Risk Factor For Autism Research Articles

A review of the risk factors for Autism

Abstract Background Autism Spectrum Disorder (or Autism) is a neurodevelopmental and neurological condition, with prevalence of 1 in 100 children globally. This review examines the most common factors associated with Autism. Methods We conducted a scoping review of factors associated with an increased risk of developing Autism. These included genetic predisposition, parental age, gender, birth complications and morbidities due to other medical conditions. Results Evidence from twin studies shows a 90% genetic predisposition towards Autism - with 102 genes strongly associated with Autism, including SCN1A and SLC6A1. There are also genetic syndromes and chromosomal disorders associated with Autism, including Fragile X syndrome and Tuberous Sclerosis complex (TSC). Several studies have demonstrated an increased risk with advanced parental age (>35 years) (e.g., fathers >50 years are 2.2 times more likely to have a child with Autism than those <30 years). Other factors include infections during pregnancy (e.g. immune dysfunction) and gestational diabetes. Prematurity, such as low birth weight (<1500g) and low gestational age (<32 weeks) are also associated with an increased risk of Autism. With regard to gender, boys are more likely to be diagnosed with Autism - gender ratio of 3:1 and 4:1 has been reported in different populations. Abnormalities in brain development during early prenatal or postnatal periods may increase the risk of Autism. These abnormalities can lead to social, communication, and behavioural challenges characteristic of Autism. Conclusions Autism is a complex and heterogeneous condition that likely arises from a combination of factors such as genetic susceptibility and pre- and postnatal factors. An understanding of these factors is important for early detection, intervention, and support for children to improve their quality of life and reduce morbidity. Key messages • Risk factors associated with an increased risk of developing Autism include genetic predisposition, parental age, gender, birth complications and other comorbidities. • There is need to increase awareness of the risk factors of Autism to improve quality of life.

Evaluating Autism Risk Factors and Their Impact on Children in Thi-Qar, Iraq

Evaluating Autism Risk Factors and Their Impact on Children in Thi-Qar, Iraq

Key roles of C2/GAP domains in SYNGAP1-related pathophysiology

Mutations in SYNGAP1 are a common genetic cause of intellectual disability (ID) and a risk factor for autism. SYNGAP1 encodes a synaptic GTPase-activating protein (GAP) that has both signaling and scaffolding roles. Most pathogenic variants of SYNGAP1 are predicted to result in haploinsufficiency. However, some affected individuals carry missense mutations in its calcium/lipid binding (C2) and GAP domains, suggesting that many clinical features result from loss of functions carried out by these domains. To test this hypothesis, we targeted the exons encoding the C2 and GAP domains of SYNGAP. Rats heterozygous for this deletion exhibit reduced exploration and fear extinction, altered social investigation, and spontaneous seizures-key phenotypes shared with Syngap heterozygous null rats. Together, these findings indicate that the reduction of SYNGAP C2/GAP domain function is a main feature of SYNGAP haploinsufficiency. This rat model provides an important system for the study of ID, autism, and epilepsy.

An alpha 5-GABAA receptor positive allosteric modulator attenuates social and cognitive deficits without changing dopamine system hyperactivity in rats exposed to valproic acid in utero.

Autism spectrum disorders (ASDs) are characterized by core behavioral symptoms in the domains of sociability, language/communication, and repetitive or stereotyped behaviors. Deficits in the prefrontal and hippocampal excitatory/inhibitory balance due to a functional loss of GABAergic interneurons are proposed to underlie these symptoms. Increasing the postsynaptic effects of GABA with compounds that selectively modulate GABAergic receptors could be a potential target for treating ASD symptoms. In addition, deficits in GABAergic interneurons have been linked to dopamine (DA) system dysregulation, and, despite conflicting evidence, abnormalities in the DA system activity may underly some ASD symptoms. Here, we investigated whether the positive allosteric modulator of α5-containing GABAA receptors (α5-GABAARs) SH-053-2'F-R-CH3 (10 mg/kg) attenuates behavioral abnormalities in rats exposed to valproic acid (VPA) in utero, an established risk factor for autism. We also evaluated if animals exposed to VPA in utero present changes in the ventral tegmental area (VTA) DA system activity using in vivo electrophysiology and if SH-053-2'F-R-CH3 could attenuate these changes. SH-053-2'F-R-CH3 was administered intraperitoneally 30 min before each behavioral test and electrophysiology. In utero VPA exposure caused male and female rats to present increased repetitive behavior (self-grooming) in early adolescence and deficits in social interaction in adulthood. Male, but not female VPA rats, also presented deficits in recognition memory as adults. SH-053-2'F-R-CH3 attenuated the impairments in sociability and cognitive function in male VPA-exposed rats without attenuating the decreased social interaction in females. Adult male and female VPA-exposed rats also showed an increased VTA DA neuron population activity, which was not changed by SH-053-2'F-R-CH3. Despite sex differences, our findings indicate that α5-GABAARs positive allosteric modulators may effectively attenuate some core ASD symptoms.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood.

