A Pooled Genome-Wide Association Study of Asperger Syndrome

Ophthalmologic diagnoses in youths with autism spectrum disorder: Prevalence and clinical correlates

Autism spectrum disorder (ASD) is associated with a high prevalence of visual dysfunction. This study aimed to investigate the rates of amblyopia, refractive errors, and strabismus, as well as their clinical correlates in ASD. This population-based matched-cohort study used data from the Taiwan National Health Insurance Research Database. A total of 3,551 youths with ASD and 35,510 non-autistic control participants matched by age and sex were included. All the participants were followed-up until they were 18 years old. The prevalence of amblyopia, refractive errors, and strabismus was compared between the ASD and control groups. Effect modifiers, including sex, ASD subgroup, and co-diagnosis of intelligence disability, were examined. Compared to the control group, youths with ASD had a significantly increased risk of amblyopia (adjusted odds ratio [aOR] = 1.75), anisometropia (aOR = 1.66), astigmatism (aOR = 1.51), hypermetropia (aOR = 2.08), exotropia (aOR = 2.86), and esotropia (aOR = 2.63), but a comparable likelihood of myopia according to age. Males with ASD had a significantly lower likelihood of exotropia, but a higher likelihood of myopia than females with ASD. The autism subgroup had a higher OR for hypermetropia, but a lower OR for myopia than the other ASD subgroups. ASD youths with intelligence disabilities demonstrated significantly higher ORs for amblyopia, hypermetropia, and all types of strabismus and lower OR for myopia than those without intelligence disabilities. In conclusion, the rates of amblyopia, refractive errors, and strabismus were higher in youths with ASD. Ocular abnormalities in youths with ASD require a comprehensive assessment and management.

Autism-like social deficit generated by Dock4 deficiency is rescued by restoration of Rac1 activity and NMDA receptor function

Genetic studies of autism spectrum disorder (ASD) have revealed multigene variations that converge on synaptic dysfunction. DOCK4, a gene at 7q31.1 that encodes the Rac1 guanine nucleotide exchange factor Dock4, has been identified as a risk gene for ASD and other neuropsychiatric disorders. However, whether and how Dock4 disruption leads to ASD features through a synaptic mechanism remain unexplored. We generated and characterized a line of Dock4 knockout (KO) mice, which intriguingly displayed a series of ASD-like behaviors, including impaired social novelty preference, abnormal isolation-induced pup vocalizations, elevated anxiety, and perturbed object and spatial learning. Mice with conditional deletion of Dock4 in hippocampal CA1 recapitulated social preference deficit in KO mice. Examination in CA1 pyramidal neurons revealed that excitatory synaptic transmission was drastically attenuated in KO mice, accompanied by decreased spine density and synaptic content of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)- and NMDA (N-methyl-_D-aspartate)-type glutamate receptors. Moreover, Dock4 deficiency markedly reduced Rac1 activity in the hippocampus, which resulted in downregulation of global protein synthesis and diminished expression of AMPA and NMDA receptor subunits. Notably, Rac1 replenishment in the hippocampal CA1 of Dock4 KO mice restored excitatory synaptic transmission and corrected impaired social deficits in these mice, and pharmacological activation of NMDA receptors also restored social novelty preference in Dock4 KO mice. Together, our findings uncover a previously unrecognized Dock4-Rac1-dependent mechanism involved in regulating hippocampal excitatory synaptic transmission and social behavior.

Two Autism/Dyslexia Linked Variations of DOCK4 Disrupt the Gene Function on Rac1/Rap1 Activation, Neurite Outgrowth, and Synapse Development

Autism spectrum disorder (ASD) and dyslexia are both neurodevelopmental disorders with high prevalence in children. Both disorders have strong genetic basis, and share similar social communication deficits co-occurring with impairments of reading or language. However, whether these two disorders share common genetic risks remain elusive. DOCK4 (dedicator for cytokinesis 4), a guanine nucleotide exchange factor (GEF) for the small GTPase Rac1, is one of few genes that are associated with both ASD and dyslexia. Dock4 is important for neuronal development and social behaviors. Two DOCK4 variations, Exon27-52 deletion (protein product: Dock4-945VS) and a missense mutation at rs2074130 (protein product: Dock4-R853H), are associated with dyslexia and/or ASD with reading difficulties. The present study explores the molecular and cellular functions of these two DOCK4 variants on neuronal development, by comparing them with the wild-type Dock4 protein. Notably, it is revealed that both mutants of Dock4 showed decreased ability to activate not only Rac1, but also another small GTPase Rap1. Consistently, both mutants were dysfunctional for regulation of cell morphology and cytoskeleton. Using Neuro-2a cells and hippocampus neurons as models, we found that both mutants had compromised function in promoting neurite outgrowth and dendritic spine formation. Electrophysiological recordings further showed that R853H partially lost the ability to promote excitatory synaptic transmission, whereas 945VS totally lost the ability. Together, we identified R853 as a previously uncharacterized site for the regulation of the integrity of Dock4 function, and provides insights in understanding the common molecular pathophysiology of ASD and dyslexia.

