Frontiers in Molecular Neuroscience

Genetic loss-of-function (LoF) variants in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been identified as one of the foremost monogenic causes of autism spectrum disorder (ASD). ASD encompasses a broad spectrum of behavioral phenotypes, with impaired sociability as a core characteristic. We have established Scn2a-deficient mice (Scn2agt/gt) to model Scn2a-related ASD and found that this model recapitulates social impairment, exhibiting severe social deficits. Scn2agt/gt mice exhibit neuronal hyperexcitability and a marked global reduction in potassium channel expression, which plays a crucial role in maintaining the resting membrane potential and repolarizing neurons after an action potential. Among these downregulated potassium channels, potassium voltage-gated channel subfamily A member 1 (Kv1.1) was one of the most affected. To explore whether Kv1.1 could be a potential therapeutic target in SCN2A-related ASD, we evaluated the in vivo efficacy of a genetic construct driven by the CaMKII promoter that allows for exogenous expression of human Kv1.1 (hKv1.1) in principal neurons. In Scn2agt/gt mice, we found that hKv1.1 expression normalizes neuronal hyperexcitability. Importantly, doxycycline-induced hKv1.1 expression enhances sociability in Scn2a-deficient mice without influencing social behavior in wild-type mice, and this effect was reversed upon doxycycline withdrawal. Overall, we demonstrate the successful use of an inducible AAV-mediated gene delivery system to supplement hKv1.1 expression to mitigate neuronal hyperexcitability and ameliorate social impairments in a mouse model of SCN2A-related ASD. These findings highlight the contribution of Kv1.1 to SCN2A-associated pathophysiology and its potential as a therapeutic target for severe social deficits.

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.

The mammillary bodies (MB) are a hypothalamic component of the limbic Papez circuit that plays a critical role in spatial and episodic memory in mammals. Degeneration of the MB occurs in disorders associated with cognitive impairment, including Korsakoff's syndrome and Alzheimer's disease, yet the molecular organization and intrinsic properties of MB neurons remain poorly understood. Recent single-cell RNA sequencing identified multiple transcriptionally distinct neuronal populations within the MB and suggested that they differentially express voltage-gated ion channels that regulate neuronal excitability. Here, we used fluorescence in situ hybridization (FISH) to define the anatomical organization of cluster-enriched molecular markers and determine the spatial distribution of transcripts encoding voltage-gated sodium (NaV), potassium (KV), and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels among defined subregions of the mouse MB. We found that marker transcripts occupy characteristic but partially overlapping spatial domains that broadly correspond to classical anatomical subdivisions. In addition, several ion channel transcripts, including Scn1a, Scn2a, Kcnq2, Kcnq3, and Hcn1, exhibited distinct patterns of enrichment across molecularly defined neuronal populations and MB subregions. Multiplex FISH further revealed unexpected co-expression of Scn1a and Scn2a within Pvalb-enriched neuronal populations, while whole-cell recordings demonstrated distinct intrinsic firing properties of neurons in the lateral and medial mammillary nuclei. Together, these findings establish a molecular framework linking neuronal population identity with voltage-gated ion channel expression in the MB and provide a foundation for future studies investigating how cell type-specific differences in intrinsic excitability contribute to memory function and neurological disease.

