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BACKGROUND: Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are rare oncogenic drivers prevalent in 0.3% of solid tumors. They are most common in salivary gland cancer (2.6%), thyroid cancer (1.6%), and soft-tissue sarcoma (1.5%). Currently, there are 2 US Food and Drug Administration-approved targeted therapies for NTRK gene fusions: larotrectinib, approved in 2018, and entrectinib, approved in 2019. To date, the real-world uptake of tyrosine receptor kinase inhibitor (TRKi) use for NTRK-positive solid tumors in academic cancer centers remains largely unknown. OBJECTIVE: To describe the demographics, clinical and genomic characteristics, and testing and treatment patterns of patients with NTRK-positive solid tumors treated at US academic cancer centers. METHODS: This was a retrospective chart review study conducted in academic cancer centers in the United States. All patients diagnosed with an NTRK fusion-positive (NTRK1, NTRK2, NTRK3) solid tumor (any stage) and who received cancer treatment at participating sites between January 1, 2012, and July 1, 2023, were included in this study. Patient demographics, clinical characteristics, genomic characteristics, NTRK testing data, and treatment patterns were collected from electronic medical records and analyzed using descriptive statistics as appropriate. RESULTS: In total, 6 centers contributed data for 55 patients with NTRK-positive tumors. The mean age was 49.3 (SD = 20.5) years, 51% patients were female, and the majority were White (78%). The median duration of time from cancer diagnosis to NTRK testing was 85 days (IQR = 44-978). At the time of NTRK testing, 64% of patients had stage IV disease, compared with 33% at cancer diagnosis. Prevalent cancer types in the overall cohort included head and neck (15%), thyroid (15%), brain (13%), lung (13%), and colorectal (11%). NTRK1 fusions were most common (45%), followed by NTRK3 (40%) and NTRK2 (15%). Across all lines of therapy, 51% of patients (n = 28) recei

The retina of the adult zebrafish express brain‐derived neurotrophic factor (BDNF) and its signaling receptor TrkB. This functional system is involved in the biology of the vertebrate retina and its expression is regulated by light. This study was designed to investigate the effects of cyclic (12 h light/12 h darkness) or continuous (24 h) exposure during 10 days to white light, white‐blue light, and blue light, as well as of darkness, on the expression of BDNF and TrkB in the retina. BDNF and TrkB were assessed in the retina of adult zebrafish using quantitative real‐time polymerase chain reaction and immunohistochemistry. Exposure to white, white‐blue, and blue light causes a decrease of BDNF mRNA and of BDNF immunostaining, independently of the pattern of light exposition. Conversely, in the same experimental conditions, the expression of TrkB mRNA was upregulated and TrkB immunostaining increased. Exposition to darkness diminished BDNF and TrkB mRNAs, and abolished the immunostaining for BDNF but not modified that for TrkB. These results demonstrate the regulation of BDNF and TrkB by light in the retina of adult zebrafish and might contribute to explain some aspects of the complex pathophysiology of light‐induced retinopathies., Depto. de Optometría y Visión, Fac. de Óptica y Optometría, TRUE, pub

Introduction: Osteoarthritis (OA) is a progressive disease of synovial joints and subchondral bone characterized by swelling, stiffness and pain. Brain-derived neurotrophic factor (BDNF) and artemin (ARTN) are neurotrophic factors that are important regulators of pain, and have recently been implicated in the pathogenesis of OA pain. This study aimed to explore roles for BDNF and ARTN in OA pain, by investigating whether the expression of BDNF and ARTN, and their receptors (TrkB and GFRa3), is altered in different tissues at different stages of OA, and whether blocking their signalling during late-stage OA can alleviate pain. Methods: The monoiodoacetate (MIA)-induced OA of the rat knee joint was used to explore roles for BDNF and ARTN signalling in OA pain. Pain behaviour was assessed using the dynamic weight-bearing apparatus to assay OA-induced changes in hindlimb weight bearing behaviour, at different stages of disease (early vs late). Histopathological alterations in the knee joint and surrounding bones were assayed using Haematoxylin and Eosin staining and scored using a modified OARSI scale. Changes in expression of BDNF/TrkB and ARTN/GFRa3 were explored using Western blot analysis of lysates from different tissues (joint, bone, and DRG), and at different timepoints of the disease (early vs late). The dynamic weight-bearing assay was used to determine if inhibiting BDNF signalling (with a peptide mimetic TrkB inhibitor) or ARTN signalling (with a sequestering antibody) could relieve pain at late-stage disease. Results: The results of this thesis highlight differential histopathological changes occurring in the early and late stages of OA, with joint involvement being prominent in early OA, and bone and cartilage involvement in late OA. BDNF expression was increased in the joint in early OA and in the bone in late OA. ARTN expression was also increased in the joint in both early and late OA and in the bone in late OA. Attempts to alleviate pain in MIA-injected

Demyelinating diseases, such as multiple sclerosis (MS), involve damage to the fatty, proteinaceous myelin sheaths surrounding nerve fibres and subsequent development of neurological symptoms related to the damaged area. Repair of the damaged myelin can completely or partially reverse the neurological deficits, however, over time with repetitive demyelinating events and incomplete remyelination this ultimately results in the degeneration of neurons and development of permanent disabilities. Currently, there is a lack of therapies effective in promoting myelin repair. A complete understanding of the factors that promote remyelination is critical for developing therapeutic strategies for myelin repair to prevent permanent neurological disability. Many studies have focused on the potential of oligodendrocytes (the myelin-generating cells in the central nervous system) to enhance the generation of myelin. However, neurons certainly have an intimate relationship with oligodendrocytes and are well-positioned to influence the process of myelination. Previously, neuronal expression of the tyrosine kinase receptor TrkB has been shown to promote myelination in early development and during ageing. However, whether neuronally expressed TrkB receptors also influences the extent of oligodendroglial and myelin damage post a demyelinating injury, and the subsequent process of remyelination has not been elucidated. In this thesis, I generated an inducible, neuron-specific TrkB receptor knockout mouse line to investigate the role of neuronal TrkB receptors in the extent of both demyelination and remyelination following the induction of a demyelinating insult with cuprizone administration. I found that following deletion of TrkB, these mice exhibit a normally myelinated nervous system, but do however develop a motor phenotype consistent with a decrease in precise motor control. Following administration with cuprizone, I revealed that neuronal expression of TrkB is important for the di

We have previously shown that recovery of visual responses to a deprived eye during the critical period in mouse primary visual cortex requires phosphorylation of the TrkB receptor for BDNF [M. Kaneko, J. L. Hanover, P. M. England, M. P. Stryker, Nat. Neurosci. 11, 497-504 (2008)]. We have now studied the temporal relationship between the production of mature BDNF and the recovery of visual responses under several different conditions. Visual cortical responses to an eye whose vision has been occluded for several days during the critical period and is then re-opened recover rapidly during binocular vision or much more slowly following reverse occlusion, when the previously intact fellow eye is occluded in a model of "patch therapy" for amblyopia. The time to recovery of visual responses differed by more than 18 h between these two procedures, but in each, the production of mature BDNF preceded the physiological recovery. These findings suggest that a spurt of BDNF production is permissive for the growth of connections serving the deprived eye to restore visual responses. Attenuation of recovery of deprived-eye responses by interference with TrkB receptor activation or reduction of BDNF production by interference with homeostatic synaptic scaling had effects consistent with this suggestion.

Brain-derived neurotrophic factor (BDNF) and its receptors tropomyosin kinase receptor B (TrkB) and the p75 neurotrophin receptor (p75) are the primary regulators of dendritic growth in the CNS. After being bound by BDNF, TrkB and p75 are endocytosed into endosomes and continue signaling within the cell soma, dendrites, and axons. We studied the functional role of BDNF axonal signaling in cortical neurons derived from different transgenic mice using compartmentalized cultures in microfluidic devices. We found that axonal BDNF increased dendritic growth from the neuronal cell body in a cAMP response element-binding protein (CREB)-dependent manner. These effects were dependent on axonal TrkB but not p75 activity. Dynein-dependent BDNF-TrkB-containing endosome transport was required for long-distance induction of dendritic growth. Axonal signaling endosomes increased CREB and mTOR kinase activity in the cell body, and this increase in the activity of both proteins was required for general protein translation and the expression of Arc, a plasticity-associated gene, indicating a role for BDNF-TrkB axonal signaling endosomes in coordinating the transcription and translation of genes whose products contribute to learning and memory regulation.

