Arid1b haploinsufficiency disrupts cortical interneuron development and mouse behavior

SWI/SNF Complex Connects Signaling and Epigenetic State in Cells of Nervous System

SWI/SNF protein complexes are evolutionarily conserved epigenetic regulators described in all eukaryotes. In metameric animals, the complexes are involved in all processes occurring in the nervous system, from neurogenesis to higher brain functions. On the one hand, the range of roles is wide because the SWI/SNF complexes act universally by mobilizing the nucleosomes in a chromatin template at multiple loci throughout the genome. On the other hand, the complexes mediate the action of multiple signaling pathways that control most aspects of neural tissue development and function. The issues are discussed to provide insight into the molecular basis of the multifaceted role of SWI/SNFs in cell cycle regulation, DNA repair, activation of immediate-early genes, neurogenesis, and brain and connectome formation. An overview is additionally provided for the molecular basis of nervous system pathologies associated with the SWI/SNF complexes and their contribution to neuroinflammation and neurodegeneration. Finally, we discuss the idea that SWI/SNFs act as an integration platform to connect multiple signaling and genetic programs.

Arid1b haploinsufficiency in cortical inhibitory interneurons causes cell-type-dependent changes in cellular and synaptic development

Autism spectrum disorder (ASD) presents with diverse cognitive and behavioral abnormalities beginning during early development. Although the neural circuit mechanisms remain unclear, recent work suggests pathology in cortical inhibitory interneurons (INs) plays a crucial role. However, we lack fundamental information regarding changes in the physiology of synapses to and from INs in ASD. Here, we used transgenic mice to conditionally knockout one copy of the high confidence ASD risk gene Arid1b from the progenitors of parvalbumin-expressing fast-spiking (PV-FS) INs and somatostatin-expressing non-fast-spiking (SST-NFS) INs. In brain slices, we performed paired whole-cell recordings between INs and excitatory projection neurons (PNs) to investigate changes in synaptic physiology. In neonates, we found reduced synaptic input to INs but not PNs, with a concomitant reduction in the frequency of spontaneous network events, which are driven by INs in immature circuits. In mature mice, we found a reduction in the number of PV-FS INs in cortical layers 2/3 and 5. However, changes in PV-FS IN synaptic physiology were cortical layer and PN cell-type dependent. In layer 5, synapses from PV-FS INs to subcortical-projecting PNs were weakened. In contrast, in layer 2/3, synapses to and from PV-FS INs and corticocortical-projecting PNs were strengthened, leading to enhanced feedforward inhibition of input from layer 4. Finally, we found a novel synaptic deficit among SST-NFS INs, in which excitatory synapses from layer 2/3 PNs failed to facilitate. Our data highlight that changes in unitary synaptic dynamics among INs in ASD depend on neuronal cell-type.

ARID1B controls transcriptional programs of axon projection in an organoid model of the human corpus callosum

Mutations in ARID1B, a member of the mSWI/SNF complex, cause severe neurodevelopmental phenotypes with elusive mechanisms in humans. The most common structural abnormality in the brain of ARID1B patients is agenesis of the corpus callosum (ACC), characterized by the absence of an interhemispheric white matter tract that connects distant cortical regions. Here, we find that neurons expressing SATB2, a determinant of callosal projection neuron (CPN) identity, show impaired maturation in ARID1B+/- neural organoids. Molecularly, a reduction in chromatin accessibility of genomic regions targeted by TCF-like, NFI-like, and ARID-like transcription factors drives the differential expression of genes required for corpus callosum (CC) development. Through an in vitro model of the CC tract, we demonstrate that this transcriptional dysregulation impairs the formation of long-range axonal projections, causing structural underconnectivity. Our study uncovers new functions of the mSWI/SNF during human corticogenesis, identifying cell-autonomous axonogenesis defects in SATB2+ neurons as a cause of ACC in ARID1B patients.

Arid1b haploinsufficiency in pyramidal neurons causes cellular and circuit changes in neocortex but is not sufficient to produce behavioral or seizure phenotypes

Arid1b is a high confidence risk gene for autism spectrum disorder that encodes a subunit of a chromatin remodeling complex expressed in neuronal progenitors. Haploinsufficiency causes a broad range of social, behavioral, and intellectual disability phenotypes, including Coffin-Siris syndrome. Recent work using transgenic mouse models suggests pathology is due to deficits in proliferation, survival, and synaptic development of cortical neurons. However, there is conflicting evidence regarding the relative roles of excitatory projection neurons and inhibitory interneurons in generating abnormal cognitive and behavioral phenotypes. Here, we conditionally knocked out either one or both copies of Arid1b from excitatory projection neuron progenitors and systematically investigated the effects on intrinsic membrane properties, synaptic physiology, social behavior, and seizure susceptibility. We found that disrupting Arid1b expression in excitatory neurons alters their membrane properties, including hyperpolarizing action potential threshold; however, these changes depend on neuronal subtype. Using paired whole-cell recordings, we found increased synaptic connectivity rate between projection neurons. Furthermore, we found reduced strength of excitatory synapses to parvalbumin (PV)-expression inhibitory interneurons. These data suggest an increase in the ratio of excitation to inhibition. However, the strength of inhibitory synapses from PV interneurons to excitatory neurons was enhanced, which may rebalance this ratio. Indeed, Arid1b haploinsufficiency in projection neurons was insufficient to cause social deficits and seizure phenotypes observed in a preclinical germline haploinsufficient mouse model. Our data suggest that while excitatory projection neurons likely contribute to autistic phenotypes, pathology in these cells is not the primary cause.

Epigenetic underpinnings of the autistic mind: Histone modifications and prefrontal excitation/inhibition imbalance

Autism spectrum disorder (ASD) is complex neurobehavioral condition influenced by several cellular and molecular mechanisms that are often concerned with synaptogenesis and synaptic activity. Based on the excitation/inhibition (E/I) imbalance theory, ASD could be the result of disruption in excitatory and inhibitory synaptic transmission across the brain. The prefrontal cortex (PFC) is the chief regulator of executive function and can be affected by altered neuronal excitation and inhibition in the course of ASD. The molecular mechanisms involved in E/I imbalance are subject to epigenetic regulation. In ASD, altered enrichment and spreading of histone H3 and H4 modifications such as the activation-linked H3K4me2/3, H3K9ac, and H3K27ac, and repression-linked H3K9me2, H3K27me3, and H4K20me2 in the PFC result in dysregulation of molecules mediating synaptic excitation (ARC, EGR1, mGluR2, mGluR3, GluN2A, and GluN2B) and synaptic inhibition (BSN, EphA7, SLC6A1). Histone modifications are a dynamic component of the epigenetic regulatory elements with a pronounced effect on patterns of gene expression with regards to any biological process. The excitation/inhibition imbalance associated with ASD is based on the excitatory and inhibitory synaptic activity in different regions of the brain, including the PFC, the ultimate outcome of which is highly influenced by transcriptional activity of relevant genes.

ARID1B maintains mesenchymal stem cell quiescence via inhibition of BCL11B-mediated non-canonical Activin signaling

ARID1B haploinsufficiency in humans causes Coffin-Siris syndrome, associated with developmental delay, facial dysmorphism, and intellectual disability. The role of ARID1B has been widely studied in neuronal development, but whether it also regulates stem cells remains unknown. Here, we employ scRNA-seq and scATAC-seq to dissect the regulatory functions and mechanisms of ARID1B within mesenchymal stem cells (MSCs) using the mouse incisor model. We reveal that loss of Arid1b in the GLI1+ MSC lineage disturbs MSCs' quiescence and leads to their proliferation due to the ectopic activation of non-canonical Activin signaling via p-ERK. Furthermore, loss of Arid1b upregulates Bcl11b, which encodes a BAF complex subunit that modulates non-canonical Activin signaling by directly regulating the expression of activin A subunit, Inhba. Reduction of Bcl11b or non-canonical Activin signaling restores the MSC population in Arid1b mutant mice. Notably, we have identified that ARID1B suppresses Bcl11b expression via specific binding to its third intron, unveiling the direct inter-regulatory interactions among BAF subunits in MSCs. Our results demonstrate the vital role of ARID1B as an epigenetic modifier in maintaining MSC homeostasis and reveal its intricate mechanistic regulatory network in vivo, providing novel insights into the linkage between chromatin remodeling and stem cell fate determination.