Systematic Review of Literature on Single-Nucleotide Polymorphisms Within the Oxytocin and Vasopressin Receptor Genes in the Development of Social Cognition Dysfunctions in Individuals Suffering From Autism Spectrum Disorder

Introduction: Autism spectrum disorder (ASD) is found in virtually all population groups regardless of ethnic or socioeconomic backgrounds. Among others, dominant symptoms of autism persistent throughout its course of development include, inter alia, qualitative disorders of social communication and social interactions. Numerous studies have been performed on animal models as well as groups of healthy individuals to assess the potential role of oxytocinergic and vasopresynergic systems in normal social functioning. These studies have also discussed their potential participation in the development of social cognition dysfunctions in the course of ASD. This literature review aimed to identify studies examining single-nucleotide polymorphisms of the oxytocin (OXT) and arginine vasopressin (AVP) receptor genes and their differential effects on social cognitive dysfunction in the development of ASD. Methods: A systematic review of literature published within the last 10 years and accessible in PubMed, Google Scholar, Cochrane Library, and APA PsycNET databases was conducted by each author separately. Inclusion criteria required that articles should 1) be published between January 2008 and August 2018; 2) be published in English or Polish; 3) be located in periodical publications; 4) focus on the role of polymorphisms within oxytocin and vasopressin receptor genes in autistic population; 5) provide a clear presentation of the applied methodology; and 6) apply proper methodology. Results: From the 491 studies qualified to the initial abstract analysis, 15 met the six inclusion criteria and were included in the full-text review. Conclusions: The analysis of available literature seems to indicate that there is an association between social cognition dysfunctions in the course of autism and selected alleles of polymorphisms within the OXT receptor AVP 1A receptor genes. However, previous studies neither specify the nature of this association in an unequivocal way nor select genotypes that are the basis for this association.

ADHD-related symptoms and attention profiles in the unaffected siblings of probands with autism spectrum disorder: focus on the subtypes of autism and Asperger's disorder

BACKGROUND

The presence of attention-deficit/hyperactive disorder (ADHD) symptoms and impaired attention performance are commonly noted in individuals with autism spectrum disorder (ASD). However, little is known about attention performance in their unaffected siblings. This study aimed to investigate the ADHD-related traits and attention performance in unaffected siblings of probands with autism and Asperger syndrome (AS), as well as the clinical correlates of ADHD-related traits.

METHODS

We assessed the intention, hyperactivity-impulsivity, and oppositional symptoms, and attention profiles of 199 probands with a diagnosis of ASD (122 autism, 77 AS), their unaffected siblings, and 196 typically developing controls (TD) by their parents' reports on the ADHD-related symptoms and the Connors' Continuous Performance Test (CCPT), respectively.

RESULTS

Compared to TD, unaffected siblings of ASD probands were more hyperactive/impulsive and oppositional, particularly unaffected siblings of AS probands. In CCPT, unaffected siblings of AS have intermediate levels of performance between probands with AS and TD on focused attention and sustained attention but were not statistically different from AS probands or TD in these attention profiles. In contrast, unaffected siblings of autism probands have significantly better CCPT performance when compared to autism probands but not to TD. In addition, stereotyped behaviors predicted ADHD-related traits in both sibling groups, but distinctive patterns of other correlates for ADHD-related traits were found between the two sibling groups.

CONCLUSIONS

This work suggested that unaffected siblings of AS, but not autism, have more hyperactive/impulsive traits and a trend of pervasive attention deficits assessed by CCPT which might serve as potential endophenotypes for genetic studies in AS.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01582256.

3p22.1p21.31 microdeletion identifies CCK as Asperger syndrome candidate gene and shows the way for therapeutic strategies in chromosome imbalances

Background

In contrast to other autism spectrum disorders, chromosome abnormalities are rare in Asperger syndrome (AS) or high-functioning autism. Consequently, AS was occasionally subjected to classical positional cloning. Here, we report on a case of AS associated with a deletion of the short arm of chromosome 3. Further in silico analysis has identified a candidate gene for AS and has suggested a therapeutic strategy for manifestations of the chromosome rearrangement.

Results

Using array comparative genomic hybridization, an interstitial deletion of 3p22.1p21.31 (~2.5 Mb in size) in a child with Asperger’s syndrome, seborrheic dermatitis and chronic pancreatitis was detected. Original bioinformatic approach to the prioritization of candidate genes/processes identified CCK (cholecystokinin) as a candidate gene for AS. In addition to processes associated with deleted genes, bioinformatic analysis of CCK gene interactome indicated that zinc deficiency might be a pathogenic mechanism in this case. This suggestion was supported by plasma zinc concentration measurements. The increase of zinc intake produced a rise in zinc plasma concentration and the improvement in the patient’s condition.

Conclusions

Our study supported previous linkage findings and had suggested a new candidate gene in AS. Moreover, bioinformatic analysis identified the pathogenic mechanism, which was used to propose a therapeutic strategy for manifestations of the deletion. The relative success of this strategy allows speculating that therapeutic or dietary normalization of metabolic processes altered by a chromosome imbalance or genomic copy number variations may be a way for treating at least a small proportion of cases of these presumably incurable genetic conditions.