Combined genome-wide linkage and targeted association analysis of head circumference in autism spectrum disorder families

Autism spectrum disorder: pathogenesis, biomarker, and intervention therapy

Autism spectrum disorder (ASD) has become a common neurodevelopmental disorder. The heterogeneity of ASD poses great challenges for its research and clinical translation. On the basis of reviewing the heterogeneity of ASD, this review systematically summarized the current status and progress of pathogenesis, diagnostic markers, and interventions for ASD. We provided an overview of the ASD molecular mechanisms identified by multi-omics studies and convergent mechanism in different genetic backgrounds. The comorbidities, mechanisms associated with important physiological and metabolic abnormalities (i.e., inflammation, immunity, oxidative stress, and mitochondrial dysfunction), and gut microbial disorder in ASD were reviewed. The non-targeted omics and targeting studies of diagnostic markers for ASD were also reviewed. Moreover, we summarized the progress and methods of behavioral and educational interventions, intervention methods related to technological devices, and research on medical interventions and potential drug targets. This review highlighted the application of high-throughput omics methods in ASD research and emphasized the importance of seeking homogeneity from heterogeneity and exploring the convergence of disease mechanisms, biomarkers, and intervention approaches, and proposes that taking into account individuality and commonality may be the key to achieve accurate diagnosis and treatment of ASD.

No Association between Polymorphisms of Vitamin D and Oxytocin Receptor Genes and Autistic Spectrum Disorder in a Sample of Turkish Children

Objective

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairment in social skills and communication with repetitive behaviors. Etiology is still unclear although it is thought to develop with interaction of genes and environmental factors. Oxytocin has extensive effects on intrauterine brain development. Vitamin D, affects neural development and differentiation and contributes to the regulation of around 900 genes including oxytocin receptor gene. In the present study, the contribution of D vitamin receptor and oxytocin receptor gene polymorphisms in the development of ASD in Turkish community was investigated. To our knowledge, this is the first study examining these two associated genes together in the literature.

Methods

Eighty-five patients diagnosed with ASD according to DSM-5 who were referred to outpatient clinics of Child and Adolescent Psychiatry of Başkent University and Mersin University and 52 healthy, age and gender-matched controls were included in the present study. Vitamin D receptor gene rs731236 (Taq1), rs2228570 (Fok1), rs1544410 (Bsm1), rs7975232 (Apa1) polymorphisms and oxytocin receptor gene rs1042778 and rs2268493 polymorphisms were investigated using real time polymerase chain reaction method.

Results

No significant difference between groups in terms of distribution of genotype and alleles in each of polymorphisms for these genes could be found.

Conclusion

Knowledge of genes and polymorphisms associated with the development of ASD may be beneficial for early diagnosis and future treatment. Further studies with larger populations are required to demonstrate molecular pathways which may play part in the development of ASD in Turkey.

A genome-wide linkage study of autism spectrum disorder and the broad autism phenotype in extended pedigrees

BACKGROUND

Although several genetic variants for autism spectrum disorder (ASD) have now been identified, these largely occur sporadically or are de novo. Much less progress has been made in identifying inherited variants, even though the disorder itself is familial in the majority of cases. The objective of this study was to identify chromosomal regions that harbor inherited variants increasing the risk for ASD using an approach that examined both ASD and the broad autism phenotype (BAP) among a unique sample of extended pedigrees.

METHODS

ASD and BAP were assessed using standardized tools in 28 pedigrees from Canada and the USA, each with at least three ASD-diagnosed individuals from two nuclear families. Genome-wide linkage analysis was performed using the posterior probability of linkage (PPL) statistic, a quasi-Bayesian method that provides strength of evidence for or against linkage in an essentially model-free manner, with outcomes on the probability scale.

RESULTS

The results confirm appreciable interfamilial heterogeneity as well as a high level of intrafamilial heterogeneity. Both ASD and combined ASD/BAP specific loci are apparent.

CONCLUSIONS

Inclusion of subclinical phenotypes such as BAP should be more widely employed in genetic studies of ASD as a way of identifying inherited genetic variants for the disorder. Moreover, the results underscore the need for approaches to identifying genetic risk factors in extended pedigrees that are robust to high levels of inter/intrafamilial locus and allelic heterogeneity.

Progress in the genetics of autism spectrum disorder

A genetic basis for autism spectrum disorder (ASD) is now well established, and with the availability of high-throughput microarray and sequencing platforms, major advances have been made in our understanding of genetic risk factors. Rare, often de novo, copy number and single nucleotide variants are both implicated, with many ASD-implicated genes showing pleiotropy and variable penetrance. Additionally, common variants are also known to play a role in ASD's genetic etiology. These new insights into the architecture of ASD's genetic etiology offer opportunities for the identification of molecular targets for novel interventions, and provide new insight for families seeking genetic counselling.

WHAT THE PAPER ADDS

A number of rare genetic variants are implicated in autism spectrum disorder (ASD), with some showing recurrence. Common genetic variants are also important and a number of loci are now being uncovered. Genetic testing for individuals with ASD offers the opportunity to identify relevant genetic etiology.

nArgBP2-SAPAP-SHANK, the core postsynaptic triad associated with psychiatric disorders

Despite the complex genetic architecture, a broad spectrum of psychiatric disorders can still be caused by mutation(s) in the same gene. These disorders are interrelated with overlapping causative mechanisms including variations in the interaction among the risk-associated proteins that may give rise to the specific spectrum of each disorder. Additionally, multiple lines of evidence implicate an imbalance between excitatory and inhibitory neuronal activity (E/I imbalance) as the shared key etiology. Thus, understanding the molecular mechanisms underlying E/I imbalance provides essential insight into the etiology of these disorders. One important class of candidate risk genes is the postsynaptic scaffolding proteins, such as nArgBP2, SAPAP, and SHANK that regulate the actin cytoskeleton in dendritic spines of excitatory synapses. This review will cover and discuss recent studies that examined how these proteins, especially nArgBP2, are associated with psychiatric disorders. Next, we propose a possibility that variations in the interaction among these proteins in a specific brain region might contribute to the onset of diverse phenotypes of psychiatric disorders.

The assembly of scaffolding proteins, key regulators of many signaling pathways, found in the brain’s synapses underpin a diverse range of neuropsychiatric disorders. Sunghoe Chang and colleagues from Seoul National University, South Korea, review how these postsynaptic proteins regulate the cellular cytoskeleton in nerve cell protrusions to maintain the balance between excitatory and inhibitory inputs in the brain. They discuss how perturbations in three particular proteins can cause an imbalance in synaptic signals that leads to conditions such as bipolar disorder, schizophrenia and autism. The authors propose that these proteins form a “core scaffolding triad” and interact in different ways to cause different mental illnesses. Dysregulation of these proteins could explain how mutations in the same genes, depending on whether they boost or decrease gene expression, contribute to the onset of diverse psychiatric disorders.