Molecular and Cellular Neuroscience

Traumatic brain injury (TBI) impacts millions of individuals annually causing death, disability, and a heightened risk for long-term neurological and neuropsychiatric disorders. In recent years the fruit fly, Drosophila melanogaster has become a valuable model organism to study the cellular and molecular responses following TBI. AP-1 mediated transcriptional responses to TBI have previously been identified in Drosophila using pan-glial approaches. Fruit flies possess multiple glial subtypes which vary greatly in both cellular morphology and function, including glia of the blood hemolymph barrier, cortex, astrocyte-like, and ensheathing glia. By generating and utilizing a nuclear localized AP-1 transcriptional reporter, we identified glial subtype-specific differences in the extent of AP-1 activation following injury. Our findings identify a strong AP-1 response in the blood hemolymph barrier and ensheathing glia, a moderate response in cortex glia and little to no AP-1 activation in astrocyte-like glia. In addition, we inhibited AP-1 signaling in each glial subtype and tested the effect on acute survival. We found that inhibition of the AP-1 response in neuropil ensheathing glia leads to increased mortality following mild and moderate TBI. These results show that AP-1 activation levels vary across glial subtypes after TBI, with activation in neuropil ensheathing glia having a particularly important role in promoting post-injury survival. ARTICLE SUMMARYUsing Drosophila as a model organism, we investigated the early molecular and cellular response to traumatic brain injury. Our findings substantiate the requirement of a functional glial associated AP-1 transcriptional activation response for survival. Using colocalization studies, we characterized the AP-1 glial response in six morphologically and functionally distinct glia subtypes. After TBI, we find high levels of AP-1 activation in glia of the hemolymph brain barrier, cortex glia, and ensheathing glia. We further show the importance of AP-1 transcription within the neuropil ensheathing glia subtype for optimal survival following TBI.

Exposure to chemical cues released by predator or pathogen can evoke anxiety or fear responses in prey/host animals such as fight, flight or freeze both at behavioral and molecular levels. Freezing is a fundamental anxiety response when fighting or fleeing arent feasible. Despite the potential relevance of freezing as a stress-coping mechanism, its behavioral and molecular underpinnings are not understood yet. At molecular level danger cues are perceived by chemosensory receptors expressed in sensory neurons which may further regulate the animals behavioral responses(Ye et al., 2024){Citation}. 2-nonanone (2-NA) is one of the principal volatile organic compounds secreted by many pathogenic bacteria infecting Caenorhabditis elegans as well as humans and may signal danger to worms. Here, we show that olfactory exposure to threat-associated cue 2-NA induces a reversible fear-like freezing response characterized by immobility and halted feeding in C. elegans. With the application of in silico and behavioral approaches we showed that 2-NA is one of the ligands for an olfactory G-protein Coupled Receptor (GPCR) STR-211 and RNAi knockdown of the receptor leads to a defect in 2-NA induced avoidance behavior in worms. We next discovered that STR-211 is required for immediate behavioral changes in C. elegans during freezing response against 2-NA. The study proposes an environment relevant animal model to mimic human anxiety and fear-like behavior, along with the identification of one of the olfactory GPCRs mediating this behavior. The model may help in understanding the neuromolecular basis of freezing response in human anxiety, contributing towards treatment of mental health disorders.

Major depressive disorder (MDD) is a leading cause of global morbidity and mortality. Unfortunately, a substantial proportion of patients do not respond adequately to currently available therapies, highlighting the need for new therapeutic targets. Here, we investigated the role of volume-regulated anion channel (VRAC) in depression-related phenotypes using zebrafish. Disruption of VRAC function, either by pharmacological inhibition or morpholino-mediated knockdown of lrrc8aa, the zebrafish ortholog of mammalian LRRC8A, the obligatory subunit required for VRAC function, induced anxiety- and depression-like behaviours in zebrafish larvae and altered the expression of genes associated with affective disorders. Transcriptomic analysis of lrrc8aa-deficient larvae revealed dysregulation of pathways involved in neuronal signalling and cellular stress responses. Conversely, pharmacological activation of VRAC with zinc pyrithione (ZPT) improved behavioural abnormalities and partially restored altered gene expression. In adult zebrafish subjected to chronic unpredictable stress, ZPT produced antidepressant- and anxiolytic-like effects comparable to those of imipramine and normalized elevated monoamine oxidase (mao) expression. Together, these findings indicate that reduced VRAC function contributes to depression- and anxiety-related behavioural and molecular phenotypes and identify VRAC as a potential target for the development of novel antidepressant therapies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/740018v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@d81884org.highwire.dtl.DTLVardef@131b8e9org.highwire.dtl.DTLVardef@162d1d0org.highwire.dtl.DTLVardef@bcdb82_HPS_FORMAT_FIGEXP M_FIG C_FIG

