Genome-wide distribution of Auts2 binding localizes with active neurodevelopmental genes

Auts2 enhances neurogenesis and promotes expansion of the cerebral cortex

INTRODUCTION

The AUTS2 gene is associated with various neurodevelopmental and psychiatric disorders and has been suggested to play a role in acquiring human-specific traits. Functional analyses of Auts2 knockout mice have focused on postmitotic neurons, and the reported phenotypes do not faithfully recapitulate the whole spectrum of AUTS2-related human diseases.

OBJECTIVE

The objective of the study is to assess the role of AUTS2 in the biology of neural progenitor cells, cortical neurogenesis and expansion; and understand how its deregulation leads to neurological disorders.

METHODS

We screened the literature and conducted a time point analysis of AUTS2 expression during cortical development. We used in utero electroporation to acutely modulate the expression level of AUTS2 in the developing cerebral cortex in vivo, and thoroughly characterized cortical neurogenesis and morphogenesis using immunofluorescence, cell tracing and sorting, transcriptomic profiling, and gene ontology enrichment analyses.

RESULTS

In addition to its expression in postmitotic neurons, we showed that AUTS2 is also expressed in neural progenitor cells at the peak of neurogenesis. Upregulation of AUTS2 dramatically altered the differentiation program and fate determination of cortical progenitors. Notably, it increased the number of basal progenitors and neurons and changed the expression of hundreds of genes, among which 444 have not been implicated in mouse brain development or function.

CONCLUSION

The study provides evidence that AUTS2 is expressed in germinal zones and plays a key role in fate decision of neural progenitor cells with impact on corticogenesis. It also presents comprehensive lists of AUTS2 target genes thus advancing the molecular mechanisms underlying AUTS2-associated diseases and the evolutionary expansion of the cerebral cortex.

Parent-of-origin regulation by maternal auts2 shapes neurodevelopment and behavior in fish

BACKGROUND

Parental experience can influence progeny behavior through gamete-mediated non-genetic inheritance, that is, mechanisms that do not involve changes in inherited DNA sequence. However, underlying mechanisms remain poorly understood in vertebrates, especially for maternal effects. Here, we use the medaka, a model fish species, to investigate the role of auts2a, the ortholog of human AUTS2, a gene repressed in the fish oocyte following maternal stress and associated with neurodevelopmental disorders.

RESULTS

We show that auts2a expression in the oocyte influences long-term progeny behavior, including anxiety-like behavior and environment recognition capabilities. Using single-nuclei RNA-sequencing, we reveal that maternal auts2a influences gene expression in neural cell populations during neurodevelopment. We also show that maternal auts2a knock-out triggers differences in maternally inherited factors, including early embryonic transcriptional and post-transcriptional regulators.

CONCLUSIONS

Together, our results reveal the unsuspected role of an autism-related gene expressed in the mother's oocyte in shaping progeny neurodevelopment and behavior. Finally, we report that auts2a/AUTS2 is part of a group of evolutionarily conserved genes associated with human neurodevelopmental disorders and expressed in oocytes across species, from fish to mammals. These findings raise important questions about their potential role in the non-genetic regulation of progeny neurodevelopment and behavior in vertebrates.

Isolated loss of the AUTS2 long isoform, brain-wide or targeted to Calbindin-lineage cells, generates a specific suite of brain, behavioral, and molecular pathologies

Rearrangements within the AUTS2 region are associated with a rare syndromic disorder with intellectual disability, developmental delay, and behavioral abnormalities as core features. In addition, smaller regional variants are linked to wide range of neuropsychiatric disorders, underscoring the gene's essential role in brain development. Like many essential neurodevelopmental genes, AUTS2 is large and complex, generating distinct long (AUTS2-l) and short (AUTS2-s) protein isoforms from alternative promoters. Although evidence suggests unique isoform functions, the contributions of each isoform to specific AUTS2-linked phenotypes have not been clearly resolved. Furthermore, Auts2 is widely expressed across the developing brain, but cell populations most central to disease presentation have not been determined. In this study, we focused on the specific roles of AUTS2-l in brain development, behavior, and postnatal brain gene expression, showing that brain-wide AUTS2-l ablation leads to specific subsets of the recessive pathologies associated with mutations in 3' exons (exons 8-19) that disrupt both major isoforms. We identify downstream genes that could explain expressed phenotypes including hundreds of putative direct AUTS2-l target genes. Furthermore, in contrast to 3' Auts2 mutations which lead to dominant hypoactivity, AUTS2-l loss-of-function is associated with dominant hyperactivity and repetitive behaviors, phenotypes exhibited by many human patients. Finally, we show that AUTS2-l ablation in Calbindin 1-expressing cell lineages is sufficient to yield learning/memory deficits and hyperactivity with abnormal dentate gyrus granule cell maturation, but not other phenotypic effects. These data provide new clues to in vivo AUTS2-l functions and novel information relevant to genotype-phenotype correlations in the human AUTS2 region.

Heterozygous deletion of the autism-associated gene CHD8 impairs synaptic function through widespread changes in gene expression and chromatin compaction

Whole-exome sequencing of autism spectrum disorder (ASD) probands and unaffected family members has identified many genes harboring de novo variants suspected to play a causal role in the disorder. Of these, chromodomain helicase DNA-binding protein 8 (CHD8) is the most recurrently mutated. Despite the prevalence of CHD8 mutations, we have little insight into how CHD8 loss affects genome organization or the functional consequences of these molecular alterations in neurons. Here, we engineered two isogenic human embryonic stem cell lines with CHD8 loss-of-function mutations and characterized differences in differentiated human cortical neurons. We identified hundreds of genes with altered expression, including many involved in neural development and excitatory synaptic transmission. Field recordings and single-cell electrophysiology revealed a 3-fold decrease in firing rates and synaptic activity in CHD8+/- neurons, as well as a similar firing-rate deficit in primary cortical neurons from Chd8+/- mice. These alterations in neuron and synapse function can be reversed by CHD8 overexpression. Moreover, CHD8+/- neurons displayed a large increase in open chromatin across the genome, where the greatest change in compaction was near autism susceptibility candidate 2 (AUTS2), which encodes a transcriptional regulator implicated in ASD. Genes with changes in chromatin accessibility and expression in CHD8+/- neurons have significant overlap with genes mutated in probands for ASD, intellectual disability, and schizophrenia but not with genes mutated in healthy controls or other disease cohorts. Overall, this study characterizes key molecular alterations in genome structure and expression in CHD8+/- neurons and links these changes to impaired neuronal and synaptic function.

