Synaptic proteins and receptors defects in autism spectrum disorders

The Role of Alpha-Synuclein in Neurodevelopmental Diseases

Neurodevelopmental disorders are a group of diseases with cognitive, motor, and emotional development deficits. Alpha-synuclein (α-syn) is a synaptic protein involved in transmission and neurodevelopment. This protein was previously shown to be associated with several disorders, including Parkinson's disease. Furthermore, a close link between neurodevelopmental disorders and Parkinson's has also been found. Changes in synaptic function have been noticed in neurodevelopmental disorders, including autism spectrum disorder. Impaired neurogenesis and related cognitive problems have been associated with altered expression of α-syn. Various studies reported α-syn in different body fluids and tissues such as blood and serum. Alpha-synuclein can help in better understanding the pathogenesis of neurodevelopmental diseases and facilitating their early diagnosis. This review aims to go over the recent advances in the role of α-syn in the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder, attention deficit hyperactivity disorder, and motor and social impairment, and its value as a diagnostic biomarker.

Gephyrin phosphorylation facilitates sexually dimorphic development and function of parvalbumin interneurons in the mouse hippocampus

The precise function of specialized GABAergic interneuron subtypes is required to provide appropriate synaptic inhibition for regulating principal neuron excitability and synchronization within brain circuits. Of these, parvalbumin-type (PV neuron) dysfunction is a feature of several sex-biased psychiatric and brain disorders, although, the underlying developmental mechanisms are unclear. While the transcriptional action of sex hormones generates sexual dimorphism during brain development, whether kinase signaling contributes to sex differences in PV neuron function remains unexplored. In the hippocampus, we report that gephyrin, the main inhibitory post-synaptic scaffolding protein, is phosphorylated at serine S268 and S270 in a developmentally-dependent manner in both males and females. When examining GphnS268A/S270A mice in which site-specific phosphorylation is constitutively blocked, we found that sex differences in PV neuron density in the hippocampal CA1 present in WT mice were abolished, coincident with a female-specific increase in PV neuron-derived terminals and increased inhibitory input onto principal cells. Electrophysiological analysis of CA1 PV neurons indicated that gephyrin phosphorylation is required for sexually dimorphic function. Moreover, while male and female WT mice showed no difference in hippocampus-dependent memory tasks, GphnS268A/S270A mice exhibited sex- and task-specific deficits, indicating that gephyrin phosphorylation is differentially required by males and females for convergent cognitive function. In fate mapping experiments, we uncovered that gephyrin phosphorylation at S268 and S270 establishes sex differences in putative PV neuron density during early postnatal development. Furthermore, patch-sequencing of putative PV neurons at postnatal day 4 revealed that gephyrin phosphorylation contributes to sex differences in the transcriptomic profile of developing interneurons. Therefore, these early shifts in male-female interneuron development may drive adult sex differences in PV neuron function and connectivity. Our results identify gephyrin phosphorylation as a new substrate organizing PV neuron development at the anatomical, functional, and transcriptional levels in a sex-dependent manner, thus implicating kinase signaling disruption as a new mechanism contributing to the sex-dependent etiology of brain disorders.

Mice lacking Astn2 have ASD-like behaviors and altered cerebellar circuit properties

Astrotactin 2 (ASTN2) is a transmembrane neuronal protein highly expressed in the cerebellum that functions in receptor trafficking and modulates cerebellar Purkinje cell (PC) synaptic activity. We recently reported a family with a paternally inherited intragenic ASTN2 duplication with a range of neurodevelopmental disorders, including autism spectrum disorder (ASD), learning difficulties, and speech and language delay. To provide a genetic model for the role of the cerebellum in ASD-related behaviors and study the role of ASTN2 in cerebellar circuit function, we generated global and PC-specific conditional Astn2 knockout (KO and cKO, respectively) mouse lines. Astn2 KO mice exhibit strong ASD-related behavioral phenotypes, including a marked decrease in separation-induced pup ultrasonic vocalization calls, hyperactivity and repetitive behaviors, altered social behaviors, and impaired cerebellar-dependent eyeblink conditioning. Hyperactivity and repetitive behaviors were also prominent in Astn2 cKO animals. By Golgi staining, Astn2 KO PCs have region-specific changes in dendritic spine density and filopodia numbers. Proteomic analysis of Astn2 KO cerebellum reveals a marked upregulation of ASTN2 family member, ASTN1, a neuron-glial adhesion protein. Immunohistochemistry and electron microscopy demonstrates a significant increase in Bergmann glia volume in the molecular layer of Astn2 KO animals. Electrophysiological experiments indicate a reduced frequency of spontaneous excitatory postsynaptic currents (EPSCs), as well as increased amplitudes of both spontaneous EPSCs and inhibitory postsynaptic currents (IPSCs) in the Astn2 KO animals, suggesting that pre- and postsynaptic components of synaptic transmission are altered. Thus, ASTN2 regulates ASD-like behaviors and cerebellar circuit properties.

Molecular and in silico analyses of SYN III gene variants in autism spectrum disorder

BACKGROUND

Defects in neurotransmission and synaptogenesis are noteworthy in the pathogenesis of ASD. Synapsin III (SYN III) is defined as a synaptic vesicle protein that plays an important role in synaptogenesis and regulation of neurotransmitter release and neurite outgrowth. Therefore, SYN III may associate with many neurodevelopmental diseases, including ASD.

AIM

The aim of this study was to investigate whether the SYN III gene -631 C > G (rs133946) and -196 G > A (rs133945) polymorphisms are associated with susceptibility to ASD.

METHODS

SYN III variants and the risk of ASD were investigated in 26 healthy children and 24 ASD children. SYN III gene variants were genotyped by PCR-RFLP methods. The differences in genotype and allele frequencies between the ASD and control groups were calculated using the chi-square (χ2). We analysed the SYN III gene using web-based tools.

RESULTS

Our results suggest that the presence of the AA genotype of the SYN III -196 G > A (rs133945) polymorphism affects the characteristics and development of ASD in children (p = 0.012). SYN III -631 C > G (rs133946) polymorphism was not associated with ASD (p = 0.524). We have shown the prediction of gene-gene interaction that SYN III is co-expressed with 17 genes, physical interaction with 3 genes, and co-localization with 12 genes. The importance of different genes (SYN I, II, III, GABRD, NOS1AP, GNAO1) for ASD pathogenesis was revealed by GO analysis.

CONCLUSION

Considering the role of SYN III and related genes, especially in the synaptic vesicle pathway and neurotransmission, its effect on ASD can be further investigated.

Association between Neuroligin-1 polymorphism and plasma glutamine levels in individuals with autism spectrum disorder

BACKGROUND

Unravelling the relationships between candidate genes and autism spectrum disorder (ASD) phenotypes remains an outstanding challenge. Endophenotypes, defined as inheritable, measurable quantitative traits, might provide intermediary links between genetic risk factors and multifaceted ASD phenotypes. In this study, we sought to determine whether plasma metabolite levels could serve as endophenotypes in individuals with ASD and their family members.

METHODS

We employed an untargeted, high-resolution metabolomics platform to analyse 14,342 features across 1099 plasma samples. These samples were collected from probands and their family members participating in the Autism Genetic Resource Exchange (AGRE) (N = 658), compared with neurotypical individuals enrolled in the PrecisionLink Health Discovery (PLHD) program at Boston Children's Hospital (N = 441). We conducted a metabolite quantitative trait loci (mQTL) analysis using whole-genome genotyping data from each cohort in AGRE and PLHD, aiming to prioritize significant mQTL and metabolite pairs that were exclusively observed in AGRE.

