The meninges act as a regulator of brain development by secreting ligands that act on neural cells to regulate neurogenesis and neuronal migration. Meningeal-derived retinoic acid (RA) promotes neocortical neural progenitor cell cycle exit; however, the underlying molecular mechanism is unknown. Here, we used spatial transcriptomics and profiling of retinoic acid receptor α (RARα) DNA binding in Foxc1-mutant embryos that lack meninges-derived signals to identify potential neurogenic transcriptional mechanisms of RA signaling in telencephalic neural progenitors. This identified upregulation of Sox2 and Notch pathway genes, and RARα binds to the Sox2ot promoter, a long noncoding RNA that regulates Sox2 expression. Our experiments using maternal RA treatment and in utero electroporation in Foxc1 mutants support that meningeal-derived RA promotes neurogenesis by suppressing Notch signaling, a progenitor self-renewal pathway. Our findings elucidate a previously unknown mechanism of how meningeal RA coordinates neocortical development and provide insight into how defects in meningeal development may cause neurodevelopmental disorders.

2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) belongs to the category of persistent environmental pollutants, and gestational exposure to TCDD can lead to cognitive, memory, and motor deficits, as well as altered neuron development in rodents. However, the molecular mechanisms underlying TCDD's neurotoxicity remain unclear. Neural stem cells (NSCs) possess the capacity for self-renewal and can generate various cell types within the brain, playing fundamental roles in brain development and regeneration. This study investigated the impact of TCDD on the proliferation of mouse NSCs, specifically focusing on the C17.2 cell line. The results demonstrated that TCDD inhibited the proliferation of C17.2 cells in a dose-dependent manner. Even low doses of TCDD (5 nM) significantly reduced C17.2 cell proliferation. Regarding the molecular mechanisms, it was found that TCDD induced the degradation of β-catenin, a key regulator of cell proliferation, through the upregulation of the E3 ubiquitin ligase, casitas B-lineage lymphoma (c-Cbl), which was dependent on the aryl-hydrocarbon Receptor (AhR). Furthermore, knockdown of c-Cbl alleviated the TCDD-induced inhibition of C17.2 proliferation and of the reduction of β-catenin expression. Our research provides foundational data to understand the mechanism of TCDD-induced neurotoxicity through the inhibition of NSCs proliferation, and suggests that the c-cbl/β-catenin pathway may serve as a potential therapeutic target for countering the neurotoxicants of TCDD.

Macroautophagy/autophagy dysregulation is associated with various neurological diseases, including Vici syndrome. We aimed to determine the role of autophagy in early brain development. We generated neurons from human embryonic stem cells and developed a Vici syndrome model by introducing a loss-of-function mutation in the EPG5 gene. Autophagy-related genes were upregulated at the neuronal progenitor cell stage. Inhibition of autolysosome formation with bafilomycin A1 treatment at the neuronal progenitor cell stage delayed neuronal differentiation. Notably, WNT (Wnt family member) signaling may be part of the underlying mechanism, which is negatively regulated by autophagy-mediated DVL2 (disheveled segment polarity protein 2) degradation. Disruption of autolysosome formation may lead to failure in the downregulation of WNT signaling, delaying neuronal differentiation. EPG5 mutations disturbed autolysosome formation, subsequently inducing defects in progenitor cell differentiation and cortical layer generation in organoids. Disrupted autophagy leads to smaller organoids, recapitulating Vici syndrome-associated microcephaly, and validating the disease relevance of our study.Abbreviations: BafA1: bafilomycin A1; co-IP: co-immunoprecipitation; DVL2: dishevelled segment polarity protein 2; EPG5: ectopic P-granules 5 autophagy tethering factor; gRNA, guide RNA; hESC: human embryonic stem cells; KO: knockout; mDA, midbrain dopamine; NIM: neural induction media; NPC: neuronal progenitor cell; qPCR: quantitative polymerase chain reaction; UPS: ubiquitin-proteasome system; WNT: Wnt family member; WT: wild type.

Attention-Deficit/Hyperactivity Disorder (ADHD) has been linked to altered neurodevelopmental processes, including proliferation and differentiation of neural stem cells (NSC). We aimed to investigate the role of Wnt signaling, a pathway critical for brain development, in ADHD and to determine if modulation of this pathway using ω-3/6 polyunsaturated fatty acids (PUFAs) may provide a beneficial treatment approach. Given the symptom heterogeneity in ADHD and the limited response to conventional therapies for some patients, we examined the effects of ω-3/6 PUFA treatment combined with Methylphenidate (MPH) on neurodevelopmental mechanisms using induced pluripotent stem cell (iPSC)-derived NSCs, comparing controls to ADHD patients. Our results show that ω-3/6 PUFAs differentially regulate Wnt activity in NSCs depending on the patient's condition and the composition of the treatments. These findings highlight the potential of ω-3 PUFA treatment as personalized support for neurodevelopmental processes in ADHD. They also emphasize the importance of investigating ADHD subgroups, including those unresponsive to stimulant treatments, as they may exhibit distinct phenotypes.

