochlear cranial nerve axons in these experiments. Subsequent genetic studies demonstrated that multiple axon types, including those of the spinal commissural neurons, are attracted to netrinin vivo; however, anin vivorole for netrin signaling in trochlear nerve repulsion has not been observed. Here, we demonstrate that mice with a null mutation in the netrin receptorUnc5con the inbred C57BL/6J (B6) genetic background have ventral/ipsilateral trochlear nerve misprojections. These misprojections are attenuated on a hybrid B6 × SJL background. In addition, B6.Unc5c−/−mice die as neonates of apparent respiratory distress and have incomplete phrenic nerve innervation of the diaphragm muscle. Neither the trochlear nerve misprojections nor the phrenic nerve phenotype was observed in B6 embryos lacking the netrin receptors DCC or Neogenin1, or the ligand netrin1, indicating these signaling molecules are dispensable for guidance of these axons. Like the trochlear nerve, the phrenic nerve phenotype is modified in a B6 × SJL hybrid background. To identify these modifier loci, we performed genome scans of the hybridUnc5c−/−mice and found a major SJL-derived suppressor locus on Chromosome 17. Our results provide the first evidence that genes involved in netrin signaling are necessary for proper mammalian spinal motor axon development and trochlear axon guidance. In addition, they demonstrate the importance of modifier genes in vertebrate axonal guidance.
- Published
- 2006
47. EUK-8, a superoxide dismutase and catalase mimetic, reduces cardiac oxidative stress and ameliorates pressure overload-induced heart failure in the harlequin mouse mutant
- Author
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Harry J.G.M. Crijns, Leon J. De Windt, Pieter A. Doevendans, Roel van der Nagel, Susan L. Ackerman, Wim Sluiter, Harold V.M. van Rijen, Ralph J. van Oort, Vanessa P. M. van Empel, Markus A. Engelen, Anne Bertrand, Cardiologie, Algemene Heelkunde, RS: CARIM School for Cardiovascular Diseases, RS: NUTRIM School of Nutrition and Translational Research in Metabolism, Other departments, and Biochemistry
- Subjects
medicine.medical_specialty ,Apoptosis ,Blood Pressure ,Mitochondrion ,medicine.disease_cause ,Antioxidants ,Superoxide dismutase ,Mice ,Necrosis ,Internal medicine ,Organometallic Compounds ,Medicine ,Animals ,Ventricular remodeling ,chemistry.chemical_classification ,Pressure overload ,Heart Failure ,Reactive oxygen species ,biology ,business.industry ,Myocardium ,Apoptosis Inducing Factor ,Free radical scavenger ,medicine.disease ,Ethylenediamines ,Fibrosis ,Survival Analysis ,Biomechanical Phenomena ,Mitochondria ,Oxidative Stress ,Endocrinology ,chemistry ,Heart failure ,Mutation ,biology.protein ,business ,Cardiology and Cardiovascular Medicine ,Reactive Oxygen Species ,Oxidative stress - Abstract
OBJECTIVES: The purpose of this study was to identify apoptosis-inducing factor (AIF) as a cardiac mitochondrial antioxidant and assess the efficacy of EUK-8, a salen-manganese catalytic free radical scavenger, to protect the AIF-deficient myocardium against pressure overload. BACKGROUND: Oxidative stress has been postulated to provoke cell death and pathologic remodeling in heart failure. We recently characterized the apoptosis-inducing factor-deficient harlequin (Hq) mouse mutant to display excessive pressure overload-induced oxidative stress, cell death, accelerated progression to heart failure, and a reduced capacity of subsarcolemmal mitochondria to scavenge free radicals, suggesting a role for AIF as a novel mitochondrial antioxidant. METHODS: Oxidative stress-sensitized Hq mutant mice and their wild-type (WT) counterparts