Motor dysfunction in Parkinson’s disease (PD) is closely linked to the dopaminergic depletion of striatal neurons and altered synaptic plasticity at corticostriatal synapses. Dopamine receptor D1 (DRD1) stimulation is a crucial step in the formation of long-term potentiation (LTP), whereas dopamine receptor D2 (DRD2) stimulation is needed for the formation of long-term depression (LTD) in striatal spiny projection neurons (SPNs). Tropomyosin receptor kinase B (TrkB) and its ligand brain-derived neurotrophic factor (BDNF) are centrally involved in plasticity regulation at the corticostriatal synapses. DRD1 activation enhances TrkB’s sensitivity for BDNF in direct pathway spiny projection neurons (dSPNs). In this study, we showed that the activation of DRD2 in cultured striatal indirect pathway spiny projection neurons (iSPNs) and cholinergic interneurons causes the retraction of TrkB from the plasma membrane. This provides an explanation for the opposing synaptic plasticity changes observed upon DRD1 or DRD2 stimulation. In addition, TrkB was found within intracellular structures in dSPNs and iSPNs from Pitx3−/− mice, a genetic model of PD with early onset dopaminergic depletion in the dorsolateral striatum (DLS). This dysregulated BDNF/TrkB signaling might contribute to the pathophysiology of direct and indirect pathway striatal projection neurons in PD.

Disturbed motor control is a hallmark of Parkinson's disease (PD). Cortico-striatal synapses play a central role in motor learning and adaption, and brain-derived neurotrophic factor (BDNF) from cortico-striatal afferents modulates their plasticity via TrkB in striatal medium spiny projection neurons (SPNs). We studied the role of dopamine in modulating the sensitivity of direct pathway SPNs (dSPNs) to BDNF in cultures of fluorescence-activated cell sorting (FACS)-enriched D1-expressing SPNs and 6-hydroxydopamine (6-OHDA)-treated rats. DRD1 activation causes enhanced TrkB translocation to the cell surface and increased sensitivity for BDNF. In contrast, dopamine depletion in cultured dSPN neurons, 6-OHDA-treated rats, and postmortem brain of patients with PD reduces BDNF responsiveness and causes formation of intracellular TrkB clusters. These clusters associate with sortilin related VPS10 domain containing receptor 2 (SORCS-2) in multivesicular-like structures, which apparently protects them from lysosomal degradation. Thus, impaired TrkB processing might contribute to disturbed motor function in PD.

Head and Neck Squamous-Cell Carcinoma (HNSCC) are a very common type of cancer. It is often associated with smoking and alcohol, but it can also be caused by certain highrisk human papillomavirus strains, usually HPV16 and 18. In this thesis the difference between the expression of TrkB in HPV-positive and HPV-negative HNSCC is described and used to show a possible treatment for HNSCC with the TrkB inhibitor ANA-12. The results of the different experiments show that ANA-12 is indeed an effective inhibitor of TrkB and it even leads to the necrosis if HPV-positive HNSCC, thus suggesting a use of ANA-12 as an additional treatment method to common head and neck cancer treatments such as surgical removal of the tumour, radiotherapy, and chemotherapy. Inhibiting TrkB also might have the side effect of inhibiting EMT in HNSCC, which is often the cause for recurring cancers after a seemingly successful treatment. However, there are still many things left that probably need further research, as they were not possible in the scope of this thesis. The actual biochemical and molecular biological effects of HPV on the overexpression of TrkB in HNSCC is not made clear in this work. Another problem might arise by looking at p16, which is commonly overexpressed in HPV-related cancers. It could be, that the TrkB overexpression is not directly tied to an HPV infection but rather to the overexpression of p16, which could be caused by something else than HPV. In this work both the HPV-infection and the overexpression of p16 was confirmed in the patient samples used. Two cell lines were also used to show the difference in TrkB expression between HPV-positive and HPV-negative HNSCC. In the end it is also discussed how age might be a factor in the expression of TrkB in HNSCC and how ANA-12 could be delivered to the cancer cells directly, as it is also known to affect neural cells, which use TrkB as a survival factor themselves., Waldnig Christoph, Masterarbeit Universität Innsbruck 2022

Obesity is a complex multifactorial disorder with genetic and environmental factors. There is an increase in the worldwide prevalence of obesity in both developed and developing countries. The development of genome-wide association studies (GWAS) and next-generation sequencing (NGS) has increased the discovery of genetic associations and awareness of monogenic and polygenic causes of obesity. The genetics of obesity could be classified into syndromic and non-syndromic obesity. Prader-Willi, fragile X, Bardet-Biedl, Cohen, and Albright Hereditary Osteodystrophy (AHO) syndromes are examples of syndromic obesity, which are associated with developmental delay and early onset obesity. Non-syndromic obesity could be monogenic, polygenic, or chromosomal in origin. Monogenic obesity is caused by variants of single genes while polygenic obesity includes several genes with the involvement of members of gene families. New advances in genetic testing have led to the identification of obesity-related genes. Leptin (LEP), the leptin receptor (LEPR), proopiomelanocortin (POMC), prohormone convertase 1 (PCSK1), the melanocortin 4 receptor (MC4R), single-minded homolog 1 (SIM1), brain-derived neurotrophic factor (BDNF), and the neurotrophic tyrosine kinase receptor type 2 gene (NTRK2) have been reported as causative genes for obesity. NGS is now in use and emerging as a useful tool to search for candidate genes for obesity in clinical settings.

Neurons depend on proper localization of neurotrophic receptors in their distal processes for their function. The Trk family of neurotrophin receptors controls neuronal survival, differentiation, and remodeling and are well known to function as retrograde signal carriers transported from the distal axon toward the cell body. However, the mechanism driving anterograde trafficking of Trk receptors into the axon is not well established. We used microfluidic compartmental devices and inducible secretion assay to systematically investigate the retrograde and anterograde trafficking routes of TrkB receptor along the axon in rat hippocampal neurons. We show that newly synthesized TrkB receptors traffic through the secretory pathway and are directly delivered into axon. We found that these TrkB carriers associate and are regulated by Rab6. Furthermore, the combined activity of kinesin-1 and kinesin-3 is needed for the formation of axon-bound TrkB secretory carriers and their effective entry and processive anterograde transport beyond the proximal axon. Neurons distribute signaling receptors to distal axons to receive extracellular information. Focusing on the neurotrophic receptor TrkB, Zahavi et al. elucidate an intracellular trafficking pathway that enables neurons to drive TrkB from its site of synthesis at the cell body, via secretory transport carriers, into the distal axon.