Genetic variation can modulate response to treatment (G×T) or environmental stimuli (G×E), both of which can be highly consequential in biomedicine. An effective approach to identifying G×T signals and gaining insight into molecular mechanisms is mapping quantitative trait loci (QTL) of molecular count phenotypes, such as gene expression and chromatin accessibility, under multiple treatment conditions, which is termed response molecular QTL mapping. Although standard approaches evaluate the interaction between genetics and treatment conditions, they do not distinguish between meaningful interpretations such as whether a genetic effect is observed only in the treated condition or whether a genetic effect is observed always but accentuated in the treated condition. To address this gap, we have developed a downstream method for classifying response molecular QTLs into subclasses with meaningful genetic interpretations. Our method uses Bayesian model selection and assigns posterior probabilities to different types of G×T interactions for a given feature-SNP pair. We compare linear and nonlinear regression of log ⁡ -scale counts, noting that the latter accounts for an expected biological relationship between the genotype and the molecular count phenotype. Through simulation and application to existing datasets of molecular response QTLs, we show that our method provides an intuitive and well-powered framework to report and interpret G×T interactions. We provide a software package, ClassifyGxT [1].

Haploinsufficiency of CHD7 (Chromo-Helicase-DNA binding protein 7) causes a severe congenital disease CHARGE syndrome. Brain anomaly such as microcephaly and olfactory bulb agenesis seen in CHARGE patients have not been mimicked in previous animal models. Here, we uncover an indispensable function of CHD7 in the neuroepithelium (NE) but not in the neural stem cells (NSCs) after NE transition. Loss of Chd7 in mouse NE resulted in CHARGE-like brain anomalies due to reduced proliferation and differentiation of neural stem and progenitor cells, which were recapitulated in CHD7 KO human forebrain organoids. Mechanistically, we find that CHD7 activates neural transcription factors by removing the repressive histone mark H3K27me3 and promoting chromatin accessibility. Importantly, neurodevelopmental defects caused by CHD7 loss in human brain organoids and mice were ameliorated by the inhibition of H3K27me3 methyltransferase EZH2. Altogether, by implementing appropriate experimental models, we uncover the pathogenesis of CHD7-associated neurodevelopmental diseases, and identify a potential therapeutic opportunity for CHARGE syndrome.

A major challenge in human evolutionary biology is to pinpoint genetic differences that underlie human-specific traits, such as increased neuron number and differences in cognitive behaviors. We used human-chimpanzee tetraploid cells to distinguish gene expression changes due to cis -acting sequence variants that change local gene regulation, from trans expression changes due to species differences in the cellular environment. In neural progenitor cells, examination of both cis and trans changes - combined with CRISPR inhibition and transcription factor motif analyses - identified cis -acting, species-specific gene regulatory changes, including to TNIK, FOSL2 , and MAZ , with widespread trans effects on neurogenesis-related gene programs. In excitatory neurons, we identified POU3F2 as a key cis -regulated gene with trans effects on synaptic gene expression and neuronal firing. This study identifies cis -acting genomic changes that cause cascading trans gene regulatory effects to contribute to human neural specializations, and provides a general framework for discovering genetic differences underlying human traits.

The alteration of neural progenitor cell (NPC) proliferation underlies autism spectrum disorders (ASD). It remains unclear whether targeting convergent downstream targets among mutations from different genes and individuals can rescue this alteration. We identified PBX1 as a convergent target of three autism risk genes: CTNNB1, PTEN, and DVL3, using isogenic iPSC-derived 2D NPCs. Overexpression of the PBX1a isoform effectively rescued increased NPC proliferation in all three isogenic ASD-related variants. Dysregulation of PBX1 in NPCs was further confirmed in publicly available datasets from other models of ASD. These findings spotlight PBX1, known to play important roles during olfactory bulb/adult neurogenesis and in multiple cancers, as an unexpected and key downstream target, influencing NPC proliferation in ASD and neurodevelopmental syndromes.

Human's robust cognitive abilities, including creativity and language, are made possible, at least in large part, by evolutionary changes made to the cerebral cortex. This paper reviews the biology and evolution of mammalian cortical radial glial cells (primary neural stem cells) and introduces the concept that a genetically step wise process, based on a core molecular pathway already in use, is the evolutionary process that has molded cortical neurogenesis. The core mechanism, which has been identified in our recent studies, is the extracellular signal-regulated kinase (ERK)-bone morphogenic protein 7 (BMP7)-GLI3 repressor form (GLI3R)-sonic hedgehog (SHH) positive feedback loop. Additionally, I propose that the molecular basis for cortical evolutionary dwarfism, exemplified by the lissencephalic mouse which originated from a larger gyrencephalic ancestor, is an increase in SHH signaling in radial glia, that antagonizes ERK-BMP7 signaling. Finally, I propose that: (1) SHH signaling is not a key regulator of primate cortical expansion and folding; (2) human cortical radial glial cells do not generate neocortical interneurons; (3) human-specific genes may not be essential for most cortical expansion. I hope this review assists colleagues in the field, guiding research to address gaps in our understanding of cortical development and evolution.

Genetic association studies have identified hundreds of largely non-coding loci associated with inter-individual differences in the structure of the human cortex, though the specific genetic variants that impact regulatory activity are unknown. We implemented a Massively Parallel Reporter Assay (MPRA) to measure the regulatory activity of 9,092 cortical structure associated DNA variants in human neural progenitor cells during Wnt stimulation and at baseline. We identified 918 variants with regulatory potential from 150 cortical structure associated loci (76% of loci studied), of which >50% showed allelic effects. Wnt stimulation modified regulatory activity at a subset of loci that functioned as condition-dependent enhancers. Regulatory activity in MPRA was largely induced by Alu elements that were hypothesized to contribute to cortical expansion. The regionally specific impact of genetic variants that disrupt motifs is likely mediated through the levels of transcription factor expression during development, further clarifying the molecular mechanisms altering cortical structure.