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

The Importance of Large-Scale Genomic Studies to Unravel Genetic Risk Factors for Autism.

Autism spectrum disorder (ASD) is a common and highly heritable neurodevelopmental disorder. During the last 15 years, advances in genomic technologies and the availability of increasingly large patient cohorts have greatly expanded our knowledge of the genetic architecture of ASD and its neurobiological mechanisms. Over two hundred risk regions and genes carrying rare de novo and transmitted high-impact variants have been identified. Additionally, common variants with small individual effect size are also important, and a number of loci are now being uncovered. At the same time, these new insights have highlighted ongoing challenges. In this perspective article, we summarize developments in ASD genetic research and address the enormous impact of large-scale genomic initiatives on ASD gene discovery.

Glutathione S Transferase Theta1 and Mu1 (GSTT1 and GSTM1) Deletion Among Autistic Population of India

Introduction: Oxidative stress is an imbalance between an organism's reactive oxygen species (ROS) production and antioxidant defence capacity. Long-term oxidative stress contributes to cellular ageing and plays a role in the pathogenesis of several diseases. Several investigations indicated that oxidative stress has a role in the pathogenesis of ASD. Objectives: Present study was undertaken to record the association of GSTTT1 and GSTM1 null genotype among the autistic population of India. Methods: Genomic DNA was isolated from 108 autistic children along with healthy agematched control. The quality and quantity of the isolated genomic DNA were analysed. GSTT1 and GSTM1 null genotype was analysed using polymerase chain reaction with internal positive control. Statistical analysis was performed using SPSS 15.0. Results: Present study included 85 males and 23 females with a mean age of 11.7 ± 3.5 and 75 males and 33 females with a mean age of 11 ± 2.0 in the control group. 32 (29.6%) autistic cases showed null genotypes for GSTT1 and 21(19.4%) autistic children showed null genotypes for GSTM1. 3 (2.85%) control children showed a null genotype for GSTT1 and 5 (4.6%) control children showed a null genotype for GSTM1. The GSTT1 and GSTM1 null genotypes were observed to be significantly associated with the risk of autism (p value-0.0001, OR-14.73, 95% CI 4.35-49.90) and (p value-0.003, OR-4.731, 95% CI 1.71-13.08) respectively. Conclusion: The findings of our study suggested that GSTT1 and GSTM1 null genotype is one of the potential risk factors for autism through oxidative stress mechanism in our population.

Neurogenic Effects of Inorganic Arsenic and Cdk5 Knockdown in Zebrafish Embryos: A Perspective on Modeling Autism.

The exact mechanisms of the development of autism, a multifactorial neurological disorder, are not clear. The pathophysiology of autism is complex, and investigations at the cellular and molecular levels are ongoing to provide clarity. Mutations in specific genes have been identified as risk factors for autism. The role of heavy metals in the pathogenesis of autism is subject to many studies and remains debatable. Although no exact neuronal phenotypes have been identified linked to autistic symptoms, overproduction and reduction of specific neurons have been implicated. A growing literature on generating genetic and non-genetic models of autism aims to help with understanding mechanistic studies that can explain the complexity of the disorder. Both genetic and non-genetic methods of zebrafish have been used to model autism. For several human autism risk genes, validated zebrafish mutant models have been generated. There is growing evidence indicating a potential link between autism and inorganic arsenic exposure. We have previously shown that inorganic arsenic induces supernumerary spinal motor neurons via Sonic hedgehog (Shh) signaling pathway, and Cdk5 knockdown causes an overproduction of cranial and spinal motor neurons in zebrafish. Here, in this review, we provide a perspective on what these findings of neurogenic phenotypes mean in terms of dysregulated pathways of motor neuron development and their applicability to understanding cellular and molecular underpinnings of autism.

