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Mitochondrial myopathies belong to a larger group of systemic diseases caused by morphological or biochemical abnormalities of mitochondria. Mitochondrial disorders can be caused by mutations in either the mitochondrial or nuclear genome. Only 5 % of all mitochondrial disorders are autosomal dominant. We analyzed DNA from members of the previously reported Puerto Rican kindred with an autosomal dominant mitochondrial myopathy (Heimann-Patterson et al. 1997). Linkage analysis suggested a putative locus on the pericentric region of the long arm of chromosome 22 (22q11). Using the tools of integrative genomics, we established chromosome 22 open reading frame 16 (C22orf16) (later designated as CHCHD10) as the only high-scoring mitochondrial candidate gene in our minimal candidate region. Sequence analysis revealed a double-missense mutation (R15S and G58R) in cis in CHCHD10 which encodes a coiled coil-helix-coiled coil-helix protein of unknown function. These two mutations completely co-segregated with the disease phenotype and were absent in 1,481 Caucasian and 80 Hispanic (including 32 Puerto Rican) controls. Expression profiling showed that CHCHD10 is enriched in skeletal muscle. Mitochondrial localization of the CHCHD10 protein was confirmed using immunofluorescence in cells expressing either wild-type or mutant CHCHD10. We found that the expression of the G58R, but not the R15S, mutation induced mitochondrial fragmentation. Our findings identify a novel gene causing mitochondrial myopathy, thereby expanding the spectrum of mitochondrial myopathies caused by nuclear genes. Our findings also suggest a role for CHCHD10 in the morphologic remodeling of the mitochondria.

Parkinson’s disease is the second most common neurodegenerative disorder without effective treatment. It is generally sporadic with unknown etiology. However, genetic studies of rare familial forms have led to the identification of mutations in several genes, which are linked to typical Parkinson’s disease or parkinsonian disorders. The pathogenesis of Parkinson’s disease remain largely elusive. Here, we report a novel genetic locus for an autosomal dominant, clinically typical and Lewy body confirmed Parkinson’s disease on the short arm of chromosome 20 (20pter-p12) and TMEM230 as the disease-causing gene. We show that TMEM230 encodes a transmembrane protein of secretory/recycling vesicles, including synaptic vesicles in neurons. The disease-linked TMEM230 mutants impair synaptic vesicle trafficking. Our data provide the first genetic evidence that a mutant transmembrane protein of synaptic vesicles in neurons is etiologically linked to Parkinson’s disease, with novel implications in understanding the pathogenic mechanism of Parkinson’s disease and for developing rational therapies.

Recent findings highlight a pathologic and functional convergence in amyotrophic lateral sclerosis (ALS) and amyotrophic lateral sclerosis with frontotemporal dementia (ALS-FTD) at the level of protein recycling and disposal. Genes linked to rare cases of familial ALS and ALS-FTD, like UBQLN2, OPTN, SQSTM1/p62, and VCP, may converge onto a unifying pathogenic pathway and thereby provide novel therapeutic targets common to a spectrum of etiologically diverse forms of ALS and ALS-FTD. Interactions between these genes need to be further explored to understand their common molecular pathways. Future efforts should be directed toward generation and characterization of in vivo models to dissect the pathogenic mechanisms of ALS and ALS-FTD and the role of protein degradation pathways, both centrally, at the cell body, and peripherally, at the level of the synapse. Such efforts will rapidly accelerate the discovery of new drugs that regulate accumulation of pathogenic proteins and their downstream consequences in ALS and ALS-FTD and, possibly, other neurodegenerative diseases as well. Muscle Nerve, 2012

Mutations in TRPV4 have been linked to three distinct axonal neuropathies. However, the pathogenic mechanism underlying these disorders remains unclear. Both gain and loss of calcium channel activity of the mutant TRPV4 have been suggested. Here, we show that the three previously reported TRPV4 mutant channels have a physiological localization and display an increased calcium channel activity, leading to increased cytotoxicity in three different cell types. Patch clamp experiments showed that cells expressing mutant TRPV4 have much larger whole-cell currents than those expressing the wild-type TRPV4 channel. Single channel recordings showed that the mutant channels have higher open probability, due to a modification of gating, and no change in single-channel conductance. These data support the hypothesis that a “gain of function” mechanism, possibly leading to increased intracellular calcium influx, underlies the pathogenesis of the TRPV4-linked axonal neuropathies, and may have immediate implications for designing rational therapies.