Aging induces a decline in cognitive function and is the primary risk factor for neurodegenerative disease, and both are associated with impairments in myelination. Oligodendrocytes and myelin in the central nervous system (CNS) are now recognised as important for plasticity in mediating learning, memory and cognitive function. It appears that with age, myelin plasticity declines in a region-specific manner and myelin loss increases. This suggests a slow decline in oligodendrogenesis occurs during aging, but the underlying cellular and molecular properties dictating the onset, progression and regional specificity of decline remain unknown. A complete understanding of oligodendrogenesis throughout the CNS over the course of healthy aging is critical in understanding the lifelong capacity for myelin plasticity, and may identify important therapeutic avenues for preventing age-related cognitive decline or onset of neurodegeneration. In this thesis, I used C57BL/6 mice to assess the homeostatic, activity-dependent and molecular basis of oligodendrogenesis throughout the CNS during adulthood and healthy aging. I used immunohistochemistry and confocal microscopy to identify oligodendroglial lineage cells, and transmission electron microscopy to investigate myelinated axon structure and myelin sheath thickness. First, I identified newly-formed oligodendrocytes with a cumulative labelling strategy, by administering thymidine analogue EdU for 6-weeks beginning at each representative timepoint of; 2-months (young-adulthood), 12-months (early aging) and 18-months (aging). I investigated homeostatic oligodendrogenesis in three distinctly myelinated regions of the CNS; the optic nerve (an almost fully myelinated white matter tract), the corpus callosum (a partially myelinated white matter tract) and the somatosensory cortex (a sparsely myelinated grey matter area). Second, I investigated activity-dependent changes in oligodendroglial behaviour in young-adult mice by inducing CNS

Ketamine is a non-competitive N-methyl-D-aspartate (NMDA)-channel blocker that has recently shown promise in the treatment of major depressive disorder, distinguishing itself from classical anti-depressants through its rapid and lasting effects when given at sub-anaesthetic doses. Animal models of depression are commonly used to research individual mechanisms of action and this literature review aimed to investigate how ketamine influences BDNF-TrkB neurotransmission in the hippocampus and prefrontal cortex within animal models of depression. Reduced levels of BDNF and TrkB-transmission, as well as downstream signalling, are common in both humans experiencing depression and in rodent models of depression, and ketamine was found to counteract this reduction in the majority of studies reviewed. In the majority of studies ketamine’s anti-depressant actions were viewed to be at least partially connected to its effects on BDNF-TrkB neurotransmission. This was supported by the anti-depressant effects being readily blocked by pharmacological inhibition of TrkB. Inhibition also blocked the downstream neurobiological changes associated with ketamines anti-depressant effects., Ketamin är en icke-kompetitiv N-methyl-D-aspartate (NMDA)-kanal antagonist som nyligen har visat lovande resultat i behandling av depression. Substansen särskiljer sig från klassiska antidepressiva läkemedel genom att dess effekt infinner sig snabbt och kvarstår under en längre period om det ges i låga doser. Djurmodeller av depression används för att undersöka individuella mekanismer relaterade till depression och denna litteraturstudie ämnade att undersöka hur ketamin påverkar BDNF-TrkB signallering inom hippocampus och prefrontala cortex i djurmodeller av depression. Minskade nivåer av BDNF och TrkB-signalering är vanligt förekommande både hos männsikor med depression och i djurmodeller av depression. I majoriteten av studierna återställde ketamin nivåerna av BDNF och TrkB-signalering till normala värden. Dess antidepressiva effekt kopplades till denna signalväg eftersom farmakologisk inhibering av TrkB i majoriteten av studierna resulterade i att den anti-depressiva effekten uteblev. Inhiberingen blockerade även nedströms neurobiologiska förändringar som anses kopplade till ketamins antidepressiva effekter.

Why layers II/III of entorhinal cortex (EC) deteriorate in advance of other regions during the earliest stages of Alzheimer's disease is poorly understood. Failure of retrograde trophic support from synapses to cell bodies is a common cause of neuronal atrophy, and we accordingly tested for early-life deterioration in projections of rodent layer II EC neurons. Using electrophysiology and quantitative imaging, changes in EC terminals during young adulthood were evaluated in male rats and mice. Field excitatory postsynaptic potentials, input/output curves, and frequency following capacity by lateral perforant path (LPP) projections from lateral EC to dentate gyrus were unchanged from 3 to 8-10 months of age. In contrast, the unusual presynaptic form of long-term potentiation (LTP) expressed by the LPP was profoundly impaired by 8 months in rats and mice. This impairment was accompanied by a reduction in the spine to terminal endocannabinoid signaling needed for LPP-LTP induction and was offset by an agent that enhances signaling. There was a pronounced age-related increase in synaptophysin within LPP terminals, an effect suggestive of incipient pathology. Relatedly, presynaptic levels of TrkB-receptors mediating retrograde trophic signaling-were reduced in the LPP terminal field. LTP and TrkB content were also reduced in the medial perforant path of 8- to 10-month-old rats. As predicted, performance on an LPP-dependent episodic memory task declined by late adulthood. We propose that memory-related synaptic plasticity in EC projections is unusually sensitive to aging, which predisposes EC neurons to pathogenesis later in life.SIGNIFICANCE STATEMENT Neurons within human superficial entorhinal cortex are particularly vulnerable to effects of aging and Alzheimer's disease, although why this is the case is not understood. Here we report that perforant path projections from layer II entorhinal cortex to the dentate gyrus exhibit rapid aging in rodents, including reduced syn

Fragile X syndrome (FXS) is associated with deficits in various types of learning, including those that require the hippocampus. Relatedly, hippocampal long-term potentiation (LTP) is impaired in the Fmr1 knockout (KO) mouse model of FXS. Prior research found that infusion of brain-derived neurotrophic factor (BDNF) rescues LTP in the KOs. Here, we tested if, in Fmr1 KO mice, up-regulating BDNF production or treatment with an agonist for BDNF's TrkB receptor restores synaptic plasticity and improves learning. In hippocampal slices, bath infusion of the TrkB agonist 7,8-dihydroxyflavone (7,8-DHF) completely restored otherwise impaired hippocampal field CA1 LTP of Fmr1 KOs without effect in wild types (WTs). Similarly, acute, semi-chronic, or chronic treatments with 7,8-DHF rescued a simple hippocampus-dependent form of spatial learning (object location memory: OLM) in Fmr1 KOs without effect in WTs. The agonist also restored object recognition memory, which depends on cortical regions. Semi-chronic, but not acute, treatment with the ampakine CX929, which up-regulates BDNF expression, lowered the training threshold for OLM in WT mice and rescued learning in the KOs. Positive results were also obtained in a test for social recognition. An mGluR5 antagonist did not improve learning. Quantification of synaptic immunolabeling demonstrated that 7,8-DHF and CX929 increase levels of activated TrkB at excitatory synapses. Moreover, CX929 induced a robust synaptic activation of the TrkB effector ERK1/2. These results suggest that enhanced synaptic BDNF signaling constitutes a plausible strategy for treating certain aspects of the cognitive disabilities associated with FXS.

BackgroundEntrectinib is a potent inhibitor of tropomyosin receptor kinase (TRK) A, B, and C, which has been shown to have anti-tumour activity against NTRK gene fusion-positive solid tumours, including CNS activity due to its ability to penetrate the blood-brain barrier. We present an integrated efficacy and safety analysis of patients with metastatic or locally advanced solid tumours harbouring oncogenic NTRK1, NTRK2, and NTRK3 gene fusions treated in three ongoing, early-phase trials.MethodsAn integrated database comprised the pivotal datasets of three, ongoing phase 1 or 2 clinical trials (ALKA-372-001, STARTRK-1, and STARTRK-2), which enrolled patients aged 18 years or older with metastatic or locally advanced NTRK fusion-positive solid tumours who received entrectinib orally at a dose of at least 600 mg once per day in a capsule. All patients had an Eastern Cooperative Oncology Group performance status of 0-2 and could have received previous anti-cancer therapy (except previous TRK inhibitors). The primary endpoints, the proportion of patients with an objective response and median duration of response, were evaluated by blinded independent central review in the efficacy-evaluable population (ie, patients with NTRK fusion-positive solid tumours who were TRK inhibitor-naive and had received at least one dose of entrectinib). Overall safety evaluable population included patients from STARTRK-1, STARTRK-2, ALKA-372-001, and STARTRK-NG (NCT02650401; treating young adult and paediatric patients [aged ≤21 years]), who received at least one dose of entrectinib, regardless of tumour type or gene rearrangement. NTRK fusion-positive safety evaluable population comprised all patients who have received at least one dose of entrectinib regardless of dose or follow-up. These ongoing studies are registered with ClinicalTrials.gov, NCT02097810 (STARTRK-1) and NCT02568267 (STARTRK-2), and EudraCT, 2012-000148-88 (ALKA-372-001).FindingsPatients were enrolled in ALKA-372-001 from