Human induced pluripotent stem cell (iPSC) derived cortical organoids (hCOs) model neurogenesis on an individual's genetic background. The degree to which hCO phenotypes recapitulate the brain growth of the participants from which they were derived is not well established. We generated up to 3 iPSC clones from each of 18 participants in the Infant Brain Imaging Study, who have undergone longitudinal brain imaging during infancy. We identified consistent hCO morphology and cortical cell types across clones from the same participant. hCO cross-sectional area and production of cortical hem cells were associated with in vivo cortical growth rates. Cell cycle associated genes expression in early progenitors at the crux of fate decision trajectories were correlated with cortical growth rate from 6-12 months of age, and were enriched in microcephaly and neurodevelopmental disorder genes. Our data suggest the hCOs capture inter-individual variation in cortical cell types influencing infant cortical surface area expansion.

Autistic individuals with disproportionate megalencephaly (ASD-DM), characterized by enlarged brains relative to body height, have higher rates of intellectual disability and face more severe cognitive challenges than autistic children with average brain sizes. The cellular and molecular mechanisms underlying this neurophenotype remain poorly understood. To investigate these mechanisms, we generated human induced pluripotent stem cells from non-autistic typically developing children and autistic children with and without disproportionate megalencephaly. We assessed these children longitudinally from ages two to twelve years using magnetic resonance imaging and comprehensive cognitive and medical evaluations. We show that neural progenitor cells (NPCs) derived from ASD-DM children exhibit increased rates of cell survival and suppressed cell death, accompanied by heightened oxidative stress and ferrous iron accumulation. Despite these stressors, ASD-DM NPCs actively suppress apoptosis and ferroptosis by regulating proteins such as caspase-3 (CASP3), poly(ADP-ribose) polymerase 1 (PARP1), and glutathione peroxidase 4 (GPX4). Cellular ferroptotic signatures are further supported by elevated expression of selenocysteine genes, including GPX4 , in the blood of ASD-DM children and their mothers, suggesting potential hereditary or environmental influences. Furthermore, we show that peripheral expression of GPX4 and other selenocysteine genes correlate with cognitive outcomes (IQ). These findings underscore the role of ferroptosis in autism, pointing to potential diagnostic biomarkers and targets for intervention.

CTNNB1 syndrome is a rare neurodevelopmental disorder, affecting children worldwide with a prevalence of 2.6-3.2 per 100,000 births and often misdiagnosed as cerebral palsy. De novo loss-of-function mutations in the Ctnnb1 gene result in dysfunction of the β-catenin protein, disrupting the canonical Wnt signaling pathway, which plays a key role in cell proliferation, differentiation, and tissue homeostasis. Additionally, these mutations impair the formation of cell junctions, adversely affecting tissue architecture. Motor and speech deficits, cognitive impairment, cardiovascular and visual problems are just some of the key symptoms that occur in CTNNB1 syndrome patients. There is currently no effective treatment option available for patients with CTNNB1 syndrome, with support largely focused on the management of symptoms and physiotherapy, yet recently some therapeutic approaches are being developed. Animal testing is still crucial in the process of new drug development, and mouse models are particularly important. These models provide researchers with new understanding of the disease mechanisms and are invaluable for testing the efficacy and safety of potential treatments. The development of various mouse models with β-catenin loss- and gain-of-function mutations successfully replicates key features of intellectual disability, autism-like behaviors, motor deficits, and more. These models provide a valuable platform for studying disease mechanisms and offer a powerful tool for testing the therapeutic potential and effectiveness of new drug candidates, paving the way for future clinical trials.

Promoting neural repair after cerebral ischemia (CI) is one of the important intervention strategies. Buyang Huanwu Decoction (BHD) is a traditional Chinese medicine prescription commonly used for the treatment of CI.Previous studies by the research group have shown that BHD can promote neural regeneration after CI. The core cause of motor, sensory, and autonomic dysfunction caused by CI injury is neuronal death. Promoting endogenous neural regeneration is of great significance for neural repair after CI. In this context, the Wnt pathway promotes endogenous neural regeneration worthy of attention.

This study aims to elucidate the mechanism by which BHD promotes neural regeneration after CI, focusing on how it mediates caveolin-1 (Cav1) to regulate the Wnt signaling pathway.

Using the middle cerebral artery occlusion (MCAO) technique, a CI model was created. To establish the neuroprotective properties of BHD and determine the ideal therapeutic dosage for CI, neurobehavioral scores and pathological alterations were found across several groups of mice after varying doses of BHD were administered. Furthermore, Cav1 knockout (Cav1-/-) mice were used to confirm Cav1's function in BHD-mediated neuronal regeneration following CI.

In CI models, BHD was shown to enhance neural regeneration. In vivo research indicate that its mechanism of action is through Cav1 stimulation of the Wnt signaling pathway, which causes related brain-derived trophic factors to be upregulated.

This study confirmed, using knockout mice, that BHD promotes nerve regeneration following CI. The results indicate that Cav1 control of the Wnt signaling pathway is likely the mechanism by which this impact is mediated, so offering insights into the possible mechanism of action of BHD and reaffirming Cav1's function in brain regeneration following CI.