Scapuloperoneal spinal muscular atrophy (SPSMA) and hereditary motor and sensory neuropathy type IIC (HMSN IIC, also known as HMSN2C or Charcot-Marie-Tooth disease type 2C (CMT2C)) are phenotypically heterogeneous disorders involving topographically distinct nerves and muscles. We originally described a large New England family of French-Canadian origin with SPSMA and an American family of English and Scottish descent with CMT2C1,2. We mapped SPSMA and CMT2C risk loci to 12q24.1–q24.31 with an overlapping region between the two diseases3,4. Further analysis reduced the CMT2C risk locus to a 4-Mb region5. Here we report that SPSMA and CMT2C are allelic disorders caused by mutations in the gene encoding the transient receptor potential cation channel, subfamily V, member 4 (TRPV4). Functional analysis revealed that increased calcium channel activity is a distinct property of both SPSMA- and CMT2C-causing mutant proteins. Our findings link mutations in TRPV4 to altered calcium homeostasis and peripheral neuropathies, implying a pathogenic mechanism and possible options for therapy for these disorders.

Mutations in the gene encoding ubiquilin2 (UBQLN2) cause amyotrophic lateral sclerosis (ALS), frontotemporal type of dementia, or both. However, the molecular mechanisms are unknown. Here, we show that ALS/dementia-linked UBQLN2(P497H) transgenic mice develop neuronal pathology with ubiquilin2/ubiquitin/p62-positive inclusions in the brain, especially in the hippocampus, recapitulating several key pathological features of dementia observed in human patients with UBQLN2 mutations. A major feature of the ubiquilin2-related pathology in these mice, and reminiscent of human disease, is a dendritic spinopathy with protein aggregation in the dendritic spines and an associated decrease in dendritic spine density and synaptic dysfunction. Finally, we show that the protein inclusions in the dendritic spines are composed of several components of the proteasome machinery, including Ub(G76V)-GFP, a representative ubiquitinated protein substrate that is accumulated in the transgenic mice. Our data, therefore, directly link impaired protein degradation to inclusion formation that is associated with synaptic dysfunction and cognitive deficits. These data imply a convergent molecular pathway involving synaptic protein recycling that may also be involved in other neurodegenerative disorders, with implications for development of widely applicable rational therapeutics.

Rasmussen encephalitis (RE) sera were screened for antibodies to human α7 nicotinic acetylcholine receptors (nAChRs) using electrophysiology, calcium imaging, and ligand binding assays. Sera from two of nine patients with RE blocked ACh-induced currents through α7 nAChRs and the ACh-induced rise in intracellular free calcium ([Ca2+]i) and inhibited 125I-α-bungarotoxin binding in cells expressing α7 nAChRs. Thus, the α7 nAChR is a potential target for pathogenic antibodies in patients with RE. Copyright © 2005 by AAN Enterprises, Inc.

The SQSTM1 gene encodes p62, a major pathologic protein involved in neurodegeneration.To examine whether SQSTM1 mutations contribute to familial and sporadic amyotrophic lateral sclerosis (ALS).Case-control study.Academic research. Patients A cohort of 546 patients with familial (n = 340) or sporadic (n = 206) ALS seen at a major academic referral center were screened for SQSTM1 mutations.We evaluated the distribution of missense, deletion, silent, and intronic variants in SQSTM1 among our cohort of patients with ALS. In silico analysis of variants was performed to predict alterations in p62 structure and function.We identified 10 novel SQSTM1 mutations (9 heterozygous missense and 1 deletion) in 15 patients (6 with familial ALS and 9 with sporadic ALS). Predictive in silico analysis classified 8 of 9 missense variants as pathogenic.Using candidate gene identification based on prior biological knowledge and the functional prediction of rare variants, we identified several novel SQSTM1 mutations in patients with ALS. Our findings provide evidence of a direct genetic role for p62 in ALS pathogenesis and suggest that regulation of protein degradation pathways may represent an important therapeutic target in motor neuron degeneration.