Srcap haploinsufficiency induced autistic-like behaviors in mice through disruption of Satb2 expression

Mutations in the SRCAP gene are among the genetic alterations identified in autism spectrum disorders (ASD). However, the pathogenic mechanisms remain unclear. In this study, we demonstrate that Srcap+/- mice manifest deficits in social novelty response, as well as increased repetitive behaviors, anxiety, and impairments in learning and memory. Notably, a reduction in parvalbumin-positive neurons is observed in the retrosplenial cortex (RSC) and dentate gyrus (DG) of these mice. Through RNA sequencing, we identify dysregulation in 27 ASD-related genes in Srcap+/- mice. Specifically, we find that Srcap regulates expression of Satb2 via H2A.z in the promoter. Therapeutic intervention via retro-orbital injection of adeno-associated virus (AAV)-Satb2 in neonatal Srcap+/- mice leads to amelioration of the neurodevelopmental and ASD-like abnormalities. Furthermore, the expression of Satb2 only in the RSC of adolescent mice rectifies social novelty impairments. These results underscore the pivotal role of Srcap in neurodevelopment, by regulating Satb2, providing valuable insights for the pathophysiology of ASD.

Genetic background determines synaptic phenotypes in Arid1b-mutant mice

ARID1B, a chromatin remodeler, is strongly implicated in autism spectrum disorders (ASD). Two previous studies on Arid1b-mutant mice with the same exon 5 deletion in different genetic backgrounds revealed distinct synaptic phenotypes underlying the behavioral abnormalities: The first paper reported decreased inhibitory synaptic transmission in layer 5 pyramidal neurons in the medial prefrontal cortex (mPFC) region of the heterozygous Arid1b-mutant (Arid1b+/-) brain without changes in excitatory synaptic transmission. In the second paper, in contrast, we did not observe any inhibitory synaptic change in layer 5 mPFC pyramidal neurons, but instead saw decreased excitatory synaptic transmission in layer 2/3 mPFC pyramidal neurons without any inhibitory synaptic change. In the present report, we show that when we changed the genetic background of Arid1b+/- mice from C57BL/6 N to C57BL/6 J, to mimic the mutant mice of the first paper, we observed both the decreased inhibitory synaptic transmission in layer 5 mPFC pyramidal neurons reported in the first paper, and the decreased excitatory synaptic transmission in mPFC layer 2/3 pyramidal neurons reported in the second paper. These results suggest that genetic background can be a key determinant of the inhibitory synaptic phenotype in Arid1b-mutant mice while having minimal effects on the excitatory synaptic phenotype.

Prolonged stress response induced by chronic stress and corticosterone exposure causes adult neurogenesis inhibition and astrocyte loss in mouse hippocampus

Chronic stress is a pervasive and complex issue that contributes significantly to various mental and physical health disorders. Using the previously established chronic unpredictable stress (CUS) model, which simulates human stress situations, it has been shown that chronic stress induces major depressive disorder (MDD) and memory deficiency. However, this established model is associated with several drawbacks, such as limited research reproducibility and the inability to sustain stress response. To resolve these issues, we developed a new CUS model (CUS+C) that included exogenous corticosterone exposure to induce continuous stress response. Thereafter, we evaluated the effect of this new model on brain health. Thus, we observed that the use of the CUS+C model decreased body and brain weight gain and induced an uncontrolled coat state as well as depressive-like behavior in adult mice. It also impaired learning memory function and cognitive abilities, reduced adult hippocampal neurogenesis as well as the number of hippocampal astrocytes, and downregulated glial fibrillary acidic protein expression in the brains of adult mice. These findings can promote the utilization and validity of the animal stress model and provide new information for the treatment of chronic stress-induced depressive and memory disorders.

Updates on brain regions and neuronal circuits of movement disorders in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with a global burden that affects more often in the elderly. The basal ganglia (BG) is believed to account for movement disorders in PD. More recently, new findings in the original regions in BG involved in motor control, as well as the new circuits or new nucleuses previously not specifically considered were explored. In the present review, we provide up-to-date information related to movement disorders and modulations in PD, especially from the perspectives of brain regions and neuronal circuits. Meanwhile, there are updates in deep brain stimulation (DBS) and other factors for the motor improvement in PD. Comprehensive understandings of brain regions and neuronal circuits involved in motor control could benefit the development of novel therapeutical strategies in PD.

Maternal exposure to polystyrene microplastics impairs social behavior in mouse offspring with a potential neurotoxicity

As plastic production has been increasing steadily, environmental pollution resulting from microplastics (MPs) continues to draw considerable attention of the researchers. Several studies have reported that MPs are risk factors for various cellular and systemic dysfunctions. However, the effects of chronic MP exposure from the embryonic stage to adulthood on mouse brain remain unclear. Accordingly, determining the impacts of maternal exposure to MPs on mouse offspring was the main goal of this study. To this end, single cells of primary cortical neurons were isolated from mouse embryos. Subsequently, the cells were exposed to 2 µm polystyrene microplastics (PS-MPs), which resulted in a notable reduction in dendritic length, and PS-MPs cannot pass through the cellular membrane of neurons. Moreover, exposure to PS-MPs caused the proliferation increase and apoptosis in primary cortical neuronal cells. We then evaluated the neurotoxicity associated with chronic PS-MP exposure from the embryonic stage to adulthood in C57BL/6 J mouse offspring. PS-MPs were found to accumulate in the digestive and excretory organs of the offspring but not in the brain tissue. However, offspring exposed to PS-MPs exhibited no differences in the levels of expression of genes related to brain cell markers or synaptic organization. Nevertheless, PS-MP-exposed mice exhibited impaired social novelty preferences; however, no changes were observed in the emotional, compulsive, or cognitive behaviors. Taken together, these results demonstrate the potential neurotoxic effects of chronic exposure to PS-MPs in mouse offspring.

Dissecting the role of SWI/SNF component ARID1B in steady-state hematopoiesis

The adenosine triphosphate (ATP)-dependent chromatin remodeling complex, SWItch/Sucrose Non-Fermentable (SWI/SNF), has been implicated in normal hematopoiesis. The AT-rich interaction domain 1B (ARID1B) and its paralog, ARID1A, are mutually exclusive, DNA-interacting subunits of the BRG1/BRM-associated factor (BAF) subclass of SWI/SNF complex. Although the role of several SWI/SNF components in hematopoietic differentiation and stem cell maintenance has been reported, the function of ARID1B in hematopoietic development has not been defined. To this end, we generated a mouse model of Arid1b deficiency specifically in the hematopoietic compartment. Unlike the extensive phenotype observed in mice deficient in its paralog, ARID1A, Arid1b knockout (KO) mice exhibited a modest effect on steady-state hematopoiesis. Nonetheless, transplantation experiments showed that the reconstitution of myeloid cells in irradiated recipient mice was dependent on ARID1B. Furthermore, to assess the effect of the complete loss of ARID1 proteins in the BAF complex, we generated mice lacking both ARID1A and ARID1B in the hematopoietic compartment. The double-KO mice succumbed to acute bone marrow failure resulting from complete loss of BAF-mediated chromatin remodeling activity. Our Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) analyses revealed that >80% of loci regulated by ARID1B were distinct from those regulated by ARID1A; and ARID1B controlled expression of genes crucial in myelopoiesis. Overall, loss of ARID1B affected chromatin dynamics in murine hematopoietic stem and progenitor cells, albeit to a lesser extent than cells lacking ARID1A.