Isolated loss of the AUTS2 long isoform, brain-wide or targeted to Calbindin -lineage cells, generates a specific suite of brain, behavioral and molecular pathologies

Rearrangements within the AUTS2 region are associated with a rare syndromic disorder with intellectual disability, developmental delay and behavioral abnormalities as core features. In addition, smaller regional variants are linked to wide range of neuropsychiatric disorders, underscoring the gene's essential role in brain development. Like many essential neurodevelopmental genes, AUTS2 is large and complex, generating distinct long (AUTS2-l) and short (AUTS2-s) protein isoforms from alternative promoters. Although evidence suggests unique isoform functions, the contributions of each isoform to specific AUTS2- linked phenotypes have not been clearly resolved. Furthermore, Auts2 is widely expressed across the developing brain, but cell populations most central to disease presentation have not been determined. In this study, we focused on the specific roles of AUTS2-l in brain development, behavior, and postnatal brain gene expression, showing that brain-wide AUTS2-l ablation leads to specific subsets of the recessive pathologies associated with C-terminal mutations that disrupt both isoforms. We identify downstream genes that could explain expressed phenotypes including hundreds of putative direct AUTS2- l target genes. Furthermore, in contrast to C-terminal Auts2 mutations which lead to dominant hypoactivity, AUTS2-l loss-of-function is associated with dominant hyperactivity, a phenotype exhibited by many human patients. Finally, we show that AUTS2-l ablation in Calbindin 1 -expressing cell lineages is sufficient to yield learning/memory deficits and hyperactivity with abnormal dentate gyrus granule cell maturation, but not other phenotypic effects. These data provide new clues to in vivo AUTS2-l functions and novel information relevant to genotype-phenotype correlations in the human AUTS2 region.

Genomic and transcriptomic analysis of checkpoint blockade response in advanced non-small cell lung cancer

Anti-PD-1/PD-L1 agents have transformed the treatment landscape of advanced non-small cell lung cancer (NSCLC). To expand our understanding of the molecular features underlying response to checkpoint inhibitors in NSCLC, we describe here the first joint analysis of the Stand Up To Cancer-Mark Foundation cohort, a resource of whole exome and/or RNA sequencing from 393 patients with NSCLC treated with anti-PD-(L)1 therapy, along with matched clinical response annotation. We identify a number of associations between molecular features and outcome, including (1) favorable (for example, ATM altered) and unfavorable (for example, TERT amplified) genomic subgroups, (2) a prominent association between expression of inducible components of the immunoproteasome and response and (3) a dedifferentiated tumor-intrinsic subtype with enhanced response to checkpoint blockade. Taken together, results from this cohort demonstrate the complexity of biological determinants underlying immunotherapy outcomes and reinforce the discovery potential of integrative analysis within large, well-curated, cancer-specific cohorts.

RINGs, DUBs and Abnormal Brain Growth-Histone H2A Ubiquitination in Brain Development and Disease

During mammalian neurodevelopment, signaling pathways converge upon transcription factors (TFs) to establish appropriate gene expression programmes leading to the production of distinct neural and glial cell types. This process is partially regulated by the dynamic modulation of chromatin states by epigenetic systems, including the polycomb group (PcG) family of co-repressors. PcG proteins form multi-subunit assemblies that sub-divide into distinct, yet functionally related families. Polycomb repressive complexes 1 and 2 (PRC1 and 2) modify the chemical properties of chromatin by covalently modifying histone tails via H2A ubiquitination (H2AK119ub1) and H3 methylation, respectively. In contrast to the PRCs, the Polycomb repressive deubiquitinase (PR-DUB) complex removes H2AK119ub1 from chromatin through the action of the C-terminal hydrolase BAP1. Genetic screening has identified several PcG mutations that are causally associated with a range of congenital neuropathologies associated with both localised and/or systemic growth abnormalities. As PRC1 and PR-DUB hold opposing functions to control H2AK119ub1 levels across the genome, it is plausible that such neurodevelopmental disorders arise through a common mechanism. In this review, we will focus on advancements regarding the composition and opposing molecular functions of mammalian PRC1 and PR-DUB, and explore how their dysfunction contributes to the emergence of neurodevelopmental disorders.

Regeneration and developmental enhancers are differentially compatible with minimal promoters

Enhancers and promoters are cis-regulatory elements that control gene expression. Enhancers are activated in a cell type-, tissue-, and condition-specific manner to stimulate promoter function and transcription. Zebrafish have emerged as a powerful animal model for examining the activities of enhancers derived from various species through transgenic enhancer assays, in which an enhancer is coupled with a minimal promoter. However, the efficiency of minimal promoters and their compatibility with multiple developmental and regeneration enhancers have not been systematically tested in zebrafish. Thus, we assessed the efficiency of six minimal promoters and comprehensively interrogated the compatibility of the promoters with developmental and regeneration enhancers. We found that the fos minimal promoter and Drosophila synthetic core promoter (DSCP) yielded high rates of leaky expression that may complicate the interpretation of enhancer assays. Notably, the adenovirus E1b promoter, the zebrafish lepb 0.8-kb (P0.8) and lepb 2-kb (P2) promoters, and a new zebrafish synthetic promoter (ZSP) that combines elements of the E1b and P0.8 promoters drove little or no ectopic expression, making them suitable for transgenic assays. We also found significant differences in compatibility among specific combinations of promoters and enhancers, indicating the importance of promoters as key regulatory elements determining the specificity of gene expression. Our study provides guidelines for transgenic enhancer assays in zebrafish to aid in the discovery of functional enhancers regulating development and regeneration.

auts2 Features and Expression Are Highly Conserved during Evolution Despite Different Evolutionary Fates Following Whole Genome Duplication

The AUTS2 gene plays major roles during brain development and is associated with various neuropathologies including autism. Data in non-mammalian species are scarce, and the aim of our study was to provide a comprehensive analysis of auts2 evolution in teleost fish, which are widely used for in vivo functional analysis and biomedical purposes. Comparative genomics in 78 species showed that auts2a and auts2b originate from the teleost-specific whole genome duplication (TGD). auts2a, which is highly similar to human AUTS2, was almost systematically retained following TGD. In contrast, auts2b, which encodes for a shorter protein similar to a short human AUTS2 isoform, was lost more frequently and independently during evolution. RNA-seq analysis in 10 species revealed a highly conserved profile with predominant expression of both genes in the embryo, brain, and gonads. Based on protein length, conserved domains, and expression profiles, we speculate that the long human isoform functions were retained by auts2a, while the short isoform functions were retained by auts2a and/or auts2b, depending on the lineage/species. auts2a showed a burst in expression during medaka brain formation, where it was expressed in areas of the brain associated with neurodevelopmental disorders. Together, our data suggest a strong conservation of auts2 functions in vertebrates despite different evolutionary scenarios in teleosts.