Mutations in optineurin have recently been linked to amyotrophic lateral sclerosis (ALS).To determine whether optineurin-positive skeinlike inclusions are a common pathologic feature in ALS, including SOD1 -linked ALS.Clinical case series.Academic referral center.We analyzed spinal cord sections from 46 clinically and pathologically diagnosed ALS cases and ALS transgenic mouse models overexpressing ALS-linked SOD1 mutations G93A or L126Z.We observed optineurin-immunoreactive skeinlike inclusions in all the sporadic ALS and familial ALS cases without SOD1 mutation, but not in cases with SOD1 mutations or in transgenic mice overexpressing the ALS-linked SOD1 mutations G93A or L126Z.The data from this study provide evidence that optineurin is involved in the pathogenesis of sporadic ALS and non- SOD1 familial ALS, thus supporting the hypothesis that these forms of ALS share a pathway that is distinct from that of SOD1-linked ALS.

Over the last couple of decades, there has been a growing body of clinical, genetic, and histopathological evidence that similar pathological processes underlie amyotrophic lateral sclerosis (ALS) and some types of frontotemporal lobe dementia (FTD). Even though there is great diversity in the genetic causes of these disorders, there is a high degree of overlap in their histopathology. Genes linked to rare cases of familial ALS and/or FTD, like FUS, TARDBP, OPTN, and UBQLN2 may converge onto a unifying pathogenic pathway and thereby provide novel therapeutic targets common to a spectrum of etiologically diverse forms of ALS and ALS–FTD. Additionally, there are major loci for ALS–FTD on chromosomes 9p and 15q. Identification of causative genetic alterations at those loci will be an important step in understanding the pathogenesis of juvenile- and adult-onset ALS and ALS–FTD. Interactions between TDP-43, FUS, optineurin, and ubiquilin 2 need to be studied to understand their common molecular pathways. Future efforts should also be directed towards generation and characterization of in vivo models to dissect the pathogenic mechanisms of these diseases. Such efforts will rapidly accelerate the discovery of new drugs that regulate accumulation of pathogenic proteins and their downstream consequences.

Objective: To improve understanding of TRPV4-associated axonal Charcot-Marie-Tooth (CMT) neuropathy phenotypes and their debated pathologic mechanism. Methods: A total of 17 CMT2C phenotypic families with vocal cord and diaphragmatic involvement and 36 clinically undifferentiated CMT2 subjects underwent sequencing analysis of the coding region of TRPV4 . Functional studies of mutant proteins were performed using transiently transfected cells for TRPV4 subcellular localization, basal and stimulated Ca 2+ channel analysis, and cell viability assay with or without channel blockade. Results: Two TRPV4 mutations R232C and R316H from 17 CMT2C families were identified in the ankyrin repeat domains. The R316H is a novel de novo mutation found in a patient with CMT2C phenotype. The family with R232C mutation had individuals with and without vocal cord and diaphragm involvement. Both mutant TRPV4 proteins had normal subcellular localization in HEK293 and HeLa cells. Cells transfected with R232C and R316H displayed increased intracellular Ca 2+ levels and reversible cell death by the TRPV channel antagonist, ruthenium red. Conclusion: TRPV4 ankyrin domain alterations including a novel de novo mutation cause axonal CMT2. Individuals with the same mutation may have nondistinct CMT2 or have phenotypic CMT2C with vocal cord paresis. Reversible hypercalcemic gain-of-function of mutant TRPV4 instead of loss-of-function appears to be pathologically important. The reversibility of cell death by channel blockade provides an attractive area of investigation in consideration of treatable axonal degeneration.