Drosophila glutathione S-transferase S1 (GstS1) is a unique member of the glutathione S-transferase family and is considered the ortholog of vertebrate hematopoietic prostaglandin D synthase based on amino acid sequence similarity. A previous forward genetic screen revealed that a null mutation in GstS1 dominantly suppresses genetically induced behavioral hyperexcitability in several seizure-prone Drosophila mutants, including paraShu, a gain-of-function mutant of the voltage-gated sodium channel gene paralytic (para), and eas2, a loss-of-function mutant of the ethanolamine kinase gene easily shocked (eas). Here, using the GAL4/UAS system combined with GstS1 RNAi, we show that hemocyte-specific GstS1 knockdown suppresses hyperexcitable phenotypes in both paraShu and eas2. Notably, suppression of adult paraShu phenotypes required GstS1 knockdown before adult eclosion, suggesting that GstS1 modulates adult neuronal excitability by influencing neural development through neuroimmune interactions. Consistent with this model, hemocyte-specific GstS1 knockdown rescued abnormal dendritic morphology in developing class IV dendritic arborization (C4da) neurons of paraShu larvae. Moreover, paraShu and eas2 larvae exhibited increased numbers of sessile hemocytes surrounding C4da neuron somata, a phenotype reversed by either GstS1 knockdown or dietary supplementation with the {omega}-3 polyunsaturated fatty acid -linolenic acid. Together, these findings reveal a previously unrecognized developmental role for GstS1 in promoting nervous system hyperexcitability through hemocyte-mediated neuroimmune interactions, potentially involving bioactive lipid signaling. Our results highlight neuroimmune crosstalk as an important mechanism linking genetic perturbations to altered neural development and seizure-associated hyperexcitability.

Background: Insufficient oxygen (hypoxia) or complete lack of oxygen (anoxia) causes cellular dysfunction and death in terrestrial animals. As a result, animals have developed homeostatic strategies, including changes in movement strategies to escape and survive stressful environments. Caenorhabditis elegans respond to changes in oxygen by increasing the frequency of reversals (backward movement) and increasing locomotor speed; these behaviors enable them to escape unfavorable environments and move to more suitable ones. The molecular and neural mechanisms underlying behavioral responses to low-oxygen environments are incomplete. Neuropeptides regulate C. elegans behaviors by modifying neural circuit function in response to hypoxia. Loss of function in C. elegans neuropeptide nlp-40 and its receptor aex-2 increased survival to anoxia [1]. However, the cells in which NLP-40 and AEX-2 function for anoxia, as well as the mechanisms underlying responses to anoxia, remain elusive. We hypothesized that NLP-40 and AEX-2 regulate anoxia by altering escape behaviors. Results: We found that neuropeptide NLP-40 functions in cholinergic neurons and AEX-2 functions in cholinergic or GLR-1 interneurons or motor neurons to regulate susceptibility to anoxia. We found that loss of either nlp-40 or aex-2 decreased locomotor activity and reversal frequency early during 48 hours of anoxia, suggesting that nlp-40 and aex-2 are required for the proper execution of these behaviors. We found that neuronal knockdown of nlp-40 recapitulated the behaviors observed in nlp-40 mutant animals and increased survival; however, restoring aex-2 function in glr-1 interneurons or motor neurons was sufficient to rescue behaviors to wild-type and restore vulnerability to anoxia. Conclusions: Overall, our results suggest that NLP-40 and AEX-2 likely function in cholinergic or glr-1 interneurons or motor neurons to regulate escape behaviors during anoxia. Escape behaviors are part of the homeostatic response and are typically protective in the wild; however, in our paradigm, we show that loss of either nlp-40 or aex-2 reduces escape responses and confers protection against 48 hours of anoxia. Collectively, these results highlight a new role for NLP-40 and AEX-2 in anoxia and shed light on mechanisms underlying the adaptive responses to anoxia.