Background: More than 90% of rare diseases lack an approved therapy, partly reflecting economic barriers in developing treatments for small patient populations. A common bottleneck is costly and resource-intensive hit-to-lead prioritization. Congenital contractures of the limbs and face, hypotonia, and developmental delay (CLIFAHDD) is an ultra-rare neurodevelopmental disease often caused by de novo gain-of-function variants in the sodium leak channel NALCN, with no approved treatments. Methods: We developed a cost and resource-efficient, AI-enabled translational drug discovery framework integrating phenotypic high-throughput screening (HTS), structural biology foundation models for hit-to-lead prioritization, and orthogonal experimental validation. We applied this framework for drug repurposing to identify NALCN inhibitors as therapeutic candidates for CLIFAHDD. We screened ~1,200 approved drugs using a fluorescence-based membrane potential assay in doxycycline-inducible HEK293 cells stably expressing the NALCN channelosome. Boltz-2 modeling predicted binding affinity and mode to prioritize hits. Lead repurposing candidates were selected by a multidisciplinary expert review panel. Lead candidates were evaluated using patch-clamp electrophysiology in HEK293 cells expressing wild-type or CLIFAHDD-associated NALCN variants, primary mouse hippocampal neurons, and a C. elegans NALCN gain-of-function model. Results: HTS identified 11 candidate NALCN inhibitors. Boltz-2 prioritized candidates based on predicted binding affinity and predicted binding within the NALCN pore, consistent with a direct pore-blocking mechanism. Aprepitant emerged as the lead candidate after multidisciplinary evaluation based on its predicted mechanism, pharmacologic properties, blood-brain barrier penetration, established safety profile, and regulatory approval in children and adults. Patch-clamp electrophysiology confirmed partial inhibition of NALCN-mediated sodium leak currents in HEK293 cells (IC50;=2.22 M), with comparable potency against Cav3.1 (IC50=1.63 M). In primary mouse hippocampal neurons, aprepitant reduced sodium leak currents, hyperpolarized resting membrane potential, and decreased spontaneous firing. Aprepitant rescued hyperlocomotor and dystonic phenotypes in a C. elegans gain-of-function NALCN model. There was notable concordance between AI-predicted hits, phenotypic screening hits, and experimental validation. Conclusion: These findings identify aprepitant as a lead therapeutic candidate for CLIFAHDD, and establish an AI-enabled translational drug discovery framework integrating phenotypic screening, structural modeling, and experimental validation for NALCN channelopathies. This scalable and resource-conscious strategy may accelerate hit-to-lead prioritization and drug discovery for rare and ultra-rare diseases lacking effective therapies.

Maximizing the morphological and molecular fidelity of preserved mammalian brain tissue is essential for basic neuroscience and brain banking, where tissue quality determines the reliability of downstream analyses. Aldehyde fixation and cryogenic storage are the most powerful preservation techniques available. However, how to best combine them is incompletely characterized. Here, we tested twelve different approaches to preserve the murine brain, including standard aldehyde perfusion fixation, variants of aldehyde-stabilized cryopreservation (ASC) using ethylene glycol (EG), aldehyde fixation followed by unprotected freezing, and several cryopreservation protocols without preceding aldehyde fixation, such as interleaved equilibration with vitrification solution. Preservation quality was assessed using light microscopy, transmission electron microscopy, and patch-level feature analysis with the DINOv2 vision foundation model. We found that ASC with sodium dodecyl sulfate (SDS)-mediated blood-brain barrier permeabilization preserved nuclear morphology, myelin periodicity, and neuropil texture comparable to standard aldehyde perfusion fixation, providing the first independent replication of ASC. Omitting SDS caused severe parenchymal dehydration, due to a mismatch between water and cryoprotectant transport. Aldehyde fixation followed by unprotected slow freezing confined ice damage primarily to perivascular zones, while fast freezing led to intranuclear clefts and cavities. Among non-fixation protocols, interleaved equilibration with vitrification solution preserved myelinated axon profiles and chromatin patterns, but induced perivascular edema. High concentration glycerol perfusion caused significant osmotic dehydration. Straight freezing of unfixed tissue without cryoprotectant was followed by membrane disruption, but resulted in the visualization of more structure than expected, likely as a result of structural restitution upon thawing. Taken together, our results provide a framework for matching preservation strategies to the needs of different types of brain banking and neuroscience research.

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.

Growing evidence supports neuroinflammation as a risk factor for neurodevelopmental and psychiatric disorders. Interleukin 6 (IL-6), a classical pro-inflammatory cytokine, has been associated with autism spectrum disorder (ASD)-related phenotypes. To better understand molecular factors that modify neuronal cytokine responses in ASD, we investigated potential roles for JAKMIP1, a gene linked to chromosome 15q-duplication syndrome (Dup15q; a form of syndromic ASD), in regulating IL-6/STAT3 signaling. We observe that JAKMIP1 deficiency impairs IL-6/STAT3 signaling and IL-6-induced neuritogenesis in SH-SY5Y cells; and discover that JAKMIP1 may regulate STAT3 expression via its C-terminus, which exhibits nucleoplasmic localization. Additionally, we find that IL-6/STAT3 signaling is altered in Dup15q hiPSCs-derived cortical neurons, which display heightened responsiveness to IL-6; though it is unclear whether and how JAKMIP1 contributes to this. Overall, our findings identify JAKMIP1 as a modulator of neuronal IL-6/STAT3 signaling and support that ASD-linked genetic variants can alter the inflammatory landscape of ASD.

