Explore the vast range of titles available.

WDR45 plays an essential role in the early stage of autophagy. De novo heterozygous mutations in WDR45 have been known to cause β-propeller protein-associated neurodegeneration (BPAN), a subtype of neurodegeneration with brain iron accumulation (NBIA). Although BPAN patients display global developmental delay with intellectual disability, the neurodevelopmental pathophysiology of BPAN remains largely unknown. In the present study, we analyzed the physiological role of Wdr45 and pathophysiological significance of the gene abnormality during mouse brain development. Morphological and biochemical analyses revealed that Wdr45 is expressed in a developmental stage-dependent manner in mouse brain. Wdr45 was also found to be located in excitatory synapses by biochemical fractionation. Since WDR45 mutations are thought to cause protein degradation, we conducted acute knockdown experiments by in utero electroporation in mice to recapitulate the pathophysiological conditions of BPAN. Knockdown of Wdr45 caused abnormal dendritic development and synaptogenesis during corticogenesis, both of which were significantly rescued by co-expression with RNAi-resistant version of Wdr45. In addition, terminal arbors of callosal axons were less developed in Wdr45-deficient cortical neurons of adult mouse when compared to control cells. These results strongly suggest a pathophysiological significance of WDR45 gene abnormalities in neurodevelopmental aspects of BPAN.

Several genes implicated in autism spectrum disorder (ASD) are chromatin regulators, including POGZ . The cellular and molecular mechanisms leading to ASD impaired social and cognitive behavior are unclear. Animal models are crucial for studying the effects of mutations on brain function and behavior as well as unveiling the underlying mechanisms. Here, we generate a brain specific conditional knockout mouse model deficient for Pogz , an ASD risk gene. We demonstrate that Pogz deficient mice show microcephaly, growth impairment, increased sociability, learning and motor deficits, mimicking several of the human symptoms. At the molecular level, luciferase reporter assay indicates that POGZ is a negative regulator of transcription. In accordance, in Pogz deficient mice we find a significant upregulation of gene expression, most notably in the cerebellum. Gene set enrichment analysis revealed that the transcriptional changes encompass genes and pathways disrupted in ASD, including neurogenesis and synaptic processes, underlying the observed behavioral phenotype in mice. Physiologically, Pogz deficiency is associated with a reduction in the firing frequency of simple and complex spikes and an increase in amplitude of the inhibitory synaptic input in cerebellar Purkinje cells. Our findings support a mechanism linking heterochromatin dysregulation to cerebellar circuit dysfunction and behavioral abnormalities in ASD. POGZ is an autism spectrum disorder risk gene. How POGZ mutations result in ASD is unclear and animal models are lacking. Here, the authors generate a brain specific Pogz deficient mouse presenting ASD-like behaviour and show the effects of Pogz deficiency in the cerebellum.

Background RAC3 encodes a Rho family small GTPase that regulates the behaviour and organisation of actin cytoskeleton and intracellular signal transduction. Variants in RAC3 can cause a phenotypically heterogeneous neurodevelopmental disorder with structural brain anomalies and dysmorphic facies. The pathomechanism of this recently discovered genetic disorder remains unclear.MethodsWe investigated an early adolescent female with intellectual disability, drug-responsive epilepsy and white matter abnormalities. Through exome sequencing, we identified the novel de novo variant (NM_005052.3): c.83T>C (p.Phe28Ser) in RAC3. We then examined the pathophysiological significance of the p.F28S variant in comparison with the recently reported disease-causing p.Q61L variant, which results in a constitutively activated version of RAC3.ResultsIn vitro analyses revealed that the p.F28S variant was spontaneously activated by substantially increased intrinsic GTP/GDP-exchange activity and bound to downstream effectors tested, such as PAK1 and MLK2. The variant suppressed the differentiation of primary cultured hippocampal neurons and caused cell rounding with lamellipodia. In vivo analyses using in utero electroporation showed that acute expression of the p.F28S variant caused migration defects of excitatory neurons and axon growth delay during corticogenesis. Notably, defective migration was rescued by a dominant negative version of PAK1 but not MLK2.ConclusionOur results indicate that RAC3 is critical for brain development and the p.F28S variant causes morphological and functional defects in cortical neurons, likely due to the hyperactivation of PAK1.