Achromatopsia (ACHM) is a rare autosomal recessive retinal disorder characterized by absent cone photoreceptor function from early life, leading to severe visual impairment. Mutations in genes involved in the cone phototransduction cascade frequently result in elevated cyclic guanosine monophosphate (cGMP) levels and activation of stress pathways, including endoplasmic reticulum (ER) stress and the unfolded protein response. Targeting common downstream mechanisms rather than individual mutations may provide a broadly applicable therapeutic strategy. Here, we investigated whether pharmacological inhibition of valosin-containing protein (VCP), a key regulator of ER and protein homeostasis, can prevent cone degeneration in the spontaneous cone photoreceptor function loss 1 (cpfl1) mouse model of ACHM. Organotypic culture of retinal explants from cpfl1 mice were treated with the selective VCP inhibitor ML240. Cone survival, cell death, opsin expression and localization were assessed by TUNEL assay, immunohistochemistry, and quantitative image analysis. ML240 treatment significantly increased cone density and improved cone opsin expression and trafficking to the outer segments (OSs) in cpfl1 explants compared to controls. Importantly, rhodopsin trafficking in rod photoreceptors was unaffected, indicating that VCP inhibition did not impair normal rod phototransduction. These findings demonstrate that VCP inhibition by ML240 effectively preserves cone photoreceptors and improves cone-specific functional markers in the cpfl1 model. Targeting VCP may represent a mutation-independent therapeutic strategy for preventing cone death in ACHM.

Metabolic alterations commonly accompany neurodevelopmental disorders and may contribute to their pathophysiology. Neurofibromatosis type 1 (OMIM 162200) is a genetic disorder that results from mutations in the NF1 gene and its encoded neurofibromin protein (Nf1). The disorder is multisystemic, affecting multiple aspects of development, physiology, and brain function. In addition, recent evidence suggests that Nf1 deficiency alters metabolic function in both humans and animal models. Whether the metabolic alterations result from changes in neurodevelopment is not known. Here we approach this question in Drosophila melanogaster, which expresses a conserved NF1 gene, exhibits phenotypes reminiscent of the human disease, and shares key developmental mechanisms with humans. Flies with nf1 mutations or RNAi-mediated knockdown exhibit altered metabolism in adulthood. Conditional Nf1 inactivation revealed that the adult metabolic phenotype resulted from loss of Nf1 in neurons during a developmental critical period (third instar larva/pupa), which corresponded to the period of nervous system maturation. Prior to the developmental critical period, nf1 mutants did not exhibit metabolic difference - rather, the metabolic alterations appeared only after the critical period. This suggests that the adult phenotype results from the onset of the developmental alteration during the critical period. High-resolution respirometry on adult mitochondria revealed no differences in complex I/II function or fatty acid oxidation between nf1 mutants and controls, suggesting that the metabolic alterations localize upstream of the electron transport chain at the cellular level. Overall, these data suggest that loss of Nf1 alters adult metabolism via effects during a critical period of nervous system development.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder traditionally characterized by motor neuron degeneration, but emerging evidence indicates sensory system involvement. Despite reports of sensory abnormalities in some patients, the molecular and functional alterations in dorsal root ganglion (DRG) neurons remain insufficiently characterized. We investigated DRG pathology at disease onset in 12-week-old SOD1G93A mice using an integrated transcriptomic, morphological, and electrophysiological approach. RNA sequencing of lumbar DRG identified 35 differentially expressed genes, predominantly upregulated, enriched in oxidative stress-related and phagosome pathways. Comparative analysis with motor neuron transcriptomes revealed distinct gene expression profiles, indicating sensory neuron-specific molecular responses. Immunohistochemistry demonstrated reduced soma diameter in both A- and C-fiber DRG neurons. Nav channel colocalization increased for Nav1.7 in A fibers and Nav1.8 in both fiber types, whereas Nav1.6 was unchanged. Whole-cell patch-clamp recordings showed depolarized resting membrane potential, increased spike amplitude, and enhanced repetitive firing in A-fiber neurons, consistent with hyperexcitability, while C fibers showed no significant functional changes. These findings demonstrate early molecular, structural, and functional alterations in primary sensory neurons in ALS, supporting pathology beyond motor neurons and identifying sensory neuron excitability as a potential therapeutic target.