Cerebral organoids containing an AUTS2 missense variant model microcephaly

Variants in the AUTS2 gene are associated with a broad spectrum of neurological conditions characterized by intellectual disability, microcephaly, and congenital brain malformations. Here, we use a human cerebral organoid model to investigate the pathophysiology of a heterozygous de novo missense AUTS2 variant identified in a patient with multiple neurological impairments including primary microcephaly and profound intellectual disability. Proband cerebral organoids exhibit reduced growth, deficits in neural progenitor cell (NPC) proliferation and disrupted NPC polarity within ventricular zone-like regions compared to control cerebral organoids. We used CRISPR-Cas9-mediated gene editing to correct this variant and demonstrate rescue of impaired organoid growth and NPC proliferative deficits. Single-cell RNA sequencing revealed a marked reduction of G1/S transition gene expression and alterations in WNT-β-catenin signalling within proband NPCs, uncovering a novel role for AUTS2 in NPCs during human cortical development. Collectively, these results underscore the value of cerebral organoids to investigate molecular mechanisms underlying AUTS2 syndrome.

AUTS2 Syndrome: Molecular Mechanisms and Model Systems

AUTS2 syndrome is a genetic disorder that causes intellectual disability, microcephaly, and other phenotypes. Syndrome severity is worse when mutations involve 3' regions (exons 9-19) of the AUTS2 gene. Human AUTS2 protein has two major isoforms, full-length (1259 aa) and C-terminal (711 aa), the latter produced from an alternative transcription start site in exon 9. Structurally, AUTS2 contains the putative "AUTS2 domain" (∼200 aa) conserved among AUTS2 and its ohnologs, fibrosin, and fibrosin-like-1. Also, AUTS2 contains extensive low-complexity sequences and intrinsically disordered regions, features typical of RNA-binding proteins. During development, AUTS2 is expressed by specific progenitor cell and neuron types, including pyramidal neurons and Purkinje cells. AUTS2 localizes mainly in cell nuclei, where it regulates transcription and RNA metabolism. Some studies have detected AUTS2 in neurites, where it may regulate cytoskeletal dynamics. Neurodevelopmental functions of AUTS2 have been studied in diverse model systems. In zebrafish, auts2a morphants displayed microcephaly. In mice, excision of different Auts2 exons (7, 8, or 15) caused distinct phenotypes, variously including neonatal breathing abnormalities, cerebellar hypoplasia, dentate gyrus hypoplasia, EEG abnormalities, and behavioral changes. In mouse embryonic stem cells, AUTS2 could promote or delay neuronal differentiation. Cerebral organoids, derived from an AUTS2 syndrome patient containing a pathogenic missense variant in exon 9, exhibited neocortical growth defects. Emerging technologies for analysis of human cerebral organoids will be increasingly useful for understanding mechanisms underlying AUTS2 syndrome. Questions for future research include whether AUTS2 binds RNA directly, how AUTS2 regulates neurogenesis, and how AUTS2 modulates neural circuit formation.

ErbB4 Is a Potential Key Regulator of the Pathways Activated by NTRK-Fusions in Thyroid Cancer

NTRK gene fusions are drivers of tumorigenesis events that specific Trk-inhibitors can target. Current knowledge of the downstream pathways activated has been previously limited to the pathways of regulator proteins phosphorylated directly by Trk receptors. Here, we aimed to detect genes whose expression is increased in response to the activation of these pathways. We identified and analyzed differentially expressed genes in thyroid cancer samples with NTRK1 or NTRK3 gene fusions, and without any NTRK fusions, versus normal thyroid gland tissues, using data from the Cancer Genome Atlas, the DESeq2 tool, and the Genome Enhancer and geneXplain platforms. Searching for the genes activated only in samples with an NTRK fusion as opposed to those without NTRK fusions, we identified 29 genes involved in nervous system development, including AUTS2, DTNA, ERBB4, FLRT2, FLRT3, RPH3A, and SCN4A. We found that genes regulating the expression of the upregulated genes (i.e., upstream regulators) were enriched in the “signaling by ERBB4” pathway. ERBB4 was also one of three genes encoding master regulators whose expression was increased only in samples with an NTRK fusion. Moreover, the algorithm searching for positive feedback loops for gene promoters and transcription factors (a so-called “walking pathways” algorithm) identified the ErbB4 protein as the key master regulator. ERBB4 upregulation (p-value = 0.004) was confirmed in an independent sample of ETV6-NTRK3-positive FFPE specimens. Thus, ErbB4 is the potential key regulator of the pathways activated by NTRK gene fusions in thyroid cancer. These results are preliminary and require additional biochemical validation.

AUTS2 Gene: Keys to Understanding the Pathogenesis of Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs), including autism spectrum disorders (ASD) and intellectual disability (ID), are a large group of neuropsychiatric illnesses that occur during early brain development, resulting in a broad spectrum of syndromes affecting cognition, sociability, and sensory and motor functions. Despite progress in the discovery of various genetic risk factors thanks to the development of novel genomics technologies, the precise pathological mechanisms underlying the onset of NDDs remain elusive owing to the profound genetic and phenotypic heterogeneity of these conditions. Autism susceptibility candidate 2 (AUTS2) has emerged as a crucial gene associated with a wide range of neuropsychological disorders, such as ASD, ID, schizophrenia, and epilepsy. AUTS2 has been shown to be involved in multiple neurodevelopmental processes; in cell nuclei, it acts as a key transcriptional regulator in neurodevelopment, whereas in the cytoplasm, it participates in cerebral corticogenesis, including neuronal migration and neuritogenesis, through the control of cytoskeletal rearrangements. Postnatally, AUTS2 regulates the number of excitatory synapses to maintain the balance between excitation and inhibition in neural circuits. In this review, we summarize the knowledge regarding AUTS2, including its molecular and cellular functions in neurodevelopment, its genetics, and its role in behaviors.

NRF1 association with AUTS2-Polycomb mediates specific gene activation in the brain

The heterogeneous family of complexes comprising Polycomb repressive complex 1 (PRC1) is instrumental for establishing facultative heterochromatin that is repressive to transcription. However, two PRC1 species, ncPRC1.3 and ncPRC1.5, are known to comprise novel components, AUTS2, P300, and CK2, that convert this repressive function to that of transcription activation. Here, we report that individuals harboring mutations in the HX repeat domain of AUTS2 exhibit defects in AUTS2 and P300 interaction as well as a developmental disorder reflective of Rubinstein-Taybi syndrome, which is mainly associated with a heterozygous pathogenic variant in CREBBP/EP300. Moreover, the absence of AUTS2 or mutation in its HX repeat domain gives rise to misregulation of a subset of developmental genes and curtails motor neuron differentiation of mouse embryonic stem cells. The transcription factor nuclear respiratory factor 1 (NRF1) has a novel and integral role in this neurodevelopmental process, being required for ncPRC1.3 recruitment to chromatin.