The rate of discovery and increased understanding of genetic causes for neurodevelopmental disorders has peaked over the past decade. It is well recognised that some genes show marked variability in neuroradiological phenotypes, and inversely, some radiological phenotypes are associated with several different genetic conditions. However, some readily recognisable brain magnetic resonance imaging (MRI) patterns, especially in the context of corresponding associated clinical findings, should prompt consideration of a pathogenic variant in a specific gene or gene pathway. As these conditions can often prove challenging to diagnose, a clinical suspicion of a specific disorder may be invaluable to guide and interpret genetic testing. This review focuses on five neurogenetic syndromes with recognisable brain findings that radiologists, paediatric neurologists, geneticists, and other specialists involved in neurodevelopmental disorders should be able to recognise in order to pinpoint the gene or gene groups involved and delve into their molecular mechanisms. The comprehensively reviewed conditions include DDX3X-related neurodevelopmental disorder, Van Maldergem syndrome, NMDAR-related disorders, EML1-associated disorder and ARFGEF2-related periventricular nodular heterotopia with microcephaly.

Dopamine receptor antagonists have recently been identified as potential anti-cancer agents in combination with radiation, and a first drug of this class is in clinical trials against pediatric glioma. Radiotherapy causes cognitive impairment primarily by eliminating neural stem/progenitor cells and subsequent loss of neurogenesis, along with inducing inflammation, vascular damage, and synaptic alterations. Here, we tested the combined effects of dopamine receptor antagonists and radiation on neural stem/progenitor cells.

Using transgenic mice that report the presence of neural stem/progenitor cells through Nestin promoter-driven expression of EGFP, the effects of dopamine receptor antagonists alone or in combination with radiation on neural stem/progenitor cells were assessed in sphere-formation assays, extreme limiting dilution assays, flow cytometry and real-time PCR in vitro and in vivo in both sexes.

We report that hydroxyzine and trifluoperazine exhibited sex-dependent effects on murine newborn neural stem/progenitor cells in vitro. In contrast, amisulpride, nemonapride, and quetiapine, when combined with radiation, significantly increased the number of neural stem/progenitor cells in both sexes. In vivo, trifluoperazine showed sex-dependent effects on adult neural stem/progenitor cells, while amisulpride demonstrated significant effects in both sexes. Further, amisulpride increased sphere forming capacity and stem cell frequency in both sexes when compared to controls.

We conclude that a therapeutic window for dopamine receptor antagonists in combination with radiation potentially exists, making it a novel combination therapy against glioblastoma. Normal tissue toxicity following this treatment scheme likely differs depending on age and sex and should be taken into consideration when designing clinical trials.

Gene regulatory effects have been difficult to detect at many non-coding loci associated with brain-related traits, likely because some genetic variants have distinct functions in specific contexts. To explore context-dependent gene regulation, we measured chromatin accessibility and gene expression after activation of the canonical Wnt pathway in primary human neural progenitors (n = 82 donors). We found that TCF/LEF motifs and brain-structure-associated and neuropsychiatric-disorder-associated variants were enriched within Wnt-responsive regulatory elements. Genetically influenced regulatory elements were enriched in genomic regions under positive selection along the human lineage. Wnt pathway stimulation increased detection of genetically influenced regulatory elements/genes by 66%/53% and enabled identification of 397 regulatory elements primed to regulate gene expression. Stimulation also increased identification of shared genetic effects on molecular and complex brain traits by up to 70%, suggesting that genetic variant function during neurodevelopmental patterning can lead to differences in adult brain and behavioral traits.

The cerebral cortex develops through a carefully conscripted series of cellular and molecular events that culminate in the production of highly specialized neuronal and glial cells. During development, cortical neurons and glia acquire a precise cellular arrangement and architecture to support higher-order cognitive functioning. Decades of study using rodent models, naturally gyrencephalic animal models, human pathology specimens, and, recently, human cerebral organoids, reveal that rodents recapitulate some but not all the cellular and molecular features of human cortices. Whereas rodent cortices are smooth-surfaced or lissencephalic, larger mammals, including humans and nonhuman primates, have highly folded/gyrencephalic cortices that accommodate an expansion in neuronal mass and increase in surface area. Several genes have evolved to drive cortical gyrification, arising from gene duplications or de novo origins, or by alterations to the structure/function of ancestral genes or their gene regulatory regions. Primary cortical folds arise in stereotypical locations, prefigured by a molecular "blueprint" that is set up by several signaling pathways (e.g., Notch, Fgf, Wnt, PI3K, Shh) and influenced by the extracellular matrix. Mutations that affect neural progenitor cell proliferation and/or neurogenesis, predominantly of upper-layer neurons, perturb cortical gyrification. Below we review the molecular drivers of cortical folding and their roles in disease.

Cerebral palsy (CP) is a clinical term used to describe a spectrum of movement and posture disorders resulting from non-progressive disturbances in the developing fetal brain. The clinical diagnosis of CP does not include pathological or aetiological defining features, therefore both genetic and environmental causal pathways are encompassed under the CP diagnostic umbrella. In this review, we explore several genetic causal pathways, including both monogenic and polygenic risks, and present evidence supporting the multifactorial contributions to CP. Historically, CP has been associated with various risk factors such as pre-term birth, multiple gestation, intrauterine growth restriction (IUGR), maternal infection, and perinatal asphyxia. Thus, we also examine genetic predispositions that may contribute to these risk factors. Understanding the specific aetiology of CP enables more tailored treatments, especially with the increasing potential for early genetic testing.