FINDINGS

Within the AGRE group, we identified 54 significant associations between genotypes and metabolite levels (P < 5.27 × 10-11), 44 of which were not observed in the PLHD group. Plasma glutamine levels were found to be associated with variants in the NLGN1 gene, a gene that encodes post-synaptic cell-adhesion molecules in excitatory neurons. This association was not detected in the PLHD group. Notably, a significant negative correlation between plasma glutamine and glutamate levels was observed in the AGRE group, but not in the PLHD group. Furthermore, plasma glutamine levels showed a negative correlation with the severity of restrictive and repetitive behaviours (RRB) in ASD, although no direct association was observed between RRB severity and the NLGN1 genotype.

INTERPRETATION

Our findings suggest that plasma glutamine levels could potentially serve as an endophenotype, thus establishing a link between the genetic risk associated with NLGN1 and the severity of RRB in ASD. This identified association could facilitate the development of novel therapeutic targets, assist in selecting specific cohorts for clinical trials, and provide insights into target symptoms for future ASD treatment strategies.

FUNDING

This work was supported by the National Institute of Health (grant numbers: R01MH107205, U01TR002623, R24OD024622, OT2OD032720, and R01NS129188) and the PrecisionLink Biobank for Health Discovery at Boston Children's Hospital.

Striatal Synaptic Changes and Behavior in Adult mouse Upon Prenatal Exposure to Valproic Acid

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by persistent deficits in social communication and social interaction. Altered synaptogenesis and aberrant connectivity responsible for social behavior and communication have been reported in autism pathogenesis. Autism has a strong genetic and heritable component; however, environmental factors including toxins, pesticides, infection and in utero exposure to drugs such as VPA have also been implicated in ASD. Administration of VPA during pregnancy has been used as a rodent model to study pathophysiological mechanisms involved in ASD, and in this study, we used the mouse model of prenatal exposure to VPA to assess the effects on striatal and dorsal hippocampus function in adult mice. Alterations in repetitive behaviors and shift habits were observed in mice prenatally exposed to VPA. In particular, such mice presented a better performance in learned motor skills and cognitive deficits in Y-maze learning frequently associated with striatal and hippocampal function. These behavioral changes were associated with a decreased level of proteins involved in the formation and maintenance of excitatory synapses, such as Nlgn-1 and PSD-95. In conclusion, motor skill abilities, repetitive behaviors, and impaired flexibility to shift habits are associated with reduced striatal excitatory synaptic function in the adult mouse prenatally exposed to VPA.

Y chromosome sequence and epigenomic reconstruction across human populations

Recent advances in long-read sequencing technologies have allowed the generation and curation of more complete genome assemblies, enabling the analysis of traditionally neglected chromosomes, such as the human Y chromosome (chrY). Native DNA was sequenced on a MinION Oxford Nanopore Technologies sequencing device to generate genome assemblies for seven major chrY human haplogroups. We analyzed and compared the chrY enrichment of sequencing data obtained using two different selective sequencing approaches: adaptive sampling and flow cytometry chromosome sorting. We show that adaptive sampling can produce data to create assemblies comparable to chromosome sorting while being a less expensive and time-consuming technique. We also assessed haplogroup-specific structural variants, which would be otherwise difficult to study using short-read sequencing data only. Finally, we took advantage of this technology to detect and profile epigenetic modifications among the considered haplogroups. Altogether, we provide a framework to study complex genomic regions with a simple, fast, and affordable methodology that could be applied to larger population genomics datasets.

Maternal Diabetes Deregulates the Expression of Mecp2 via miR-26b-5p in Mouse Embryonic Neural Stem Cells

Maternal diabetes has been associated with a greater risk of neurodevelopmental disorders in offspring. It has been established that hyperglycemia alters the expression of genes and microRNAs (miRNAs) regulating the fate of neural stem cells (NSCs) during brain development. In this study, the expression of methyl-CpG-binding protein-2 (Mecp2), a global chromatin organizer and a crucial regulator of synaptic proteins, was analyzed in NSCs obtained from the forebrain of embryos of diabetic mice. Mecp2 was significantly downregulated in NSCs derived from embryos of diabetic mice when compared to controls. miRNA target prediction revealed that the miR-26 family could regulate the expression of Mecp2, and further validation confirmed that Mecp2 is a target of miR-26b-5p. Knockdown of Mecp2 or overexpression of miR-26b-5p altered the expression of tau protein and other synaptic proteins, suggesting that miR-26b-5p alters neurite outgrowth and synaptogenesis via Mecp2. This study revealed that maternal diabetes upregulates the expression of miR-26b-5p in NSCs, resulting in downregulation of its target, Mecp2, which in turn perturbs neurite outgrowth and expression of synaptic proteins. Overall, hyperglycemia dysregulates synaptogenesis that may manifest as neurodevelopmental disorders in offspring from diabetic pregnancy.

Contrastsing synaptic roles of MDGA1 and MDGA2

Neurodevelopmental disorders are frequently linked to mutations in synaptic organizing molecules. MAM domain containing glycosylphosphatidylinositol anchor 1 and 2 (MDGA1 and MDGA2) are a family of synaptic organizers suggested to play an unusual role as synaptic repressors, but studies offer conflicting evidence for their localization. Using epitope-tagged MDGA1 and MDGA2 knock-in mice, we found that native MDGAs are expressed throughout the brain, peaking early in postnatal development. Surprisingly, endogenous MDGA1 was enriched at excitatory, but not inhibitory, synapses. Both shRNA knockdown and CRISPR/Cas9 knockout of MDGA1 resulted in cell-autonomous, specific impairment of AMPA receptor-mediated synaptic transmission, without affecting GABAergic transmission. Conversely, MDGA2 knockdown/knockout selectively depressed NMDA receptor-mediated transmission but enhanced inhibitory transmission. Our results establish that MDGA2 acts as a synaptic repressor, but only at inhibitory synapses, whereas both MDGAs are required for excitatory transmission. This nonoverlapping division of labor between two highly conserved synaptic proteins is unprecedented.

A synaptic molecular dependency network in knockdown of autism- and schizophrenia-associated genes revealed by multiplexed imaging

The complex functions of neuronal synapses depend on their tightly interconnected protein network, and their dysregulation is implicated in the pathogenesis of autism spectrum disorders and schizophrenia. However, it remains unclear how synaptic molecular networks are altered biochemically in these disorders. Here, we apply multiplexed imaging to probe the effects of RNAi knockdown of 16 autism- and schizophrenia-associated genes on the simultaneous joint distribution of 10 synaptic proteins, observing several protein composition phenotypes associated with these risk genes. We apply Bayesian network analysis to infer hierarchical dependencies among eight excitatory synaptic proteins, yielding predictive relationships that can only be accessed with single-synapse, multiprotein measurements performed simultaneously in situ. Finally, we find that central features of the network are affected similarly across several distinct gene knockdowns. These results offer insight into the convergent molecular etiology of these widespread disorders and provide a general framework to probe subcellular molecular networks.