delta(9)-tetrahydrocannabinol (THC) is one of the most used drugs during pregnancy and lactation and efficiently crosses the placental and blood-brain barriers. Despite the recent legalization initiatives worldwide, the adverse outcome pathway (AOP) of THC following exposure during brain development is incompletely understood. We have previously reported that a single injection of THC on postnatal day (PND) 10 altered adult spontaneous behavior and habituation rates in adult mice. Similar behavioral alterations have been reported following PND 10 exposure to the commonly used over-the-counter analgesic acetaminophen (AAP; also known as paracetamol); as both THC and AAP interact with the endocannabinoid system, we hypothesize that this system might be involved in the AOP of both these pharmaceuticals/drugs. Here, we report that a single THC dose on PND 10 decreased transcript levels of tropomyosin receptor kinase b (Trkb) 24 h after exposure in both the frontal and parietal cortex, and in the hippocampus in mice. An increase in the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) ratio were also found in both the parietal cortex and hippocampus following neonatal exposure to THC. In addition, THC exposure increased transcript levels of cannabinoid receptor type 1 (Cb1r) in the parietal cortex and increased the apoptosis regulator BAX in the frontal cortex. This study is important for mainly 3 reasons: 1) we are starting to get information on the developmental neurotoxic AOP of PND 10 exposure to THC, where we suggest that transcriptional changes of the neurotrophic receptor Trkb are central, 2) our PND 10 exposure model provides information relevant to human exposure and 3) since PND 10 exposure to AAP also decreased Trkb transcript levels, we suggest THC and AAP may share key events in their respective AOP through endocannabinoid-mediated alterations of the brain-derived neurotrophic factor (BDNF)TRKB signaling pathway.

More reliable and cheaper sequencing technologies have revealed the vast mutational landscapes characteristic of many phenotypes. The analysis of such genetic variants has led to successful identification of altered proteins underlying many Mendelian disorders. Nevertheless the simple one-variant one-phenotype model valid for many monogenic diseases does not capture the complexity of polygenic traits and disorders. Although experimental and computational approaches have improved detection of functionally deleterious variants and important interactions between gene products, the development of comprehensive models relating genotype and phenotypes remains a challenge in the field of genomic medicine. In this context, a new view of the pathologic state as significant perturbation of the network of interactions between biomolecules is crucial for the identification of biochemical pathways associated with complex phenotypes. Seminal studies in systems biology combined the analysis of genetic variation with protein-protein interaction networks to demonstrate that even as biological systems evolve to be robust to genetic variation, their topologies create disease vulnerabilities. More recent analyses model the impact of genetic variants as changes to the "wiring" of the interactome to better capture heterogeneity in genotype-phenotype relationships. These studies lay the foundation for using networks to predict variant effects at scale using machine-learning or algorithmic approaches. A wealth of databases and resources for the annotation of genotype-phenotype relationships have been developed to support developments in this area. This overview describes how study of the molecular interactome has generated insights linking the organization of biological systems to disease mechanism, and how this information can enable precision medicine. This article is categorized under: Translational, Genomic, and Systems Medicine > Translational Medicine Biological Mechanisms > Ce

Myelin, the specialised membrane surrounding many axons in the nervous system, is vital for the normal sensory and motor function as well as high order function such as learning and memory. Despite the importance of myelin in neural development and functions, little is known whether neuronally expressed molecules can promote the central nervous system (CNS) myelinating process. Through selectively deleting the expression of neurotrophin receptor TrkB in neurons in vivo (TrKB cKO), I have found that neuronal TrkB is essential for oligodendroglial cell production and lineage progression in multiple CNS regions including the lumbar spinal cord white matter tracts, cerebral cortex and corpus callosum and importantly de novo myelination, independent of axonal number and calibre in vivo. I have performed ultrastructural analysis of myelinated axons and found that TrkB cKO mice have significantly fewer myelinated axons compared to control mice during early postnatal development, indicative of delayed initiation of myelination. The analysis of myelin thickness via G ratio has revealed thinner myelin membranes in TrkB cKO mice compared to littermate control mice during development, persisting to late adulthood (n=3 mice/genotype/timepoint). This hypomyelinating phenotype has resulted in impaired myelin function, as evident by reduced optomoter responses in TrkB cKO mice compared to control mice. Moreover, I have found that TrkB cKO mice have significantly fewer oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes in both white and grey matter regions throughout postnatal development and into adulthood compared to littermate controls. A 24-hour EdU labelling experiment has demonstrated that neuronal TrkB expression is required for oligodendroglial production. Interestingly, the overall number of astrocytes and microglia has remained unchanged after neuronal TrkB deletion, suggesting a specific effect upon oligodendroglial lineage cells and myelination. In addit

Pilocytic astrocytomas are typically grade I astrocytomas, only rarely progressing to anaplastic counterparts [1]. In the case of anaplastic pilocytic astrocytomas, some are associated with neurofibromatosis type 1 (NF1) [2], others are associated with radiation treatment [2], and the remainder appear de novo. These de novo tumours can be particularly challenging to distinguish from glioblastomas, which are grade IV and carry a worse prognosis. Here we report an unusual case of malignant transformation of a pilocytic astrocytoma in the absence of NF1 alterations or radiation treatment.

type:Regular Article, source:http://igakkai.kms-igakkai.com/wp/wp-content/uploads/2018en/KMJ-E44(2)41.pdf

Autism spectrum disorder is a neurodevelopmental syndrome diagnosed primarily by persistent deficits in social interactions and communication, unusual sensory reactivity, motor stereotypies, repetitive behaviors, and restricted interests. No FDA-approved medical treatments exist for the diagnostic symptoms of autism. Here we interrogate multiple pharmacological targets in two distinct mouse models that incorporate well-replicated autism-relevant behavioral phenotypes. Compounds that modify inhibitory or excitatory neurotransmission were selected to address hypotheses based on previously published biological abnormalities in each model. Shank3B is a genetic model of a mutation found in autism and Phelan-McDermid syndrome, in which deficits in excitatory neurotransmission and synaptic plasticity have been reported. BTBR is an inbred strain model of forms of idiopathic autism in which reduced inhibitory neurotransmission and excessive mTOR signaling have been reported. The GABA-A receptor agonist gaboxadol significantly reduced repetitive self-grooming in three independent cohorts of BTBR. The TrkB receptor agonist 7,8-DHF improved spatial learning in Shank3B mice, and reversed aspects of social deficits in BTBR. CX546, a positive allosteric modulator of the glutamatergic AMPA receptor, and d-cycloserine, a partial agonist of the glycine site on the glutamatergic NMDA receptor, did not rescue aberrant behaviors in Shank3B mice. The mTOR inhibitor rapamycin did not ameliorate social deficits or repetitive behavior in BTBR mice. Comparison of positive and negative pharmacological outcomes, on multiple phenotypes, evaluated for replicability across independent cohorts, enhances the translational value of mouse models of autism for therapeutic discovery. GABA agonists present opportunities for personalized interventions to treat components of autism spectrum disorder. Autism Res 2019, 12: 401-421 © 2019 The Authors. Autism Research published by International Society for Au

Brain-derived neurotrophic factor (BDNF) promotes neuron survival in adulthood in the central nervous system. In the peripheral nervous system, BDNF is a contraction-inducible protein that, through its binding to tropomyosin-related kinase B receptor (TrkB), contributes to the retrograde neuroprotective control done by muscles, which is necessary for motor neuron function. BDNF/TrkB triggers downstream presynaptic pathways, involving protein kinase C, essential for synaptic function and maintenance. Undeniably, this reciprocally regulated system exemplifies the tight communication between nerve terminals and myocytes to promote synaptic function and reveals a new view about the complementary and essential role of pre and postsynaptic interplay in keeping the synapse healthy and strong. This signaling at the neuromuscular junction (NMJ) could establish new intervention targets across neuromuscular diseases characterized by deficits in presynaptic activity and muscle contractility and by the interruption of the connection between nervous and muscular tissues, such as amyotrophic lateral sclerosis (ALS). Indeed, exercise and other therapies that modulate kinases are effective at delaying ALS progression, preserving NMJs and maintaining motor function to increase the life quality of patients. Altogether, we review synaptic activity modulation of the BDNF/TrkB/PKC signaling to sustain NMJ function, its and other kinases' disturbances in ALS and physical and molecular mechanisms to delay disease progression.