Altered motor learning and coordination in mouse models of autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with increasing prevalence. Over 1,000 risk genes have now been implicated in ASD, suggesting diverse etiology. However, the diagnostic criteria for the disorder still comprise two major behavioral domains - deficits in social communication and interaction, and the presence of restricted and repetitive patterns of behavior (RRBs). The RRBs associated with ASD include both stereotyped repetitive movements and other motor manifestations including changes in gait, balance, coordination, and motor skill learning. In recent years, the striatum, the primary input center of the basal ganglia, has been implicated in these ASD-associated motor behaviors, due to the striatum's role in action selection, motor learning, and habit formation. Numerous mouse models with mutations in ASD risk genes have been developed and shown to have alterations in ASD-relevant behaviors. One commonly used assay, the accelerating rotarod, allows for assessment of both basic motor coordination and motor skill learning. In this corticostriatal-dependent task, mice walk on a rotating rod that gradually increases in speed. In the extended version of this task, mice engage striatal-dependent learning mechanisms to optimize their motor routine and stay on the rod for longer periods. This review summarizes the findings of studies examining rotarod performance across a range of ASD mouse models, and the resulting implications for the involvement of striatal circuits in ASD-related motor behaviors. While performance in this task is not uniform across mouse models, there is a cohort of models that show increased rotarod performance. A growing number of studies suggest that this increased propensity to learn a fixed motor routine may reflect a common enhancement of corticostriatal drive across a subset of mice with mutations in ASD-risk genes.

Effects of prenatal bisphenol S and bisphenol F exposure on behavior of offspring mice

Bisphenol A (BPA) is a representative endocrine-disrupting chemical that exhibits hormonal disturbance reactions. Various alternatives, such as Bisphenol S (BPS) and Bisphenol F (BPF), are being developed. BPS and BPF (which are representative alternatives to BPA) are used in consumer products such as polycarbonate plastics and epoxy resins. They have structures similar to those of BPA and have also been proven to be exogenous endocrine disruptors. However, although there are many studies on BPA, there are few studies on the neurodevelopmental effects of BPS and BPF. Therefore, in this study, we analyzed neurobehavioral changes in offspring mice exposed to BPS and BPF during brain development by administering BPS and BPF to pregnant mice. We found that prenatal exposure to BPS and BPF did not affect anxiety-and depression-like behaviors, locomotion, sociability, memory, or cognition functions in offspring mice. However, exposure to BPS and BPF decreased the preference for social novelty in the offspring mice. Taken together, these findings suggest that perinatal exposure to BPS and BPF affects changes in social behaviors, but not other behavioral changes such as emotion, memory, or cognition in the offspring mice.

A Carboxy-terminal Smarcb1 Point Mutation Induces Hydrocephalus Formation and Affects AP-1 and Neuronal Signalling Pathways in Mice

The BAF (BRG1/BRM-associated factor) chromatin remodelling complex is essential for the regulation of DNA accessibility and gene expression during neuronal differentiation. Mutations of its core subunit SMARCB1 result in a broad spectrum of pathologies, including aggressive rhabdoid tumours or neurodevelopmental disorders. Other mouse models have addressed the influence of a homo- or heterozygous loss of Smarcb1, yet the impact of specific non-truncating mutations remains poorly understood. Here, we have established a new mouse model for the carboxy-terminal Smarcb1 c.1148del point mutation, which leads to the synthesis of elongated SMARCB1 proteins. We have investigated its impact on brain development in mice using magnetic resonance imaging, histology, and single-cell RNA sequencing. During adolescence, Smarcb11148del/1148del mice demonstrated rather slow weight gain and frequently developed hydrocephalus including enlarged lateral ventricles. In embryonic and neonatal stages, mutant brains did not differ anatomically and histologically from wild-type controls. Single-cell RNA sequencing of brains from newborn mutant mice revealed that a complete brain including all cell types of a physiologic mouse brain is formed despite the SMARCB1 mutation. However, neuronal signalling appeared disturbed in newborn mice, since genes of the AP-1 transcription factor family and neurite outgrowth-related transcripts were downregulated. These findings support the important role of SMARCB1 in neurodevelopment and extend the knowledge of different Smarcb1 mutations and their associated phenotypes.

Circuit-level theories for sensory dysfunction in autism: convergence across mouse models

Individuals with autism spectrum disorder (ASD) exhibit a diverse range of behavioral features and genetic backgrounds, but whether different genetic forms of autism involve convergent pathophysiology of brain function is unknown. Here, we analyze evidence for convergent deficits in neural circuit function across multiple transgenic mouse models of ASD. We focus on sensory areas of neocortex, where circuit differences may underlie atypical sensory processing, a central feature of autism. Many distinct circuit-level theories for ASD have been proposed, including increased excitation-inhibition (E-I) ratio and hyperexcitability, hypofunction of parvalbumin (PV) interneuron circuits, impaired homeostatic plasticity, degraded sensory coding, and others. We review these theories and assess the degree of convergence across ASD mouse models for each. Behaviorally, our analysis reveals that innate sensory detection behavior is heightened and sensory discrimination behavior is impaired across many ASD models. Neurophysiologically, PV hypofunction and increased E-I ratio are prevalent but only rarely generate hyperexcitability and excess spiking. Instead, sensory tuning and other aspects of neural coding are commonly degraded and may explain impaired discrimination behavior. Two distinct phenotypic clusters with opposing neural circuit signatures are evident across mouse models. Such clustering could suggest physiological subtypes of autism, which may facilitate the development of tailored therapeutic approaches.

Autism spectrum disorder and Coffin-Siris syndrome-Case report

Introduction

Autism spectrum disorders (ASDs) are a group of developmental disorders characterized by deficits in social communicative skills and the occurrence of repetitive and/or stereotyped behaviors. Coffin-Siris syndrome (CSS) is classically characterized by aplasia or hypoplasia of the distal phalanx or nail of the fifth and additional digits, developmental or cognitive delay of varying degrees, distinctive facial features, hypotonia, hirsutism/hypertrichosis, and sparse scalp hair. In this study, we present a detailed description of autistic traits in a boy diagnosed with CSS and further discuss their genetic backgrounds.

Case description

An 8-year-old boy with ASD, congenital anomalies, and neurological problems had been diagnosed with Coffin-Siris syndrome after genetic testing. Genetic testing revealed a heterozygous de novo pathogenic variant (class 5) c.1638_1647del in the ARID1B gene that is causative of Coffin-Siris syndrome but also other intellectual disability (ID)-related disorders, including autism. Tests that preceded the diagnoses, as well as congenital anomalies and developmental issues, were further described in an attempt to better present his phenotype.

Conclusion

Both autism and ARID1B-related disorders are on a spectrum. This report points out the importance and necessity of further research regarding the genetic backgrounds of these disorders to understand their complex etiology.

Comprehensive Analysis of lncRNA-mRNA Expression Profiles in Depression-like Responses of Mice Related to Polystyrene Nanoparticle Exposure

Plastics in the environment can break down into nanoplastics (NPs), which pose a potential threat to public health. Studies have shown that the nervous system constitutes a significant target for nanoplastics. However, the potential mechanism behind nanoplastics' neurotoxicity remains unknown. This study aimed to investigate the role of lncRNA in the depressive-like responses induced by exposure to 25 nm polystyrene nanoplastics (PS NPs). Forty mice were divided into four groups administered doses of 0, 10, 25, and 50 mg/kg via gavage for 6 months. After conducting behavioral tests, RNA sequencing was used to detect changes in mRNAs, miRNAs, and lncRNAs in the prefrontal cortex of the mice in the 0 and 50 mg/kg PS NPs groups. The results revealed that mice exposed to chronic PS NPs developed depressive-like responses in a dose-dependent manner. It was demonstrated that 987 mRNAs, 29 miRNAs, and 116 lncRNAs were significantly different between the two groups. Then, a competing endogenous RNA (ceRNA) network containing 6 lncRNAs, 18 miRNAs, and 750 mRNAs was constructed. Enrichment results suggested that PS NPs may contribute to the onset of depression-like responses through the activation of axon guidance, neurotrophin-signaling pathways, and dopaminergic synapses. This study provided evidence of the molecular relationship between PS NPs and depression-like responses.