High Behavioral Variability Mediated by Altered Neuronal Excitability in auts2 Mutant Zebrafish

Autism spectrum disorders (ASDs) are characterized by abnormal behavioral traits arising from neural circuit dysfunction. While a number of genes have been implicated in ASDs, in most cases, a clear understanding of how mutations in these genes lead to circuit dysfunction and behavioral abnormality is absent. The autism susceptibility candidate 2 (AUTS2) gene is one such gene, associated with ASDs, intellectual disability and a range of other neurodevelopmental conditions. However, the role of AUTS2 in neural development and circuit function is not at all known. Here, we undertook functional analysis of Auts2a, the main homolog of AUTS2 in zebrafish, in the context of the escape behavior. Escape behavior in wild-type zebrafish is critical for survival and is therefore, reliable, rapid, and has well-defined kinematic properties. auts2a mutant zebrafish are viable, have normal gross morphology and can generate escape behavior with normal kinematics. However, the behavior is unreliable and delayed, with high trial-to-trial variability in the latency. Using calcium imaging we probed the activity of Mauthner neurons during otic vesicle (OV) stimulation and observed lower probability of activation and reduced calcium transients in the mutants. With direct activation of Mauthner by antidromic stimulation, the threshold for activation in mutants was higher than that in wild-type, even when inhibition was blocked. Taken together, these results point to reduced excitability of Mauthner neurons in auts2a mutant larvae leading to unreliable escape responses. Our results show a novel role for Auts2a in regulating neural excitability and reliability of behavior.

Erotomania and phenotypic continuum in a family frameshift variant of AUTS2: a case report and review

BACKGROUND

Pathogenic variants of the AUTS2 (Autism Susceptibility candidate 2) gene predispose to intellectual disability, autism spectrum disorder, attention deficit hyperactivity disorder, facial dysmorphism and short stature. This phenotype is therefore associated with neurocognitive disturbances and social cognition, indicating potential functional maladjustment in the affected subjects, and a potentially significant impact on quality of life. Although many isolated cases have been reported in the literature, to date no families have been described. This case reports on a family (three generations) with a frameshift variant in the AUTS2 gene.

CASE PRESENTATION

The proband is 13 years old with short stature, dysmorphic features, moderate intellectual disability and autism spectrum disorder. His mother is 49 years old and also has short stature and similar dysmorphic features. She does not have autism disorder but presents an erotomaniac delusion. Her cognitive performance is heterogeneous. The two aunts are also of short stature. The 50-year-old aunt has isolated social cognition disorders. The 45-year-old aunt has severe cognitive impairment and autism spectrum disorder. The molecular analysis of the three sisters and the proband shows the same AUTS2 heterozygous duplication leading to a frame shift expected to produce a premature stop codon, p.(Met593Tyrfs*85). Previously reported isolated cases revealed phenotypic and cognitive impairment variability. In this case report, these variabilities are present within the same family, presenting the same variant.

CONCLUSIONS

The possibility of a phenotypic spectrum within the same family highlights the need for joint psychiatry and genetics research.

AUTS2 Regulates RNA Metabolism and Dentate Gyrus Development in Mice

Human AUTS2 mutations are linked to a syndrome of intellectual disability, autistic features, epilepsy, and other neurological and somatic disorders. Although it is known that this unique gene is highly expressed in developing cerebral cortex, the molecular and developmental functions of AUTS2 protein remain unclear. Using proteomics methods to identify AUTS2 binding partners in neonatal mouse cerebral cortex, we found that AUTS2 associates with multiple proteins that regulate RNA transcription, splicing, localization, and stability. Furthermore, AUTS2-containing protein complexes isolated from cortical tissue bound specific RNA transcripts in RNA immunoprecipitation and sequencing assays. Deletion of all major functional isoforms of AUTS2 (full-length and C-terminal) by conditional excision of exon 15 caused breathing abnormalities and neonatal lethality when Auts2 was inactivated throughout the developing brain. Mice with limited inactivation of Auts2 in cerebral cortex survived but displayed abnormalities of cerebral cortex structure and function, including dentate gyrus hypoplasia with agenesis of hilar mossy neurons, and abnormal spiking activity on EEG. Also, RNA transcripts that normally associate with AUTS2 were dysregulated in mutant mice. Together, these findings indicate that AUTS2 regulates RNA metabolism and is essential for development of cerebral cortex, as well as subcortical breathing centers.

Untangle the Multi-Facet Functions of Auts2 as an Entry Point to Understand Neurodevelopmental Disorders

Neurodevelopmental disorders are psychiatric diseases that are usually first diagnosed in infancy, childhood and adolescence. Autism spectrum disorder (ASD) is a neurodevelopmental disorder, characterized by core symptoms including impaired social communication, cognitive rigidity and repetitive behavior, accompanied by a wide range of comorbidities such as intellectual disability (ID) and dysmorphisms. While the cause remains largely unknown, genetic, epigenetic, and environmental factors are believed to contribute toward the onset of the disease. Autism Susceptibility Candidate 2 (Auts2) is a gene highly associated with ID and ASD. Therefore, understanding the function of Auts2 gene can provide a unique entry point to untangle the complex neuronal phenotypes of neurodevelpmental disorders. In this review, we discuss the recent discoveries regarding the molecular and cellular functions of Auts2. Auts2 was shown to be a key-regulator of transcriptional network and a mediator of epigenetic regulation in neurodevelopment, the latter potentially providing a link for the neuronal changes of ASD upon environmental risk-factor exposure. In addition, Auts2 could synchronize the balance between excitation and inhibition through regulating the number of excitatory synapses. Cytoplasmic Auts2 could join the fine-tuning of actin dynamics during neuronal migration and neuritogenesis. Furthermore, Auts2 was expressed in developing mouse and human brain regions such as the frontal cortex, dorsal thalamus, and hippocampus, which have been implicated in the impaired cognitive and social function of ASD. Taken together, a comprehensive understanding of Auts2 functions can give deep insights into the cause of the heterogenous manifestation of neurodevelopmental disorders such as ASD.