During development, activity-dependent synaptic plasticity refines neuronal networks with high precision. For example, spontaneous activity helps sorting synaptic inputs with similar activity patterns into clusters to enhance neuronal computations in the mature brain. Here, we show that TrkB activation and postsynaptic brain-derived neurotrophic factor (BDNF) are required for synaptic clustering in developing hippocampal neurons. Moreover, BDNF and TrkB modulate transmission at synapses depending on their clustering state, indicating that endogenous BDNF/TrkB signaling stabilizes locally synchronized synapses. Together with our previous data on proBDNF/p75NTR signaling, these findings suggest a push-pull plasticity mechanism for synaptic clustering: BDNF stabilizes clustered synapses while proBDNF downregulates out-of-sync synapses. This idea is supported by our observation that synaptic clustering requires matrix-metalloproteinase-9 activity, a proBDNF-to-BDNF converting enzyme. Finally, NMDA receptor activation mediates out-of-sync depression upstream of proBDNF signaling. Together, these data delineate an efficient plasticity mechanism where proBDNF and mature BDNF establish synaptic clustering through antagonistic modulation of synaptic transmission. Niculescu et al. found that synaptic clustering requires BDNF/TrkB signaling, activity of the proBDNF-to-BDNF conversion enzyme MMP9, and NMDA receptor activation. Their study delineates a push-pull plasticity mechanism where BDNF stabilizes clustered synapses while its precursor, proBDNF, depresses unclustered synapses, together ensuring robust clustering of synaptic inputs in developing neurons.

Atrophy of neurons in the prefrontal cortex (PFC) plays a key role in the pathophysiology of depression and related disorders. The ability to promote both structural and functional plasticity in the PFC has been hypothesized to underlie the fast-acting antidepressant properties of the dissociative anesthetic ketamine. Here, we report that, like ketamine, serotonergic psychedelics are capable of robustly increasing neuritogenesis and/or spinogenesis both in vitro and in vivo. These changes in neuronal structure are accompanied by increased synapse number and function, as measured by fluorescence microscopy and electrophysiology. The structural changes induced by psychedelics appear to result from stimulation of the TrkB, mTOR, and 5-HT2A signaling pathways and could possibly explain the clinical effectiveness of these compounds. Our results underscore the therapeutic potential of psychedelics and, importantly, identify several lead scaffolds for medicinal chemistry efforts focused on developing plasticity-promoting compounds as safe, effective, and fast-acting treatments for depression and related disorders.

BackgroundGene fusions involving NTRK1, NTRK2, or NTRK3 (TRK fusions) are found in a broad range of paediatric and adult malignancies. Larotrectinib, a highly selective small-molecule inhibitor of the TRK kinases, had shown activity in preclinical models and in adults with tumours harbouring TRK fusions. This study aimed to assess the safety of larotrectinib in paediatric patients.MethodsThis multicentre, open-label, phase 1/2 study was done at eight sites in the USA and enrolled infants, children, and adolescents aged 1 month to 21 years with locally advanced or metastatic solid tumours or CNS tumours that had relapsed, progressed, or were non-responsive to available therapies regardless of TRK fusion status; had a Karnofsky (≥16 years of age) or Lansky (<16 years of age) performance status score of 50 or more, adequate organ function, and full recovery from the acute toxic effects of all previous anticancer therapy. Following a protocol amendment on Sept 12, 2016, patients with locally advanced infantile fibrosarcoma who would require disfiguring surgery to achieve a complete surgical resection were also eligible. Patients were enrolled to three dose cohorts according to a rolling six design. Larotrectinib was administered orally (capsule or liquid formulation), twice daily, on a continuous 28-day schedule, in increasing doses adjusted for age and bodyweight. The primary endpoint of the phase 1 dose escalation component was the safety of larotrectinib, including dose-limiting toxicity. All patients who received at least one dose of larotrectinib were included in the safety analyses. Reported here are results of the phase 1 dose escalation cohort. Phase 1 follow-up and phase 2 are ongoing. This trial is registered with ClinicalTrials.gov, number NCT02637687.FindingsBetween Dec 21, 2015, and April 13, 2017, 24 patients (n=17 with tumours harbouring TRK fusions, n=7 without a documented TRK fusion) with a median age of 4·5 years (IQR 1·3-13·3) were enrolled to thr

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© 2018 Tomàs, Garcia, Lanuza, Santafé, Tomàs, Nadal, Hurtado, Simó-Ollé, Cilleros-Mañé and Just-Borràs. In the last few years, we have studied the presence and involvement in synaptogenesis and mature transmitter release of the adenosine autoreceptors (AR) in the mammalian neuromuscular junction (NMJ). Here, we review and bring together the previously published data to emphasize the relevance of these receptors for developmental axonal competition, synaptic loss and mature NMJ functional modulation. However, in addition to AR, activity-dependent mediators originating from any of the three cells that make the synapse (nerve, muscle, and glial cells) cross the extracellular cleft to generate signals in target metabotropic receptors. Thus, the integrated interpretation of the complementary function of all these receptors is needed. We previously studied, in the NMJ, the links of AR with mAChR and the neurotrophin receptor TrkB in the control of synapse elimination and transmitter release. We conclude that AR cooperate with these receptors through synergistic and antagonistic effects in the developmental synapse elimination process. In the adult NMJ, this cooperation is manifested so as that the functional integrity of a given receptor group depends on the other receptors operating normally (i.e., the functional integrity of mAChR depends on AR operating normally). These observations underlie the relevance of AR in the NMJ function.

Binge eating disorder (BED) is defined as recurrent, distressing over-consumption of palatable food (PF) in a short time period. Clinical studies suggest that individuals with BED may have impairments in cognitive processes, executive functioning, impulse control, and decision-making, which may play a role in sustaining binge eating behavior. These clinical reports, however, are limited and often conflicting. In this study, we used a limited access rat model of binge-like behavior in order to further explore the effects of binge eating on cognition. In binge eating prone (BEP) rats, we found novel object recognition (NOR) as well as Barnes maze reversal learning (BM-RL) deficits. Aberrant gene expression of brain derived neurotrophic factor (Bdnf) and tropomyosin receptor kinase B (TrkB) in the hippocampus (HPC)-prefrontal cortex (PFC) network was observed in BEP rats. Additionally, the NOR deficits were correlated with reductions in the expression of TrkB and insulin receptor (Ir) in the CA3 region of the hippocampus. Furthermore, up-regulation of serotonin-2C (5-HT2C) receptors in the orbitoprefrontal cortex (OFC) was associated with BM-RL deficit. Finally, in the nucleus accumbens (NAc), we found decreased dopamine receptor 2 (Drd2) expression among BEP rats. Taken together, these data suggest that binge eating vegetable shortening may induce contextual and reversal learning deficits which may be mediated, at least in part, by the altered expression of genes in the CA3-OFC-NAc neural network.

Maternal tobacco use in pregnancy increases the risk of neurodevelopmental disorders and neurobehavioral deficits in postnatal life. The present study tested the hypothesis that perinatal nicotine exposure exacerbated brain vulnerability to hypoxic-ischemic (HI) injury in neonatal rats through up-regulation of miR-210 expression in the developing brain. Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps. Experiments of HI brain injury were performed in 10-day-old pups. Perinatal nicotine treatment significantly decreased neonatal body and brain weights, but increased the brain to body weight ratio. Perinatal nicotine exposure caused a significant increase in HI brain infarct size in the neonates. In addition, nicotine enhanced miR-210 expression and significantly attenuated brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase isoform B (TrkB) protein abundance in the brain. Of importance, intracerebroventricular administration of a miR-210 inhibitor (miR-210-LNA) significantly decreased HI-induced brain infarct size and reversed the nicotine-increased vulnerability to brain HI injury in the neonate. Furthermore, miR-210-LNA treatment also reversed nicotine-mediated down-regulation of BDNF and TrkB protein expression in the neonatal brains. These findings provide novel evidence that the increased miR-210 plays a causal role in perinatal nicotine-induced developmental programming of ischemic sensitive phenotype in the brain. It represents a potential novel therapeutic approach for treatment of brain hypoxic-ischemic encephalopathy in the neonate-induced by fetal stress.