Pleiotropic effects of a high confidence Autism Spectrum Disorder gene, arid1b, on zebrafish sleep

Sleep fulfills critical functions in neurodevelopment, such as promoting synaptic plasticity, neuronal wiring, and brain connectivity which are critical phenomena in Autism Spectrum Disorder (ASD) pathophysiology. Sleep disturbance, specifically insomnia, accompanies ASD and is associated with more severe core symptoms (e.g., social impairment). It is possible that focusing on identifying effective ways to treat sleep problems can help alleviate other ASD-related symptoms. A body of evidence indicates shared mechanisms and neurobiological substrates between sleep and ASD and investigation of these may inform therapeutic effects of improving sleep at both behavioral and molecular levels. In this study, we tested if sleep and social behavior were different in a zebrafish model with the arid1b gene mutated compared to controls. This gene was selected for study as expert curations conducted for the Simons Foundation for Autism Research Institute (SFARI) Gene database define it is as a 'high confidence' ASD gene (i.e., clearly implicated) encoding a chromatin remodeling protein. Homozygous arid1b mutants displayed increased arousability and light sleep compared to their heterozygous and wild type counterparts, based on testing a mechano-acoustic stimulus presenting different vibration frequencies of increasing intensity to detect sleep depth. In addition, decreased social preference was observed in arid1b heterozygous and homozygous mutant zebrafish. The behavioral phenotypes reported in our study are in line with findings from mouse models and human studies and demonstrate the utility of zebrafish as a vertebrate model system with high throughput phenotyping in the investigation of changes in sleep in models relevant to ASD. Furthermore, we demonstrate the importance of including assessments of arousal threshold when studying sleep using in vivo models.

Critical periods and Autism Spectrum Disorders, a role for sleep

Brain development relies on both experience and genetically defined programs. Time windows where certain brain circuits are particularly receptive to external stimuli, resulting in heightened plasticity, are referred to as "critical periods". Sleep is thought to be essential for normal brain development. Importantly, studies have shown that sleep enhances critical period plasticity and promotes experience-dependent synaptic pruning in the developing mammalian brain. Therefore, normal plasticity during critical periods depends on sleep. Problems falling and staying asleep occur at a higher rate in Autism Spectrum Disorder (ASD) relative to typical development. In this review, we explore the potential link between sleep, critical period plasticity, and ASD. First, we review the importance of critical period plasticity in typical development and the role of sleep in this process. Next, we summarize the evidence linking ASD with deficits in synaptic plasticity in rodent models of high-confidence ASD gene candidates. We then show that the high-confidence rodent models of ASD that show sleep deficits also display plasticity deficits. Given how important sleep is for critical period plasticity, it is essential to understand the connections between synaptic plasticity, sleep, and brain development in ASD. However, studies investigating sleep or plasticity during critical periods in ASD mouse models are lacking. Therefore, we highlight an urgent need to consider developmental trajectory in studies of sleep and plasticity in neurodevelopmental disorders.

Exposure to polystyrene particles causes anxiety-, depression-like behavior and abnormal social behavior in mice

In the era of plastic use, organisms are constantly exposed to polystyrene particles (PS-Ps). PS-Ps accumulated in living organisms exert negative effects on the body, although studies evaluating their effects on brain development are scarce. In this study, the effects of PS-Ps on nervous system development were investigated using cultured primary cortical neurons and mice exposed to PS-Ps at different stages of brain development. The gene expression associated with brain development was downregulated in embryonic brains following PS-Ps exposure, and Gabra2 expression decreased in the embryonic and adult mice exposed to PS-Ps. Additionally, offspring of PS-Ps-treated dams exhibited signs of anxiety- and depression-like behavior, and abnormal social behavior. We propose that PS-Ps accumulation in the brain disrupts brain development and behavior in mice. This study provides novel information regarding PS-Ps toxicity and its harmful effects on neural development and behavior in mammals.

ARID1B blocks methionine-stimulated mTOR activation to inhibit milk fat and protein synthesis in and proliferation of mouse mammary epithelial cells

Met can function through the mTOR signaling pathway, but the molecular mechanism is not fully understood. Here we investigated the role of ARID1B in this regulatory process. ARID1B knockdown promoted milk fat and protein synthesis in and cell proliferation of HC11 cells and increased mTOR mRNA expression and protein phosphorylation, whereas ARID1B gene activation had the opposite effects. ARID1B gene activation totally blocked Met's stimulation on mTOR mRNA expression. ARID1B bound to one region of the mTOR promoter, and Met reduced the binding of ARID1B on this promoter. LY294002 blocked Met-induced reduction of ARID1B mRNA and protein level. Cycloheximide treatment did not affect the decrease of ARID1B by Met. MG132 but not chloroquine restored ARID1B degradation induced by Met. Our data reveal that ARID1B is a key negative regulator of milk fat and protein synthesis in and proliferation of HC11 cells, and blocks Met-stimulated mTOR gene transcription.

Cortical interneuron specification and diversification in the era of big data

Inhibition in the mammalian cerebral cortex is mediated by a small population of highly diverse GABAergic interneurons. These largely local neurons are interspersed among excitatory projection neurons and exert pivotal regulation on the formation and function of cortical circuits. We are beginning to understand the extent of GABAergic neuron diversity and how this is generated and shaped during brain development in mice and humans. In this review, we summarise recent findings and discuss how new technologies are being used to further advance our knowledge. Understanding how inhibitory neurons are generated in the embryo is an essential pre-requisite of stem cell therapy, an evolving area of research, aimed at correcting human disorders that result in inhibitory dysfunction.

A Novel Early Life Stress Model Affects Brain Development and Behavior in Mice

Early life stress (ELS) in developing children has been linked to physical and psychological sequelae in adulthood. In the present study, we investigated the effects of ELS on brain and behavioral development by establishing a novel ELS model that combined the maternal separation paradigm and mesh platform condition. We found that the novel ELS model caused anxiety- and depression-like behaviors and induced social deficits and memory impairment in the offspring of mice. In particular, the novel ELS model induced more enhanced depression-like behavior and memory impairment than the maternal separation model, which is the established ELS model. Furthermore, the novel ELS caused upregulation of arginine vasopressin expression and downregulation of GABAergic interneuron markers, such as parvalbumin (PV), vasoactive intestinal peptide, and calbindin-D_28k (CaBP-28k), in the brains of the mice. Finally, the offspring in the novel ELS model showed a decreased number of cortical PV-, CaBP-28k-positive cells and an increased number of cortical ionized calcium-binding adaptors-positive cells in their brains compared to mice in the established ELS model. Collectively, these results indicated that the novel ELS model induced more negative effects on brain and behavioral development than the established ELS model.

Therapeutic strategies for autism: targeting three levels of the central dogma of molecular biology

The past decade has yielded much success in the identification of risk genes for Autism Spectrum Disorder (ASD), with many studies implicating loss-of-function (LoF) mutations within these genes. Despite this, no significant clinical advances have been made so far in the development of therapeutics for ASD. Given the role of LoF mutations in ASD etiology, many of the therapeutics in development are designed to rescue the haploinsufficient effect of genes at the transcriptional, translational, and protein levels. This review will discuss the various therapeutic techniques being developed from each level of the central dogma with examples including: CRISPR activation (CRISPRa) and gene replacement at the DNA level, antisense oligonucleotides (ASOs) at the mRNA level, and small-molecule drugs at the protein level, followed by a review of current delivery methods for these therapeutics. Since central nervous system (CNS) penetrance is of utmost importance for ASD therapeutics, it is especially necessary to evaluate delivery methods that have higher efficiency in crossing the blood-brain barrier (BBB).