Metabotropic glutamate receptors (mGluR) are G-protein coupled receptors that regulate neuroplasticity and have been shown to play a role in auditory processing. However, not much is known about the expression of mGluRs during cochlear nucleus development in the context of Fragile X syndrome (FXS). FXS is the most common heritable form of intellectual disability and autism and is associated with auditory processing deficits including hypersensitivity. Audiogenic seizure is a notable feature of the Fmr1 knock-out (KO) mouse model for FXS, in which mGluR5 has been shown to be necessary. In this study, we investigated the expression of eight metabotropic glutamate receptors (mGluRs) in the cochlear nucleus at both young and adult ages and in wildtype and Fmr1 KO mice. While it is established that mGluR1 is the predominantly expressed mGluR in adult cochlear nucleus, we report the following new finding that mGluR5 is the more abundant receptor during early development. The expression of Group II and III mGluRs (2,3,4,6,7,8) was relatively stable during development. We show that mGluR1 and mGluR5 are co-expressed across multiple neuron types. Fmr1 genotype did not have statistically significant impact on the expression pattern of mGluRs in cochlear nucleus. Although hearing onset occurs during this mGluR5 to 1 transition period, mGluR expression patterns were not impacted by cochlear activity. We conclude that there is an mGluR5 is to mGluR1 transition that occurs within cochlear nucleus neurons during the critical period closure that is intrinsic to neuronal development.

Neural organoids represent a promising approach for modelling neural circuits and neurological disease, yet their utility depends on whether they can recapitulate the molecular complexity of mature brain synapses. Here, we optimized a protocol to generate mature forebrain organoids from mouse embryonic stem cells and used time-resolved proteomics to define the emergence of synaptic proteins during maturation. Using fluorescence-activated synaptosome sorting coupled with mass spectrometry, we quantified the synapse-enriched proteome and found a high correlation with matched in vivo synaptic proteomes. These findings demonstrate that complex mature synaptic molecular architecture is present within an in vitro organoid environment.

TBR1 haploinsufficiency causes a neurodevelopmental disorder associated with intellectual disability and autistic features, but the therapeutic potential of postnatal gene replacement remains incompletely defined. Here, we evaluated adeno associated virus (AAV) mediated human TBR1 replacement in Tbr1 haploinsufficient mice. A single retroorbital injection of AAV.PHP.eB expressing human TBR1 under the human synapsin promoter was administered at postnatal day 3 at a dose of 2 E11 vector genomes. Compared with control vector treated mutants, treated mice exhibited increased TBR1 protein abundance and TBR1, CTIP2, and parvalbumin positive cell counts in selected brain regions. Treatment improved sociability, social transmission of food preference, and buried food seeking. Electroencephalographic (EEG) recordings showed attenuation of elevated relative theta power and improved theta suppression and gamma enhancement during social interaction. However, anterior commissure abnormalities persisted, correction of other EEG abnormalities was incomplete, and sleep wake proportions showed no significant treatment improvement. These findings demonstrate that neonatal TBR1 replacement improves selected behavioral and electrophysiological outcomes despite persistent anatomical abnormalities. These findings support further development of gene replacement for TBR1 haploinsufficiency and highlight EEG measures as candidate biomarkers for monitoring treatment response.