Intestinal Barrier Dysfunction and Microbiota–Gut–Brain Axis: Possible Implications in the Pathogenesis and Treatment of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with multifactorial etiology, characterized by impairment in two main functional areas: (1) communication and social interactions, and (2) skills, interests and activities. ASD patients often suffer from gastrointestinal symptoms associated with dysbiotic states and a “leaky gut.” A key role in the pathogenesis of ASD has been attributed to the gut microbiota, as it influences central nervous system development and neuropsychological and gastrointestinal homeostasis through the microbiota–gut–brain axis. A state of dysbiosis with a reduction in the Bacteroidetes/Firmicutes ratio and Bacteroidetes level and other imbalances is common in ASD. In recent decades, many authors have tried to study and identify the microbial signature of ASD through in vivo and ex vivo studies. In this regard, the advent of metabolomics has also been of great help. Based on these data, several therapeutic strategies, primarily the use of probiotics, are investigated to improve the symptoms of ASD through the modulation of the microbiota. However, although the results are promising, the heterogeneity of the studies precludes concrete evidence. The aim of this review is to explore the role of intestinal barrier dysfunction, the gut–brain axis and microbiota alterations in ASD and the possible role of probiotic supplementation in these patients.

Brain insulin resistance linked Alzheimer's and Parkinson's disease pathology: An undying implication of epigenetic and autophagy modulation

In metabolic syndrome, dysregulated signalling activity of the insulin receptor pathway in the brain due to persistent insulin resistance (IR) condition in the periphery may lead to brain IR (BIR) development. BIR causes an upsurge in the activity of glycogen synthase kinase-3 beta, increased amyloid beta (Aβ) accumulation, hyperphosphorylation of tau, aggravated formation of Aβ oligomers and simultaneously neurofibrillary tangle formation, all of which are believed to be direct contributors in Alzheimer's Disease (AD) pathology. Likewise, for Parkinson's Disease (PD), BIR is associated with alpha-synuclein alterations, dopamine loss in brain areas which ultimately succumbs towards the appearance of classical motor symptoms corresponding to the typical PD phenotype. Modulation of the autophagy process for clearing misfolded proteins and alteration in histone proteins to alleviate disease progression in BIR-linked AD and PD have recently evolved as a research hotspot, as the majority of the autophagy-related proteins are believed to be regulated by histone posttranslational modifications. Hence, this review will provide a timely update on the possible mechanism(s) converging towards BIR induce AD and PD. Further, emphasis on the potential epigenetic regulation of autophagy that can be effectively targeted for devising a complete therapeutic cure for BIR-induced AD and PD will also be reviewed.

Reduced epilepsy development in synapsin 2 knockout mice with autistic behavior following early systemic treatment with interleukin-6 receptor antibody

BACKGROUND

Individuals with autism spectrum disorder (ASD) have an increased risk of developing epilepsy. Both ASD and epilepsy have been associated with increased levels of immune factors in the blood, including the proinflammatory cytokine interleukin 6 (IL-6). Mice lacking the synapsin 2 gene (Syn2 KO) exhibit ASD-like behavior and develop epileptic seizures. Their brains display neuroinflammatory changes including elevated IL-6 levels. We aimed to investigate the effect of systemic IL-6 receptor antibody (IL-6R ab) treatment on seizure development and frequency in Syn2 KO mice.

MATERIAL AND METHODS

Weekly systemic (i.p.) injections of IL-6R ab or saline were given to Syn2 KO mice starting either early in life at 1 month of age, before seizure debut or at 3 months of age, directly after seizure debut and continued for 4 or 2 months, respectively. Seizures were provoked by handling the mice three times per week. The neuroinflammatory response and synaptic protein levels in the brain were determined by ELISA, immunohistochemistry and western blots. In an additional group of Syn2 KO mice, with IL-6R ab treatment early in life, ASD-related behavioral tests including social interaction and repetitive self-grooming, as well as cognitive memory and depressive-/anxiety-like tests, and actigraphy measurements of circadian sleep-awake rhythm were analyzed.

RESULTS

The IL-6R ab treatment reduced seizure development and frequency in Syn2 KO mice when initiated before, but not after, seizure debut. However, early treatment did not reverse the neuroinflammatory response or the imbalance in synaptic protein levels in the brain previously reported in Syn2 KO mice. The treatment did not affect social interaction, performance in memory, depressive-/anxiety-like tests or the sleep-awake rhythm of Syn2 KO mice.

CONCLUSION

These findings suggest the involvement of IL-6 receptor signaling during epilepsy development in Syn2 KO mice, without significant alterations of the immune reaction in the brain, and independently of cognitive performance, mood and circadian sleep-awake rhythm.

Role of SHANK3 in concentrated ambient PM2. 5 exposure induced autism-like phenotype

Perinatal air pollution plays an important role in the development of autism. However, research on the pathogenic mechanism remains limited. In this study, the model of systemic inhalation of concentrated approximately 8-fold the level (mean concentration was 224 μg/m³) reported in ambient outdoor air of PM2.5 (particulate matters that are 2.5 μm or less in diameter)in early-postnatal male Sprague-Dawley (SD) rats was established. Through a series of autism-related behavioral tests, it was identified that young rats (postnatal day 1-day21, named PND1-PND21) exposed to PM2.5 exhibited typical autistic phenotypes, such as impaired language communication, abnormal repetitive and stereotyped behaviors, and impaired social skills. Moreover, synaptic abnormalities have been found in the brain tissues of young rats exposed to PM2.5. In terms of the molecular mechanism, we found that the levels of SH3 and multiple ankyrin repeat domains 3 (SHANK3) expression and key molecular proteins in the downstream signaling pathways were decreased in the brain tissues of the exposed rats. Finally, at the epigenetic level, SHANK3 methylation levels were increased in young rats exposed to PM2.5. In conclusion, the study revealed that PM2.5 exposure might induce the early postnatal autism through the SHANK3 signaling pathway by affecting the SHANK3 methylation levels and reducing the SHANK3 expression levels. The study could provide new ideas for autism etiology and a theoretical basis for the prevention and treatment of autism in children.

Physical Activity, Gut Microbiota, and Genetic Background for Children and Adolescents with Autism Spectrum Disorder

It is estimated that one in 100 children worldwide has been diagnosed with autism spectrum disorder (ASD). Children with ASD frequently suffer from gut dysbiosis and gastrointestinal issues, findings which possibly play a role in the pathogenesis and/or severity of their condition. Physical activity may have a positive effect on the composition of the intestinal microbiota of healthy adults. However, the effect of exercise both on the gastrointestinal problems and intestinal microbiota (and thus possibly on ASD) itself in affected children is unknown. In terms of understanding the physiopathology and manifestations of ASD, analysis of the gut-brain axis holds some promise. Here, we discuss the physiopathology of ASD in terms of genetics and microbiota composition, and how physical activity may be a promising non-pharmaceutical approach to improve ASD-related symptoms.

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.

Cross-Disorder Analysis of Genic and Regulatory Copy Number Variations in Bipolar Disorder, Schizophrenia, and Autism Spectrum Disorder

BACKGROUND

We aimed to determine the similarities and differences in the roles of genic and regulatory copy number variations (CNVs) in bipolar disorder (BD), schizophrenia (SCZ), and autism spectrum disorder (ASD).

METHODS

Based on high-resolution CNV data from 8708 Japanese samples, we performed to our knowledge the largest cross-disorder analysis of genic and regulatory CNVs in BD, SCZ, and ASD.

RESULTS

In genic CNVs, we found an increased burden of smaller (<100 kb) exonic deletions in BD, which contrasted with the highest burden of larger (>500 kb) exonic CNVs in SCZ/ASD. Pathogenic CNVs linked to neurodevelopmental disorders were significantly associated with the risk for each disorder, but BD and SCZ/ASD differed in terms of the effect size (smaller in BD) and subtype distribution of CNVs linked to neurodevelopmental disorders. We identified 3 synaptic genes (DLG2, PCDH15, and ASTN2) as risk factors for BD. Whereas gene set analysis showed that BD-associated pathways were restricted to chromatin biology, SCZ and ASD involved more extensive and similar pathways. Nevertheless, a correlation analysis of gene set results indicated weak but significant pathway similarities between BD and SCZ or ASD (r = 0.25-0.31). In SCZ and ASD, but not BD, CNVs were significantly enriched in enhancers and promoters in brain tissue.

