New insights into the genetic mechanism of IQ in autism spectrum disorders

A bibliometrics analysis and visualization of autism spectrum disorder

BACKGROUND

The prevalence of autism spectrum disorder (ASD) increased rapidly in the last 20 years. Although related research has developed rapidly, little is known about its etiology, diagnostic marker, or drug treatment, which forces researchers to review and summarize its development process and look for the future development direction.

METHODS

We used bibliometrics to analyze papers of ASD in the Web of Science from 1998 to 2021, to draw the network of authors, institutions, countries, and keywords in the ASD field, and visualize the results.

RESULTS

A total of 40,597 papers were included with a continually increasing trend. It turns out that the research on ASD is mainly concentrated in universities. The United States has the largest number of ASD studies, followed by England and Canada. The quality of papers related to ASD is generally high, which shows that ASD research has become a hot spot of scientific research. The keywords of ASD etiology and diagnostic markers can be classified into at least 7 aspects. The detection of keywords shows that ASD research is mostly based on its subtypes, takes children as the study population, focuses on neurodevelopmental imaging or genetics, and pays attention to individual differences. And ASD research has changed greatly under the impact of Corona Virus Disease 2019 in the past 2 years.

CONCLUSION

We consider the future development direction should be based on the improvement of case identification, accurate clinical phenotype, large-scale cohort study, the discovery of ASD etiology and diagnostic markers, drug randomized controlled trials, and telehealth.

Autism spectrum disorder in females with fragile X syndrome: a systematic review and meta-analysis of prevalence

BACKGROUND

Whilst up to 60% of males with fragile X syndrome (FXS) meet criteria for autism spectrum disorder (ASD), the prevalence and nature of ASD in females with FXS remains unclear.

METHOD

A systematic literature search identified papers reporting ASD prevalence and/or symptomatology in females with FXS.

RESULTS AND CONCLUSION

Meta-analysis suggested that rates of ASD for females with FXS are reliably higher than for females in the general population (a random effects model estimated weighted average prevalence at 14%, 95% CI 13-18%). Whilst papers highlighted a number of social and repetitive difficulties for females with FXS, characteristic profiles of impairment are not clear. Possible associations between ASD traits and IQ, and between ASD and levels of fragile X mental retardation protein, are suggested, but data are equivocal.

Understanding the genetic contribution of the human leukocyte antigen system to common major psychiatric disorders in a world pandemic context

The human leukocyte antigen (HLA) is a complex genetic system that encodes proteins which predominantly regulate immune/inflammatory processes. It can be involved in a variety of immuno-inflammatory disorders ranging from infections to autoimmunity and cancers. The HLA system is also suggested to be involved in neurodevelopment and neuroplasticity, especially through microglia regulation and synaptic pruning. Consequently, this highly polymorphic gene region has recently emerged as a major player in the etiology of several major psychiatric disorders, such as schizophrenia, autism spectrum disorder and bipolar disorder and with less evidence for major depressive disorders and attention deficit hyperactivity disorder. We thus review here the role of HLA genes in particular subgroups of psychiatric disorders and foresee their potential implication in future research. In particular, given the prominent role that the HLA system plays in the regulation of viral infection, this review is particularly timely in the context of the Covid-19 pandemic.

Autism spectrum disorders and natural killer cells: a review on pathogenesis and treatment

Introduction: Autism spectrum disorder (ASD), as a wide spectrum of neurodevelopmental disorders, is characterized by early-onset impairments in social-communication, repetitive behaviors, and restrictive interests.Areas covered: Although still unknown, there are some pieces of evidence suggesting altered immune function in the etiology of ASD. This review aims to summarize studies linking Natural Killer (NK) cells to ASD by searching through databases like MEDLINE and Scopus up to October 2020. NK cells play important roles in the innate immune system and immune regulation. As parts of the immune system, they interact with the neural system as well. Immune dysregulations such as autoimmunity and improper immune responses to both internal and external stimulations, especially in early developmental stages of the brain, may induce neurodevelopmental disorders. NK cells' dysfunction in children with ASD as well as their parents have been highlighted in many studies.Expert opinion: Changes in the frequency, gene expressions, cytotoxicity features, and receptors of NK cells are reported in children with ASD. Immune therapy for children with ASD with immune abnormality has shown promising results. However, further studies are needed to elucidate the exact role of NK cells in the pathogenesis of ASD providing future treatment options for these children.