Traumatic Brain Injury (TBI) produces acute challenges including seizures and neuroinflammation, and these then exacerbate lifelong difficulties including epilepsy, dementias, and anxiety. Applying antiepileptic drugs (AED) to manage acute seizures after TBI has promise to slow these progressive deficits. Levetiracetam (LEV) is an AED that mitigates seizures and neuroinflammation in various contexts. Here, we explore the utility of the larval zebrafish TBI model by documenting long term behavioural deficits (if any) induced by larval neurotrauma and whether they can be mitigated by LEV. We induced a mild blast TBI in three days-post-fertilization larvae, administered LEV (3 x 10-2 mM) for two days, and assessed behaviour in adults (9 +/- 1 or 22 +/- 1 months later). In open field tests, adult zebrafish that experienced TBI as larvae exhibited increased anxiety-like behaviour compared to sham-treated larvae, but this resolved by later adulthood. LEV treatment immediately following larval TBI did not significantly alter these outcomes. Novel object approach tests revealed sustained deficits in exploratory behaviour: adults that experienced larval TBI spent significantly less time investigating a novel object compared to sham controls throughout adulthood; this suggests long-term alterations in fear-related cognitive processing or threat evaluation. LEV treatment increased time spent near the novel object in early adulthood, but not later adulthood, suggesting a time-dependent efficacy of early pharmacological intervention. In sum, the larval zebrafish TBI model is suitable for investigating the progression and treatment of behavioural deficits. LEV showed only limited efficacy, but adjusted AED regimens have potential to mitigate long-term behavioural outcomes of TBI.

A key pathophysiological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is loss of nuclear localization and abnormal cytoplasmic aggregation of TAR DNA-binding protein 43 (TDP-43). Upstream factors that trigger the onset and progression of such neurodegenerative diseases are largely unknown. Aging and environmental factors contribute as potential risk factors. But epidemiological evidence suggests psychological stressors such as social isolation and loneliness are also associated with increased risks of neurodegenerative disease [1-8]. We examined the impacts of social isolation on TDP-43 related neurodegeneration. To investigate the potential for causative impact on neurodegeneration, we compared the effects of social isolation versus social enrichment in Drosophila. We utilized an established social isolation paradigm in which flies were either housed alone or in groups as young adults. We found that early-life social isolation acts as a primer to exacerbate the rate of neurodegeneration in response to subsequent induction of pathological levels of TDP-43. Social isolation stress drives more rapid activation of mdg4, an endogenous retrovirus that functionally mediates TDP-43 effects and more aggressive propagation of TDP-43 protein pathology from surface glial cells to nearby neurons. Shortened life span also ensues. We demonstrate that providing isolated flies with visual, olfactory and tactile social cues from conspecifics living behind a divider was insufficient to alleviate these effects of social isolation on neurodegeneration. Our findings have implications for the association between psychological stressors such as loneliness and risk of neurodegenerative diseases in humans and provide a platform to investigate mechanistic underpinnings in animal models.

Axonal projections and precise synapse formation are essential for the establishment of functional neural circuits, and their dysregulation contributes to various psychiatric and neurodegenerative disorders. Although numerous extracellular cues secreted from surrounding tissues regulate axon guidance and synapse formation, the mechanisms by which neurons locally regulate terminal patterning within their projection fields remain poorly understood. Bone morphogenetic protein 4 (BMP4) is a classical morphogen that is involved in early neural tube patterning during development. However, its postnatal function remains unclear. Previous in vitro studies using hippocampal glutamatergic neurons demonstrated that BMP4 can act locally on axons to suppress synapse formation, raising the possibility that BMP4 regulates terminal differentiation after target innervation. Here, we investigated the role of BMP4 in postnatal cholinergic circuit development using cholinergic neuron-specific Bmp4 conditional knockout (Bmp4 cKO) mice, with adult analyses performed in males. Basal forebrain cholinergic neurons project extensively throughout the neocortex and are essential for higher brain functions, including arousal and attention. Bmp4 cKO mice exhibited increased cholinergic axon terminals in the neocortex, hippocampus, and amygdala, as well as increased axonal ramification in the neocortex without affecting cytoarchitectonic organization or cholinergic neuron numbers in the basal forebrain. These findings demonstrate that BMP4 functions as a negative regulator of cholinergic terminal formation and axonal arborization, suggesting that BMP4 may act locally to restrict cholinergic axonal expansion during neural circuit maturation.