CONCLUSIONS

BD and SCZ/ASD differ in terms of CNV burden, characteristics of CNVs linked to neurodevelopmental disorders, and regulatory CNVs. On the other hand, they have shared molecular mechanisms, including chromatin biology. The BD risk genes identified here could provide insight into the pathogenesis of BD.

Multiple Recurrent Copy Number Variations (CNVs) in Chromosome 22 Including 22q11.2 Associated with Autism Spectrum Disorder

Introduction

Autism spectrum disorder (ASD) is a developmental disorder that can cause substantial social, communication, and behavioral challenges. Genetic factors play a significant role in ASD, where the risk of ASD has been increased for unclear reasons. Twin studies have shown important evidence of both genetic and environmental contributions in ASD, where the level of contribution of these factors has not been proven yet. It has been suggested that copy number variation (CNV) duplication and the deletion of many genes in chromosome 22 (Ch22) may have a strong association with ASD. This study screened the CNVs in Ch22 in autistic Saudi children and assessed the candidate gene in the CNVs region of Ch22 that is most associated with ASD.

Methods

This study included 15 autistic Saudi children as well as 4 healthy children as controls; DNA was extracted from samples and analyzed using array comparative genomic hybridization (aCGH) and DNA sequencing.

Results

The aCGH detected (in only 6 autistic samples) deletion and duplication in many regions of Ch22, including some critical genes. Moreover, DNA sequencing determined a genetic mutation in the TBX1 gene sequence in autistic samples. This study, carried out using aCGH, found that six autistic patients had CNVs in Ch22, and DNA sequencing revealed mutations in the TBX1 gene in autistic samples but none in the control.

Conclusion

CNV deletion and the duplication of the TBX1 gene could be related to ASD; therefore, this gene needs more analysis in terms of expression levels.

Genetics of glutamate and its receptors in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental impairment characterized by deficits in social interaction skills, impaired communication, and repetitive and restricted behaviors that are thought to be due to altered neurotransmission processes. The amino acid glutamate is an essential excitatory neurotransmitter in the human brain that regulates cognitive functions such as learning and memory, which are usually impaired in ASD. Over the last several years, increasing evidence from genetics, neuroimaging, protein expression, and animal model studies supporting the notion of altered glutamate metabolism has heightened the interest in evaluating glutamatergic dysfunction in ASD. Numerous pharmacological, behavioral, and imaging studies have demonstrated the imbalance in excitatory and inhibitory neurotransmitters, thus revealing the involvement of the glutamatergic system in ASD pathology. Here, we review the effects of genetic alterations on glutamate and its receptors in ASD and the role of non-invasive imaging modalities in detecting these changes. We also highlight the potential therapeutic targets associated with impaired glutamatergic pathways.

Integration of Transcriptome and Exome Genotyping Identifies Significant Variants with Autism Spectrum Disorder

Autism is a complex disease with genetic predisposition factors. Real factors for treatment and early diagnosis are yet to be defined. This study integrated transcriptome and exome genotyping for identifying functional variants associated with autism spectrum disorder and their impact on gene expression to find significant variations. More than 1800 patients were screened, and 70 (47 male/23 female) with an average age of 7.56 ± 3.68 years fulfilled the DSM-5 criteria for autism. Analysis revealed 682 SNPs of 589 genes significantly (p < 0.001) associated with autism among the putative functional exonic variants (n = 243,345) studied. Olfactory receptor genes on chromosome 6 were significant after Bonferroni correction (α = 0.05/243345 = 2.05 × 10−7) with a high degree of linkage disequilibrium on 6p22.1 (p = 6.71 × 10−9). The differentially expressed gene analysis of autistic patients compared to controls in whole RNA sequencing identified significantly upregulated (foldchange ≥ 0.8 and p-value ≤ 0.05; n = 125) and downregulated (foldchange ≤ −0.8 and p-value ≤ 0.05; n = 117) genes. The integration of significantly up- and downregulated genes and genes of significant SNPs identified regulatory variants (rs6657480, rs3130780, and rs1940475) associated with the up- (ITGB3BP) and downregulation (DDR1 and MMP8) of genes in autism spectrum disorder in people of Arab ancestries. The significant variants could be a biomarker of interest for identifying early autism among Arabs and helping to characterize the genes involved in the susceptibility mechanisms for autistic subjects.

Postsynaptic autism spectrum disorder genes and synaptic dysfunction

This review provides an overview of the synaptic dysfunction of neuronal circuits and the ensuing behavioral alterations caused by mutations in autism spectrum disorder (ASD)-linked genes directly or indirectly affecting the postsynaptic neuronal compartment. There are plenty of ASD risk genes, that may be broadly grouped into those involved in gene expression regulation (epigenetic regulation and transcription) and genes regulating synaptic activity (neural communication and neurotransmission). Notably, the effects mediated by ASD-associated genes can vary extensively depending on the developmental time and/or subcellular site of expression. Therefore, in order to gain a better understanding of the mechanisms of disruptions in postsynaptic function, an effort to better model ASD in experimental animals is required to improve standardization and increase reproducibility within and among studies. Such an effort holds promise to provide deeper insight into the development of these disorders and to improve the translational value of preclinical studies.

Symptomatic, Genetic, and Mechanistic Overlaps between Autism and Alzheimer's Disease

Autism spectrum disorder (ASD) and Alzheimer's disease (AD) are neurodevelopmental and neurodegenerative disorders affecting two opposite ends of life span, i.e., childhood and old age. Both disorders pose a cumulative threat to human health, with the rate of incidences increasing considerably worldwide. In the context of recent developments, we aimed to review correlated symptoms and genetics, and overlapping aspects in the mechanisms of the pathogenesis of ASD and AD. Dementia, insomnia, and weak neuromuscular interaction, as well as communicative and cognitive impairments, are shared symptoms. A number of genes and proteins linked with both disorders have been tabulated, including MECP2, ADNP, SCN2A, NLGN, SHANK, PTEN, RELN, and FMR1. Theories about the role of neuron development, processing, connectivity, and levels of neurotransmitters in both disorders have been discussed. Based on the recent literature, the roles of FMRP (Fragile X mental retardation protein), hnRNPC (heterogeneous ribonucleoprotein-C), IRP (Iron regulatory proteins), miRNAs (MicroRNAs), and α-, β0, and γ-secretases in the posttranscriptional regulation of cellular synthesis and processing of APP (amyloid-β precursor protein) have been elaborated to describe the parallel and overlapping routes and mechanisms of ASD and AD pathogenesis. However, the interactive role of genetic and environmental factors, oxidative and metal ion stress, mutations in the associated genes, and alterations in the related cellular pathways in the development of ASD and AD needs further investigation.

Update on the Development of MNK Inhibitors as Therapeutic Agents

Mitogen-activated protein kinase-interacting kinases 1 and 2 (MNK1/2) represent a central class of enzymes that are activated by extracellular signal-regulated kinase (ERK) or p38 mitogen-activated protein (MAP) kinases. MNK1 and MNK2 coordinate cellular signaling, control production of inflammatory chemokines, and regulate cell proliferation and survival. MNK1/2 are referred to as serine/threonine kinases as they phosphorylate serine or threonine residues on their substrates. Upon activation, MNK1/2 phosphorylate eukaryotic translation initiation factor 4E (eIF4E) at Ser209, which in turn initiates ribosome assembly and protein translation. Deleterious overexpression of MNK1/2 and/or eIF4E have been reported in several diseases including cancers, neurological disorders, autism, and inflammation. Recently, there have been intense efforts toward the development of potent and selective inhibitors of MNK1/2 in both academia and industry. Herein, we review the current understanding of the structural and biological aspects of MNK1/2 and provide an update of pharmacological inhibitors of MNK1/2 including candidates in clinical trials.