Guiding synaptic plasticity: Novel roles for netrin-1 in synaptic plasticity and memory formation in the adult brain

Adult neural plasticity engages mechanisms that change synapse structure and function, yet many of the underlying events bear a striking similarity to processes that occur during the initial establishment of neural circuits during development. It is a long-standing hypothesis that the molecular mechanisms critical for neural development may also regulate synaptic plasticity related to learning and memory in adults. Netrins were initially described as chemoattractant guidance cues that direct cell and axon migration during embryonic development, yet they continue to be expressed by neurons in the adult brain. Recent findings have identified roles for netrin-1 in synaptogenesis during postnatal maturation, and in synaptic plasticity in the adult mammalian brain, regulating AMPA glutamate receptor trafficking at excitatory synapses. These findings provide an example of a conserved developmental guidance cue that is expressed by neurons in the adult brain and functions as a key regulator of activity-dependent synaptic plasticity. Notably, in humans, genetic polymorphisms in netrin-1 and its receptors have been linked to neurodevelopmental and neurodegenerative disorders. The molecular mechanisms associated with the synaptic function of netrin-1 therefore present new therapeutic targets for neuropathologies associated with memory dysfunction. Here, we summarize recent findings that link netrin-1 signalling to synaptic plasticity, and discuss the implications of these discoveries for the neurobiological basis of memory consolidation.

Persistence of dysfunctional natural killer cells in adults with high-functioning autism spectrum disorders: stigma/consequence of unresolved early infectious events?

Background

Autism spectrum disorders (ASD) are characterized by abnormal neurodevelopment, genetic, and environmental risk factors, as well as immune dysfunctions. Several lines of evidence suggest alterations in innate immune responses in children with ASD. To address this question in adults with high-functioning ASD (hf-ASD), we sought to investigate the role of natural killer (NK) cells in the persistence of ASD.

Methods

NK cells from 35 adults with hf-ASD were compared to that of 35 healthy controls (HC), selected for the absence of any immune dysfunctions, at different time-points, and over a 2-year follow-up period for four patients. The phenotype and polyfunctional capacities of NK cells were explored according to infectious stigma and clinical parameters (IQ, social, and communication scores).

Results

As compared to HC, NK cells from patients with hf-ASD showed a high level of cell activation (p < 0.0001), spontaneous degranulation (p < 0.0001), and interferon-gamma production (p = 0.0004), whereas they were exhausted after in vitro stimulations (p = 0.0006). These data yielded a specific HLA-DR⁺KIR2DL1⁺NKG2C⁺ NK-cell signature. Significant overexpression of NKG2C in hf-ASD patients (p = 0.0005), indicative of viral infections, was inversely correlated with the NKp46 receptor level (r = − 0.67; p < 0.0001), regardless of the IgG status of tested pathogens. Multivariate linear regression analysis also revealed that expression of the late-activating HLA-DR marker was both associated with structural language (r = 0.48; p = 0.007) and social awareness (r = 0.60; p = 0.0007) scores in adult patients with hf-ASD, while KIR2DL1 expression correlated with IQ scores (p = 0.0083).

Conclusions

This study demonstrates that adults with hf-ASD have specific NK-cell profile. Presence of NKG2C overexpression together with high-level activation of NK cells suggest an association with underlying pathogens, a hypothesis warranting further exploration in future studies.

Electronic supplementary material

The online version of this article (10.1186/s13229-019-0269-1) contains supplementary material, which is available to authorized users.

AU040320 deficiency leads to disruption of acrosome biogenesis and infertility in homozygous mutant mice

Study of knockout (KO) mice has helped understand the link between many genes/proteins and human diseases. Identification of infertile KO mice provides valuable tools to characterize the molecular mechanisms underlying gamete formation. The KIAA0319L gene has been described to have a putative association with dyslexia; surprisingly, we observed that homozygous KO males for AU040320, KIAA0319L ortholog, are infertile and present a globozoospermia-like phenotype. Mutant spermatozoa are mostly immotile and display a malformed roundish head with no acrosome. In round spermatids, proacrosomal vesicles accumulate close to the acroplaxome but fail to coalesce into a single acrosomal vesicle. In wild-type mice AU040320 localises to the trans-Golgi-Network of germ cells but cannot be detected in mature acrosomes. Our results suggest AU040320 may be necessary for the normal formation of proacrosomal vesicles or the recruitment of cargo proteins required for downstream events leading to acrosomal fusion. Mutations in KIAA0319L could lead to human infertility; we screened for KIAA0319L mutations in a selected cohort of globozoospermia patients in which no genetic abnormalities have been previously identified, but detected no pathogenic changes in this particular cohort.