Chronic alcohol consumption is associated with increased breast cancer risk; however, the long-term effects of alcohol exposure on DNA damage response (DDR) signaling and therapeutic vulnerability in breast epithelial cells remain incompletely understood. In the present study, we established a chronic alcohol exposure model using immortalized human breast epithelial MCF-10A cells to investigate persistent alterations in DNA damage signaling and sensitivity to poly (ADP-ribose) polymerase (PARP) inhibition. MCF-10A cells that chronically exposed to 0.2% alcohol for 20 weeks and then withdrew alcohol treatment for 4 weeks still retained elevated {gamma}H2AX levels and sustained activation of ATM/ATR-associated DDR pathways. Chronic alcohol-exposed cells also exhibited increased sensitivity to the PARP inhibitors olaparib and veliparib, as demonstrated by reduced cell viability, decreased clonogenic survival, and enhanced apoptosis. Mechanistically, olaparib induced greater G2/M checkpoint activation and replication-associated DNA damage in chronic alcohol-exposed cells compared with control cells. In addition, chronic alcohol exposure increased PARP expression and enhanced activation of DDR signaling following PARP inhibition. These findings demonstrate that chronic alcohol exposure induces persistent DNA repair stress and sensitizes breast epithelial cells to PARP inhibition. Our study suggests that chronic alcohol-associated genomic stress may create potential vulnerability to PARP inhibition.

Traumatic brain injury (TBI) is one of the world's leading causes of death and disability and a major risk factor for dementias. The primary dementia associated with TBI is chronic traumatic encephalopathy (CTE), a neurodegenerative disease classified as a tauopathy, in which toxic tau molecules lead to disease pathologies and degeneration. The processes that lead to tauopathy and subsequent dementia after TBI remain unclear. Here, we built upon the finding that seizures after TBI may be a mechanism leading to tauopathy, by dissecting the functions of the metabotropic glutamate receptor 5 - cellular prion protein (mGluR5-PrPC) pathway. We delivered TBI to larval in a blast paradigm, and quantified aggregation of Tau via a genetically-encoded Tau-GFP fusion reporter. Zebrafish larvae lacking prp2 (homolog of mammalian cellular Prion Protein, PrPC) displayed a 168% increase in post-traumatic seizures activity after TBI. An mGluR5 agonist (CHPG) reduced post-traumatic seizures, whereas an mGluR5 antagonist (MPEP) increased post-traumatic seizures. Moreover, agonizing mGluR5 reduced tau aggregation and antagonizing mGluR5 increased tau burden. Larvae seizing from convulsants, rather than TBI, were treated with CHPG/MPEP and provided a similar pattern of outcomes, suggesting seizures may be a factor needed for mGluR5 activity to influence tau aggregation. The PrPC-mGluR5 pathway is proposed as one candidate pathomechanism linking TBI to subsequent seizures and tauopathy, and thus it warrants investigation as a target for prophylactic interventions.

Amacrine cells (ACs) are the most diverse neuron in the retina, with more than sixty different subtypes, each contributing to the detection of specific visual features. Despite their importance in visual feature detection, the genetic basis for this diversity is still not well understood. Recent single-cell transcriptomic datasets have identified several potential genes that may regulate cellular diversity, but the underlying mechanisms have not been investigated. For example, the transcription factor Meis2 is selectively expressed in the GABAergic subclass of ACs. In this study, we focused on how Meis2 regulates the development of GABAergic ACs. We hypothesized that Meis2 is required for specification and survival of GABAergic ACs. To test this, we used the Meis2 conditional knockout mouse (Meis2-CKO) where Meis2 was deleted from either the entire retina or specifically from AC precursor cells. The deletion of Meis2 led to a ~60% reduction in total GABAergic ACs in the retina. This loss of GABAergic ACs occurred only after postnatal day 5 (P5), suggesting Meis2 is not required for early specification but may be required for survival. To further investigate cell death and survival, we quantified cleaved caspase-3 positive cells in the retina at several developmental timepoints. In Meis2-CKO mice, we found an increase in cleaved caspase-3 immunolabeling at P5 and P6 timepoints coinciding with the reduction of GABAergic ACs. Further analysis of GABAergic AC subtypes demonstrated a subtype-specific cell death in Meis2-CKO retinas. For example, the total number of dopaminergic (TH) ACs were significantly reduced, whereas starburst (ChAT) ACs remained unchanged. These findings suggest that Meis2 is important for the survival of a subset of GABAergic AC subtypes in the mammalian retina. In addition, Meis2 may control the expression of specific survival factors that prevent apoptosis during developmental cell death in the retina.