Transition from Animal-Based to Human Induced Pluripotent Stem Cells (iPSCs)-Based Models of Neurodevelopmental Disorders: Opportunities and Challenges

Neurodevelopmental disorders (NDDs) arise from the disruption of highly coordinated mechanisms underlying brain development, which results in impaired sensory, motor and/or cognitive functions. Although rodent models have offered very relevant insights to the field, the translation of findings to clinics, particularly regarding therapeutic approaches for these diseases, remains challenging. Part of the explanation for this failure may be the genetic differences-some targets not being conserved between species-and, most importantly, the differences in regulation of gene expression. This prompts the use of human-derived models to study NDDS. The generation of human induced pluripotent stem cells (hIPSCs) added a new suitable alternative to overcome species limitations, allowing for the study of human neuronal development while maintaining the genetic background of the donor patient. Several hIPSC models of NDDs already proved their worth by mimicking several pathological phenotypes found in humans. In this review, we highlight the utility of hIPSCs to pave new paths for NDD research and development of new therapeutic tools, summarize the challenges and advances of hIPSC-culture and neuronal differentiation protocols and discuss the best way to take advantage of these models, illustrating this with examples of success for some NDDs.

Identifying foetal forebrain interneurons as a target for monogenic autism risk factors and the polygenic 16p11.2 microdeletion

BACKGROUND

Autism spectrum condition or 'autism' is associated with numerous genetic risk factors including the polygenic 16p11.2 microdeletion. The balance between excitatory and inhibitory neurons in the cerebral cortex is hypothesised to be critical for the aetiology of autism making improved understanding of how risk factors impact on the development of these cells an important area of research. In the current study we aim to combine bioinformatics analysis of human foetal cerebral cortex gene expression data with anatomical and electrophysiological analysis of a 16p11.2^+/- rat model to investigate how genetic risk factors impact on inhibitory neuron development.

METHODS

We performed bioinformatics analysis of single cell transcriptomes from gestational week (GW) 8-26 human foetal prefrontal cortex and anatomical and electrophysiological analysis of 16p11.2^+/- rat cerebral cortex and hippocampus at post-natal day (P) 21.

RESULTS

We identified a subset of human interneurons (INs) first appearing at GW23 with enriched expression of a large fraction of risk factor transcripts including those expressed from the 16p11.2 locus. This suggests the hypothesis that these foetal INs are vulnerable to mutations causing autism. We investigated this in a rat model of the 16p11.2 microdeletion. We found no change in the numbers or position of either excitatory or inhibitory neurons in the somatosensory cortex or CA1 of 16p11.2^+/- rats but found that CA1 Sst INs were hyperexcitable with an enlarged axon initial segment, which was not the case for CA1 pyramidal cells.

LIMITATIONS

The human foetal gene expression data was acquired from cerebral cortex between gestational week (GW) 8 to 26. We cannot draw inferences about potential vulnerabilities to genetic autism risk factors for cells not present in the developing cerebral cortex at these stages. The analysis 16p11.2^+/- rat phenotypes reported in the current study was restricted to 3-week old (P21) animals around the time of weaning and to a single interneuron cell-type while in human 16p11.2 microdeletion carriers symptoms likely involve multiple cell types and manifest in the first few years of life and on into adulthood.

CONCLUSIONS

We have identified developing interneurons in human foetal cerebral cortex as potentially vulnerable to monogenic autism risk factors and the 16p11.2 microdeletion and report interneuron phenotypes in post-natal 16p11.2^+/- rats.

Dendritic spine and synapse pathology in chromatin modifier-associated autism spectrum disorders and intellectual disability

Formation of dendritic spine and synapse is an essential final step of brain wiring to establish functional communication in the developing brain. Recent findings have displayed altered dendritic spine and synapse morphogenesis, plasticity, and related molecular mechanisms in animal models and post-mortem human brains of autism spectrum disorders (ASD) and intellectual disability (ID). Many genes and proteins are shown to be associated with spines and synapse development, and therefore neurodevelopmental disorders. In this review, however, particular attention will be given to chromatin modifiers such as AT-Rich Interactive Domain 1B (ARID1B), KAT8 regulatory non-specific lethal (NSL) complex subunit 1 (KANSL1), and WD Repeat Domain 5 (WDR5) which are among strong susceptibility factors for ASD and ID. Emerging evidence highlights the critical status of these chromatin remodeling molecules in dendritic spine morphogenesis and synaptic functions. Molecular and cellular insights of ARID1B, KANSL1, and WDR5 will integrate into our current knowledge in understanding and interpreting the pathogenesis of ASD and ID. Modulation of their activities or levels may be an option for potential therapeutic treatment strategies for these neurodevelopmental conditions.

Paraspeckles interact with SWI/SNF subunit ARID1B to regulate transcription and splicing

Paraspeckles are subnuclear RNA-protein structures that are implicated in important processes including cellular stress response, differentiation, and cancer progression. However, it is unclear how paraspeckles impart their physiological effect at the molecular level. Through biochemical analyses, we show that paraspeckles interact with the SWI/SNF chromatin-remodeling complex. This is specifically mediated by the direct interaction of the long-non-coding RNA NEAT1 of the paraspeckles with ARID1B of the cBAF-type SWI/SNF complex. Strikingly, ARID1B depletion, in addition to resulting in loss of interaction with the SWI/SNF complex, decreases the binding of paraspeckle proteins to chromatin modifiers, transcription factors, and histones. Functionally, the loss of ARID1B and NEAT1 influences the transcription and the alternative splicing of a common set of genes. Our findings reveal that dynamic granules such as the paraspeckles may leverage the specificity of epigenetic modifiers to impart their regulatory effect, thus providing a molecular basis for their function.

Involvement of gut-brain communication in arsenite-induced neurobehavioral impairments in adult male mice

Arsenite is a well-documented neurotoxic metalloid that widely distributes in the natural environment. However, it remains largely unclear how arsenite affects neurological function. Therefore, in this study, the healthy adult male mice were exposed to 0.5 mg/L and 5 mg/L arsenite through drinking water for 30 and 90 days, respectively. Our results showed that there was no significant alteration in the intestine and brain for 30 days exposure, but exposure to arsenite for 90 days significantly induced a reduction of locomotor activity and anxiety-like behavior, caused pathological damage and inflammatory responses in the brain and intestine. We also found that arsenite remarkably disrupted intestinal barrier integrity, decreased the levels of lysozyme and digestive enzymes. Intriguingly, chronic exposure to arsenite significantly changed the levels of gut-brain peptides. Taken together, this study provides meaningful insights that gut-brain communication may involve in the neurobehavioral impairments of arsenite.

Lactobacillus reuteri normalizes altered fear memory in male Cntnap4 knockout mice

BACKGROUND

Autism spectrum disorder (ASD) is a common neurodevelopmental disease, characterized by deficits in social communication, restricted and repetitive behaviours, and impaired fear memory processing. Severe gastrointestinal dysfunction and altered gut microbiome have been reported in ASD patients and animal models. Contactin associated protein-like 4 (CNTNAP4) has been suggested to be a novel risk gene, though its role in ASD remains unelucidated.

METHODS

Cntnap4^-/- mice were generated to explore its role in ASD-related behavioural abnormalities. Electrophysiological recording was employed to examine GABAergic transmission in the basolateral amygdala (BLA) and prefrontal cortex. RNA-sequencing was performed to assess underlying mechanisms. 16S rDNA analysis was performed to explore changes in faecal microbial composition. Male Cntnap4^-/- mice were fed with Lactobacillus reuteri (L. reuteri) or faecal microbiota to evaluate the effects of microbiota supplementation on the impaired fear conditioning mediated by Cntnap4 deficiency.

FINDINGS

Male Cntnap4^-/- mice manifested deficiency in social behaviours and tone-cue fear conditioning. Notably, reduced GABAergic transmission and GABA receptor expression were found in the BLA but not the prefrontal cortex. In addition, gut Lactobacillus were less abundant in male Cntnap4^-/- mice, and L. reuteri treatment or faecal microbiota transplantation rescued abnormal tone-cued fear memory and improved local GABAergic transmission in the BLA of male Cntnap4^-/- mice.

INTERPRETATION

Cntnap4 shapes GABAergic transmission of amygdala and fear conditioning, and microbial intervention represents a promising therapy in ASD intervention.

FUNDING

National Natural Science Foundation of China, Science and Technology Planning Project of Guangzhou, Guangzhou Medical University, and China Postdoctoral Science Foundation.