were given low-dose EUK-8 (25 mg/kg/day), an antioxidant with superoxide dismutase, catalase, and oxyradical scavenging properties, or vehicle for 4 weeks, and subjected to pressure overload (transverse aortic constriction) for 4 weeks. Myocardial geometry and function was serially assessed by echocardiography. RESULTS: EUK-8 ameliorated survival in Hq and WT mice subjected to pressure overload. EUK-8 also improved left ventricular end-systolic dimensions and fractional shortening, prevented myocardial oxidant stress, attenuated necrotic and apoptotic cell death, and attenuated cardiac hypertrophy and fibrosis in both mutant and WT mice. CONCLUSIONS: The protection against pressure overload-induced heart failure in Hq mice by EUK-8 substantiates the notion that AIF functions as an important mitochondrial antioxidant in the heart. Furthermore, because antioxidant treatment protected both the oxidative stress-prone Hq mouse model and WT mice against pressure overload-induced maladaptive left ventricular remodeling and cardiac decompensation, it may be useful as a novel therapeutic tool in the treatment of human heart failure
- Published
- 2005
48. Downregulation of apoptosis-inducing factor in harlequin mutant mice sensitizes the myocardium to oxidative stress-related cell death and pressure overload-induced decompensation
- Author
-
Pieter A. Doevendans, Elly A. de Wit, Wim Sluiter, Harry J.G.M. Crijns, Vanessa P. M. van Empel, Roel van der Nagel, Anne Bertrand, Leon J. De Windt, Susan L. Ackerman, and Sawa Kostin
- Subjects
Male ,Programmed cell death ,Physiology ,Mitochondrial intermembrane space ,Down-Regulation ,Apoptosis ,Myocardial Reperfusion Injury ,Biology ,medicine.disease_cause ,Mice ,Downregulation and upregulation ,medicine ,Animals ,Decompensation ,cardiovascular diseases ,RNA, Small Interfering ,Cells, Cultured ,Pressure overload ,Heart Failure ,Flavoproteins ,Ventricular Remodeling ,Myocardium ,Apoptosis Inducing Factor ,Membrane Proteins ,Hydrogen Peroxide ,Fibrosis ,Mice, Mutant Strains ,Cell biology ,Biomechanical Phenomena ,Oxidative Stress ,Biochemistry ,Apoptosis-inducing factor ,Female ,Cardiology and Cardiovascular Medicine ,Oxidative stress - Abstract
Apoptosis-inducing factor (AIF), or programmed cell death 8 (Pdcd8), is a highly conserved, ubiquitous flavoprotein localized in the mitochondrial intermembrane space. In vivo, AIF provides protection against neuronal apoptosis induced by oxidative stress. Conversely, in vitro, AIF has been demonstrated to have a proapoptotic role when, on induction of the mitochondrial death pathway, AIF translocates to the nucleus where it facilitates chromatin condensation and large scale DNA fragmentation. To determine the role of AIF in myocardial apoptotic processes, we examined cardiomyocytes from an AIF-deficient mouse mutant, Harlequin ( Hq ). Hq mutant cardiomyocytes demonstrated increased sensitivity to H 2 O 2 -induced cell death. Further, Hq hearts subjected to ischemia/reperfusion revealed more cardiac damage and, unlike wild-type mice, the amount of damage increased with the age of the animal. Aortic banding caused enhanced hypertrophy, increased cardiomyocyte apoptotic and necrotic cell death, and accelerated progression toward maladaptive left ventricular remodeling in Hq mutant mice compared with wild-type counterparts. These findings correlated with a reduced capacity of subsarcolemmal mitochondria from Hq mutant hearts to scavenge free radicals. Together, these data demonstrate a critical role for AIF as a cardiac antioxidant in the protection against oxidative stress–induced cell death and development of heart failure induced by pressure overload.