3q29 deletion (3q29Del) is a genetic risk variant for autism spectrum disorder and schizophrenia that often results in developmental delays, cognitive disability, and impaired fine motor function. People with 3q29Del have reduced cerebellar volume, which correlates with symptom severity, and many 3q29Del-associated phenotypes also commonly occur after cerebellar injury or dysfunction. However, it is unknown whether the existing 3q29Del mouse model recapitulates the cerebellar dysfunction observed in humans. To characterize cerebellar phenotypes and uncover pathological differences in the 3q29Del mouse model, we investigated cerebellar structure, motor and vocal behaviors, protein expression, and mitochondrial function. We found uniformly reduced cerebellar volume in 3q29Del mice. Behavioral assays revealed vocal impairments in 3q29Del pups, fine motor impairments in adult mice, and reduced social mating calls in adult male mice. Proteomic analysis revealed enrichment of synaptic and mitochondrial proteins among the differentially expressed proteins in 3q29Del cerebellum tissue. Furthermore, mitochondria from 3q29Del mouse cerebellum displayed reduced oxygen flux and increased electron leak. These results recapitulate many human 3q29Del phenotypes in the 3q29Del mouse model and indicate mitochondrial dysfunction as a potential driver of 3q29Del pathology. Our findings also point to cerebellar involvement in 3q29Del phenotypes and provide a foundation for further research on cerebellar development in 3q29Del.

Transactive response DNA-binding protein 43 (TDP-43) aggregation and loss of function are hallmark features of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) among other neurodegenerative diseases. Despite epidemiological evidence linking environmental exposures to neurodegeneration, few toxicants have been directly associated with neurodegeneration. Here, we performed a high-content imaging screen, using a library of over a thousand chemical compounds that are considered high risk for human exposure and identified 21 toxicants that drive TDP-43 aggregation. Among the top chemical hits, five belonged to the dithiocarbamate (DTC) class of thiol-reactive compounds including the agricultural pesticides thiram and ziram. Thiram directly promoted TDP-43 cysteine oxidation and intermolecular crosslinking, whereas ziram induced TDP-43 aggregation via zinc imbalance and enhanced oxidative stress, suggesting DTCs disrupt redox homeostasis. In primary neurons and human iPSC-derived neurons, DTCs led to TDP-43 aggregation and prominent splicing defects consistent with loss of TDP-43 function. In exposed zebrafish, DTCs impaired TDP-43 function and triggered widespread transcriptional changes reflected by perturbed stress response and metabolic signatures. By combining TDP-43 loss of function mutations with chemical exposures, we observed accelerated TDP-43 loss of function and chemical-induced aggregation, supporting a multiple hit mechanism driving TDP-43 dysfunction. Together, these findings identify DTCs, particularly those used as agricultural pesticides, as dominant modifiers of TDP-43 proteostasis and identify redox imbalance and zinc homeostasis as a central molecular mechanism linking toxicant exposure to TDP-43 proteinopathy.

The FoxP family of transcription factors has been linked to neurodevelopmental disorders. FoxP1 and FoxP2 were identified as genes associated with autism spectrum disorders (ASD). FoxP1, FoxP2, and FoxP4 are expressed in many brain regions, including the cerebellum that has been of particular interest in the context of ASD. However, their role in the development of the peripheral nervous system (PNS) has been neglected. In view of the fact that a majority of ASD patients show some signs of sensory perception deficits that could go beyond the central nervous system, we focused on neural circuit formation in the PNS. Our in vivo and in vitro studies revealed a role of all three FoxP transcription factors in neural circuit formation in the hindlimb of the chicken embryo. Silencing of FoxP genes altered motor axon guidance and also impacted neural crest cell migration. This in turn resulted in aberrant formation of dorsal root ganglia and deficits in neural circuits in the PNS. Taken together, our results are in line with the hypothesis that some of the sensory perception deficits in ASD patients, either hyper- or hyposensitivity, are due to aberrant neural circuits in the PNS.