Histone Deacetylase Inhibition Restores Behavioral and Synaptic Function in a Mouse Model of 16p11.2 Deletion

BACKGROUND

Microdeletion of the human 16p11.2 gene locus confers risk for autism spectrum disorders and intellectual disability. How 16p11.2 deletion is linked to these neurodevelopmental disorders and whether there are treatment avenues for the manifested phenotypes remain to be elucidated. Emerging evidence suggests that epigenetic aberrations are strongly implicated in autism.

METHODS

We performed behavioral and electrophysiological experiments to examine the therapeutic effects of epigenetic drugs in transgenic mice carrying 16p11.2 deletion (16p11del/+).

RESULTS

We found that 16p11del/+ mice exhibited a significantly reduced level of histone acetylation in the prefrontal cortex (PFC). A short (3-day) treatment with class I histone deacetylase (HDAC) inhibitor MS-275 or Romidepsin led to the prolonged (3-4 weeks) rescue of social and cognitive deficits in 16p11del/+ mice. Concomitantly, MS-275 treatment reversed the hypoactivity of PFC pyramidal neurons and the hyperactivity of PFC fast-spiking interneurons. Moreover, the diminished N-methyl-D-aspartate (NMDA) receptor-mediated synaptic currents and the elevated GABAA receptor-mediated synaptic currents in PFC pyramidal neurons of 16p11del/+ mice were restored to control levels by MS-275 treatment.

CONCLUSIONS

Our results suggest that HDAC inhibition provides a highly effective therapeutic strategy for behavioral deficits and excitation/inhibition imbalance in 16p11del/+ mice, likely via normalization of synaptic function in the PFC.

Cytotoxicity evaluation and mechanism of endocrine-disrupting chemicals by the embryoid body test

Endocrine-disrupting chemicals (EDCs) are a structurally diverse class of synthetic and natural compounds. EDCs can cause non-communicable diseases such as obesity, type 2 diabetes, thyroid disorders, neurodevelopmental disease, hormone-dependent cancers, and reproductive disorders. The embryoid body test (EBT) is a developmental toxicity test method that determines the size of embryoid bodies (EBs) and the viability of mouse embryonic stem cells (mESCs) and fibroblasts (3T3 cells). The present study used the EBT to perform cytotoxicity evaluations of 10 EDCs and assessed the mechanistic relationship between endoplasmic reticulum (ER) stress and cytotoxicity. According to the statistical analysis and prediction model results, methylparaben, butylparaben, propylparaben, ethylparaben, triclosan, octylphenol, methoxychlor, bisphenol A, and diethylstilbestrol were classified as cytotoxic, but trichloroacetic acid was non-toxic. Classification accuracy was 90%. The mechanistic study showed that the cytotoxicities of butylparaben, propylparaben, octylphenol, and triclosan were induced by ER stress. The mRNA expressions of BiP, CHOP, and ATF4 were significantly higher following treatments with four EDCs compared to those after the control treatment. Compared to the control treatment, the mRNA levels of XBP1u and XBP1s increased significantly after butylparaben and propylparaben treatments, but did not increase with octylphenol and triclosan treatments. These results indicate that the EBT can be applied as an alternative toxicity test when evaluating the cytotoxicity of EDCs.

MACF1, Involved in the 1p34.2p34.3 Microdeletion Syndrome, is Essential in Cortical Progenitor Polarity and Brain Integrity

1p34.2p34.3 deletion syndrome is characterized by an increased risk for autism. Microtubule Actin Crosslinking Factor 1 (MACF1) is one candidate gene for this syndrome. It is unclear, however, how MACF1 deletion is linked to brain development and neurodevelopmental deficits. Here we report on Macf1 deletion in the developing mouse cerebral cortex, focusing on radial glia polarity and morphological integrity, as these are critical factors in brain formation. We found that deleting Macf1 during cortical development resulted in double cortex/subcortical band heterotopia as well as disrupted cortical lamination. Macf1-deleted radial progenitors showed increased proliferation rates compared to control cells but failed to remain confined within their defined proliferation zone in the developing brain. The overproliferation of Macf1-deleted radial progenitors was associated with elevated cell cycle speed and re-entry. Microtubule stability and actin polymerization along the apical ventricular area were decreased in the Macf1 mutant cortex. Correspondingly, there was a disconnection between radial glial fibers and the apical and pial surfaces. Finally, we observed that Macf1-mutant mice exhibited social deficits and aberrant emotional behaviors. Together, these results suggest that MACF1 plays a critical role in cortical progenitor proliferation and localization by promoting glial fiber stabilization and polarization. Our findings may provide insights into the pathogenic mechanism underlying the 1p34.2p34.3 deletion syndrome.

FTH1- and SAT1-Induced Astrocytic Ferroptosis Is Involved in Alzheimer’s Disease: Evidence from Single-Cell Transcriptomic Analysis

Objectives: Despite significant advances in neuroscience, the mechanisms of AD are not fully understood. Single-cell RNA sequencing (scRNA-seq) techniques provide potential solutions to analyze cellular composition of complex brain tissue and explore cellular and molecular biological mechanisms of AD. Methods: We investigated cellular heterogeneity in AD via utilization of bioinformatic analysis of scRNA-seq in AD patients and healthy controls from the Gene Expression Omnibus (GEO) database. The “GOplot” package was applied to explore possible biological processes in oligodendrocytes, astrocytes, and oligodendrocyte progenitor cells (OPCs). Expression patterns and biological functions of differentially expressed genes (DEGs) from scRNA-seq data were validated in RNA sequencing data. DEGs in astrocytes interacted with ferroptosis-related genes in FerrDb. CCK-8 and EdU assays were performed to measure cell proliferation ability. ROS, Fe²⁺ level, mitochondrial membrane potentials, iron concentrations, and total iron binding capacity (TIBC) in serum were evaluated. Y-maze and elevated maze were used to measure anxiety-like behavior. Autonomous and exploration behaviors or learning and memory ability in mice were analyzed using open field test and novel object recognition test. Results: Multiple clusters were identified, including oligodendrocytes, astrocytes, OPCs, neurons, microglia, doublets, and endothelial cells. Astrocytes were significantly decreased in AD, while oligodendrocytes and OPCs increased. Cell-to-cell ligand–receptor interaction analysis revealed that astrocytes, neurons, and OPCs mainly established contacts with other cells via the NRG3–ERBB4 ligand–receptor pair. GO and KEGG analyses found that astrocytes were enriched in the ferroptosis pathway. FTH1 and SAT1 in astrocytes were identified as hub mRNAs associated with ferroptosis. Serum iron concentration of 5xFAD mice was higher than that of WT, and emotional and cognitive function were significantly impaired as compared to WT. Serum iron concentration was negatively correlated with number of astrocytes and percentage of time spent entering the novelty arm in the Y-maze test, while it was positively correlated with percentage of time spent in the central area. Meanwhile, number of astrocytes was negatively correlated with percentage of time spent in the central area, while it was positively correlated with percentage of time spent entering the novelty arm. Conclusions: Through scRNA-seq analysis, we found that ferroptosis was activated in astrocytes and may contribute to the pathophysiological process in the entorhinal cortex. FTH1 and SAT1 were identified to impact astrocyte ferroptosis. Emotional and cognitive impairment in AD was associated with astrocyte ferroptosis. Our findings provide clues to reveal the pathophysiological processes following AD at the cellular level and highlight potential drug targets for the treatment of AD.