Hearing loss and deafness as a result of hair cell loss cannot be restored due to the incapacity of spontaneous regeneration of these cells. Compounds that manipulate key signaling pathways can potentially regenerate cochlear hair cells. In order to test different compounds that promote hair cell regeneration in vitro models can be used. Three-dimensional cultures have allowed the expansion and experimentation of human and mouse inner ear organoids. This is mainly performed in the embryonic or the early postnatal developmental stage. However, since the majority of patients with hearing loss are adult, it is crucial to understand the adult inner ear regenerative capacity. Here, we evaluated progenitor cell markers in the adult human and mouse inner ear and the generation, expansion and differentiation of cochlear organoids derived from the adult human and mouse inner ear. Cochlear and vestibular sensory epithelium from adult humans; and from adult and aged mice express the progenitor markers SOX2 and LGR5; and can generate organoids in vitro. By optimizing the culture conditions, organoids derived from the cochlea and vestibular organ from adult human and adult and aged mouse differentiated to Myosin 7A positive cells. This indicates that the adult inner ear has regenerative capacity. These findings are encouraging for future regenerative therapies to cure hair cell-related hearing loss and deafness.

Suspension mass cytometry can measure 50 or more markers per cell and is not impacted by cellular autofluorescence, making it an appealing platform for comprehensive phenotyping of single cells in tissue with high innate fluorescence, such as brain. However, this organ is challenging to reduce to a single cell suspension: it is a deeply interconnected tissue rich in extracellular material and contains a wide variety of cell types including neurons, their supporting glia, and hematopoietic cells from peripheral circulation, any or all of which may have competing requirements for survival through the dissociation process. This study compares approaches for producing single-cell preparations from white and gray matter enriched regions of adult mouse brain, testing simple mechanical dissociation, Accutase, and three gentle enzymes plus DNase: papain, collagenase II, and collagenase plus dispase, all with or without Percoll gradient centrifugation to separate intact cells from debris. Live cells were counted by hemocytometer and Trypan blue exclusion to assess yield and compare across enzyme conditions. Mass cytometry was used to assess cellular composition after representative dissociation, debris removal, and viable cryopreservation. Key proteins measured included beta III-tubulin for neurons, glial fibrillary acidic protein (GFAP) for astrocytes, oligodendrocyte transcription factor (OLIG2) for oligodendrocytes, CD31 for endothelial cells, CD24 for ependymal cells, purinergic receptor P2Y12 (P2RY12) for microglia, and CD45 for leukocytes. Mechanical disaggregation paired with enzymatic dissociation by papain, Collagenase/Disapse, or Collagenase II plus DNase produced approximately 400,000 live cells per 100 grams of tissue. Cell yield was not significantly different between conditions and yields were similar between white and grey matter. Addition of Percoll gradient centrifugation substantially reduced the number of viable cells recovered (average decrease of 88%) and resulted in viable cell numbers that were insufficient for robust analysis of less common cell subsets. In addition to neurons, mass cytometry identified six major populations of non-neuronal cells: oligodendrocytes, astrocytes, endothelial cells, ependymal cells, microglia, and leukocytes. The relative abundance of these six populations was generally unchanged by cryopreservation in both grey matter (r = 0.95), and white matter (r = 0.90), though loss of oligodendrocytes did occur in both tissues. Proliferation, as measured by Ki67 positivity, was non-existent; consistent with this, levels of phosphorylated STAT1 (p-STAT1) and p-STAT3 proteins were low in all cell populations and unchanged by cryopreservation. A modest increase in p-S6(S235/236) after cryopreservation was consistently observed only in microglia. Together, these results establish standardized procedures for generating viable single cell suspensions for cytometry that preserve the cellular diversity of the adult murine brain with minimal perturbation of intracellular signaling cascades.

Microglial morphology is widely used as an indicator of cellular state, yet existing analytical approaches are often labor-intensive, require proprietary software, or depend on high-resolution imaging platforms. Here, SkeleSketch is presented as an open-source Fiji/ImageJ plugin that automates microglial skeletonization, morphological quantification, and data organization while allowing optional user-guided correction. Using spinal cord microglia from PBS- and LPS-treated mice, SkeleSketch accurately reconstructed cellular morphology and captured expected LPS-induced morphological remodeling, including enlarged soma size and reduced branching complexity. Comparable measurements were obtained from both CX3CR1-GFP reporter mice and Iba1 immunostaining, demonstrating robustness across labeling strategies. Additionally, SkeleSketch morphometrics were positively correlated with those generated by the commercial software Imaris. Our pipeline provides an accessible, reproducible, and flexible platform for quantitative microglial morphology analysis using standard epifluorescence microscopy.