REV-ERB{beta} is a transcriptional repressor of nuclear receptors that regulates the circadian rhythm and plays an important role in regulation of the proliferation, differentiation, and maturation of neurons. Dysregulation of the circadian rhythm has been associated with neuropsychiatric disorders, and activation of REV-ERBs can induce anxiolytic behavior in mice. Furthermore, hippocampal neurogenesis is important in the effects of antidepressants. However, the role of REV-ERB{beta} in adult hippocampal neurogenesis in vivo at the single-cell level is not known. In this study, protein localization of REV-ERB{beta} in the subgranular zone of the hippocampal dentate gyrus (DG) was mainly shown in NeuN-positive neurons, and the effect of expressing a dominant negative form of REV-ERB{beta} lacking the C-terminal region on newborn neurons in the hippocampal DG of adult mice was examined to investigate the role of REV-ERB{beta} in neurogenesis. A retroviral vector containing the dominant negative REV-ERB{beta} or a control vector was injected into the mouse DG. At 4 weeks after injection, the morphology of dendrites and dendritic spines of newborn neurons labeled by the virus was examined. Expression of the dominant negative form of REV-ERB{beta} inhibited dendrite outgrowth and branching and decreased dendritic spine formation in newborn neurons in the adult mouse hippocampal DG. This study revealed a new role for REV-ERB&{beta} in adult hippocampal neurogenesis at the single cell level, and the results will provide insight into neurogenesis in the adult brain and its relationship with psychiatric disorders.

Tubulin polymerization promoting proteins (TPPPs) are known for their cytoskeletal regulation across species; however, emerging evidence suggests broader cellular functions, including potential roles in mitochondrial biology. Here, we identify the Drosophila homolog of human TPPP, Ringer, as a previously unrecognized regulator of mitochondrial bioenergetics and electron transport chain complex I (CI) function. Ringer is enriched in the mitochondrial matrix, and its loss results in reduced levels of multiple CI subunits and assembly factors and a significant decrease in CI enzymatic activity. Notably, similar deficits are observed in postmortem human Parkinsons disease (PD) brain tissues, underscoring the translational relevance of our Drosophila model and highlighting conserved, disease-associated mechanisms. Pharmacological administration of the CI-specific reactive oxygen species (ROS) scavenger, resveratrol, ameliorates superoxide levels and improves CI enzymatic activity and ATP production in ringer mutants, demonstrating that targeted antioxidant therapeutics can improve bioenergetic function with Ringer loss. Together, these findings establish Ringer as a key regulator of mitochondrial bioenergetics and reveal CI instability as a potential mechanism underlying PD-associated mitochondrial dysfunction, providing a robust and translationally meaningful framework for future therapeutic exploration.

Intracellular neurofibrillary tangles formed from hyperphosphorylated tau and extracellular amyloid plaques containing aggregated A{beta}-peptides, specific cleavage products of the Amyloid Precursor Protein (APP), are the primary histopathological hallmarks of Alzheimers Disease (AD), the leading cause of dementia in humans. However, the initiating steps that lead to these pathologies and early neurodegeneration, and the mechanisms by which tau- and A{beta}-induced effects might be linked remain unclear. Using the prostate-like secondary cell (SC) in Drosophila, we recently showed that A{beta} modulates normal APP- and membrane-associated protein aggregation in the dense-core granule (DCG) compartments of the regulated secretory pathway by interfering with subsequent membrane:DCG dissociation. This disrupts endolysosomal trafficking and propagates the resulting endolysosomal defects to other cells that endocytose the secreted abnormal DCG proteins. Here we show that overexpressing human tau also disrupts DCG aggregation and membrane:DCG dissociation inside SC secretory compartments, leading to increased endolysosomal targeting of these compartments. In a genetic screen, we find that knockdown of cofilin, which encodes an actin-severing protein required for dynamic remodelling of microfilaments, generates a similar phenotype. Consistent with this, overexpression of Cofilin, which is known to suppress tau-induced neurodegeneration in flies, reduces tau-induced DCG defects in SCs. Indeed, we find that Cofilin overexpression also suppresses A{beta}-induced degeneration in the fly eye. We conclude that membrane:DCG aggregate dissociation in DCG compartments is disrupted by both tau- and A{beta}-induced genetic changes that are relevant to AD, and this partially involves inhibition of actin cytoskeleton dynamics. Increasing actin remodelling activity can suppress neurodegeneration induced by both tau and A{beta}, suggesting that this process provides an important functional link between them that might be targeted therapeutically.