Whole Exome Sequencing Reveals a Novel AUTS2 In-Frame Deletion in a Boy with Global Developmental Delay, Absent Speech, Dysmorphic Features, and Cerebral Anomalies

Neurodevelopmental disorders (NDDs) are a group of highly prevalent, clinically and genetically heterogeneous pediatric disorders comprising, according to the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-V), intellectual disability, developmental delay, autism spectrum disorders, and other neurological and cognitive disorders manifesting in the developmental age. To date, more than 1000 genes have been implicated in the etiopathogenesis of NNDs. Among them, AUTS2 (OMIM # 607270) encodes a protein involved in neural migration and neuritogenesis, and causes NNDs with different molecular mechanisms including copy number variations, single or multiple exonic deletion and single nucleotide variants. We describes a 9-year-old boy with global developmental delay, absent speech, minor craniofacial anomalies, hypoplasia of the cerebellar vermis and thinning of the corpus callosum, resulted carrier of the de novo AUTS2 c.1603_1626del deletion at whole exome sequencing (WES) predicted to cause the loss of eight amino acids [p.(His535_Thr542del)]. Notably, our patient is the first reported so far in medical literature carrying an in-frame deletion and the first in which absent language, hypoplasia of the cerebellar vermis and thinning of the corpus callosum has been observed thus useful to expand the molecular spectrum of AUTS2 pathogenic variants and to broaden our knowledge on the clinical phenotype associated.

AUTS2 isoforms control neuronal differentiation

Mutations in AUTS2 are associated with autism, intellectual disability, and microcephaly. AUTS2 is expressed in the brain and interacts with polycomb proteins, yet it is still unclear how mutations in AUTS2 lead to neurodevelopmental phenotypes. Here we report that when neuronal differentiation is initiated, there is a shift in expression from a long isoform to a short AUTS2 isoform. Yeast two-hybrid screen identified the splicing factor SF3B1 as an interactor of both isoforms, whereas the polycomb group proteins, PCGF3 and PCGF5, were found to interact exclusively with the long AUTS2 isoform. Reporter assays showed that the first exons of the long AUTS2 isoform function as a transcription repressor, but the part that consist of the short isoform acts as a transcriptional activator, both influenced by the cellular context. The expression levels of PCGF3 influenced the ability of the long AUTS2 isoform to activate or repress transcription. Mouse embryonic stem cells (mESCs) with heterozygote mutations in Auts2 had an increase in cell death during in vitro corticogenesis, which was significantly rescued by overexpressing the human AUTS2 transcripts. mESCs with a truncated AUTS2 protein (missing exons 12-20) showed premature neuronal differentiation, whereas cells overexpressing AUTS2, especially the long transcript, showed increase in expression of pluripotency markers and delayed differentiation. Taken together, our data suggest that the precise expression of AUTS2 isoforms is essential for regulating transcription and the timing of neuronal differentiation.

De novo small deletion affecting transcription start site of short isoform of AUTS2 gene in a patient with syndromic neurodevelopmental defects

Disruption of the autism susceptibility candidate 2 (AUTS2) gene through genomic rearrangements, copy number variations (CNVs), and intragenic deletions and mutations, has been recurrently involved in syndromic forms of developmental delay and intellectual disability, known as AUTS2 syndrome. The AUTS2 gene plays an important role in regulation of neuronal migration, and when altered, associates with a variable phenotype from severely to mildly affected patients. The more severe phenotypes significantly correlate with the presence of defects affecting the C-terminus part of the gene. This article reports a new patient with a syndromic neurodevelopmental disorder, who presents a deletion of 30 nucleotides in the exon 9 of the AUTS2 gene. Importantly, this deletion includes the transcription start site for the AUTS2 short transcript isoform, which has an important role in brain development. Gene expression analysis of AUTS2 full-length and short isoforms revealed that the deletion found in this patient causes a remarkable reduction in the expression level, not only of the short isoform, but also of the full AUTS2 transcripts. This report adds more evidence for the role of mutated AUTS2 short transcripts in the development of a severe phenotype in the AUTS2 syndrome.

Ancestry of the AUTS2 family-A novel group of polycomb-complex proteins involved in human neurological disease

Autism susceptibility candidate 2 (AUTS2) is a neurodevelopmental regulator associated with an autosomal dominant intellectual disability syndrome, AUTS2 syndrome, and is implicated as an important gene in human-specific evolution. AUTS2 exists as part of a tripartite gene family, the AUTS2 family, which includes two relatively undefined proteins, Fibrosin (FBRS) and Fibrosin-like protein 1 (FBRSL1). Evolutionary ancestors of AUTS2 have not been formally identified outside of the Animalia clade. A Drosophila melanogaster protein, Tay bridge, with a role in neurodevelopment, has been shown to display limited similarity to the C-terminal of AUTS2, suggesting that evolutionary ancestors of the AUTS2 family may exist within other Protostome lineages. Here we present an evolutionary analysis of the AUTS2 family, which highlights ancestral homologs of AUTS2 in multiple Protostome species, implicates AUTS2 as the closest human relative to the progenitor of the AUTS2 family, and demonstrates that Tay bridge is a divergent ortholog of the ancestral AUTS2 progenitor gene. We also define regions of high relative sequence identity, with potential functional significance, shared by the extended AUTS2 protein family. Using structural predictions coupled with sequence conservation and human variant data from 15,708 individuals, a putative domain structure for AUTS2 was produced that can be used to aid interpretation of the consequences of nucleotide variation on protein structure and function in human disease. To assess the role of AUTS2 in human-specific evolution, we recalculated allele frequencies at previously identified human derived sites using large population genome data, and show a high prevalence of ancestral alleles, suggesting that AUTS2 may not be a rapidly evolving gene, as previously thought.

Genome-wide association study identifies 7q11.22 and 7q36.3 associated with noise-induced hearing loss among Chinese population

Noise-induced hearing loss (NIHL) seriously affects the life quality of humans and causes huge economic losses to society. To identify novel genetic loci involved in NIHL, we conducted a genome-wide association study (GWAS) for this symptom in Chinese populations. GWAS scan was performed in 89 NIHL subjects (cases) and 209 subjects with normal hearing who have been exposed to a similar noise environment (controls), followed by a replication study consisting of 53 cases and 360 controls. We identified that four candidate pathways were nominally significantly associated with NIHL, including the Erbb, Wnt, hedgehog and intraflagellar transport pathways. In addition, two novel index single-nucleotide polymorphisms, rs35075890 in the intron of AUTS2 gene at 7q11.22 (combined P = 1.3 × 10^-6 ) and rs10081191 in the intron of PTPRN2 gene at 7q36.3 (combined P = 2.1 × 10^-6 ), were significantly associated with NIHL. Furthermore, the expression quantitative trait loci analyses revealed that in brain tissues, the genotypes of rs35075890 are significantly associated with the expression levels of AUTS2, and the genotypes of rs10081191 are significantly associated with the expressions of PTPRN2 and WDR60. In conclusion, our findings highlight two novel loci at 7q11.22 and 7q36.3 conferring susceptibility to NIHL.