Genetic regulation of neurodevelopmental disorders that impair brain development and social interaction is complex and poorly understood. Although emerging evidence suggests a link between neurodevelopmental disorders and autophagy deficits, congenital autophagy gene disorders are rare in humans, and underlying molecular mechanisms remain unknown. Here we demonstrate that the autophagy protein BECN1 is a regulator of neuronal and social development in vertebrate species. We identify rare deleterious biallelic BECN1 variants that cause neurodevelopmental disorders in two unrelated families. Becn1 disruption also causes neuronal and social developmental defects in mouse and zebrafish models. BECN1 serves as an adaptor to recruit Arc to the E3 ubiquitin ligase UBE3A for polyubiquitination and degradation, thereby maintaining postsynaptic AMPA receptor (AMPAR) stability, AMPAR-mediated excitatory neurotransmission, and normal social interaction. Thus, our study illustrates new biology and a non-canonical mechanism by which BECN1 regulates neurodevelopment in humans, mice and zebrafish, via a crosstalk with the ubiquitin-proteasomal machinery.

Peripheral neurons exhibit robust regeneration after nerve injury in adulthood; a process linked to the activation of regeneration-associated genes (RAGs). However, the mechanisms underlying nerve regeneration during early postnatal development remain poorly understood. In a previous work, we observed that motoneurons axotomized at early postnatal stages regenerate without overexpressing RAGs, contrasting with the expected RAG activation observed in postnatal day 30 (P30) mice. To determine whether this phenomenon extends to sensory neurones, we investigated two paradigmatic dorsal root ganglia populations: proprioceptive (PV) and nociceptive (TrpV1) neurones, which exhibit distinct regenerative capacities in adult mice. Following sciatic nerve crush injury at P4, P10, and P30, both neuronal subtypes demonstrated robust axonal regeneration across all postnatal stages, with nociceptors exhibiting significantly superior regeneration compared to proprioceptors. Remarkably, no substantial neuronal death was observed at any developmental timepoint. However, RNA sequencing revealed that P4 and P10 sensory neurones failed to upregulate RAGs following injury, whereas P30 neurones exhibited the expected pro-regenerative transcriptional programme. Pathway enrichment analysis confirmed that classical regeneration-associated signalling pathways were activated exclusively in young adults, whilst developmental and inflammatory pathways predominated in early postnatal stages. Using the conditioning lesion paradigm in primary dorsal root ganglia cultures, we demonstrated that only P30 neurones exhibited enhanced neurite outgrowth following conditioning lesion, whilst P4 and P10 neurones showed no conditioning effect or reduced outgrowth, respectively. These findings indicate that early postnatal sensory neurones possess intrinsic growth capacity independent of RAG activation, suggesting fundamentally distinct regenerative mechanisms across developmental stages.

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.

Pathogenic variants in ATP1A3, encoding the neuronal Na/K-ATPase, are associated with a spectrum of neuro-developmental disorders including alternating hemiplegia of childhood (AHC). ATP1A3 is expressed throughout the cortex during early development, and later becomes enriched in GABAergic neurons. Here, we interrogated the underlying mechanisms and neurophysiological consequences of a recurrent AHC-associated variant (ATP1A3-G947R) in human induced pluripotent stem cell (hiPSC) derived glutamatergic and GABAergic neu-rons. We found that glutamatergic and GABAergic AHC neurons exhibited smaller ouabain-sensitive pump cur-rents compared to isogenic mutation-corrected control neurons. This impairment of pump function correlated with a depolarized potassium reversal potential, lower intracellular potassium concentration, and depolarized resting membrane potential for both cell types compared to isogenic control neurons. Additionally, using a Na+ sensitive dye, we observed that AHC neurons had a higher basal intracellular Na+ concentration that recovered more slowly following Na+ loading compared to isogenic control neurons. As an additional consequence of impaired pump function and abnormal Na+ dynamics, glutamatergic and GABAergic AHC neurons were more prone to depolarization block. Finally, the time course by which GABA neurotransmission switches from excita-tory to inhibitory was delayed in glutamatergic AHC neurons compared to isogenic controls. Our findings pro-vide evidence that impairment of ATP1A3 function has direct effects on ionic homeostasis, leading to cascading effects on intrinsic neuronal firing and maturation of GABAergic neurotransmission that advance understanding of the pathophysiology of AHC.