Suppressor of cytokine signalling 2 (SOCS2) negatively regulates cytokine signalling but it also has a positive effect on neurite outgrowth of cortical and dorsal root ganglion neurons. It has a high expression profile in the central nervous system in early development stages; hence any changes in the expression of SOCS2 results could result in alternations in the structure of neurites and dendritic morphology. SOCS2 has the highest expression in the hippocampus compared to other members of the SOCS family and this study aims to reveal the role of SOCS2 in the growth of hippocampal neurites in the presence of BDNF. Hippocampal neurons derived from neonatal mice are a great model of BDNF dependent study mediated by neurotrophin receptor BDNF. Neurons were derived from mice with overexpression or knock out of SOCS2 and the length of neurites were analysed in response to BDNF. While normal levels of SOCS2 did not result in any change in the length of neurites, neurons with overexpression of SOCS2 had increased length in response to BDNF. Knockout of SOCS2 resulted in shorter neurites although with BDNF treatment the length of neurites reached normal levels. The co-regulatory role of SOCS2 and BDNF in neurite outgrowth of hippocampal neurons in-vitro draws a possible link between SOCS2 and BDNF receptor, TrkB. The interaction of SOCS2 and TrkB was shown and studies in detail. Truncated isoforms and deleted mutants of TrkB and SOCS2 were employed to reveal the regions involved in the interaction. This study showed the complex interaction of SOCS2 and TrkB happens at two points. The first point is the protein-protein link between the kinase domain of TrkB and the SH2 region of SOCS2. The second point of interaction is through the juxtamembrane region of TrkB. Domains of SOCS2 that are involved in interacting with TrkB were assessed in their ability to regulate neurite outgrowth. Rat hippocampal neurons transfected with deleted mutants of SOCS2 shows that deletion in the B

BackgroundStudies in vitro demonstrate that neuronal membrane/lipid rafts (MLRs) establish cell polarity by clustering progrowth receptors and tethering cytoskeletal machinery necessary for neuronal sprouting. However, the effect of MLR and MLR-associated proteins on neuronal aging is unknown.MethodsHere, we assessed the impact of neuron-targeted overexpression of an MLR scaffold protein, caveolin-1 (Cav-1) (via a synapsin promoter, SynCav1), in the hippocampus in vivo in adult (6-month-old) and aged (20-month-old) mice on biochemical, morphologic, and behavioral changes.ResultsSynCav1 resulted in increased expression of Cav-1, MLRs, and MLR-localization of Cav-1 and tropomyosin-related kinase B receptor independent of age and time post gene transfer. Cav-1 overexpression in adult mice enhanced dendritic arborization within the apical dendrites of hippocampal cornu ammonis 1 and granule cell neurons, effects that were also observed in aged mice, albeit to a lesser extent, indicating preserved impact of Cav-1 on structural plasticity of hippocampal neurons with age. Cav-1 overexpression enhanced contextual fear memory in adult and aged mice demonstrating improved hippocampal function.ConclusionsNeuron-targeted overexpression of Cav-1 in the adult and aged hippocampus enhances functional MLRs with corresponding roles in cell signaling and protein trafficking. The resultant structural alterations in hippocampal neurons in vivo are associated with improvements in hippocampal-dependent learning and memory. Our findings suggest Cav-1 as a novel therapeutic strategy in disorders involving impaired hippocampal function.

© 2017 Tomàs, Garcia, Lanuza, Santafé, Tomàs, Nadal, Hurtado, Simó and Cilleros. During the histogenesis of the nervous system a lush production of neurons, which establish an excessive number of synapses, is followed by a drop in both neurons and synaptic contacts as maturation proceeds. Hebbian competition between axons with different activities leads to the loss of roughly half of the neurons initially produced so connectivity is refined and specificity gained. The skeletal muscle fibers in the newborn neuromuscular junction (NMJ) are polyinnervated but by the end of the competition, 2 weeks later, the NMJ are innervated by only one axon. This peripheral synapse has long been used as a convenient model for synapse development. In the last few years, we have studied transmitter release and the local involvement of the presynaptic muscarinic acetylcholine autoreceptors (mAChR), adenosine autoreceptors (AR) and trophic factor receptors (TFR, for neurotrophins and trophic cytokines) during the development of NMJ and in the adult. This review article brings together previously published data and proposes a molecular background for developmental axonal competition and loss. At the end of the first week postnatal, these receptors modulate transmitter release in the various nerve terminals on polyinnervated NMJ and contribute to axonal competition and synapse elimination.

TrkB is a high affinity receptor for the brain derived neurotrophic factor (BDNF) and its phosphorylation stimulates activation of several intracellular signalling pathways linked to cellular growth, differentiation and maintenance. Identification of various activators and inhibitors of the TrkB receptor and greater understanding their binding mechanisms is critical to elucidate the biochemical and pharmacological pathways and analyse various protein crystallization studies. The data presented here is related to the research article entitled "Brain Derived neurotrophic factor is involved in the regulation of glycogen synthase kinase 3β (GSK3β) signalling" [1]. Cyclotraxin B (CTXB) is a disulphide bridge linked cyclic peptide molecule that interacts with TrkB receptor and inhibits the BDNF/TrkB downstream signalling. This article reports for the first time binding mechanism and interaction parameters of CTXB with the TrkB receptor. The molecular model of CTXB has been generated and it's docking with TrkB domain carried out to determine the critical residues involved in the protein peptide interaction. © 2016 The Authors.

Even though many extracellular factors have been identified as promoters of general dendritic growth and branching, little is known about the cell-intrinsic modulators that allow neurons to sculpt distinctive patterns of dendrite arborization. Here, we identify Lrig1, a nervous system-enriched LRR protein, as a key physiological regulator of dendrite complexity of hippocampal pyramidal neurons. Lrig1-deficient mice display morphological changes in proximal dendrite arborization and defects in social interaction. Specifically, knockdown of Lrig1 enhances both primary dendrite formation and proximal dendritic branching of hippocampal neurons, two phenotypes that resemble the effect of BDNF on these neurons. In addition, we show that Lrig1 physically interacts with TrkB and attenuates BDNF signaling. Gain and loss of function assays indicate that Lrig1 restricts BDNF-induced dendrite morphology. Together, our findings reveal a novel and essential role of Lrig1 in regulating morphogenic events that shape the hippocampal circuits and establish that the assembly of TrkB with Lrig1 represents a key mechanism for understanding how specific neuronal populations expand the repertoire of responses to BDNF during brain development.

Recent evidence implicates epigenetic mechanisms in drug-associated memory processes. However, a possible role for one major epigenetic mechanism, nucleosome remodelling, in drug-associated memories remains largely unexplored. Here we examine mice with genetic manipulations targeting a neuron-specific nucleosome remodelling complex subunit, BAF53b. These mice display deficits in cocaine-associated memory that are more severe in BAF53b transgenic mice compared with BAF53b heterozygous mice. Similar to the memory deficits, theta-induced long-term potentiation (theta-LTP) in the nucleus accumbens (NAc) is significantly impaired in slices taken from BAF53b transgenic mice but not heterozygous mice. Further experiments indicate that theta-LTP in the NAc is dependent on TrkB receptor activation, and that BDNF rescues theta-LTP and cocaine-associated memory deficits in BAF53b transgenic mice. Together, these results suggest a role for BAF53b in NAc neuronal function required for cocaine-associated memories, and also that BDNF/TrkB activation in the NAc may overcome memory and plasticity deficits linked to BAF53b mutations.