A novel relationship for schizophrenia, bipolar and major depressive disorder Part 3: Evidence from chromosome 3 high density association screen

Familial clustering of schizophrenia (SCZ), bipolar disorder (BPD), and major depressive disorder (MDD) was systematically reported (Aukes et al, Genet Med 2012, 14, 338-341) and convergent evidence from genetics, symptomatology, and psychopharmacology imply that there are intrinsic connections between these three major psychiatric disorders, for example, any two or even three of these disorders could co-exist in some families. A total of 60, 838 single-nucleotide polymorphisms (SNPs) on chromosome 3 were genotyped by Affymetrix Genome-Wide Human SNP array 6.0 on 119 SCZ, 253 BPD (type-I), 177 MDD patients and 1,000 controls. The population of Shandong province was formed in 14 century and believed that it belongs to homogenous population. Associated SNPs were systematically revealed and outstanding susceptibility genes (CADPS, GRM7,KALRN, LSAMP, NLGN1, PRICKLE2, ROBO2) were identified. Unexpectedly, flanking genes for the associated SNPs distinctive for BPD and/or MDD were replicated in an enlarged cohort of 986 SCZ patients. The evidence from this chromosome 3 analysis supports the notion that both of bipolar and MDD might be subtypes of schizophrenia rather than independent disease entity. Also, a similar finding was detected on chromosome 5, 6, 7, and 8 (Chen et al. Am J Transl Res 2017;9 (5):2473-2491; Curr Mol Med 2016;16(9):840-854; Behav Brain Res 2015;293:241-251; Mol Neurobiol 2016. doi: 10.1007/s12035-016-0102-1). Furthermore, PRICKLE2 play an important role in the pathogenesis of three major psychoses in this population.

Autism Symptoms in Fragile X Syndrome

Fragile X syndrome (FXS) is recognized as the most common genetic cause of intellectual disability and autism spectrum disorder (ASD). Although symptoms of ASD are frequently observed in patients with FXS, researchers have not yet clearly determined whether the symptoms in patients with FXS differ from the symptoms in patients without ASD or nonsyndromic ASD. Behavioral similarities and differences between FXS and ASD are important to improve our understanding of the causes and correlations of ASD with FXS. Based on the evidence presented in this review, individuals with FXS and comorbid ASD have more severe behavioral problems than individuals with FXS alone. However, patients with FXS and comorbid ASD exhibit less severe impairments in the social and communication symptoms than patients with nonsyndromic ASD. Individuals with FXS also present with anxiety and seizures in addition to comorbid ASD symptoms, and differences in these conditions are noted in patients with FXS and ASD. This review also discusses the role of fragile X mental retardation 1 protein (FMRP) in FXS and ASD phenotypes.

[Research advances in susceptible genes for developmental dyslexia in children]

Developmental dyslexia in children is one of the neurodevelopmental disorders and is affected by various susceptible genes. In recent years, researchers have found some susceptible genes for dyslexia via chromosome analysis, genome-wide association studies, association analysis, gene function research, neuroimaging, and neurophysiological techniques. This article reviews the research advances in susceptible genes for developmental dyslexia, and with the study on susceptible genes for dyslexia, it lays a foundation for in-depth studies on the "gene-brain-behavior" level and provides scientific clues for exploring etiology and pathogenesis of dyslexia.

[Research advances in susceptible genes for developmental dyslexia in children]

Developmental dyslexia in children is one of the neurodevelopmental disorders and is affected by various susceptible genes. In recent years, researchers have found some susceptible genes for dyslexia via chromosome analysis, genome-wide association studies, association analysis, gene function research, neuroimaging, and neurophysiological techniques. This article reviews the research advances in susceptible genes for developmental dyslexia, and with the study on susceptible genes for dyslexia, it lays a foundation for in-depth studies on the "gene-brain-behavior" level and provides scientific clues for exploring etiology and pathogenesis of dyslexia.

Dectin-1 Polymorphism: A Genetic Disease Specifier in Autism Spectrum Disorders?