- Published
- 2005
49. Genomewide two-generation screens for recessive mutations by ES cell mutagenesis
- Author
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Susan L. Ackerman, John C. Schimenti, and Robert J. Munroe
- Subjects
Ethyl methanesulfonate ,Mutagenesis (molecular biology technique) ,Genes, Recessive ,Biology ,medicine.disease_cause ,Genome ,Germline ,chemistry.chemical_compound ,Mice ,Genetics ,medicine ,Animals ,Genetic Testing ,Crosses, Genetic ,Mutation ,Mice, Inbred C3H ,Chimera ,Stem Cells ,fungi ,Homozygote ,food and beverages ,Phenotype ,Human genetics ,Mice, Inbred C57BL ,chemistry ,Mutagenesis ,Ethyl Methanesulfonate ,Genetic screen ,Mutagens - Abstract
Forward genetic mutation screens in mice are typically begun by mutagenizing the germline of male mice with N-ethyl-N-nitrosourea (ENU). Genomewide recessive mutations transmitted by these males can be rendered homozygous after three generations of breeding, at which time phenotype screens can be performed. An alternative strategy for randomly mutagenizing the mouse genome is by chemical treatment of embryonic stem (ES) cells. Here we demonstrate the feasibility of performing genome-wide mutation screens with only two generations of breeding. Mice potentially homozygous for mutations were obtained by crossing chimeras derived from ethylmethane sulfonate (EMS)-mutagenized ES cells to their daughters, or by intercrossing offspring of chimeras. This strategy was possible because chimeras transmit variations of the same mutagenized diploid genome, whereas ENU-treated males transmit numerous unrelated genomes. This also results in a doubling of screenable mutations in a pedigree compared to germline ENU mutagenesis. Coupled with the flexibility to treat ES cells with a variety of potent mutagens and the ease of producing distributable, quality-controlled, long-term supplies of cells in a single experiment, this strategy offers a number of advantages for conducting forward genetic screens in mice.
- Published
- 2004
50. The Netrin 1 Receptors Unc5h3 and Dcc Are Necessary at Multiple Choice Points for the Guidance of Corticospinal Tract Axons
- Author
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Stefan Przyborski, Jacqueline H. Finger, Susan L. Ackerman, Rod Bronson, Belinda S. Harris, and Kenneth O. Johnson
- Subjects
Gene Dosage ,Pyramidal Tracts ,Mice, Inbred Strains ,Receptors, Cell Surface ,Nervous System Malformations ,Mice ,Mice, Neurologic Mutants ,Netrin ,medicine ,Animals ,Nerve Growth Factors ,ARTICLE ,Caenorhabditis elegans Proteins ,Caenorhabditis elegans ,In Situ Hybridization ,Pyramidal tracts ,biology ,General Neuroscience ,Tumor Suppressor Proteins ,fungi ,Cell migration ,Netrin-1 ,Granule cell ,biology.organism_classification ,DCC Receptor ,Immunohistochemistry ,Axons ,Posterior Horn Cells ,Rhombencephalon ,medicine.anatomical_structure ,Nerve growth factor ,nervous system ,Corticospinal tract ,Calcium-Calmodulin-Dependent Protein Kinases ,Axon guidance ,Calcium-Calmodulin-Dependent Protein Kinase Type 2 ,Netrin Receptors ,Neuroscience ,Cell Adhesion Molecules - Abstract
Migrating axons require the correct presentation of guidance molecules, often at multiple choice points, to find their target. Netrin 1, a bifunctional cue involved in both attracting and repelling axons, is involved in many cell migration and axon pathfinding processes in the CNS. The netrin 1 receptor DCC and its Caenorhabditis elegans homolog UNC-40 have been implicated in directing the guidance of axons toward netrin sources, whereas the C. elegans UNC-6 receptor, UNC-5 is necessary for migrations away from UNC-6. However, a role of vertebrate UNC-5 homologs in axonal migration has not been demonstrated. We demonstrate that the Unc5h3 gene product, shown previously to regulate cerebellar granule cell migrations, also controls the guidance of the corticospinal tract, the major tract responsible for coordination of limb movements. Furthermore, we show that corticospinal tract fibers respond differently to loss of UNC5H3. In addition, we observe corticospinal tract defects in mice homozygous for a spontaneous mutation that truncates the Dcc transcript. Postnatal day 0 netrin 1 mutant mice also demonstrate corticospinal tract abnormalities. Last, interactions between the Dcc and Unc5h3 mutations were observed in gene dosage experiments. This is the first evidence of an involvement in axon guidance for any member of the vertebrate unc-5 family and confirms that both the cellular and axonal guidance functions of C. elegans unc-5 have been conserved in vertebrates.
- Published
- 2002
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