Amyotrophic lateral sclerosis (ALS) is a paralytic and usually fatal disorder caused by motor-neuron degeneration in the brain and spinal cord. Most cases of ALS are sporadic but about 5-10% are familial. Mutations in superoxide dismutase 1 (SOD1), TAR DNA-binding protein (TARDBP, also known as TDP43) and fused in sarcoma (FUS, also known as translocated in liposarcoma (TLS)) account for approximately 30% of classic familial ALS. Mutations in several other genes have also been reported as rare causes of ALS or ALS-like syndromes. The causes of the remaining cases of familial ALS and of the vast majority of sporadic ALS are unknown. Despite extensive studies of previously identified ALS-causing genes, the pathogenic mechanism underlying motor-neuron degeneration in ALS remains largely obscure. Dementia, usually of the frontotemporal lobar type, may occur in some ALS cases. It is unclear whether ALS and dementia share common aetiology and pathogenesis in ALS/dementia. Here we show that mutations in UBQLN2, which encodes the ubiquitin-like protein ubiquilin 2, cause dominantly inherited, chromosome-X-linked ALS and ALS/dementia. We describe novel ubiquilin 2 pathology in the spinal cords of ALS cases and in the brains of ALS/dementia cases with or without UBQLN2 mutations. Ubiquilin 2 is a member of the ubiquilin family, which regulates the degradation of ubiquitinated proteins. Functional analysis showed that mutations in UBQLN2 lead to an impairment of protein degradation. Therefore, our findings link abnormalities in ubiquilin 2 to defects in the protein degradation pathway, abnormal protein aggregation and neurodegeneration, indicating a common pathogenic mechanism that can be exploited for therapeutic intervention.

Objective: Amyotrophic lateral sclerosis (ALS) is a progressive paralytic disorder caused by degeneration of motor neurons. Mutations in the FUS gene were identified in patients with familial ALS (FALS) and patients with sporadic ALS (SALS) from a variety of genetic backgrounds. This work further explores the spectrum of FUS mutations in patients with FALS and patients with FALS with features of frontotemporal dementia (FALS/FTD) or parkinsonism and dementia (FALS/PD/DE). Methods: All exons of the FUS gene were sequenced in 476 FALS index cases negative for mutations in SOD1 and TARDBP . A total of 561–726 controls were analyzed for genetic variants observed. Clinical data from patients with FUS mutations were compared to those of patients with known SOD1 and TARDBP mutations. Results: We identified 17 FUS mutations in 22 FALS families, 2 FALS/FTD families, and 1 FALS/PD/DE family from diverse genetic backgrounds; 11 mutations were novel. There were 4 frameshift, 1 nonsense, and 1 possible alternate splicing mutation. Patients with FUS mutations appeared to have earlier symptom onset, a higher rate of bulbar onset, and shorter duration of symptoms than those with SOD1 mutations. Conclusions: FUS gene mutations are not an uncommon cause in patients with FALS from diverse genetic backgrounds, and have a prevalence of 5.6% in non- SOD1 and non- TARDBP FALS, and ∼4.79% in all FALS. The pathogenicity of some of these novel mutations awaits further studies. Patients with FUS mutations manifest earlier symptom onset, a higher rate of bulbar onset, and shorter duration of symptoms.

We report a case of familial amyotrophic lateral sclerosis (FALS) with clinical signs of cerebellar and posterior column involvement. The patient's work-up showed a known mutation (E100K) in the gene for Cu/Zn superoxide dismutase 1 (SOD1). Our case illustrates that extramotor symptoms, such as prominent cerebellar signs, can be seen in patients with FALS.

Many progressive neurodegenerative diseases, including Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, and frontotemporal lobe dementia, are associated with the formation of insoluble intracellular proteinaceous inclusions. It is therefore imperative to understand the factors that regulate normal, as well as abnormal, protein recycling in neurons. Dysfunction of the ubiquitin-proteasome or autophagy pathways might contribute to the pathology of various neurodegenerative diseases. Induction of these pathways may offer a rational therapeutic strategy for a number of these diseases.