An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders

Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.

FMR1 and Autism, an Intriguing Connection Revisited

Autism Spectrum Disorder (ASD) represents a distinct phenotype of behavioral dysfunction that includes deficiencies in communication and stereotypic behaviors. ASD affects about 2% of the US population. It is a highly heritable spectrum of conditions with substantial genetic heterogeneity. To date, mutations in over 100 genes have been reported in association with ASD phenotypes. Fragile X syndrome (FXS) is the most common single-gene disorder associated with ASD. The gene associated with FXS, FMR1 is located on chromosome X. Accordingly, the condition has more severe manifestations in males. FXS results from the loss of function of FMR1 due to the expansion of an unstable CGG repeat located in the 5'' untranslated region of the gene. About 50% of the FXS males and 20% of the FXS females meet the Diagnostic Statistical Manual 5 (DSM-5) criteria for ASD. Among the individuals with ASD, about 3% test positive for FXS. FMRP, the protein product of FMR1, is a major gene regulator in the central nervous system. Multiple pathways regulated by FMRP are found to be dysfunctional in ASD patients who do not have FXS. Thus, FXS presents the opportunity to study cellular phenomena that may have wider applications in the management of ASD and to develop new strategies for ASD therapy.

Glutamate and functional connectivity - support for the excitatory-inhibitory imbalance hypothesis in autism spectrum disorders

It has been proposed that the Glutamate (Glu) system is implicated in autism spectrum disorders (ASD) via an imbalance between excitatory and inhibitory brain circuits, which impacts on brain function. Here, we investigated the excitatory-inhibitory imbalance theory by measuring Glu-concentrations and the relationship with resting-state function. Nineteen adult males with ASD and 19 age and sex-matched healthy controls (HC) (23 - 58 years) underwent Proton Magnetic Resonance Spectroscopy of the dorsal anterior cingulate cortex (dACC) and resting-state functional Magnetic Resonance Imaging (fMRI). Glu and Glx concentrations were compared between groups. Seed-based functional connectivity was analyzed with a priori seeds of the right and left dACC. Finally, metabolite concentrations were related to functional connectivity coefficients and compared between both groups. Individuals with ASD showed significantly negative associations between increased Glx concentrations and reduced functional connectivity between the dACC and insular, limbic and parietal regions. In contrast, HC displayed a positive relationship between the same metabolite and connectivity measures. We provided new evidence to support the excitatory-inhibitory imbalance theory, where excitatory Glx concentrations were related to functional dysconnectivity in ASD. Future research is needed to investigate large-scale functional networks in association with both excitatory and inhibitory metabolites in subpopulations of ASD.

Early postnatal allergic airway inflammation induces dystrophic microglia leading to excitatory postsynaptic surplus and autism-like behavior

Microglia play key roles in synaptic pruning, which primarily occurs from the postnatal period to adolescence. Synaptic pruning is essential for normal brain development and its impairment is implicated in neuropsychiatric developmental diseases such as autism spectrum disorders (ASD). Recent epidemiological surveys reported a strong link between ASD and atopic/allergic diseases. However, few studies have experimentally investigated the relationship between allergy and ASD-like manifestations, particularly in the early postnatal period, when allergic disorders occur frequently. Therefore, we aimed to characterize how allergic inflammation in the early postnatal period influences microglia and behavior using mouse models of short- and long-term airway allergy. Male mice were immunized by an intraperitoneal injection of aluminum hydroxide and ovalbumin (OVA) or phosphate-buffered saline (control) on postnatal days (P) 3, 7, and 11, followed by intranasal challenge with OVA or phosphate-buffered saline solution twice a week until P30 or P70. In the hippocampus, Iba-1-positive areas, the size of Iba-1-positive microglial cell bodies, and the ramification index of microglia by Sholl analysis were significantly smaller in the OVA group than in the control group on P30 and P70, although Iba-1-positive microglia numbers did not differ significantly between the two groups. In Iba-1-positive cells, postsynaptic density protein 95 (PSD95)-occupied areas and CD68-occupied areas were significantly decreased on P30 and P70, respectively, in the OVA group compared with the control group. Immunoblotting using hippocampal tissues demonstrated that amounts of PSD95, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor 2, and N-methyl-D-aspartate (NMDA) receptor 2B were significantly increased in the OVA group compared with the control group on P70, and a similar increasing trend for PSD95 was observed on P30. Neurogenesis was not significantly different between the two groups on P30 or P70 by doublecortin immunohistochemistry. The social preference index was significantly lower in the three chamber test and the number of buried marbles was significantly higher in the OVA group than in the control group on P70 but not on P30, whereas locomotion and anxiety were not different between the two groups. Compared with the control group, serum basal corticosterone levels were significantly elevated and hippocampal glucocorticoid receptor (GR) amounts and nuclear GR translocation in microglia, but not in neurons or astrocytes, were significantly decreased in the OVA group on P70 but not on P30. Gene set enrichment analysis of isolated microglia revealed that genes related to immune responses including Toll-like receptor signaling and chemokine signaling pathways, senescence, and glucocorticoid signaling were significantly upregulated in the OVA group compared with the control group on P30 and P70. These findings suggest that early postnatal allergic airway inflammation induces dystrophic microglia that exhibit defective synaptic pruning upon short- and long-term allergen exposure. Furthermore, long-term allergen exposure induced excitatory postsynaptic surplus and ASD-like behavior. Hypothalamo-pituitary-adrenal axis activation and the compensatory downregulation of microglial GR during long-term allergic airway inflammation may also facilitate these changes.

Regulation of Neural Circuit Development by Cadherin-11 Provides Implications for Autism

Autism spectrum disorder (ASD) is a neurologic condition characterized by alterations in social interaction and communication, and restricted and/or repetitive behaviors. The classical Type II cadherins cadherin-8 (Cdh8, CDH8) and cadherin-11 (Cdh11, CDH11) have been implicated as autism risk gene candidates. To explore the role of cadherins in the etiology of autism, we investigated their expression patterns during mouse brain development and in autism-specific human tissue. In mice, expression of cadherin-8 and cadherin-11 was developmentally regulated and enriched in the cortex, hippocampus, and thalamus/striatum during the peak of dendrite formation and synaptogenesis. Both cadherins were expressed in synaptic compartments but only cadherin-8 associated with the excitatory synaptic marker neuroligin-1. Induced pluripotent stem cell (iPSC)-derived cortical neural precursor cells (NPCs) and cortical organoids generated from individuals with autism showed upregulated CDH8 expression levels, but downregulated CDH11. We used Cdh11 knock-out (KO) mice of both sexes to analyze the function of cadherin-11, which could help explain phenotypes observed in autism. Cdh11-/- hippocampal neurons exhibited increased dendritic complexity along with altered neuronal and synaptic activity. Similar to the expression profiles in human tissue, levels of cadherin-8 were significantly elevated in Cdh11 KO brains. Additionally, excitatory synaptic markers neuroligin-1 and postsynaptic density (PSD)-95 were both increased. Together, these results strongly suggest that cadherin-11 is involved in regulating the development of neuronal circuitry and that alterations in the expression levels of cadherin-11 may contribute to the etiology of autism.