A perspective on molecular signalling dysfunction, its clinical relevance and therapeutics in autism spectrum disorder

Intellectual disability (ID) and autism spectrum disorder (ASD) are neurodevelopmental disorders that have become a primary clinical and social concern, with a prevalence of 2-3% in the population. Neuronal function and behaviour undergo significant malleability during the critical period of development that is found to be impaired in ID/ASD. Human genome sequencing studies have revealed many genetic variations associated with ASD/ID that are further verified by many approaches, including many mouse and other models. These models have facilitated the identification of fundamental mechanisms underlying the pathogenesis of ASD/ID, and several studies have proposed converging molecular pathways in ASD/ID. However, linking the mechanisms of the pathogenic genes and their molecular characteristics that lead to ID/ASD has progressed slowly, hampering the development of potential therapeutic strategies. This review discusses the possibility of recognising the common molecular causes for most ASD/ID based on studies from the available models that may enable a better therapeutic strategy to treat ID/ASD. We also reviewed the potential biomarkers to detect ASD/ID at early stages that may aid in diagnosis and initiating medical treatment, the concerns with drug failure in clinical trials, and developing therapeutic strategies that can be applied beyond a particular mutation associated with ASD/ID.

Early postnatal serotonin modulation prevents adult-stage deficits in Arid1b-deficient mice through synaptic transcriptional reprogramming

Autism spectrum disorder is characterized by early postnatal symptoms, although little is known about the mechanistic deviations that produce them and whether correcting them has long-lasting preventive effects on adult-stage deficits. ARID1B, a chromatin remodeler implicated in neurodevelopmental disorders, including autism spectrum disorder, exhibits strong embryonic- and early postnatal-stage expression. We report here that Arid1b-happloinsufficient (Arid1b^+/–) mice display autistic-like behaviors at juvenile and adult stages accompanied by persistent decreases in excitatory synaptic density and transmission. Chronic treatment of Arid1b^+/– mice with fluoxetine, a selective serotonin-reuptake inhibitor, during the first three postnatal weeks prevents synaptic and behavioral deficits in adults. Mechanistically, these rescues accompany transcriptomic changes, including upregulation of FMRP targets and normalization of HDAC4/MEF2A-related transcriptional regulation of the synaptic proteins, SynGAP1 and Arc. These results suggest that chronic modulation of serotonergic receptors during critical early postnatal periods prevents synaptic and behavioral deficits in adult Arid1b^+/– mice through transcriptional reprogramming.

ARID1B is a chromatin remodeler associated with autism spectrum disorders. Here the authors demonstrate that early postnatal serotonin modulation prevents adult stage deficits in Arid1b-deficient mice through synaptic transcriptional reprogramming.

Studying Chromatin Epigenetics with Fluorescence Microscopy

Epigenetic modifications of histones (methylation, acetylation, phosphorylation, etc.) are of great importance in determining the functional state of chromatin. Changes in epigenome underlay all basic biological processes, such as cell division, differentiation, aging, and cancerous transformation. Post-translational histone modifications are mainly studied by immunoprecipitation with high-throughput sequencing (ChIP-Seq). It enables an accurate profiling of target modifications along the genome, but suffers from the high cost of analysis and the inability to work with living cells. Fluorescence microscopy represents an attractive complementary approach to characterize epigenetics. It can be applied to both live and fixed cells, easily compatible with high-throughput screening, and provide access to rich spatial information down to the single cell level. In this review, we discuss various fluorescent probes for histone modification detection. Various types of live-cell imaging epigenetic sensors suitable for conventional as well as super-resolution fluorescence microscopy are described. We also focus on problems and future perspectives in the development of fluorescent probes for epigenetics.

WDR5-HOTTIP Histone Modifying Complex Regulates Neural Migration and Dendrite Polarity of Pyramidal Neurons via Reelin Signaling

WD-repeat domain 5 (WDR5), a core component of histone methyltransferase complexes, is associated with Kabuki syndrome and Kleefstra syndrome that feature intellectual disability and neurodevelopmental delay. Despite its critical status in gene regulation and neurological disorders, the role of WDR5 in neural development is unknown. Here we show that WDR5 is required for normal neuronal placement and dendrite polarization in the developing cerebral cortex. WDR5 knockdown led to defects in both entry into the bipolar transition of pyramidal neurons within the intermediate zone and radial migration into cortical layers. Moreover, WDR5 deficiency disrupted apical and basal polarity of cortical dendrites. Aberrant dendritic spines and synapses accompanied the dendrite polarity phenotype. WDR5 deficiency reduced expression of reelin signaling receptors, ApoER and VdldR, which were associated with abnormal H3K4 methylation and H4 acetylation on their promoter regions. Finally, an lncRNA, HOTTIP, was found to be a partner of WDR5 to regulate dendritic polarity and reelin signaling via histone modification. Our results demonstrate a novel role for WDR5 in neuronal development and provide mechanistic insights into the neuropathology associated with histone methyltransferase dysfunction.

Signalling pathways in autism spectrum disorder: mechanisms and therapeutic implications

Autism spectrum disorder (ASD) is a prevalent and complex neurodevelopmental disorder which has strong genetic basis. Despite the rapidly rising incidence of autism, little is known about its aetiology, risk factors, and disease progression. There are currently neither validated biomarkers for diagnostic screening nor specific medication for autism. Over the last two decades, there have been remarkable advances in genetics, with hundreds of genes identified and validated as being associated with a high risk for autism. The convergence of neuroscience methods is becoming more widely recognized for its significance in elucidating the pathological mechanisms of autism. Efforts have been devoted to exploring the behavioural functions, key pathological mechanisms and potential treatments of autism. Here, as we highlight in this review, emerging evidence shows that signal transduction molecular events are involved in pathological processes such as transcription, translation, synaptic transmission, epigenetics and immunoinflammatory responses. This involvement has important implications for the discovery of precise molecular targets for autism. Moreover, we review recent insights into the mechanisms and clinical implications of signal transduction in autism from molecular, cellular, neural circuit, and neurobehavioural aspects. Finally, the challenges and future perspectives are discussed with regard to novel strategies predicated on the biological features of autism.

A novel heterozygous missense variant of the ARID4A gene identified in Han Chinese families with schizophrenia-diagnosed siblings that interferes with DNA-binding activity

ARID4A plays an important role in regulating gene expression and cell proliferation. ARID4A belongs to the AT-rich interaction domain (ARID)-containing family, and a PWWP domain immediately precedes its ARID region. The molecular mechanism and structural basis of ARID4A are largely unknown. Whole-exome sequencing (WES) revealed that a novel heterozygous missense variant, ARID4A c.1231 C > G (p.His411Asp), was associated with schizophrenia (SCZ) in this study. We determined the crystal structure of the PWWP-ARID tandem at 2.05 Å, revealing an unexpected mode in which ARID4A assembles with its PWWP and ARID from a structural and functional supramodule. Our results further showed that compared with the wild type, the p.His411Asp ARID mutant protein adopts a less compact conformation and exhibits a weaker dsDNA-binding ability. The p.His411Asp mutation decreased the number of cells that were arrested in the G0-G1 phase and caused more cells to progress to the G2-M phase. In addition, the missense mutation promoted the proliferation of HEK293T cells. In conclusion, our data provide evidence that ARID4A p.His411Asp could cause a conformational change in the ARID4A ARID domain, influence the DNA binding function, and subsequently disturb the cell cycle arrest in the G1 phase. ARID4A is likely a susceptibility gene for SCZ; thus, these findings provide new insight into the role of ARID4A in psychiatric disorders.

Early and Late Corrections in Mouse Models of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social and repetitive symptoms. A key feature of ASD is early-life manifestations of symptoms, indicative of early pathophysiological mechanisms. In mouse models of ASD, increasing evidence indicates that there are early pathophysiological mechanisms that can be corrected early to prevent phenotypic defects in adults, overcoming the disadvantage of the short-lasting effects that characterize adult-initiated treatments. In addition, the results from gene restorations indicate that ASD-related phenotypes can be rescued in some cases even after the brain has fully matured. These results suggest that we need to consider both temporal and mechanistic aspects in studies of ASD models and carefully compare genetic and nongenetic corrections. Here, we summarize the early and late corrections in mouse models of ASD by genetic and pharmacological interventions and discuss how to better integrate these results to ensure efficient and long-lasting corrections for eventual clinical translation.