Human neurogenesis is disproportionately protracted, lasting >10 times longer than in mouse, allowing neural progenitors to undergo more rounds of self-renewing cell divisions and generate larger neuronal populations. In the human spinal cord, expansion of the motor neuron lineage is achieved through a newly evolved progenitor domain called vpMN (ventral motor neuron progenitor) that uniquely extends and expands motor neurogenesis. This behavior of vpMNs is controlled by transcription factor NKX2-2, which in vpMNs is co-expressed with classical motor neuron progenitor (pMN) marker OLIG2. In this study, we sought to determine the molecular basis of NKX2-2-mediated extension and expansion of motor neurogenesis. We found that NKX2-2 represses proneural gene NEUROG2 by two distinct, Notch-independent mechanisms that are respectively apparent in rodent and human spinal progenitors: in rodents (and chick), NKX2-2 represses Olig2 and the motor neuron lineage through its tinman domain, leading to loss of Neurog2 expression. In human vpMNs, however, NKX2-2 represses NEUROG2 but not OLIG2, thereby allowing motor neurogenesis to proceed, albeit in a delayed and protracted manner. Interestingly, we found that ectopic expression of tinman-mutant Nkx2-2 in mouse pMNs phenocopies human vpMNs, repressing Neurog2 but not Olig2, and leading to delayed and protracted motor neurogenesis. Our studies identify a Notch- and tinman-independent mode of Nkx2-2-mediated Neurog2 repression that is observed in human spinal progenitors, but is normally masked in rodents and chicks due to Nkx2-2's tinman-dependent repression of Olig2.

Neurogenesis is tightly regulated in space and time, ensuring the correct development and organization of the central nervous system. Critical regulators of brain development and morphogenesis in mice include two members of the p53 family: p53 and p73. However, dissecting the in vivo functions of these factors and their various isoforms in brain development is challenging due to their pleiotropic effects. Understanding their role, particularly in neurogenesis and brain morphogenesis, requires innovative experimental approaches.

To address these challenges, we developed an efficient and highly reproducible protocol to generate mouse brain organoids from pluripotent stem cells. These organoids contain neural progenitors and neurons that self-organize into rosette-like structures resembling the ventricular zone of the embryonic forebrain. Using this model, we generated organoids from p73-deficient mouse cells to investigate the roles of p73 and its isoforms (TA and DNp73) during brain development.

Organoids derived from p73-deficient cells exhibited increased neuronal apoptosis and reduced neural progenitor proliferation, linked to compensatory activation of p53. This closely mirrors previous in vivo observations, confirming that p73 plays a pivotal role in brain development. Further dissection of p73 isoforms function revealed a dual role of p73 in regulating brain morphogenesis, whereby TAp73 controls transcriptional programs essential for the establishment of the neurogenic niche structure, while DNp73 is responsible for the precise and timely regulation of neural cell fate. These findings highlight the distinct roles of p73 isoforms in maintaining the balance of neural progenitor cell biology, providing a new understanding of how p73 regulates brain morphogenesis.

Tightly controlled neurogenesis is crucial for generating the precise number of neurons and establishing the intricate architecture of the cortex, with deficiencies often leading to neurodevelopmental disorders. Neuroepithelial progenitors (NPs) transit into radial glial progenitors (RGPs) to initiate neural differentiation, yet the governing mechanisms remain elusive. Here, we found that histone deacetylases 1 and 2 (HDAC1/2) mediated suppression of Wnt signaling is essential for the NP-to-RGP transition. Conditional depletion of HDAC1/2 from NPs upregulated Wnt signaling genes, impairing the transition to RGPs and resulting in rosette structures within the neocortex. Multi-omics analysis revealed that HDAC1/2 are critical for downregulating Wnt signaling, identifying Wnt9a as a key target. Overexpression of Wnt9a led to an increased population of NPs and the disruption of cortical organization. Notably, Wnt inhibitor administration partially rescued the disrupted cortical architecture. Our findings reveal the significance of tightly controlled Wnt signaling through epigenetic mechanisms in neocortical development.

Infantile spasms, with an incidence of 1.6 to 4.5 per 10,000 live births, are a relentless and devastating childhood epilepsy marked by severe seizures but also leads to lifelong intellectual disability. Alarmingly, up to 5% of males with this condition carry a mutation in the Aristaless-related homeobox ( ARX ) gene. Our current lack of human-specific models for developmental epilepsy, coupled with discrepancies between animal studies and human data, underscores the gap in knowledge and urgent need for innovative human models, organoids being one of the best available. Here, we used human neural organoid models, cortical organoids (CO) and ganglionic eminences organoids (GEO) which mimic cortical and interneuron development respectively, to study the consequences of PAE mutations, one of the most prevalent mutation in ARX . ARX PAE produces a decrease expression of ARX in GEOs, and an enhancement in interneuron migration. That accelerated migration is cell autonomously driven, and it can be rescued by inhibiting CXCR4. We also found that PAE mutations result in an early increase in radial glia cells and intermediate progenitor cells, followed by a subsequent loss of cortical neurons at later timepoints. Moreover, ARX expression is upregulated in COs derived from patients at 30 DIV and is associated with alterations in the expression of CDKN1C . Furthermore, ARX PAE assembloids had hyperactivity which were evident at early stages of development. With effective treatments for infantile spasms and developmental epilepsies still elusive, delving into the role of ARX PAE mutations in human brain organoids represents a pivotal step toward uncovering groundbreaking therapeutic strategies.