Experiences affect social behaviors via altering neuronal morphology and oxytocin system

Life experiences, such as maternal deprivation (MD) and environment enrichment (EE), affect social behaviors in the adult. But, the underlying mechanism remains unclear. In the present study, we determined whether neonatal MD induces social deficits, whether postweaning EE restores the deficits, and their effects on neuron morphology and oxytocin (OT)-oxytocin receptor (OTR) system. We found that MD induced repetitive behavior and deficits in novel object recognition and sociability, and EE alleviated these deficits. MD decreased oxytocinergic neurons in the magnocellular hypothalamic paraventricular nucleus (mPVH), which was parallel to the increased OTR levels and dendritic branches of projection neurons in the basolateral amygdala (BLA). EE increased the OTR levels in the prelimbic cortex (PL) and the oxytocinergic neurons in the parvocellular PVH (vPVH), which were parallel to the increased dendritic branches of small pyramidal neurons in the PL and synaptic connections marked with synaptophysin and postsynaptic density protein 95 in the BLA and PL. Together, the results suggest that postweaning EE alleviates the social impairments induced by neonatal MD and OT-OTR system are experience-dependent and associated with social behaviors and neuron morphology.

Autistic-like traits in laboratory rodents exposed to phthalic acid esters during early development - an animal model of autism?

Phthalates are chemical substances that are widely used to provide flexibility and durability to plastic materials. They leach from products in which they are mixed and reach living organisms. Results from experimental studies suggest that exposure to phthalates can have a negative impact on an individual's neuronal system and behavior. In this regard, exposure during early ontogenesis seems to be particularly dangerous due to the extensive growth and development of body structures and functions. Disruption during this critical time can result in alterations of behavior and the emergence of neurodevelopmental disorders, such as autism spectrum disorder (ASD). Various animal models have been used to elucidate the pathogenesis of this disease. They are fundamental for research, and although the translation of results to humans is difficult, new animal models are being developed. The aim of this review is to summarize laboratory rodent studies in which early developmental phthalate exposure resulted in brain alterations and autistic-like behavioral traits. We also discuss the possibility of using early developmental phthalate exposure in rodents to create a new animal model of autism.

CNTNAP2 gene polymorphisms in autism spectrum disorder and language impairment among Bangladeshi children: a case-control study combined with a meta-analysis

Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental disorder characterized by communication deficits, impaired social interactions, repetitive and stereotyped behaviors with restricted interests, and connected with the interaction between environmental factors and genetic vulnerability. CNTNAP2 gene has been extensively investigated for ASD and related neurodevelopment diseases. However, previous studies have resulted in an inconsistent outcome. Based on this fact, we conducted a case-control study followed by a meta-analysis to investigate the association of rs7794745 and rs2710102 polymorphisms with ASD. A total of 216 autistic children and 240 healthy volunteers were recruited, and genotyping was performed using the PCR-RFLP method. We observed that SNP rs7794745 revealed a significantly (p < 0.05) increased association with the development of ASD in children in all genetic models. No significant association was found for rs2710102 with ASD. Besides, rs2710102 exhibited a significant association with language impairment in TC genotype, C allele, and dominant model. From the meta-analysis of both SNPs, we found a significant association in codominant 1, 2, and the dominant model of rs2710102 and codominant 1 and dominant model of rs7794745 with ASD. Our case-control study suggests that rs7794745 polymorphism is associated with ASD, while rs2710102 is correlated with language impairment. Moreover, meta-analysis results indicated the association between both rs7794745 and rs2710102 polymorphisms and ASD.

Regulation of CREB Phosphorylation in Nucleus Accumbens after Relief Conditioning

Relief learning is the association of environmental cues with the cessation of aversive events. While there is increasing knowledge about the neural circuitry mediating relief learning, the respective molecular pathways are not known. Therefore, the aim of the present study was to examine different putative molecular pathways underlying relief learning. To this purpose, male rats were subjected either to relief conditioning or to a pseudo conditioning procedure. Forty-five minutes or 6 h after conditioning, samples of five different brain regions, namely the prefrontal cortex, nucleus accumbens (NAC), dorsal striatum, dorsal hippocampus, and amygdala, were collected. Using quantitative Western blots, the expression level of CREB, pCREB, ERK1/2, pERK1/2, CaMKIIα, MAP2K, PKA, pPKA, Akt, pAkt, DARPP-32, pDARPP-32, 14-3-3, and neuroligin2 were studied. Our analyses revealed that relief conditioned rats had higher CREB phosphorylation in NAC 6 h after conditioning than pseudo conditioned rats. The data further revealed that this CREB phosphorylation was mainly induced by dopamine D1 receptor-mediated activation of PKA, however, other kinases, downstream of the NMDA receptor, may also contribute. Taken together, the present study suggests that CREB phosphorylation, induced by a combination of different molecular pathways downstream of dopamine D1 and NMDA receptors, is essential for the acquisition and consolidation of relief learning.

Research Advances in the Molecular Functions and Relevant Diseases of TAOKs, Novel STE20 Kinase Family Members

As serine/threonine-protein kinases, Thousand and One Kinases(TAOKs) are members of the GCKlike superfamily, one of two well-known branches of the Ste20 kinase family. Within the last two decades, three functionally similar kinases, namely TAOK1-3, were identified. TAOKs are involved in many molecular and cellular events. Scholars widely believe that TAOKs act as kinases upstream of the MAPK cascade and as factors that interact with MST family kinases, the cytoskeleton, and apoptosis-associated proteins. Therefore, TAOKs are thought to function in tumorigenesis. Additionally, TAOKs participate in signal transduction induced by Notch, TCR, and IL-17. Recent studies found that TAOKs play roles in a series of diseases and conditions, such as the central nervous system dysfunction, herpes viral infection, immune system imbalance, urogenital system malformation during development, cardiovascular events, and childhood obesity. Therefore, inhibitory chemicals targeting TAOKs may be of great significance as potential drugs for these diseases.

Plasma Levels of Alpha and Gamma Synucleins in Autism Spectrum Disorder: An Indicator of Severity

OBJECTIVES

The aim of this study was to correlate plasma levels of the synaptic proteins α-synuclein and γ-synuclein in autism spectrum disorder (ASD) children in order to elucidate their possible contribution to the pathogenesis of ASD and to study their association with the severity of the disorder.

SUBJECTS AND METHODS

Plasma levels of α-synuclein and γ-synuclein were measured in 38 male children diagnosed with ASD and 40 healthy age-matched male children by ELISA.

RESULTS

Our results showed that plasma levels of α-synuclein (18.02 ± 5.3 pg/mL) were significantly higher in ASD children than in control children (14.39 ± 2 pg/mL), and plasma levels of γ-synuclein were decreased in the ASD group (23.74 ± 7.7 pg/mL) compared to the control group (32.40 ± 6.8 pg/mL) (p < 0.0001). Our data also indicate that plasma levels of both α-synuclein and γ-synuclein are significantly associated with the severity of ASD.

CONCLUSIONS

Our study showed that alteration in α-synuclein and γ-synuclein might be associated with ASD pathogenesis and could be an indicator of the severity of the disorder.