Screened potential risk factors for autism and autistic behaviour in children. Literature review

Screened potential risk factors for autism and autistic behaviour in children. Literature review

Induction of autism-related behavior in male mice by early-life vitamin D deficiency: association with disruption of the gut microbial composition and homeostasis.

Vitamin D deficiency (VDD) during early life emerges as a potential risk factor for autism spectrum disorder (ASD). Individuals with autism commonly exhibit lower vitamin D (VD) levels compared to the general population, and VD deficiency is prevalent during pregnancy and lactation. Moreover, gastrointestinal comorbidity, prevalent in ASD patients, correlates closely with disruptions in the gut microbiota and altered intestinal permeability. Therefore, it is fascinating and significant to explore the effects of maternal VD deficiency during pregnancy and lactation on the maturation of the gut microbiota of the offspring and its relevance to autism spectrum disorders. In this study, we established maternal pregnancy and lactation VD-deficient mouse models, employed shotgun macrogenomic sequencing to unveil alterations in the gut microbiome of offspring mice, and observed autism-related behaviours. Furthermore, fecal microbial transplantation (FMT) reversed repetitive and anxious behaviours and alleviated social deficits in offspring mice by modulating the gut microbiota and increasing short-chain fatty acid levels in the cecum, along with influencing the concentrations of claudin-1 and occludin in the colon. Our findings confirm that VDD during pregnancy and lactation is a risk factor for autism in the offspring, with disturbances in the structure and function of the offspring's gut microbiota contributing at least part of the effect. The study emphasises the importance of nutrition and gut health early in life. Simultaneously, this study further demonstrates the effect of VDD on ASD and provides potential ideas for early prevention and intervention of ASD.

Environmental risk factors for Autism

Environmental risk factors for Autism

Might the fungus candida albicans a risk factor for autism? A meta-analysis study.

Due to the high increase in rate of autism, it has gained great importance to determine the etiology of autism spectrum disorder. The purpose of our study was to assess the role of Candida albicans as a risk factor to cause autism behavior. We searched Scopus, PubMed, Web of Science and PsycINFO for articles up to December, 2021. The studies involving children diagnosed with autism spectrum disorder were included. Children' outcomes were selected as Candida albicans (positive) and Candida albicans (negative). Odds ratios were reported using fixed-effect and random-effect meta-analysis. The heterogeneity was assessed by the Chi-square test and Higgins' I2 test. The publication bias was examined via funnel plot and Hegger's test. Our meta-analysis was conducted based on 254 diagnosed with Autism Spectrum Disease cases and 161 healthy cases from 4 studies. Compared to the healthy cases, the odds of presence of Candida albicans (OR=7.21; 95% CI: 3.75-13.85; p<0.001) were higher in those diagnosed with autism spectrum disorder. This study as a whole showed that children diagnosed with autism spectrum disorder have higher frequency of the presence of the fungus Candida albicans. Therefore, Candida albicans may be an etiological factor for the autistic behavior in children.

Gestational Fisetin Exerts Neuroprotection by Regulating Mitochondria-Directed Canonical Wnt Signaling, BBB Integrity, and Apoptosis in Prenatal VPA-Induced Rodent Model of Autism.

Embryonic valproic acid (VPA) has been considered a potential risk factor for autism. Majority of studies indicated that targeting autism-associated alterations in VPA-induced autistic model could be promising in defining and designing therapeutics for autism. Numerous investigations in this field investigated the role of canonical Wnt signaling cascade in regulating the pathophysiology of autism. The impaired blood-brain barrier (BBB) permeability and mitochondrial dysfunction are some key implied features of the autistic brain. So, the current study was conducted to target canonical Wnt signaling pathway with a natural polyphenolic modulator cum antioxidant namely fisetin. A single dose of intraperitoneal VPA sodium salt (400 mg/kg) at gestational day 12.5 induced developmental delays, social behaviour impairments (tube dominance test), and anxiety-like behaviour (sucrose preference test) similar to autism. VPA induced mitochondrial damage and over-activated the canonical Wnt signaling which further increased the blood-brain barrier (BBB) disruption, apoptosis, and neuronal damage. Our findings revealed that oral administration of 10 mg/kg gestational fisetin (GD 13-till parturition) improved social and anxiety-like behaviour by modulating the ROS-regulated mitochondrial-canonical Wnt signaling. Moreover, fisetin controls BBB permeability, apoptosis, and neuronal damage in autism model proving its neuroprotective efficacy. Collectively, our findings revealed that fisetin-evoked modulation of the Wnt signaling cascade successfully relieved the associated symptoms of autism along with developmental delays in the model and indicates its potential as a bioceutical against autism.