Heterogeneous nuclear ribonucleoprotein H2 (hnRNP H2) is a member of the hnRNP family of RNA-binding proteins that regulate neuronal function through multiple aspects of RNA metabolism. Mutations in the nuclear localisation signal (NLS) and quasi-RNA recognition motifs (qRRMs) of hnRNP H2 have recently been linked to a severe developmental syndrome, termed HNRNPH2-related neurodevelopmental disorder. Despite its emerging importance, the physiological roles of hnRNP H2 in neuronal development and synaptic maturation, and how disease-associated variants alter these processes to drive pathology, remain poorly understood. Here, we show that hnRNP H2 is expressed in hippocampal neurons and localises to the synaptic compartment. Knockdown of hnRNP H2 revealed essential roles of the protein in the regulation of neuronal morphology, dendritic spine maturation, synaptic transmission, and cortical neuronal migration in vivo. Disease-associated hnRNP H2 variants altered protein localisation and activity-dependent synaptic recruitment, resulting in defects in neuronal morphology, in vivo cortical neuronal migration and laminar orientation, dendritic spine maturation, and synaptic function. Together, these findings establish hnRNP H2 as a critical regulator of neurodevelopment and identify a molecular basis for HNRNPH2-related neurodevelopmental disorder.

Tau is a microtubule-associated protein important for neuronal structure and function, with abnormal phosphorylation associated with neuronal dysfunction and degeneration. While tau pathology has been extensively studied in neurodegenerative diseases and traumatic brain injury, its role in spinal cord injury (SCI) remains unclear. This study investigates changes in the levels of tau isoforms and phosphorylation following a high lateral C2 hemisection (C2Hx) in adult female rats. Western blot analysis was performed on spinal cord tissue collected caudal to the lesion at 4 weeks post-injury. Low-molecular-weight (LMW) tau and high-molecular-weight, Big tau did not differ significantly between injured and control groups. In contrast, phosphorylated tau (p-tau), detected using the AT8 antibody, was significantly elevated after injury, suggesting a shift in tau functional state. Assessment of microtubule stability markers revealed increased acetylated tubulin and decreased tyrosinated tubulin after SCI, indicating a shift toward a more stable cytoskeletal state. Immunohistochemistry was performed on spinal cord sections at 6 weeks post-injury and dorsal root ganglia (DRG) at 8 weeks post-injury. These analyses demonstrated increased p-tau immunoreactivity within the ipsilateral dorsal horn of the injured spinal cord and a higher proportion of p-tau-positive neurons in DRGs from injured animals compared with controls. Together, these findings demonstrate that cervical SCI induces persistent tau phosphorylation without altering total tau levels, and that this modification extends beyond the lesion site into distal spinal regions and beyond the acute phase of injury. These alterations may influence neural plasticity and remodeling in the injured spinal cord.

The cerebellum plays an emerging, but understudied, role in neurodevelopmental disorders (NDDs). Mutations in CHD8 cause a monogenic NDD (CHD8-NDD) characterized by autism and other manifestations, and prior work in Chd8 mutant mice reported cerebellar abnormalities, raising the possibility of cerebellar contribution to CHD8-NDD. To comprehensively characterize the impact of Chd8 haploinsufficiency on cerebellar development and function, we profiled the postnatal day 12 (P12) cerebellum of germline Chd8+/- mice using transcriptomic, morphological, and electrophysiological approaches. Gross cerebellar morphology was unaffected, but single-nucleus RNA sequencing revealed transcriptomic signatures of pathophysiology across cell types, including accelerated maturation of molecular layer interneurons and granule cells, and altered myelination state of oligodendrocytes. Purkinje cells (PCs) showed the strongest transcriptomic burden of any cell type and, consistent with this, exhibited altered morphology and electrophysiological properties. Bulk RNA sequencing confirmed that transcriptomic pathology persists into adulthood, indicating lasting impacts on both neuronal and glial gene expression. Together, these results capture cell-type-specific cerebellar perturbations associated with Chd8 haploinsufficiency and support the cerebellum as a relevant site of pathology in CHD8-NDD.