Current Approaches to the Pharmacologic Treatment of Core Symptoms Across the Lifespan of Autism Spectrum Disorder

There are no approved medications for autism spectrum disorder (ASD) core symptoms. However, given the significant clinical need, children and adults with ASD are prescribed medication off label for core or associated conditions, sometimes based on limited evidence for effectiveness. Recent developments in the understanding of biologic basis of ASD have led to novel targets with potential to impact core symptoms, and several clinical trials are underway. Heterogeneity in course of development, co-occurring conditions, and age-related treatment response variability hampers study outcomes. Novel measures and approaches to ASD clinical trial design will help in development of effective pharmacologic treatments.

An Overview of the Main Genetic, Epigenetic and Environmental Factors Involved in Autism Spectrum Disorder Focusing on Synaptic Activity

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects social interaction and communication, with restricted interests, activity and behaviors. ASD is highly familial, indicating that genetic background strongly contributes to the development of this condition. However, only a fraction of the total number of genes thought to be associated with the condition have been discovered. Moreover, other factors may play an important role in ASD onset. In fact, it has been shown that parental conditions and in utero and perinatal factors may contribute to ASD etiology. More recently, epigenetic changes, including DNA methylation and micro RNA alterations, have been associated with ASD and proposed as potential biomarkers. This review aims to provide a summary of the literature regarding ASD candidate genes, mainly focusing on synapse formation and functionality and relevant epigenetic and environmental aspects acting in concert to determine ASD onset.

Structural Neuroplastic Responses Preserve Functional Connectivity and Neurobehavioural Outcomes in Children Born Without Corpus Callosum

The corpus callosum is the largest white matter pathway in the brain connecting the two hemispheres. In the context of developmental absence (agenesis) of the corpus callosum (AgCC), a proposed candidate for neuroplastic response is strengthening of intrahemispheric pathways. To test this hypothesis, we assessed structural and functional connectivity in a uniquely large cohort of children with AgCC (n = 20) compared with typically developing controls (TDC, n = 29), and then examined associations with neurobehavioral outcomes using a multivariate data-driven approach (partial least squares correlation, PLSC). For structural connectivity, children with AgCC showed a significant increase in intrahemispheric connectivity in addition to a significant decrease in interhemispheric connectivity compared with TDC, in line with the aforementioned hypothesis. In contrast, for functional connectivity, children with AgCC and TDC showed a similar pattern of intrahemispheric and interhemispheric connectivity. In conclusion, we observed structural strengthening of intrahemispheric pathways in children born without corpus callosum, which seems to allow for functional connectivity comparable to a typically developing brain, and were relevant to explain neurobehavioral outcomes in this population. This neuroplasticity might be relevant to other disorders of axonal guidance, and developmental disorders in which corpus callosum alteration is observed.

Cell-Type-Specific Proteogenomic Signal Diffusion for Integrating Multi-Omics Data Predicts Novel Schizophrenia Risk Genes

Accumulation of diverse types of omics data on schizophrenia (SCZ) requires a systems approach to model the interplay between genome, transcriptome, and proteome. We introduce Markov affinity-based proteogenomic signal diffusion (MAPSD), a method to model intra-cellular protein trafficking paradigms and tissue-wise single-cell protein abundances. MAPSD integrates multi-omics data to amplify the signals at SCZ risk loci with small effect sizes, and reveal convergent disease-associated gene modules in the brain. We predicted a set of high-confidence SCZ risk loci followed by characterizing the subcellular localization of proteins encoded by candidate SCZ risk genes, and illustrated that most are enriched in neuronal cells in the cerebral cortex as well as Purkinje cells in the cerebellum. We demonstrated how the identified genes may be involved in neurodevelopment, how they may alter SCZ-related biological pathways, and how they facilitate drug repurposing. MAPSD is applicable in other polygenic diseases and can facilitate our understanding of disease mechanisms.

The role of clustered protocadherins in neurodevelopment and neuropsychiatric diseases

During development, individual neurons extend highly branched arbors that innervate the surrounding territory, enabling the formation of appropriate synaptic connections. The clustered protocadherins (cPCDH), a family of diverse cell-surface homophilic proteins, provide each neuron with a cell specific identity required for distinguishing between self versus non-self. While only 52 unique cPcdh isoforms are encoded in the human genome, a combination of stochastic promoter choice and the formation of a protein lattice through engagement of adjacent cPCDH protein cis/trans-tetramers confer the high degree of cellular specificity required for self-recognition. Studies of mice bearing deletions of individual cPcdh gene clustees have identified deficits in circuit formation and behavior. In humans, single nucleotide variants scattered across the cPCDH locus have been identified, which associate with multiple neurodevelopmental disorders, including autism and schizophrenia. To advance our understanding of cPCDH stochastic choice and maintenance, function across cell types, and contribution to neuropsychiatric disease pathogenesis, hiPSC-based models have been developed. Ultimately, integration of human genetic data, biochemical assays, and functional studies is needed to uncover the mechanism underlying neurite repulsion, which has been implicated in neurodevelopmental disorders.

Maternal Immune Activation Induces Neuroinflammation and Cortical Synaptic Deficits in the Adolescent Rat Offspring

Maternal immune activation (MIA), induced by infection during pregnancy, is an important risk factor for neuro-developmental disorders, such as autism. Abnormal maternal cytokine signaling may affect fetal brain development and contribute to neurobiological and behavioral changes in the offspring. Here, we examined the effect of lipopolysaccharide-induced MIA on neuro-inflammatory changes, as well as synaptic morphology and key synaptic protein level in cerebral cortex of adolescent male rat offspring. Adolescent MIA offspring showed elevated blood cytokine levels, microglial activation, increased pro-inflammatory cytokines expression and increased oxidative stress in the cerebral cortex. Moreover, pathological changes in synaptic ultrastructure of MIA offspring was detected, along with presynaptic protein deficits and down-regulation of postsynaptic scaffolding proteins. Consequently, ability to unveil MIA-induced long-term alterations in synapses structure and protein level may have consequences on postnatal behavioral changes, associated with, and predisposed to, the development of neuropsychiatric disorders.

Adenosine A2A Receptor Agonist PSB-0777 Modulates Synaptic Proteins and AMPA Receptor Expression in a Dose- and Time-Dependent Manner in Rat Primary Cortical Neurons

Regulating synaptic formation and transmission is critical for the physiology and pathology of psychiatric disorders. The adenosine A_2A receptor subtype has attracted widespread attention as a key regulator of neuropsychiatric activity, neuroprotection and injury. In this study, we systematically investigated the regulatory effects of a novel A_2A receptor agonist, PSB-0777, on the expression of synaptic proteins and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors (AMPA receptors) at the cellular level in a time- and dose-dependent manner. After 30 min of high-dose PSB-0777 stimulation, the expression of Synapsin-1 (Syn-1), postsynaptic density protein 95 (PSD95), and AMPA receptors and the number of synapses were rapidly and significantly increased in rat primary cortical neurons compared with the control. Sustained elevation was found in the low and medium-dose groups after 24 h and 3 d of treatment. In contrast, after stimulation with PSB-0777 for 3 consecutive days, the expression of Syn-1 was decreased, and PSD95, AMPA receptors and the number of synapses were no longer increased in the high-dose group. Our study focuses on the detailed and systematic regulation of synaptic proteins and AMPA receptors by an A_2A receptor agonist, PSB-0777, which may result in both beneficial and detrimental effects on neurotransmission and neuroprotection and may contribute to the pathophysiology of psychiatric disorders related to A_2A receptors. These experimental data may contribute to understanding of the mechanisms for neuroprotective and therapeutic effect of A_2A receptor agonists.