Objective: To report a novel causative gene for an autosomal dominant mitochondrial myopathy. Background Mitochondrial myopathies belong to a larger group of systemic diseases caused by morphological or biochemical abnormalities of mitochondria. Mitochondrial disorders can be caused by mutation either in the mitochondrial or in the nuclear genome. Design/Methods: Patients are part of previously reported Hispanic kindred with autosomal dominant mitochondrial myopathy (Heiman-Patterson et al 1997). Linkage analysis was established using fluorescent microsatellite markers and illumina genome wide SNP markers. Candidate gene was identified using MitoCarta (Vamsi K. Mootha, personal communication). Candidate gene was sequenced using Beckman Coulter CEQ 8000 DNA analysis system. The cDNA of wild type, single and double mutant gene were cloned in pCMV-Myc vector and co-transfected with pDsRed2-mito in HEK293 cells. The co-localization was monitored with confocal microscopy. Results: In this five generation Hispanic family we established linkage to chromosome 22q11. Using the tools of integrative gneomics, we established CHCHD10/ C22orf16 as the high scoring mitochondrial candidate gene in our minimal candidate region. Sequence analysis revealed a double heterozygote missense mutation in this gene. These two mutations segregated with disease phenotype and were absent in 500 Caucasians and Hispanic non affected controls. Both wild types, single and double mutant proteins co-localized with mitochondria. Conclusions: We identified a new nuclear encoded mitochondrial gene ( CHCHD10 ) as the cause of an autosomal dominant mitochondrial myopathy. CHCHD10 encodes a non characterized 142 aa protein with a target mitochondrial signaling peptide and a conserved CHCH domain. This CHCH domain is present in many intermembrane space proteins, such as the family of small Tim proteins. The exact function of this protein remains to be determined. Our findings expands the spectrum of mitochondrial myopathies caused by nuclear gene dysfunction. Disclosure: Dr. Ajroud-Driss has nothing to disclose. Dr. Fecto has nothing to disclose. Dr. Ajroud has nothing to disclose. Dr. Siddique has nothing to disclose.

Objective: To identify the genetic defect causing dominant X-linked ALS and ALS/dementia, and characterize the functional and pathological determinants. Background Most cases of ALS are sporadic but about 5-10% are familial. Mutations in SOD1, TDP43 and FUS account for approximately 30% of classic familial ALS. The causes of the remaining cases of familial ALS and of the vast majority of sporadic ALS are unknown. Despite extensive studies of previously identified ALS-causing genes, the pathogenic mechanism underlying motor-neuron degeneration in ALS remains largely obscure. Dementia, usually of the frontotemporal lobar type, may occur in some ALS cases. It is unclear whether ALS and dementia share common aetiology and pathogenesis in ALS/dementia. More than a decade ago, we had linked a large ALS family to the pericentric region of the X chromosome. Design/Methods: Detailed mapping was done with dense microsatellite markers and Illumina Sentrix HumanHap300 Genotyping BeadChip. Candidate genes were sequenced using Beckman Coulter CEQ 8000 DNA analysis system. Immunohistochemistry and light and confocal microscopy were performed according to standard protocols. Neuro2a and SHSY-5Y cells were transiently co-transfected with a ubiquitin-proteasome system (UPS) reporter plasmid (Ub-G76V-GFP) and pIRES2-DsRed2 dual expression vectors containing either wildtype or mutant UBQLN2 and analyzed using a MoFlo cell sorter and Summit software. Results: We show mutations of ubiquilin2, a ubiquitin-like protein, in five families with ALS and ALS/dementia. We also show that inclusions containing ubiquilin2 are a common pathological feature in a wide spectrum of ALS and ALS/dementia. Functional studies indicate an impairment of ubiquitin-mediated proteasomal degradation in cells expressing mutant ubiquilin2. Conclusions: These data provide evidence for an impairment of protein turnover in the pathogenesis of ALS and ALS/dementia. Further elucidation of these processes may be central to the understanding of pathogenic pathways. These pathways should provide novel molecular targets for the design of rational therapies for these disorders. Supported by: The National Institute of Neurological Disorders and Stroke (NS050641), the Les Turner ALS Foundation, the Vena E. Schaff ALS Research Fund, the Harold Post Research Professorship, the Herbert and Florence C. Wenske Foundation, the David C. Asselin MD Memorial Fund, the Help America Foundation and the Les Turner ALS Foundation/Herbert C. Wenske Foundation Professorship. F.F. has support from NIH (T32 AG20506). K.A. is a postdoctoral fellow of the Blazeman Foundation for ALS. G.H.G. received travel funds from MND Scotland. Disclosure: Dr. Fecto has nothing to disclose. Dr. Deng has nothing to disclose. Dr. Chen has nothing to disclose. Dr. Hong has nothing to disclose. Dr. Boycott has nothing to disclose. Dr. Gorrie has nothing to disclose. Dr. Siddique has nothing to disclose. Dr. Yang has nothing to disclose. Dr. Shi has nothing to disclose. Dr. Zhai has nothing to disclose. Dr. Jiang has nothing to disclose. Dr. Hirano has nothing to disclose. Dr. Rampersaud has nothing to disclose. Dr. Jansen has nothing to disclose. Dr. Donkervoort has nothing to disclose. Dr. Bigio has nothing to disclose. Dr. Brooks has received personal compensation for activities with Avanir Pharmaceuticals, Bayer Healthcare Pharmaceuticals, Biogen Idec, Genentech, Inc., and Teva Neuroscience. Dr. Brooks has received research support from Avanir Pharmaceuticals, Biogen Idec, NINDS, Novartis, and Teva Neuroscience. Dr. Ajroud has nothing to disclose. Dr. Sufit has nothing to disclose. Dr. Haines has nothing to disclose. Dr. Mugnaini has nothing to disclose. Dr. Pericak-Vance has nothing to disclose. Dr. Siddique has nothing to disclose.