BackgroundAntidepressant-worsening suicidal ideation is a rare but serious phenomenon. This study aimed to test for association between antidepressant-worsening suicidal ideation and polymorphisms of BDNF/NTRK2 neurotrophin pathway genes, known to be involved in depression and suicide.MethodsThis was a case-control study comparing patients with antidepressant-worsening suicidal ideation to patients without. Patients were collected from the GENESE cohort (3771 depressed tianeptine-treated outpatients). Antidepressant-worsening suicidal ideation was defined by an increase of at least 2 points on the Montgomery-Åsberg Depression Rating Scale-item10 during treatment. Controls were matched for age, sex, and baseline Montgomery-Åsberg Depression Rating Scale-item10 score. Thirteen single nucleotide polymorphisms covering 5 BDNF/NTRK2 pathway genes were genotyped.ResultsA total 78 cases and 312 controls were included. Two NTRK2 single nucleotide polymorphisms were associated to antidepressant-worsening suicidal ideation: rs1439050 (P=.01) and rs1867283 (P=.04). Association with rs1439050 remained significant after adjustment for potentially confounding factors, including previous suicide attempts (P<.01).ConclusionsThis naturalistic prospective study is consistent with previous studies on highlighting the potential role of the neurotrophin pathway, and especially of NTRK2, in antidepressant-worsening suicidal ideation.

BackgroundThe valine 66 to methionine (Met) polymorphism within the brain-derived neurotrophic factor (BDNF) sequence reduces activity-dependent BDNF release and is associated with psychiatric disorders in humans. Alcoholism is one of the most prevalent psychiatric diseases. Here, we tested the hypothesis that this polymorphism increases the severity of alcohol abuse disorders.MethodsWe generated transgenic mice carrying the mouse homolog of the human Met66BDNF allele (Met68BDNF) and used alcohol-drinking paradigms in combination with viral-mediated gene delivery and pharmacology.ResultsWe found that Met68BDNF mice consumed excessive amounts of alcohol and continued to drink despite negative consequences, a hallmark of addiction. Importantly, compulsive alcohol intake was reversed by overexpression of the wild-type valine68BDNF allele in the ventromedial prefrontal cortex of the Met68BDNF mice or by systemic administration of the tropomyosin receptor kinase B agonist, LM22A-4.ConclusionsOur findings suggest that carrying this BDNF allele increases the risk of developing uncontrolled and excessive alcohol drinking that can be reversed by directly activating the BDNF receptor, tropomyosin receptor kinase B. Importantly, this work identifies a potential therapeutic strategy for the treatment of compulsive alcohol drinking in humans carrying the Met66BDNF allele.

In chronic pain states, the neurotrophin brain-derived neurotrophic factor (BDNF) transforms the output of lamina I spinal neurons by decreasing synaptic inhibition. Pain hypersensitivity also depends on N-methyl-D-aspartate receptors (NMDARs) and Src-family kinases, but the locus of NMDAR dysregulation remains unknown. Here, we show that NMDAR-mediated currents at lamina I synapses are potentiated in a peripheral nerve injury model of neuropat

Corticostriatal atrophy is a cardinal manifestation of Huntington's disease (HD). However, the mechanism(s) by which mutant huntingtin (mHTT) protein contributes to the degeneration of the corticostriatal circuit is not well understood. We recreated the corticostriatal circuit in microfluidic chambers, pairing cortical and striatal neurons from the BACHD model of HD and its WT control. There were reduced synaptic connectivity and atrophy of striatal neurons in cultures in which BACHD cortical and striatal neurons were paired. However, these changes were prevented if WT cortical neurons were paired with BACHD striatal neurons; synthesis and release of brain-derived neurotrophic factor (BDNF) from WT cortical axons were responsible. Consistent with these findings, there was a marked reduction in anterograde transport of BDNF in BACHD cortical neurons. Subunits of the cytosolic chaperonin T-complex 1 (TCP-1) ring complex (TRiC or CCT for chaperonin containing TCP-1) have been shown to reduce mHTT levels. Both CCT3 and the apical domain of CCT1 (ApiCCT1) decreased the level of mHTT in BACHD cortical neurons. In cortical axons, they normalized anterograde BDNF transport, restored retrograde BDNF transport, and normalized lysosomal transport. Importantly, treating BACHD cortical neurons with ApiCCT1 prevented BACHD striatal neuronal atrophy by enhancing release of BDNF that subsequently acts through tyrosine receptor kinase B (TrkB) receptor on striatal neurons. Our findings are evidence that TRiC reagent-mediated reductions in mHTT enhanced BDNF delivery to restore the trophic status of BACHD striatal neurons.

The maturation of inhibitory circuits during adolescence may be tied to the onset of mental health disorders such as schizophrenia. Neurotrophin signaling likely plays a critical role in supporting inhibitory circuit development and is also implicated in psychiatric disease. Within the neocortex, subcircuits may mature at different times and show differential sensitivity to neurotrophin signaling. We measured miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSCs) in Layer 5 cell-types in the mouse anterior cingulate (Cg) across the periadolescent period. We differentiated cell-types mainly by Thy1 YFP transgene expression and also retrobead injection labeling in the contralateral Cg and ipsilateral pons. We found that YFP- neurons and commissural projecting neurons had lower frequency of mIPSCs than neighboring YFP+ neurons or pons projecting neurons in juvenile mice (P21-25). YFP- neurons and to a lesser extent commissural projecting neurons also showed a significant increase in mIPSC amplitude during the periadolescent period (P21-25 vs. P40-50), which was not seen in YFP+ neurons or pons projecting neurons. Systemic disruption of tyrosine kinase receptor B (TrkB) signaling during P23-50 in TrkBF616A mice blocked developmental changes in mIPSC amplitude, without affecting miniature excitatory post synaptic currents (mEPSCs). Our data suggest that the maturation of inhibitory inputs onto Layer 5 pyramidal neurons is cell-type specific. These data may inform our understanding of adolescent brain development across species and aid in identifying candidate subcircuits that may show greater vulnerability in mental illness.

IntroductionHuntington's disease (HD) is an autosomal dominant disorder caused by an expanded CAG repeat (greater than 38) on the short arm of chromosome 4, resulting in loss and dysfunction of neurons in the neostriatum and cortex, leading to cognitive decline, motor dysfunction, and death, typically occurring 15 to 20 years after the onset of motor symptoms. Although an effective treatment for HD has remained elusive, current studies using transplants of bone-marrow-derived mesenchymal stem cells provides considerable promise. This study further investigates the efficacy of these transplants with a focus on comparing how passage number of these cells may affect subsequent efficacy following transplantation.MethodsIn this study, mesenchymal stem cells isolated from the bone-marrow of mice (BM MSCs), were labeled with Hoechst after low (3 to 8) or high (40 to 50) numbers of passages and then transplanted intrastriatally into 5-week-old R6/2 mice, which carries the N-terminal fragment of the human HD gene (145 to 155 repeats) and rapidly develops symptoms analogous to the human form of the disease.ResultsIt was observed that the transplanted cells survived and the R6/2 mice displayed significant behavioral and morphological sparing compared to untreated R6/2 mice, with R6/2 mice receiving high passage BM MSCs displaying fewer deficits than those receiving low-passage BM MSCs. These beneficial effects are likely due to trophic support, as an increase in brain derived neurotrophic factor mRNA expression was observed in the striatum following transplantation of BM MSCs.ConclusionThe results from this study demonstrate that BM MSCs hold significant therapeutic value for HD, and that the amount of time the cells are exposed to in vitro culture conditions can alter their efficacy.

Exposure to drugs of abuse can produce many neurobiological changes which may lead to increased valuation of rewards and decreased sensitivity to their costs. Many of these behavioral alterations are associated with activity of D2-expressing medium spiny neurons in the striatum. Additionally, Bdnf in the striatum has been shown to play a role in flexible reward-seeking behavior. Given that voluntary aerobic exercise can affect the expression of these proteins in healthy subjects, and that exercise has shown promise as an anti-addictive therapy, we set out to quantify changes in D2 and Bdnf expression in methamphetamine-exposed rats given access to running wheels. Sixty-four rats were treated for two weeks with an escalating dose of methamphetamine or saline, then either sacrificed, housed in standard cages, or given free access to a running wheel for 6 weeks prior to sacrifice. Rats treated with methamphetamine ran significantly greater distances than saline-treated rats, suggesting an augmentation in the reinforcement value of voluntary wheel running. Transcription of Drd2 and Bdnf was assessed via RT-qPCR. Protein expression levels of D2 and phosphorylation of the TrkB receptor were measured via western blot. Drd2 and Bdnf mRNA levels were impacted independently by exercise and methamphetamine, but exposure to methamphetamine prior to the initiation of exercise blocked the exercise-induced changes seen in rats treated with saline. Expression levels of both proteins were elevated immediately after methamphetamine, but returned to baseline after six weeks, regardless of exercise status.