Modular Splicing Is Linked to Evolution in the Synapse-Specificity Molecule Kirrel3.

Kirrel3 is a cell-adhesion molecule that instructs the formation of specific synapses during brain development in mouse and Kirrel3 variants may be risk factors for autism and intellectual disabilities in humans. Kirrel3 is predicted to undergo alternative splicing but brain isoforms have not been studied. Here, we present the first in-depth characterization of Kirrel3 isoform diversity in brain using targeted, long-read mRNA sequencing of mouse hippocampus. We identified 19 isoforms with predicted transmembrane and secreted forms and show that even rare isoforms generate detectable protein in the brain. We also analyzed publicly-available long-read mRNA databases from human brain tissue and found 11 Kirrel3 isoforms that, similar to mouse, encode transmembrane and secreted forms. In mice and humans, Kirrel3 diversity arises from alternative, independent use of protein-domain coding exons and alternative early translation-stop signals. Intriguingly, the alternatively spliced exons appear at branch points in the chordate phylogenetic tree, including one exon only found in humans and their closest living relatives, the great apes. Together, these results validate a simple pipeline for analyzing isoform diversity in genes with low expression and suggest that Kirrel3 function is fine-tuned by alternative splicing and may play a role in brain evolution.

Single-cell analysis of prenatal and postnatal human cortical development.

We analyzed >700,000 single-nucleus RNA sequencing profiles from 106 donors during prenatal and postnatal developmental stages and identified lineage-specific programs that underlie the development of specific subtypes of excitatory cortical neurons, interneurons, glial cell types, and brain vasculature. By leveraging single-nucleus chromatin accessibility data, we delineated enhancer gene regulatory networks and transcription factors that control commitment of specific cortical lineages. By intersecting our results with genetic risk factors for human brain diseases, we identified the cortical cell types and lineages most vulnerable to genetic insults of different brain disorders, especially autism. We find that lineage-specific gene expression programs up-regulated in female cells are especially enriched for the genetic risk factors of autism. Our study captures the molecular progression of cortical lineages across human development.

Association between cumulative psychosocial adversity in the family and ADHD and autism: a family-based cohort study

Cumulative exposure to psychosocial adversity at an early age has been shown to be a risk factor for attention-deficit hyperactivity disorder (ADHD) and autism that often co-occur. However, it is not clear if this association reflects a causal effect or familial confounding. We aimed to assess whether cumulative psychosocial adversity in the family increases the risk for ADHD and autism in offspring while accounting for unmeasured familial confounding. We used a population-based cohort of 1,877,901 individuals born in Sweden between 1990 and 2009. Participants were followed from the age of 3 until 2013, with a median follow up time of 13.8 years. We created a cumulative index based on 7 psychosocial adversity factors. We used Cox regression to estimate the hazard ratios (HRs) relating neurodevelopmental conditions to cumulative psychosocial adversity. To address familial confounding, the analyses were repeated in groups of relatives of different kinship: siblings and half-siblings and cousins. A dose-response relationship was observed between cumulative exposure to psychosocial adversity and ADHD at a general population level (covariate adjusted HRs (aHRs) with 95% confidence intervals ranged from 1.55 [one adversity; 1.53–1.58] to 2.65 [ ≥ 4 adversities; 1.98–3.54]). No clear dose-response relation was seen for autism (aHRs ranged from 1.04 [.59–1.84] to 1.37 [1.30–1.45]). HRs of ADHD and autism decreased with increasing level of kinship in the analysis of relatives. Cumulative exposure to psychosocial adversity was associated with both ADHD and autism in the general population, these associations were partly explained by unmeasured familial confounding between relatives. This highlights the need for using family-based designs in studies of psychosocial adversity and ADHD and autism.