Introduction

In autism spectrum disorders (ASD), complex gene-environment interactions contribute to disease onset and progress. Given that gastro-intestinal dysfunctions are common in ASD, we postulated involvement of microbial dysbiosis in ASD and investigated, under a case-control design, the influence of DNA polymorphisms in the CLEC7A gene that encodes a pivotal fungal sensor, Dectin-1.

Material and methods

DNAs from 478 ASD patients and 351 healthy controls (HC) were analyzed for the CLEC7A rs16910631G/A and rs2078178 A/G single nucleotide polymorphisms (SNPs). Differences in the distribution of allele, genotype and haplotype by Chi-square testing and nonparametric analysis by Kruskal-Wallis/Mann–Whitney tests, where appropriate, were performed. The free statistical package R.2.13 software was used for the statistical analysis.

Results

We found that the CLEC7A rs2078178 G allele and GG genotype were more prevalent in HC as compared to ASD but failed to reach statistical significance for the latter (pc = 0.01, 0.06 respectively). However, after phenotype-based stratification, the CLEC7A rs2078178 G allele and GG genotype were found to be significantly more frequent in the Asperger group as compared to other ASD subsets (pc = 0.02, 0.01), a finding reinforced by haplotype analysis (rs2078178/rs16910631 G-G/G-G) (pc = 0.002). Further, intellectual quotient (IQ)-based stratification of ASD patients revealed that IQ values increase linearly along the CLEC7A rs2078178 AA, AG and GG genotypes (p = 0.05) and in a recessive manner (GG vs. AA+AG p = 0.02), further confirmed by haplotype distribution (CLEC7A rs2078178-16910631; A-G/A-G, A-G/G-G and G-G/G-G, p = 0.02, G-G/G-G vs. others, p = 0.01).

Conclusion

Our data suggest that the genetic diversity of CLEC7A gene influences the ASD phenotype by behaving as a disease specifier and imply that the genetic control of innate immune response could determine the ASD phenotype.

The fragile X syndrome-autism comorbidity: what do we really know?

Autism spectrum disorder (ASD) is a common comorbid condition in people with fragile X syndrome (FXS). It has been assumed that ASD symptoms reflect the same underlying psychological and neurobiological impairments in both FXS and non-syndromic ASD, which has led to the claim that targeted pharmaceutical treatments that are efficacious for core symptoms of FXS are likely to be beneficial for non-syndromic ASD as well. In contrast, we present evidence from a variety of sources suggesting that there are important differences in ASD symptoms, behavioral and psychiatric correlates, and developmental trajectories between individuals with comorbid FXS and ASD and those with non-syndromic ASD. We also present evidence suggesting that social impairments may not distinguish individuals with FXS with and without ASD. Finally, we present data that demonstrate that the neurobiological substrates of the behavioral impairments, including those reflecting core ASD symptoms, are different in FXS and non-syndromic ASD. Together, these data suggest that there are clinically important differences between FXS and non-syndromic ASD that are masked by reliance on the categorical diagnosis of ASD. We argue for use of a symptom-based approach in future research, including studies designed to evaluate treatment efficacy.

Kernel-machine testing coupled with a rank-truncation method for genetic pathway analysis

Traditional genome-wide association studies (GWASs) usually focus on single-marker analysis, which only accesses marginal effects. Pathway analysis, on the other hand, considers biological pathway gene marker hierarchical structure and therefore provides additional insights into the genetic architecture underlining complex diseases. Recently, a number of methods for pathway analysis have been proposed to assess the significance of a biological pathway from a collection of single-nucleotide polymorphisms. In this study, we propose a novel approach for pathway analysis that assesses the effects of genes using the sequence kernel association test and the effects of pathways using an extended adaptive rank truncated product statistic. It has been increasingly recognized that complex diseases are caused by both common and rare variants. We propose a new weighting scheme for genetic variants across the whole allelic frequency spectrum to be analyzed together without any form of frequency cutoff for defining rare variants. The proposed approach is flexible. It is applicable to both binary and continuous traits, and incorporating covariates is easy. Furthermore, it can be readily applied to GWAS data, exome-sequencing data, and deep resequencing data. We evaluate the new approach on data simulated under comprehensive scenarios and show that it has the highest power in most of the scenarios while maintaining the correct type I error rate. We also apply our proposed methodology to data from a study of the association between bipolar disorder and candidate pathways from Wellcome Trust Case Control Consortium (WTCCC) to show its utility.