AUTS2 Governs Cerebellar Development, Purkinje Cell Maturation, Motor Function and Social Communication

Autism susceptibility candidate 2 (AUTS2), a risk gene for autism spectrum disorders (ASDs), is implicated in telencephalon development. Because AUTS2 is also expressed in the cerebellum where defects have been linked to ASDs, we investigated AUTS2 functions in the cerebellum. AUTS2 is specifically localized in Purkinje cells (PCs) and Golgi cells during postnatal development. Auts2 conditional knockout (cKO) mice exhibited smaller and deformed cerebella containing immature-shaped PCs with reduced expression of Cacna1a. Auts2 cKO and knock-down experiments implicated AUTS2 participation in elimination and translocation of climbing fiber synapses and restriction of parallel fiber synapse numbers. Auts2 cKO mice exhibited behavioral impairments in motor learning and vocal communications. Because Cacna1a is known to regulate synapse development in PCs, it suggests that AUTS2 is required for PC maturation to elicit normal development of PC synapses and thus the impairment of AUTS2 may cause cerebellar dysfunction related to psychiatric illnesses such as ASDs.

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Loss of Auts2 leads to the reduction of cerebellar size

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AUTS2 promotes the dendritic maturation of Purkinje cells

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AUTS2 participates in PF and CF synapse development of Purkinje cells

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Auts2 cKO mice exhibit the impaired motor learning and vocal communications

A genetic window to auditory-verbal problems in bipolar disorder

Bipolar disorder is a high prevalent psychiatric condition entailing recurrent episodes of elevated mood and depression, but also diverse cognitive problems. One deficit observed in patients concerns to auditory-verbal processing. Being a hereditary condition with a complex genetic architecture, it is not clear which genes contribute to this deficit. We show that candidates for bipolar disorder significantly overlap with candidates for clinical conditions resulting from a deficit in the phonological loop of working memory, particularly, developmental dyslexia and specific language impairment. The overlapping genes are involved in aspects of brain development and function (particularly, brain oscillations) potentially underlying phonological processing and accordingly, emerge as promising candidates for auditory-verbal deficits in bipolar disorder.

Functional characterization of the ZEB2 regulatory landscape

Zinc finger E-box–binding homeobox 2 (ZEB2) is a key developmental regulator of the central nervous system (CNS). Although the transcriptional regulation of ZEB2 is essential for CNS development, the elements that regulate ZEB2 expression have yet to be identified. Here, we identified a proximal regulatory region of ZEB2 and characterized transcriptional enhancers during neuronal development. Using chromatin immunoprecipitation sequencing for active (H3K27ac) and repressed (H3K27me3) chromatin regions in human neuronal progenitors, combined with an in vivo zebrafish enhancer assay, we functionally characterized 18 candidate enhancers in the ZEB2 locus. Eight enhancers drove expression patterns that were specific to distinct mid/hindbrain regions (ZEB2#e3 and 5), trigeminal-like ganglia (ZEB2#e6 and 7), notochord (ZEB2#e2, 4 and 12) and whole brain (ZEB2#e14). We further dissected the minimal sequences that drive enhancer-specific activity in the mid/hindbrain and notochord. Using a reporter assay in human cells, we showed an increased activity of the minimal notochord enhancer ZEB2#e2 in response to AP-1 and DLX1/2 expressions, while repressed activity of this enhancer was seen in response to ZEB2 and TFAP2 expressions. We showed that Dlx1 but not Zeb2 and Tfap2 occupies Zeb2#e2 enhancer sequence in the mouse notochord at embryonic day 11.5. Using CRISPR/Cas9 genome editing, we deleted the ZEB2#e2 region, leading to reduction of ZEB2 expression in human cells. We thus characterized distal transcriptional enhancers and trans-acting elements that govern regulation of ZEB2 expression during neuronal development. These findings pave the path toward future analysis of the role of ZEB2 regulatory elements in neurodevelopmental disorders, such as Mowat–Wilson syndrome.

Research and Discussion on the Relationships between Noise-Induced Hearing Loss and ATP2B2 Gene Polymorphism

Long-term and continuous noise exposure can result in noise-induced hearing loss (NIHL), which is a worldwide problem resulting from the interaction of environmental and genetic factors. The ATP2B2 gene polymorphism can destroy cochlear hair cells and increase the risk of NIHL. A case-control study of 760 Chinese textile workers was conducted to investigate the relationship between ATP2B2 polymorphisms and NIHL susceptibility. Venous blood was collected and questionnaires were conducted by professional physicians. A case group and a control group which were typed by individuals' pure-tone audiometry test results were set. Three polymorphism sites of ATP2B2 were genotyped by using the PCR technique. Analysis results revealed that the C allele of rs3209637 (95%CI = 1.08-2.58, odds ratio (OR) = 1.67, P = 0.027) was a dangerous factor and could add to risks of NIHL in the Chinese employees. The data of stratified analysis revealed that individuals who are exposed to noise > 95 dB with the rs3209637 C genotype have a higher susceptibility to NIHL (OR = 1.34, 95%CI = 1.07-1.68). Multifactor dimensionality reduction analysis revealed that the interaction between rs14154 and rs3209637 is linked to increased NIHL risk, and for the interaction among rs14154, smoking and drinking had the same function (OR = 1.54 and 1.77, 95%CI = 1.15-2.07, 1.33-2.37, and P = 0.0037 and P < 0.0001, respectively). Our results suggest that genetic polymorphism rs3209637 C within ATP2B2 is a risk factor for NIHL among Chinese employees and rs3209637 C could be a potential biomarker for NIHL patients.