Down Syndrome (DS), trisomy 21, is characterized by synaptic abnormalities and cognitive deficits throughout the lifespan and with development of Alzheimer's disease (AD) neuropathology and progressive cognitive decline in adults. Synaptic abnormalities are also present in the Ts65Dn mouse model of DS, but which synapses are affected and the mechanisms underlying synaptic dysfunction are unknown. Here we show marked increases in the levels and activation status of TrkB and associated signaling proteins in cortical synapses in Ts65Dn mice. Proteomic analysis at the single synapse level of resolution using array tomography (AT) uncovered increased colocalization of activated TrkB with signaling endosome related proteins, and demonstrated increased TrkB signaling. The extent of increases in TrkB signaling differed in each of the cortical layers examined and with respect to the type of synapse, with the most marked increases seen in inhibitory synapses. These findings are evidence of markedly abnormal TrkB-mediated signaling in synapses. They raise the possibility that dysregulated TrkB signaling contributes to synaptic dysfunction and cognitive deficits in DS.

Autosomal dominant mutations of the RNA/DNA binding protein FUS are linked to familial amyotrophic lateral sclerosis (FALS); however, it is not clear how FUS mutations cause neurodegeneration. Using transgenic mice expressing a common FALS-associated FUS mutation (FUS-R521C mice), we found that mutant FUS proteins formed a stable complex with WT FUS proteins and interfered with the normal interactions between FUS and histone deacetylase 1 (HDAC1). Consequently, FUS-R521C mice exhibited evidence of DNA damage as well as profound dendritic and synaptic phenotypes in brain and spinal cord. To provide insights into these defects, we screened neural genes for nucleotide oxidation and identified brain-derived neurotrophic factor (Bdnf) as a target of FUS-R521C-associated DNA damage and RNA splicing defects in mice. Compared with WT FUS, mutant FUS-R521C proteins formed a more stable complex with Bdnf RNA in electrophoretic mobility shift assays. Stabilization of the FUS/Bdnf RNA complex contributed to Bdnf splicing defects and impaired BDNF signaling through receptor TrkB. Exogenous BDNF only partially restored dendrite phenotype in FUS-R521C neurons, suggesting that BDNF-independent mechanisms may contribute to the defects in these neurons. Indeed, RNA-seq analyses of FUS-R521C spinal cords revealed additional transcription and splicing defects in genes that regulate dendritic growth and synaptic functions. Together, our results provide insight into how gain-of-function FUS mutations affect critical neuronal functions.

ObjectiveAlthough low weight is a key factor contributing to the high mortality in anorexia nervosa (AN), it is unclear how AN patients sustain low weight compared with bulimia nervosa (BN) patients with similar psychopathology. Studies of genes involved in appetite and weight regulation in eating disorders have yielded variable findings, in part due to small sample size and clinical heterogeneity. This study: (1) assessed the role of leptin, melanocortin, and neurotrophin genetic variants in conferring risk for AN and BN; and (2) explored the involvement of these genes in body mass index (BMI) variations within AN and BN.MethodOur sample consisted of 745 individuals with AN without a history of BN, 245 individuals with BN without a history of AN, and 321 controls. We genotyped 20 markers with known or putative function among genes selected from leptin, melanocortin, and neurotrophin systems.ResultsThere were no significant differences in allele frequencies among individuals with AN, BN, and controls. AGRP rs13338499 polymorphism was associated with lowest illness-related BMI in those with AN (p = 0.0013), and NTRK2 rs1042571 was associated with highest BMI in those with BN (p = 0.0018).DiscussionTo our knowledge, this is the first study to address the issue of clinical heterogeneity in eating disorder genetic research and to explore the role of known or putatively functional markers in genes regulating appetite and weight in individuals with AN and BN. If replicated, our results may serve as an important first step toward gaining a better understanding of weight regulation in eating disorders.

Schizophrenia may result from aberrations in maturational neurodevelopmental processes. While many genetic and environmental factors increase the risk of schizophrenia, it is currently unclear how these factors interact across the course of adolescent development to result in the emergence of the illness during this period. New neurons are produced in the mammalian hippocampus through adolescence into adult life. Dysregulated hippocampal neurogenesis produces memory impairments that resemble those found in schizophrenia. In addition, factors that are known to regulate neurogenesis, including sex steroids and neurotrophins, have been identified as potential schizophrenia risk factors. However, there are few studies of neurogenesis in schizophrenia, and limited experimental studies on hormones and adolescent neurogenesis. This thesis investigated hippocampal cell proliferation in schizophrenia, and explored how adolescent testosterone influences neurogenesis and neurotrophin expression in the rat and monkey hippocampus. We hypothesised that cell proliferation would be reduced in the hippocampus in schizophrenia, and found a 60% decrease relative to controls, replicating the results of a previous study. We show for the first time that adolescent gonadectomy in monkeys increased neurogenesis via increasing cell survival and immature neurons. In contrast to existing studies in adult rats, two-week testosterone replacement in rat adolescence decreased cell proliferation. In young adult rats, testosterone had mixed and complex effects on cell proliferation and survival, which may underlie age-related changes in the influence of testosterone on neurogenesis. In monkeys and rats, the mechanism of action of testosterone on neurogenesis was not via changing mRNA levels of two key factors regulating new neuron proliferation and survival, brain-derived neurotrophic factor (BDNF) or its receptor (TrkB), but testosterone appears to modulate the relationship between cell proliferat

Brain-derived neurotrophic factor (BDNF) plays an important role in nervous system function and has therapeutic potential. Microbial production of BDNF has resulted in a low-fidelity protein product, often in the form of large, insoluble aggregates incapable of binding to cognate TrkB or p75 receptors. In this study, employing Saccharomyces cerevisiae display and secretion systems, it was found that BDNF was poorly expressed and partially inactive on the yeast surface and that BDNF was secreted at low levels in the form of disulfide-bonded aggregates. Thus, for the purpose of increasing the compatibility of yeast as an expression host for BDNF, directed-evolution approaches were employed to improve BDNF folding and expression levels. Yeast surface display was combined with two rounds of directed evolution employing random mutagenesis and shuffling to identify BDNF mutants that had 5-fold improvements in expression, 4-fold increases in specific TrkB binding activity, and restored p75 binding activity, both as displayed proteins and as secreted proteins. Secreted BDNF mutants were found largely in the form of soluble homodimers that could stimulate TrkB phosphorylation in transfected PC12 cells. Site-directed mutagenesis studies indicated that a particularly important mutational class involved the introduction of cysteines proximal to the native cysteines that participate in the BDNF cysteine knot architecture. Taken together, these findings show that yeast is now a viable alternative for both the production and the engineering of BDNF.

Activation of N-methyl-D-aspartate subtype of glutamate receptors (NMDARs) in postsynaptic dendrites is required for long-term potentiation (LTP) of many excitatory synapses, but the role of presynaptic axonal NMDARs in synaptic plasticity remains to be clarified. Here we report that axonal NMDARs play an essential role in LTP induction at mouse corticostriatal synapses by triggering activity-induced presynaptic secretion of brain-derived neurotrophic factor (BDNF). Genetic depletion of either BDNF or the NMDAR subunit GluN1 specifically in cortical axons abolished corticostriatal LTP in response to theta burst stimulation (TBS). Furthermore, functional axonal NMDARs were required for TBS-triggered prolonged axonal Ca(2+) elevation and BDNF secretion, supporting the notion that activation of axonal NMDARs induces BDNF secretion via enhancing Ca(2+) signals in the presynaptic nerve terminals. These results demonstrate that presynaptic NMDARs are equally important as postsynaptic NMDARs in LTP induction of corticostriatal synapses due to their role in mediating activity-induced presynaptic BDNF secretion.