Transcription Pause and Escape in Neurodevelopmental Disorders

Transcription pause-release is an important, highly regulated step in the control of gene expression. Modulated by various factors, it enables signal integration and fine-tuning of transcriptional responses. Mutations in regulators of pause-release have been identified in a range of neurodevelopmental disorders that have several common features affecting multiple organ systems. This review summarizes current knowledge on this novel subclass of disorders, including an overview of clinical features, mechanistic details, and insight into the relevant neurodevelopmental processes.

Metformin modulates microbiota-derived inosine and ameliorates methamphetamine-induced anxiety and depression-like withdrawal symptoms in mice

BACKGROUND

Metformin exhibits therapeutic potential in behavioural deficits induced by methamphetamine (METH) in rats. Emerging studies suggest gut microbiota may impact psychiatric symptoms, but there is no direct evidence supporting metformin's participation in the pathophysiology of withdrawal symptoms via modulation of gut microbiota.

METHODS

In order to define the functional impacts of gut microbiota and metformin to the behavioural deficits during METH withdrawal, we utilized a combination of fecal microbiota transplantation (FMT), high-throughput sequencing, and untargeted metabolomics technologies.

RESULTS

First, METH addicts exhibited higher α diversity and distinct microbial structures compared to healthy controls. In particular, the relative abundance of Rikenellaceae was positively correlated with the severity of anxiety and depression. Second, both human-to-mouse and mouse-to-mouse FMTs confirmed that METH-altered-microbiota transplantation is sufficient to promote anxiety and depression-like behaviours in recipient germ-free mice, and these behavioural disturbances could be ameliorated by metformin. In-depth analysis revealed that METH significantly altered the bacterial composition and structure as well as relative abundance of several bacterial taxa and metabolites, including Rikenellaceae and inosine, respectively, whereas add-on metformin could remodel these alterations. Finally, the inosine complementation successfully restored METH-induced anxiety and depression-like behaviours in mice.

CONCLUSION

This study demonstrates that METH withdrawal-induced anxiety and depression-like behaviours are reversible and transmissible via gut microbiota in a mouse model. The therapeutic effects of metformin on psychiatric manifestations are associated with microbiota-derived metabolites, highlighting the role of the gut microbiota in substance use disorders and the pathophysiology of withdrawal symptoms.

Sequencing of selected chromatin remodelling genes reveals increased burden of rare missense variants in ASD patients from the Japanese population

Chromatin remodelling is an important process in neural development and is related to autism spectrum disorder (ASD) and schizophrenia (SCZ) aetiology. To further elucidate the involvement of chromatin remodelling genes in the genetic aetiology of ASD and SCZ in the Japanese population, we performed a case-control study. Targeted sequencing was conducted on coding regions of four BAF chromatin remodelling complex genes: SMARCA2, SMARCA4, SMARCC2, and ARID1B in 185 ASD, 432 SCZ patients, and 517 controls. 27 rare non-synonymous variants were identified in ASD and SCZ patients, including 25 missense, one in-frame deletion in SMRACA4, and one frame-shift variant in SMARCC2. Association analysis was conducted to investigate the burden of rare variants in BAF genes in ASD and SCZ patients. Significant enrichment of rare missense variants in BAF genes, but not synonymous variants, was found in ASD compared to controls. Rare pathogenic variants indicated by in silico tools were significantly enriched in ASD, but not statistically significant in SCZ. Pathogenic-predicted variants were located in disordered binding regions and may confer risk for ASD and SCZ by disrupting protein-protein interactions. Our study supports the involvement of rare missense variants of BAF genes in ASD and SCZ susceptibility.

Language Impairments in Individuals With Coffin-Siris Syndrome

Coffin-Siris syndrome (CSS, MIM 135900) is a now well-described, multiple congenital anomaly/intellectual disability syndrome classically characterized by fifth digit/nail hypoplasia, coarse facial features, and a range of organ-system related anomalies. Since its initial description in 1970, and the discovery of associated genes in 2011, CSS now encompasses a wide range of phenotypes and abilities caused by pathogenic variants in the BAF complex (often referred to as “BAFopathy”). It appears that the BAF complex leads to speech and language impairments in this population, and subsequently we have reviewed individuals in the CSS/BAF registry to understand the prevalence and degree of this particular learning difference. We have examined the frequency of delayed language acquisition, augmented communication device use, and speech intervention therapies. To aid in language progression, childhood speech interventions are necessary in children with a diagnosis of CSS. While the majority of children with pathogenic variants in the BAF complex have language-related struggles, the exact mechanism is not yet fully understood. At the time of writing, there are 284 individuals in the CSS/BAF registry with known variants in the following genes; ARID1B (n = 174), SMARCA4 (n = 41), ARID1A (n = 20), SMARCB1 (n = 20), ARID2 (n = 14), SOX11 (n = 10), and SMARCE1 (n = 5). While speech delays in individuals with CSS are expected, a full analysis of these delays has yet to be detailed. In the CSS/BAF registry, we identified 183 (64%) individuals with language-related challenges and 90 (32%) individuals that are non-verbal.

Neurobiology of ARID1B haploinsufficiency related to neurodevelopmental and psychiatric disorders

ARID1B haploinsufficiency is a frequent cause of intellectual disability (ID) and autism spectrum disorder (ASD), and also leads to emotional disturbances. In this review, we examine past and present clinical and preclinical research into the neurobiological function of ARID1B. The presentation of ARID1B-related disorders (ARID1B-RD) is highly heterogeneous, including varying degrees of ID, ASD, and physical features. Recent research includes the development of suitable clinical readiness assessments for the treatment of ARID1B-RD, as well as similar neurodevelopmental disorders. Recently developed mouse models of Arid1b haploinsufficiency successfully mirror many of the behavioral phenotypes of ASD and ID. These animal models have helped to solidify the molecular mechanisms by which ARID1B regulates brain development and function, including epigenetic regulation of the Pvalb gene and promotion of Wnt/β-catenin signaling in neural progenitors in the ventral telencephalon. Finally, preclinical studies have identified the use of a positive allosteric modulator of the GABA_A receptor as an effective treatment for some Arid1b haploinsufficiency-related behavioral phenotypes, and there is potential for the refinement of this therapy in order to translate it into clinical use.

Autism risk gene POGZ promotes chromatin accessibility and expression of clustered synaptic genes

Deleterious genetic variants in POGZ, which encodes the chromatin regulator Pogo Transposable Element with ZNF Domain protein, are strongly associated with autism spectrum disorder (ASD). Although it is a high-confidence ASD risk gene, the neurodevelopmental functions of POGZ remain unclear. Here we reveal the genomic binding of POGZ in the developing forebrain at euchromatic loci and gene regulatory elements (REs). We profile chromatin accessibility and gene expression in Pogz-/- mice and show that POGZ promotes the active chromatin state and transcription of clustered synaptic genes. We further demonstrate that POGZ forms a nuclear complex and co-occupies loci with ADNP, another high-confidence ASD risk gene, and provide evidence that POGZ regulates other neurodevelopmental disorder risk genes as well. Our results reveal a neurodevelopmental function of an ASD risk gene and identify molecular targets that may elucidate its function in ASD.

Dysfunction of Trio GEF1 involves in excitatory/inhibitory imbalance and autism-like behaviors through regulation of interneuron migration

Autism spectrum disorders (ASDs) are a group of highly inheritable neurodevelopmental disorders. Functional mutations in TRIO, especially in the GEF1 domain, are strongly implicated in ASDs, whereas the underlying neurobiological pathogenesis and molecular mechanisms remain to be clarified. Here we characterize the abnormal morphology and behavior of embryonic migratory interneurons (INs) upon Trio deficiency or GEF1 mutation in mice, which are mediated by the Trio GEF1-Rac1 activation and involved in SDF1α/CXCR4 signaling. In addition, the migration deficits are specifically associated with altered neural microcircuit, decreased inhibitory neurotransmission, and autism-like behaviors, which are reminiscent of some features observed in patients with ASDs. Furthermore, restoring the excitatory/inhibitory (E/I) imbalance via activation of GABA signaling rescues autism-like deficits. Our findings demonstrate a critical role of Trio GEF1 mediated signaling in IN migration and E/I balance, which are related to autism-related behavioral phenotypes.