WDR83 (WD Repeat Domain 83), also known as MORG1 (Mitogen-activated protein kinase Organizer 1), functions as a scaffold protein regulating diverse cellular processes, including cell signaling, proliferation, protein degradation, cell polarity, and autophagy. Through whole-exome sequencing, we identified a novel de novo WDR83 variant [NM_001099737; c.653 T > C,p.(L218P)] in a Japanese female patient presenting with global developmental delay, intellectual disability, and dysmorphic features. As the p.L218P variant was suspected to exert a dominant-negative effect, we investigated its impact on neuronal development. In vivo, acute expression via in utero electroporation promoted premature cell cycle exit of neural stem cells, impaired cortical neuron migration, and disrupted dendritic arborization, whereas axonal projections to the contralateral hemisphere remained unaffected. Additionally, cortical neurons expressing WDR83-L218P exhibited reduced spine head diameter. In vitro, WDR83-L218P expression inhibited axon elongation in primary cultured hippocampal neurons. Collectively, these findings suggest that WDR83 is a novel gene associated with neurodevelopmental disorders. Based on expression profiles and functional analyses, we conclude that WDR83 plays a crucial role in regulating neuronal morphology during brain development, and that the p.L218P variant disrupts this function, contributing to the patient’s phenotype.

Astrocytes are one of the most abundant cell types in the mammalian brain. They play essential roles in synapse formation, maturation, and elimination. However, how astrocytes migrate into the gray matter to accomplish these processes is poorly understood. Here, we show that, by combinational analyses of in vitro and in vivo time-lapse observations and lineage traces, astrocyte progenitors move rapidly and irregularly within the developing cortex, which we call erratic migration. Astrocyte progenitors also adopt blood vessel-guided migration. These highly motile progenitors are generated in the restricted prenatal stages and differentiate into protoplasmic astrocytes in the gray matter, whereas postnatally generated progenitors do not move extensively and differentiate into fibrous astrocytes in the white matter. We found Cxcr4/7, and integrin β1 regulate the blood vessel-guided migration, and their functional blocking disrupts their positioning. This study provides insight into astrocyte development and may contribute to understanding the pathogenesis caused by their defects. During development, astrocytes are generated from radial glia, and migrate to the cortical plate, but the process of astrocyte migration during development is not fully understood. Here the authors labelled cells derived from the cortical ventricular zone in the late stages of cortical plate development in mice, and identified a migration mode in which cells move rapidly and almost at random within the intermediate zone and the cortical plate.

Growth-associated protein 43 (GAP43) is a membrane-associated phosphoprotein predominantly expressed in the nervous systems, and controls axonal growth, branching, and pathfinding. While the association between GAP43 and human neurological disorders have been reported, the underlying mechanisms remain largely unknown. We performed whole exome sequencing on a patient with intellectual disability (ID), neurodevelopmental disorders, short stature, and skeletal abnormalities such as left–right difference in legs and digital deformities, and identified a heterozygous missense variation in the GAP43 gene [NM_001130064.2: c.436G > A/p.(E146K)]. The variant GAP43 protein was unstable in primary cultured cortical neurons and hippocampal neurons in vitro. In utero electroporation of the variant protein also confirmed its instability in vivo, suggesting that the variant led to a condition similar with haploinsufficiency in the patient. Silencing of GAP43 via in utero electroporation of RNAi vectors demonstrated that loss of GAP43 suppressed axon elongation into the contralateral hemisphere and impaired the dendritic arbor formation as shown by decreased dendritic branch points and shortened total dendritic lengths. Collectively, these findings confirmed the critical roles of GAP43 in brain development and the pathological basis of GAP43-associated diseases. Our study will contribute to a better understanding of how dysregulation of GAP43 leads to human diseases.