Zinc and RING finger 3 (ZNRF3) is a negative-feedback regulator of Wnt/β-catenin signaling, which plays an important role in human brain development. Although somatically frequently mutated in cancer, germline variants in ZNRF3 have not been established as causative for neurodevelopmental disorders (NDDs). We identified 12 individuals with ZNRF3 variants and various phenotypes via GeneMatcher/Decipher and evaluated genotype-phenotype correlation. We performed structural modeling and representative deleterious and control variants were assessed using in vitro transcriptional reporter assays with and without Wnt-ligand Wnt3a and/or Wnt-potentiator R-spondin (RSPO). Eight individuals harbored de novo missense variants and presented with NDD. We found missense variants associated with macrocephalic NDD to cluster in the RING ligase domain. Structural modeling predicted disruption of the ubiquitin ligase function likely compromising Wnt receptor turnover. Accordingly, the functional assays showed enhanced Wnt/β-catenin signaling for these variants in a dominant negative manner. Contrarily, an individual with microcephalic NDD harbored a missense variant in the RSPO-binding domain predicted to disrupt binding affinity to RSPO and showed attenuated Wnt/β-catenin signaling in the same assays. Additionally, four individuals harbored de novo truncating or de novo or inherited large in-frame deletion variants with non-NDD phenotypes, including heart, adrenal, or nephrotic problems. In contrast to NDD-associated missense variants, the effects on Wnt/β-catenin signaling were comparable between the truncating variant and the empty vector and between benign variants and the wild type. In summary, we provide evidence for mirror brain size phenotypes caused by distinct pathomechanisms in Wnt/β-catenin signaling through protein domain-specific deleterious ZNRF3 germline missense variants.

Despite uncertainty about the specific molecular mechanisms driving major depressive disorder (MDD), the Wnt signaling pathway stands out as a potentially influential factor in the pathogenesis of MDD. Known for its role in intercellular communication, cell proliferation, and fate, Wnt signaling has been implicated in diverse biological phenomena associated with MDD, spanning neurodevelopmental to neurodegenerative processes. In this systematic review, we summarize the functional differences in protein and gene expression of the Wnt signaling pathway, and targeted genetic association studies, to provide an integrated synthesis of available human data examining Wnt signaling in MDD. Thirty-three studies evaluating protein expression (n = 15), gene expression (n = 9), or genetic associations (n = 9) were included. Only fifteen demonstrated a consistently low overall risk of bias in selection, comparability, and exposure. We found conflicting observations of limited and distinct Wnt signaling components across diverse tissue sources. These data do not demonstrate involvement of Wnt signaling dysregulation in MDD. Given the well-established role of Wnt signaling in antidepressant response, we propose that a more targeted and functional assessment of Wnt signaling is needed to understand its role in depression pathophysiology. Future studies should include more components, assess multiple tissues concurrently, and follow a standardized approach.

Neuromyelitis optica (NMO) arises from primary astrocytopathy induced by autoantibodies targeting the astroglial protein aquaporin 4 (AQP4), leading to severe neurological sequelae such as vision loss, motor deficits, and cognitive decline. Mounting evidence has shown that dysregulated activation of complement components contributes to NMO pathogenesis. Complement C3 deficiency has been shown to protect against hippocampal neurodegeneration and cognitive decline in neurodegenerative disorders (e.g., Alzheimer's disease, AD) and autoimmune diseases (e.g., multiple sclerosis, MS). However, whether inhibiting the C3 signaling can ameliorate cognitive dysfunctions in NMO remains unclear. In this study, we found that the levels of C3a, a split product of C3, significantly correlate with cognitive impairment in our patient cohort. In response to the stimulation of AQP4 autoantibodies, astrocytes were activated to secrete complement C3, which inhibited the development of cultured neuronal dendritic arborization. NMO mouse models exhibited reduced adult hippocampal newborn neuronal dendritic and spine development, as well as impaired learning and memory functions, which could be rescued by decreasing C3 levels in astrocytes. Mechanistically, we found that C3a engaged with C3aR to impair neuronal development by dampening β-catenin signalling. Additionally, inhibition of the C3-C3aR-GSK3β/β-catenin cascade restored neuronal development and ameliorated cognitive impairments. Collectively, our results suggest a pivotal role of the activation of the C3-C3aR network in neuronal development and cognition through mediating astrocyte and adult-born neuron communication, which represents a potential therapeutic target for autoimmune-related cognitive impairment diseases.

Individuals with the Autism Susceptibility Candidate 2 (AUTS2) gene disruptions exhibit symptoms such as intellectual disability, microcephaly, growth retardation, and distinct skeletal and facial differences. The role of AUTS2 in neurodevelopment has been investigated using animal and embryonic stem cell models. However, the precise molecular mechanisms of how AUTS2 influences neurodevelopment, particularly in humans, are not thoroughly understood. Our study employed a 3D human cerebral organoid culture system, in combination with genetic, genomic, cellular, and molecular approaches, to investigate how AUTS2 impacts neurodevelopment through cellular signaling pathways. We used CRISPR/Cas9 technology to create AUTS2-deficient human embryonic stem cells and then generated cerebral organoids with these cells. Our transcriptomic analyses revealed that the absence of AUTS2 in cerebral organoids reduces the populations of cells committed to the neuronal lineage, resulting in an overabundance of cells with a transcription profile resembling that of choroid plexus (ChP) cells. Intriguingly, we found that AUTS2 negatively regulates the WNT/β-catenin signaling pathway, evidenced by its overactivation in AUTS2-deficient cerebral organoids and in luciferase reporter cells lacking AUTS2. Importantly, treating the AUTS2-deficient cerebral organoids with a WNT inhibitor reversed the overexpression of ChP genes and increased the downregulated neuronal gene expression. This study offers new insights into the role of AUTS2 in neurodevelopment and suggests potential targeted therapies for neurodevelopmental disorders.