A Mouse Mutation That Dysregulates Neighboring Galnt17 and Auts2 Genes Is Associated with Phenotypes Related to the Human AUTS2 Syndrome

AUTS2 was originally discovered as the gene disrupted by a translocation in human twins with Autism spectrum disorder, intellectual disability, and epilepsy. Since that initial finding, AUTS2-linked mutations and variants have been associated with a very broad array of neuropsychiatric disorders, sugg esting that AUTS2 is required for fundamental steps of neurodevelopment. However, genotype-phenotype correlations in this region are complicated, because most mutations could also involve neighboring genes. Of particular interest is the nearest downstream neighbor of AUTS2, GALNT17, which encodes a brain-expressed N-acetylgalactosaminyltransferase of unknown brain function. Here we describe a mouse (Mus musculus) mutation, T(5G2;8A1)GSO (abbreviated 16Gso), a reciprocal translocation that breaks between Auts2 and Galnt17 and dysregulates both genes. Despite this complex regulatory effect, 16Gso homozygotes model certain human AUTS2-linked phenotypes very well. In addition to abnormalities in growth, craniofacial structure, learning and memory, and behavior, 16Gso homozygotes display distinct pathologies of the cerebellum and hippocampus that are similar to those associated with autism and other types of AUTS2-linked neurological disease. Analyzing mutant cerebellar and hippocampal transcriptomes to explain this pathology, we identified disturbances in pathways related to neuron and synapse maturation, neurotransmitter signaling, and cellular stress, suggesting possible cellular mechanisms. These pathways, coupled with the translocation's selective effects on Auts2 isoforms and coordinated dysregulation of Galnt17, suggest novel hypotheses regarding the etiology of the human "AUTS2 syndrome" and the wide array of neurodevelopmental disorders linked to variance in this genomic region.

A case of autism spectrum disorder with cleft lip and palate carrying a mutation in exon 8 of AUTS2

We report a patient with autism and cleft lip and palate carrying a de novo heterozygous AUTS2 mutation, c.1464_1467del ACTC (p.Tyr488*). Although the causal relationship between cleft lip and palate and this mutation is unclear, this case report may expand the clinical phenotype of AUTS2 syndrome.

Mitochondrial function and abnormalities implicated in the pathogenesis of ASD

Mitochondria are the powerhouse that generate over 90% of the ATP produced in cells. In addition to its role in energy production, the mitochondrion also plays a major role in carbohydrate, fatty acid, amino acid and nucleotide metabolism, programmed cell death (apoptosis), generation of and protection against reactive oxygen species (ROS), immune response, regulation of intracellular calcium ion levels and even maintenance of gut microbiota. With its essential role in bio-energetic as well as non-energetic biological processes, it is not surprising that proper cellular, tissue and organ function is dependent upon proper mitochondrial function. Accordingly, mitochondrial dysfunction has been shown to be directly linked to a variety of medical disorders, particularly neuromuscular disorders and increasing evidence has linked mitochondrial dysfunction to neurodegenerative and neurodevelopmental disorders such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Rett Syndrome (RS) and Autism Spectrum Disorders (ASD). Over the last 40 years there has been a dramatic increase in the diagnosis of ASD and, more recently, an increasing body of evidence indicates that mitochondrial dysfunction plays an important role in ASD development. In this review, the latest evidence linking mitochondrial dysfunction and abnormalities in mitochondrial DNA (mtDNA) to the pathogenesis of autism will be presented. This review will also summarize the results of several recent `approaches used for improving mitochondrial function that may lead to new therapeutic approaches to managing and/or treating ASD.

Toward the Language Oscillogenome

Language has been argued to arise, both ontogenetically and phylogenetically, from specific patterns of brain wiring. We argue that it can further be shown that core features of language processing emerge from particular phasal and cross-frequency coupling properties of neural oscillations; what has been referred to as the language ‘oscillome.’ It is expected that basic aspects of the language oscillome result from genetic guidance, what we will here call the language ‘oscillogenome,’ for which we will put forward a list of candidate genes. We have considered genes for altered brain rhythmicity in conditions involving language deficits: autism spectrum disorders, schizophrenia, specific language impairment and dyslexia. These selected genes map on to aspects of brain function, particularly on to neurotransmitter function. We stress that caution should be adopted in the construction of any oscillogenome, given the range of potential roles particular localized frequency bands have in cognition. Our aim is to propose a set of genome-to-language linking hypotheses that, given testing, would grant explanatory power to brain rhythms with respect to language processing and evolution.

Tay bridge and extracellular-regulated kinase activity are required for motoneuron function in the Drosophila neural system

Extracellular regulated kinase (Erk) activity is required during neural development for the specification of cell fates in neuroblasts and neuronal lineages, and also regulates several aspects of the activity and survival of mature neurons. The activation of Erk is regulated at multiple levels by kinases and phosphatases that alter its phosphorylation state and by other proteins that regulate its subcellular localization. Here, we find that tay bridge (tay), a negative regulator of Erk in Drosophila imaginal discs, is required in the motoneurons to regulate the number and size of neuromuscular synapses in these cells. The expression of Tay is maximal in motoneurons with low levels of activated ERK, suggesting that Tay modulates the activity of Erk in these cells. We also found that loss of tay expression and increased Erk activity specifically in the motoneurons cause a reversible decrease in walking speed. Impaired motoneurons activity may be caused by alterations in the functionality and number of synaptic boutons developing at the neuromuscular junction in tay mutants.

Epigenetic Effect of Environmental Factors on Neurodevelopmenal Disorders

Epigenetics is an important mechanism of gene regulation that is dependent on the chromatin structure, which is determined by the epigenetic chemical modification of DNA and histone proteins. It is known that the failure of epigenetic mechanisms causes congenital neurodevelopmental disorders (NDs), and that early life exposure to mental stress and endocrine disrupting chemicals, such as phthalates, bisphenol A, and tobacco, can change epigenetic mechanism and gene expression in the brain and cause NDs. Moreover, environmentally induced epigenetic changes are not erased during gametogenesis and are transmitted to subsequent generations, leading to changes in behavior phenotypes. However, epigenetics has a reversible nature because it is based on the addition or removal of chemical residues, and thus the original epigenetic status may be restored. Indeed, several drugs used for mental disorders and NDs restore the epigenetic state and gene expression. Improved epigenetic understanding of NDs will provide important clues for the development of new drugs that take advantage of epigenetic reversibility.

Glycosphingolipid metabolic reprogramming drives neural differentiation

Neural development is accomplished by differentiation events leading to metabolic reprogramming. Glycosphingolipid metabolism is reprogrammed during neural development with a switch from globo- to ganglio-series glycosphingolipid production. Failure to execute this glycosphingolipid switch leads to neurodevelopmental disorders in humans, indicating that glycosphingolipids are key players in this process. Nevertheless, both the molecular mechanisms that control the glycosphingolipid switch and its function in neurodevelopment are poorly understood. Here, we describe a self-contained circuit that controls glycosphingolipid reprogramming and neural differentiation. We find that globo-series glycosphingolipids repress the epigenetic regulator of neuronal gene expression AUTS2. AUTS2 in turn binds and activates the promoter of the first and rate-limiting ganglioside-producing enzyme GM3 synthase, thus fostering the synthesis of gangliosides. By this mechanism, the globo-AUTS2 axis controls glycosphingolipid reprogramming and neural gene expression during neural differentiation, which involves this circuit in neurodevelopment and its defects in neuropathology.