Per3 is one of the primary components of circadian clock system. While circadian dysregulation is known to be involved in the pathogenesis of several neuropsychiatric diseases. It remains largely unknown whether they participate in embryonic brain development. Here, we examined the role of clock gene Per3 in the development of mouse cerebral cortex. In situ hybridization analysis revealed that Per3 is expressed in the developing mouse cortex. Acute knockdown of Per3 with in utero electroporation caused abnormal positioning of cortical neurons, which was rescued by RNAi-resistant Per3. Per3-deficient cells showed abnormal migration phenotypes, impaired axon extension and dendritic arbor formation. Taken together, Per3 was found to play a pivotal role in corticogenesis via regulation of excitatory neuron migration and synaptic network formation.

The Connector Enhancer of Kinase Suppressor of Ras-2 (CNKSR2), also known as CNK2 or MAGUIN, is a scaffolding molecule that contains functional protein binding domains: Sterile Alpha Motif (SAM) domain, Conserved Region in CNK (CRIC) domain, PSD-95/Dlg-A/ZO-1 (PDZ) domain, Pleckstrin Homology (PH) domain, and C-terminal PDZ binding motif. CNKSR2 interacts with different molecules, including RAF1, ARHGAP39, and CYTH2, and regulates the Mitogen-Activated Protein Kinase (MAPK) cascade and small GTPase signaling. CNKSR2 has been reported to control the development of dendrite and dendritic spines in primary neurons. CNKSR2 is encoded by the CNKSR2 gene located in the X chromosome. CNKSR2 is now considered as a causative gene of the Houge type of X-linked syndromic mental retardation (MRXHG), an X-linked Intellectual Disability (XLID) that exhibits delayed development, intellectual disability, early-onset seizures, language delay, attention deficit, and hyperactivity. In this review, we summarized molecular features, neuronal function, and neurodevelopmental disorder-related variations of CNKSR2.

Gene abnormalities in RBFOX1, encoding an mRNA-splicing factor, have been shown to cause autism spectrum disorder and other neurodevelopmental disorders. Since pathophysiological significance of the dominant nuclear isoform in neurons, RBFOX1 -isoform1 (iso1), remains to be elucidated, we performed comprehensive analyses of Rbfox1 -iso1 during mouse corticogenesis. Knockdown of Rbfox1 -iso1 by in utero electroporation caused abnormal neuronal positioning during corticogenesis, which was attributed to impaired migration. The defects were found to occur during radial migration and terminal translocation, perhaps due to impaired nucleokinesis. Axon extension and dendritic arborization were also suppressed in vivo in Rbfox1 -iso1-deficient cortical neurons. In addition, electrophysiology experiments revealed significant defects in the membrane and synaptic properties of the deficient neurons. Aberrant morphology was further confirmed by in vitro analyses; Rbfox1 -iso1-konckdown in hippocampal neurons resulted in the reduction of primary axon length, total length of dendrites, spine density and mature spine number. Taken together, this study shows that Rbfox1 -iso1 plays an important role in neuronal migration and synapse network formation during corticogenesis. Defects in these critical processes may induce structural and functional defects in cortical neurons, and consequently contribute to the pathophysiology of neurodevelopmental disorders with RBFOX1 abnormalities.

Rho family guanosine triphosphatases (GTPases) regulate cellular signaling and cytoskeletal dynamics, playing a pivotal role in cell adhesion, migration, and cell cycle progression. The Rac subfamily of Rho GTPases consists of three highly homologous proteins, Rac 1–3. The proper function of Rac1 and Rac3, and their correct interaction with guanine nucleotide-exchange factors (GEFs) and GTPase-activating proteins (GAPs) are crucial for neural development. Pathogenic variants affecting these delicate biological processes are implicated in different medical conditions in humans, primarily neurodevelopmental disorders (NDDs). In addition to a direct deleterious effect produced by genetic variants in the RAC genes, a dysregulated GTPase activity resulting from an abnormal function of GEFs and GAPs has been involved in the pathogenesis of distinctive emerging conditions. In this study, we reviewed the current pertinent literature on Rac-related disorders with a primary neurological involvement, providing an overview of the current knowledge on the pathophysiological mechanisms involved in the neuro-RACopathies.