The corpus callosum (CC) is the largest set of white matter fibers connecting the two hemispheres of the brain. In humans, it is essential for coordinating sensorimotor responses, performing associative/executive functions, and representing information in multiple dimensions. Understanding which genetic variants underpin corpus callosum morphometry, and their shared influence on cortical structure and susceptibility to neuropsychiatric disorders, can provide molecular insights into the CC's role in mediating cortical development and its contribution to neuropsychiatric disease. To characterize the morphometry of the midsagittal corpus callosum, we developed a publicly available artificial intelligence based tool to extract, parcellate, and calculate its total and regional area and thickness. Using the UK Biobank (UKB) and the Adolescent Brain Cognitive Development study (ABCD), we extracted measures of midsagittal corpus callosum morphometry and performed a genome-wide association study (GWAS) meta-analysis of European participants (combined N = 46,685). We then examined evidence for generalization to the non-European participants of the UKB and ABCD cohorts (combined N = 7,040). Post-GWAS analyses implicate prenatal intracellular organization and cell growth patterns, and high heritability in regions of open chromatin, suggesting transcriptional activity regulation in early development. Results suggest programmed cell death mediated by the immune system drives the thinning of the posterior body and isthmus. Global and local genetic overlap, along with causal genetic liability, between the corpus callosum, cerebral cortex, and neuropsychiatric disorders such as attention-deficit/hyperactivity and bipolar disorders were identified. These results provide insight into variability of corpus callosum development, its genetic influence on the cerebral cortex, and biological mechanisms related to neuropsychiatric dysfunction.

Spinal cord injury (SCI) denotes damage to both the structure and function of the spinal cord, primarily manifesting as sensory and motor deficits caused by disruptions in neural transmission pathways, potentially culminating in irreversible paralysis. Its pathophysiological processes are complex, with numerous molecules and signaling pathways intricately involved. Notably, the pronounced upregulation of the Wnt signaling pathway post-SCI holds promise for neural regeneration and repair. Activation of the Wnt pathway plays a crucial role in neuronal differentiation, axonal regeneration, local neuroinflammatory responses, and cell apoptosis, highlighting its potential as a therapeutic target for treating SCI. However, excessive activation of the Wnt pathway can also lead to negative effects, highlighting the need for further investigation into its applicability and significance in SCI. This paper provides an overview of the latest research advancements in the Wnt signaling pathway in SCI, summarizing the recent progress in treatment strategies associated with the Wnt pathway and analyzing their advantages and disadvantages. Additionally, we offer insights into the clinical application of the Wnt signaling pathway in SCI, along with prospective avenues for future research direction.

Man's natural inclination to classify and hierarchize the living world has prompted neurophysiologists to explore possible differences in brain organisation between mammals, with the aim of understanding the diversity of their behavioural repertoires. But what really distinguishes the human brain from that of a platypus, an opossum or a rodent? In this review, we compare the structural and electrical properties of neocortical neurons in the main mammalian radiations and examine their impact on the functioning of the networks they form. We discuss variations in overall brain size, number of neurons, length of their dendritic trees and density of spines, acknowledging their increase in humans as in most large-brained species. Our comparative analysis also highlights a remarkable consistency, particularly pronounced in marsupial and placental mammals, in the cell typology, intrinsic and synaptic electrical properties of pyramidal neuron subtypes, and in their organisation into functional circuits. These shared cellular and network characteristics contribute to the emergence of strikingly similar large-scale physiological and pathological brain dynamics across a wide range of species. These findings support the existence of a core set of neural principles and processes conserved throughout mammalian evolution, from which a number of species-specific adaptations appear, likely allowing distinct functional needs to be met in a variety of environmental contexts.

Human cytomegalovirus (HCMV) infection in infants infected in utero can lead to a variety of neurodevelopmental disorders. However, mechanisms underlying altered neurodevelopment in infected infants remain poorly understood. We have previously described a murine model of congenital HCMV infection in which murine CMV (MCMV) spreads hematogenously and establishes a focal infection in all regions of the brain of newborn mice, including the cerebellum. Infection resulted in disruption of cerebellar cortical development characterized by reduced cerebellar size and foliation. This disruption was associated with altered cell cycle progression of the granule cell precursors (GCPs), which are the progenitors that give rise to granule cells (GCs), the most abundant neurons in the cerebellum. In the current study, we have demonstrated that MCMV infection leads to prolonged GCP cell cycle, premature exit from the cell cycle, and reduced numbers of GCs resulting in cerebellar hypoplasia. Treatment with TNF-α neutralizing antibody partially normalized the cell cycle alterations of GCPs and altered cerebellar morphogenesis induced by MCMV infection. Collectively, our results argue that virus-induced inflammation altered the cell cycle of GCPs resulting in a reduced numbers of GCs and cerebellar cortical hypoplasia, thus providing a potential mechanism for altered neurodevelopment in fetuses infected with HCMV.