Prenatal Exposure to Valproic Acid Affects Microglia and Synaptic Ultrastructure in a Brain-Region-Specific Manner in Young-Adult Male Rats: Relevance to Autism Spectrum Disorders

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental conditions categorized as synaptopathies. Environmental risk factors contribute to ASD aetiology. In particular, prenatal exposure to the anti-epileptic drug valproic acid (VPA) may increase the risk of autism. In the present study, we investigated the effect of prenatal exposure to VPA on the synaptic morphology and expression of key synaptic proteins in the hippocampus and cerebral cortex of young-adult male offspring. To characterize the VPA-induced autism model, behavioural outcomes, microglia-related neuroinflammation, and oxidative stress were analysed. Our data showed that prenatal exposure to VPA impaired communication in neonatal rats, reduced their exploratory activity, and led to anxiety-like and repetitive behaviours in the young-adult animals. VPA-induced pathological alterations in the ultrastructures of synapses accompanied by deregulation of key pre- and postsynaptic structural and functional proteins. Moreover, VPA exposure altered the redox status and expression of proinflammatory genes in a brain region-specific manner. The disruption of synaptic structure and plasticity may be the primary insult responsible for autism-related behaviour in the offspring. The vulnerability of specific synaptic proteins to the epigenetic effects of VPA may highlight the potential mechanisms by which prenatal VPA exposure generates behavioural changes.

GABAARα2 is Decreased in the Axon Initial Segment of Pyramidal Cells in Specific Areas of the Prefrontal Cortex in Autism

Some forms of Autism Spectrum Disorder, a neurodevelopmental syndrome characterized by impaired communication and social skills as well as repetitive behaviors, are purportedly associated with dysregulation of the excitation/inhibition balance in the cerebral cortex. Through human postmortem tissue analysis, we previously found a significant decrease in the number of a gamma-aminobutyric acid (GABA)ergic interneuron subtype, the chandelier (Ch) cell, in the prefrontal cortex of subjects with autism. Ch cells exclusively target the axon initial segment (AIS) of excitatory pyramidal (Pyr) neurons, and a single Ch cell forms synapses on hundreds of Pyr cells, indicating a possible role in maintaining electrical balance. Thus, we herein investigated this crucial link between Ch and Pyr cells in the anatomy of autism neuropathology by examining GABA receptor protein expression in the Pyr cell AIS in subjects with autism. We collected tissue from the prefrontal cortex (Brodmann Areas (BA) 9, 46, and 47) of 20 subjects with autism and 20 age- and sex-matched control subjects. Immunohistochemical staining with antibodies against the GABA_A receptor subunit α2 (GABA_ARα2) - the subunit most prevalent in the Pyr cell AIS - revealed a significantly decreased GABA_ARα2 protein in the Pyr cell AIS in supragranular layers of prefrontal cortical areas BA9 and BA47 in autism. Downregulated GABA_ARα2 protein in the Pyr cell AIS may result from decreased GABA synthesis in the prefrontal cortex of subjects with autism, and thereby contribute to an excitation/inhibition imbalance. Our findings support the potential for GABA receptor agonists asa therapeutic tool for autism.

Current Approaches to the Pharmacologic Treatment of Core Symptoms Across the Lifespan of Autism Spectrum Disorder

There are no approved medications for autism spectrum disorder (ASD) core symptoms. However, given the significant clinical need, children and adults with ASD are prescribed medication off label for core or associated conditions, sometimes based on limited evidence for effectiveness. Recent developments in the understanding of biologic basis of ASD have led to novel targets with potential to impact core symptoms, and several clinical trials are underway. Heterogeneity in course of development, co-occurring conditions, and age-related treatment response variability hampers study outcomes. Novel measures and approaches to ASD clinical trial design will help in development of effective pharmacologic treatments.

In Vivo Imaging of Gray Matter Microstructure in Major Psychiatric Disorders: Opportunities for Clinical Translation

Postmortem studies reveal that individuals with major neuropsychiatric disorders such as schizophrenia and autism spectrum disorder have gray matter microstructural abnormalities. These include abnormalities in neuropil organization, expression of proteins supporting neuritic and synaptic integrity, and myelination. Genetic and postmortem studies suggest that these changes may be causally linked to the pathogenesis of these disorders. Advances in diffusion-weighted magnetic resonance image (dMRI) acquisition techniques and biophysical modeling allow for the quantification of gray matter microstructure in vivo. While several biophysical models for imaging microstructural properties are available, one in particular, neurite orientation dispersion and density imaging (NODDI), holds great promise for clinical applications. NODDI can be applied to both gray and white matter and requires only a single extra shell beyond a standard dMRI acquisition. Since its development only a few years ago, the NODDI algorithm has been used to characterize gray matter microstructure in schizophrenia, Alzheimer's disease, healthy aging, and development. These investigations have shown that microstructural findings in vivo, using NODDI, align with postmortem findings. Not only do NODDI and other advanced dMRI-based modeling methods provide a window into the brain previously only available postmortem, but they may be more sensitive to certain brain changes than conventional magnetic resonance imaging approaches. This opens up exciting new possibilities for clinicians to more rapidly detect disease signatures and allows earlier intervention in the course of the disease. Given that neurites and gray matter microstructure have the capacity to rapidly remodel, these novel dMRI-based methods represent an opportunity to noninvasively monitor neuroplastic changes posttherapy within much shorter time scales.

mTOR signalling pathway - A root cause for idiopathic autism?

Autism spectrum disorder (ASD) is a complex neurodevelopmental monogenic disorder with a strong genetic influence. Idiopathic autism could be defined as a type of autism that does not have a specific causative agent. Among signalling cascades, mTOR signalling pathway plays a pivotal role not only in cell cycle, but also in protein synthesis and regulation of brain homeostasis in ASD patients. The present review highlights, underlying mechanism of mTOR and its role in altered signalling cascades as a triggering factor in the onset of idiopathic autism. Further, this review discusses how distorted mTOR signalling pathway stimulates truncated translation in neuronal cells and leads to downregulation of protein synthesis at dendritic spines of the brain. This review concludes by suggesting downstream regulators such as p70S6K, eIF4B, eIF4E of mTOR signalling pathway as promising therapeutic targets for idiopathic autistic individuals. [BMB Reports 2019; 52(7): 424-433].

Further evidence of GABRA4 and TOP3B as autism susceptibility genes

Chromosomal copy number variants (CNVs) are known contributors to neurodevelopmental conditions such as autism spectrum disorder (ASD). Both array comparative genomic hybridization and next-generation sequencing techniques have led to an increased detection of small CNVs and the identification of many candidate susceptibility genes for ASD. We report familial inheritance of two CNVs that include genes with known involvement in neurodevelopment. These CNVs are found in various combinations among four siblings with autism spectrum disorder, as well as in their neurodevelopmentally normal parents. We describe a 2.4 Mb duplication of 4p12 to 4p11 that includes GABRA4 (OMIM: 137141) and other GABA receptor genes, as well as a 246 kb deletion at 22q11.22 involving the TOP3B gene (OMIM: 603582). The maternally inherited 4p duplication was detected in three siblings, two of whom also had the paternally inherited 22q11.22 deletion. The fourth sibling only had the 22q11.22 deletion. These CNVs have rarely been reported in the literature. Upon review, a single publication was found describing a similar 4p duplication in three generations of a family with neurodevelopmental and neuropsychiatric disorders, as well as in an unrelated patient with autism (Polan et al., 2014). TOP3B falls within the distal 22q11.22 microdeletion syndrome and has been associated with schizophrenia, neurodevelopmental disorders including epilepsy, and cardiac defects. The identification of this family contributes to the understanding of specific genetic contributors to neurodevelopmental disorders and an emerging phenotype associated with proximal 4p duplication.