PCSK9 Involvement in Autism Etiology: Sequence Variations, Protein Concentration, and Promoter Methylation

Besides its main role in the control of blood cholesterol, PCSK9 has a role in the regulation of neuronal development and apoptosis. We suggest, for the first time, the possible involvement of PCSK9 in autism. In this case-control study, Sanger sequencing was used to analyze sequence variations in the PCSK9 gene exons and their flanking intronic sequences. ELISA assay was used to determine the plasma concentration of PCSK9. The methylation percentage of the PCSK9 gene promoter was assessed by methylation-specific PCR (MSP). Forty-three variants were found; out of them, seven showed differential frequency between patients and controls. rs.45448095, rs.45613943, rs.630431, rs.529500286, and rs.45439391 are risk factors for autism, while rs.11800231 and rs.483462 are protective variants. The concentration of plasma PCSK9 protein was significantly elevated and the methylation percentage of PCSK9 gene promoter was significantly lower in cases than in controls (P <0.001 and = 0.002, respectively). ROC curve analysis identified an area under the curve (AUC) of 0.915 for plasma protein concentration and 0.693 for percent gene promoter methylation. In addition, two new variants were identified (g.23809C>T in intron 11 and g.24071T>G in 3' UTR). This is the first study to investigate the correlation between PCSK9 protein and autism and suggests the potential involvement of PCSK9 as one of the susceptibility genes for autism. Further studies with a larger number of subjects are recommended.

A Comparative Analysis of the Full and Short Versions of the Social Responsiveness Scale in Estimating an Established Autism Risk Factor Association in ECHO: Do we Get the Same Estimates?

Prior work developed a shortened 16-item version of the Social Responsiveness Scale (SRS), a quantitative measure of social communication and autism spectrum disorder (ASD)-related traits. However, its properties for use in risk factor estimation have not been fully tested compared to the full SRS. We compared the associations between gestational age (previously established risk factor for ASD) and the 65-item "full" and 16-item "short" versions of the SRS to test the shortened version's ability to capture associations in epidemiologic analyses of ASD risk factors. We used data from participants in the Environmental influences on Child Health Outcomes (ECHO) Program (n = 2,760). SRS scores were collected via maternal/caregiver report when children were aged 2.5-18 years. We compared estimates of associations between gestational age and preterm birth between the full and short SRS using multivariable linear regression, quantile regression, and prediction methods. Overall, associations based on full and short SRS scores were highly comparable. For example, we observed positive associations between preterm birth with both full ([Formula: see text]=2.8; 95% CI [1.7, 4.0]) and short ([Formula: see text]=2.9; 95% CI [1.6, 4.3]) SRS scores. Quantile regression analyses indicated similar direction and magnitude of associations across the distribution of SRS scores between gestational age with both short and full SRS scores. The comparability in estimates obtained for full and short SRS scores with an "established" ASD risk factor suggests ability of the shortened SRS in assessing associations with potential ASD-related risk factors and has implications for large-scale research studies seeking to reduce participant burden.

Early developmental deletion of forebrain Ank2 causes seizure-related phenotypes by reshaping the synaptic proteome

Rare genetic variants in ANK2, which encodes ankyrin-B, are associated with neurodevelopmental disorders (NDDs); however, their pathogenesis is poorly understood. We find that mice with prenatal deletion in cortical excitatory neurons and oligodendrocytes (Ank2-/-:Emx1-Cre), but not with adolescent deletion in forebrain excitatory neurons (Ank2-/-:CaMKIIα-Cre), display severe spontaneous seizures, increased mortality, hyperactivity, and social deficits. Calcium imaging of cortical slices from Ank2-/-:Emx1-Cre mice shows increased neuronal calcium event amplitude and frequency, along with network hyperexcitability and hypersynchrony. Quantitative proteomic analysis of cortical synaptic membranes reveals upregulation of dendritic spine plasticity-regulatory proteins and downregulation of intermediate filaments. Characterization of the ankyrin-B interactome identifies interactors associated with autism and epilepsy risk factors and synaptic proteins. The AMPA receptor antagonist, perampanel, restores cortical neuronal activity and partially rescues survival in Ank2-/-:Emx1-Cre mice. Our findings suggest that synaptic proteome alterations resulting from Ank2 deletion impair neuronal activity and synchrony, leading to NDDs-related behavioral impairments.