Background The SQSTM1 gene encodes p62, a major pathologic protein involved in neurodegeneration. Objective To examine whether SQSTM1 mutations contribute to familial and sporadic amyotrophic lateral sclerosis (ALS). Design Case-control study. Setting Academic research. Patients A cohort of 546 patients with familial (n = 340) or sporadic (n = 206) ALS seen at a major academic referral center were screened for SQSTM1 mutations. Main Outcome Measures We evaluated the distribution of missense, deletion, silent, and intronic variants in SQSTM1 among our cohort of patients with ALS. In silico analysis of variants was performed to predict alterations in p62 structure and function. Results We identified 10 novel SQSTM1 mutations (9 heterozygous missense and 1 deletion) in 15 patients (6 with familial ALS and 9 with sporadic ALS). Predictive in silico analysis classified 8 of 9 missense variants as pathogenic. Conclusions Using candidate gene identification based on prior biological knowledge and the functional prediction of rare variants, we identified several novel SQSTM1 mutations in patients with ALS. Our findings provide evidence of a direct genetic role for p62 in ALS pathogenesis and suggest that regulation of protein degradation pathways may represent an important therapeutic target in motor neuron degeneration.

Background Mutations in optineurin have recently been linked to amyotrophic lateral sclerosis (ALS). Objective To determine whether optineurin-positive skeinlike inclusions are a common pathologic feature in ALS, including SOD1 -linked ALS. Design Clinical case series. Setting Academic referral center. Subjects We analyzed spinal cord sections from 46 clinically and pathologically diagnosed ALS cases and ALS transgenic mouse models overexpressing ALS-linked SOD1 mutations G93A or L126Z. Results We observed optineurin-immunoreactive skeinlike inclusions in all the sporadic ALS and familial ALS cases without SOD1 mutation, but not in cases with SOD1 mutations or in transgenic mice overexpressing the ALS-linked SOD1 mutations G93A or L126Z. Conclusion The data from this study provide evidence that optineurin is involved in the pathogenesis of sporadic ALS and non- SOD1 familial ALS, thus supporting the hypothesis that these forms of ALS share a pathway that is distinct from that of SOD1 -linked ALS.