Neuroplastin deletion in glutamatergic neurons impairs selective brain functions and calcium regulation: implication for cognitive deterioration

The cell adhesion molecule neuroplastin (Np) is a novel candidate to influence human intelligence. Np-deficient mice display complex cognitive deficits and reduced levels of Plasma Membrane Ca²⁺ ATPases (PMCAs), an essential regulator of the intracellular Ca²⁺ concentration ([iCa²⁺]) and neuronal activity. We show abundant expression and conserved cellular and molecular features of Np in glutamatergic neurons in human hippocampal-cortical pathways as characterized for the rodent brain. In Nptn^{lox/loxEmx1Cre} mice, glutamatergic neuron-selective Np ablation resulted in behavioral deficits indicating hippocampal, striatal, and sensorimotor dysfunction paralleled by highly altered activities in hippocampal CA1 area, sensorimotor cortex layers I-III/IV, and the striatal sensorimotor domain detected by single-photon emission computed tomography. Altered hippocampal and cortical activities correlated with reduction of distinct PMCA paralogs in Nptn^{lox/loxEmx1Cre} mice and increased [iCa²⁺] in cultured mutant neurons. Human and rodent Np enhanced the post-transcriptional expression of and co-localized with PMCA paralogs in the plasma membrane of transfected cells. Our results indicate Np as essential for PMCA expression in glutamatergic neurons allowing proper [iCa²⁺] regulation and normal circuit activity. Neuron-type-specific Np ablation empowers the investigation of circuit-coded learning and memory and identification of causal mechanisms leading to cognitive deterioration.

Neuronal Migration and AUTS2 Syndrome

Neuronal migration is one of the pivotal steps to form a functional brain, and disorganization of this process is believed to underlie the pathology of psychiatric disorders including schizophrenia, autism spectrum disorders (ASD) and epilepsy. However, it is not clear how abnormal neuronal migration causes mental dysfunction. Recently, a key gene for various psychiatric diseases, the Autism susceptibility candidate 2 (AUTS2), has been shown to regulate neuronal migration, which gives new insight into understanding this question. Interestingly, the AUTS2 protein has dual functions: Cytoplasmic AUTS2 regulates actin cytoskeleton to control neuronal migration and neurite extension, while nuclear AUTS2 controls transcription of various genes as a component of the polycomb complex 1 (PRC1). In this review, we discuss AUTS2 from the viewpoint of human genetics, molecular function, brain development, and behavior in animal models, focusing on its role in neuronal migration.

Epigenetic alterations induced by environmental stress associated with metabolic and neurodevelopmental disorders

Epigenetics is a gene regulation mechanism that does not depend on genomic DNA sequences but depends on chemical modification of genomic DNA and histone proteins around which DNA is wrapped. The failure of epigenetic mechanisms is known to cause various congenital disorders. It is also known that the failures of epigenetic mechanisms causes various acquired disorders since epigenetic modifications of the genome (i.e., "epigenome") are more vulnerable to environmental stress, such as malnutrition, environmental chemicals, and mental stress, than the "genome," especially during the early period of life. However, the epigenome has a reversible property since it is based on removable residues on genomic DNA. Thus, environmentally induced epigenomic alterations can be potentially restored. In fact, some medicines, especially for psychiatric diseases, are known to restore an altered epigenome, resulting in the correction of gene expression. Several lines of evidence suggest that environmentally induced epigenomic alterations are not erased completely during gametogenesis, but are transmitted to subsequent generations with disease phenotypes. In accordance with these understandings, I would like to propose the development of epigenomic-based preemptive medicine that consists of the early detection of the developmental origins of diseases using epigenomic signatures and the early intervention that take advantages of the use of epigenomic reversibility.

Language deficits in schizophrenia and autism as related oscillatory connectomopathies: An evolutionary account

Schizophrenia (SZ) and autism spectrum disorders (ASD) are characterised by marked language deficits, but it is not clear how these arise from gene mutations associated with the disorders. Our goal is to narrow the gap between SZ and ASD and, ultimately, give support to the view that they represent abnormal (but related) ontogenetic itineraries for the human faculty of language. We will focus on the distinctive oscillatory profiles of the SZ and ASD brains, in turn using these insights to refine our understanding of how the brain implements linguistic computations by exploring a novel model of linguistic feature-set composition. We will argue that brain rhythms constitute the best route to interpreting language deficits in both conditions and mapping them to neural dysfunction and risk alleles of the genes. Importantly, candidate genes for SZ and ASD are overrepresented among the gene sets believed to be important for language evolution. This translational effort may help develop an understanding of the aetiology of SZ and ASD and their high prevalence among modern populations.

Epigenetic Effect of Environmental Factors on Autism Spectrum Disorders

Both environmental factors and genetic factors are involved in the pathogenesis of autism spectrum disorders (ASDs). Epigenetics, an essential mechanism for gene regulation based on chemical modifications of DNA and histone proteins, is also involved in congenital ASDs. It was recently demonstrated that environmental factors, such as endocrine disrupting chemicals and mental stress in early life, can change epigenetic status and gene expression, and can cause ASDs. Moreover, environmentally induced epigenetic changes are not erased during gametogenesis and are transmitted to subsequent generations, leading to changes in behavior phenotypes. However, epigenetics has a reversible nature since it is based on the addition or removal of chemical residues, and thus the original epigenetic status may be restored. Indeed, several antidepressants and anticonvulsants used for mental disorders including ASDs restore the epigenetic state and gene expression. Therefore, further epigenetic understanding of ASDs is important for the development of new drugs that take advantages of epigenetic reversibility.

Possible functional links among brain- and skull-related genes selected in modern humans

The sequencing of the genomes from extinct hominins has revealed that changes in some brain-related genes have been selected after the split between anatomically-modern humans and Neanderthals/Denisovans. To date, no coherent view of these changes has been provided. Following a line of research we initiated in Boeckx and Benítez-Burraco (2014a), we hypothesize functional links among most of these genes and their products, based on the existing literature for each of the gene discussed. The genes we focus on are found mutated in different cognitive disorders affecting modern populations and their products are involved in skull and brain morphology, and neural connectivity. If our hypothesis turns out to be on the right track, it means that the changes affecting most of these proteins resulted in a more globular brain and ultimately brought about modern cognition, with its characteristic generativity and capacity to form and exploit cross-modular concepts, properties most clearly manifested in language.