Approximately 7% of children have developmental language disorder (DLD), a neurodevelopmental condition associated with persistent language learning difficulties without a known cause. Our understanding of the neurobiological basis of DLD is limited. Here, we used FreeSurfer to investigate cortical surface area and thickness in a large cohort of 156 children and adolescents aged 10-16 years with a range of language abilities, including 54 with DLD, 28 with a history of speech-language difficulties who did not meet criteria for DLD, and 74 age-matched controls with typical language development (TD). We also examined cortical asymmetries in DLD using an automated surface-based technique. Relative to the TD group, those with DLD showed smaller surface area bilaterally in the inferior frontal gyrus extending to the anterior insula, in the posterior temporal and ventral occipito-temporal cortex, and in portions of the anterior cingulate and superior frontal cortex. Analysis of the whole cohort using a language proficiency factor revealed that language ability correlated positively with surface area in similar regions. There were no differences in cortical thickness, nor in asymmetry of these cortical metrics between TD and DLD. This study highlights the importance of distinguishing between surface area and cortical thickness in investigating the brain basis of neurodevelopmental disorders and suggests the development of cortical surface area to be of importance to DLD. Future longitudinal studies are required to understand the developmental trajectory of these cortical differences in DLD and how they relate to language maturation.

Microglia are resident macrophages of the central nervous system that selectively emerge in embryonic cortical proliferative zones and regulate neurogenesis by altering molecular and phenotypic states. Despite their important roles in inflammatory phagocytosis and neurodegenerative diseases, microglial homeostasis during early brain development has not been fully elucidated. Here, we demonstrate a notable interplay between microglial homeostasis and neural progenitor cell signal transduction during embryonic neurogenesis. ARID1A, an epigenetic subunit of the SWI/SNF chromatin-remodeling complex, disrupts genome-wide H3K9me3 occupancy in microglia and changes the epigenetic chromatin landscape of regulatory elements that influence the switching of microglial states. Perturbation of microglial homeostasis impairs the release of PRG3, which regulates neural progenitor cell self-renewal and differentiation during embryonic development. Furthermore, the loss of microglia-driven PRG3 alters the downstream cascade of the Wnt/β-catenin signaling pathway through its interaction with the neural progenitor receptor LRP6, which leads to misplaced regulation in neuronal development and causes autism-like behaviors at later stages. Thus, during early fetal brain development, microglia progress toward a more homeostatic competent phenotype, which might render neural progenitor cells respond to environmental cross-talk perturbations.

Foundational mathematical abilities, acquired in early childhood, are essential for success in our technology-driven society. Yet, the neurobiological mechanisms underlying individual differences in children's mathematical abilities and learning outcomes remain largely unexplored. Leveraging one of the largest multicohort datasets from children at a pivotal stage of knowledge acquisition, we first establish a replicable mathematical ability-related imaging phenotype (MAIP). We then show that brain gene expression profiles enriched for candidate math ability-related genes, neuronal signaling, synaptic transmission, and voltage-gated potassium channel activity contributed to the MAIP. Furthermore, the similarity between MAIP gene expression signatures and brain structure, acquired before intervention, predicted learning outcomes in two independent math tutoring cohorts. These findings advance our knowledge of the interplay between neuroanatomical, transcriptomic, and molecular mechanisms underlying mathematical ability and reveal predictive biomarkers of learning. Our findings have implications for the development of personalized education and interventions.

Cognitive dysfunction is a feature in multiple sclerosis (MS), a chronic inflammatory demyelinating disorder. A notable aspect of MS brains is hippocampal demyelination, which is closely associated with cognitive decline. However, the mechanisms underlying this phenomenon remain unclear. Chitinase-3-like (CHI3L1), secreted by activated astrocytes, has been identified as a biomarker for MS progression. Our study investigates CHI3L1's function within the demyelinating hippocampus and demonstrates a correlation between CHI3L1 expression and cognitive impairment in patients with MS. Activated astrocytes release CHI3L1 in reaction to induced demyelination, which adversely affects the proliferation and differentiation of neural stem cells and impairs dendritic growth, complexity, and spine formation in neurons. Our findings indicate that the astrocytic deletion of CHI3L1 can mitigate neurogenic deficits and cognitive dysfunction. We showed that CHI3L1 interacts with CRTH2/receptor for advanced glycation end (RAGE) by attenuating β-catenin signaling. The reactivation of β-catenin signaling can revitalize neurogenesis, which holds promise for therapy of inflammatory demyelination.

The size of the human head is highly heritable, but genetic drivers of its variation within the general population remain unmapped. We perform a genome-wide association study on head size (N = 80,890) and identify 67 genetic loci, of which 50 are novel. Neuroimaging studies show that 17 variants affect specific brain areas, but most have widespread effects. Gene set enrichment is observed for various cancers and the p53, Wnt, and ErbB signaling pathways. Genes harboring lead variants are enriched for macrocephaly syndrome genes (37-fold) and high-fidelity cancer genes (9-fold), which is not seen for human height variants. Head size variants are also near genes preferentially expressed in intermediate progenitor cells, neural cells linked to evolutionary brain expansion. Our results indicate that genes regulating early brain and cranial growth incline to neoplasia later in life, irrespective of height. This warrants investigation of clinical implications of the link between head size and cancer.