The genetic architecture of autism spectrum disorder involves the interplay of common and rare variants and their impact on hundreds of genes. Using exome sequencing, here we show that analysis of rare coding variation in 3,871 autism cases and 9,937 ancestry-matched or parental controls implicates 22 autosomal genes at a false discovery rate (FDR) < 0.05, plus a set of 107 autosomal genes strongly enriched for those likely to affect risk (FDR < 0.30). These 107 genes, which show unusual evolutionary constraint against mutations, incur de novo loss-of-function mutations in over 5% of autistic subjects. Many of the genes implicated encode proteins for synaptic formation, transcriptional regulation and chromatin-remodelling pathways. These include voltage-gated ion channels regulating the propagation of action potentials, pacemaking and excitability-transcription coupling, as well as histone-modifying enzymes and chromatin remodellers-most prominently those that mediate post-translational lysine methylation/demethylation modifications of histones.

/pdf/synaptic-transcriptional-and-chromatin-genes-disrupted-in-2xzlntcq5u.pdf

Synaptic, transcriptional and chromatin genes disrupted in autism

Autism is a severe neurobehavioral syndrome, arising largely as an inherited disorder, which can arise from several diseases. Despite recent advances in identifying some genes that can cause autism, its underlying neurological mechanisms are uncertain. Autism is best conceptualized by considering the neural systems that may be defective in autistic individuals. Recent advances in understanding neural systems that process sensory information, various types of memories and social and emotional behaviors are reviewed and compared with known abnormalities in autism. Then, specific genetic abnormalities that are linked with autism are examined. Synthesis of this information leads to a model that postulates that some forms of autism are caused by an increased ratio of excitation/inhibition in sensory, mnemonic, social and emotional systems. The model further postulates that the increased ratio of excitation/inhibition can be caused by combinatorial effects of genetic and environmental variables that impinge upon a given neural system. Furthermore, the model suggests potential therapeutic interventions.

https://onlinelibrary.wiley.com/doi/epdf/10.1034/j.1601-183X.2003.00037.x

Model of autism: increased ratio of excitation/inhibition in key neural systems

The autism spectrum disorders (ASDs) are a group of conditions characterized by impairments in reciprocal social interaction and communication, and the presence of restricted and repetitive behaviours. Individuals with an ASD vary greatly in cognitive development, which can range from above average to intellectual disability. Although ASDs are known to be highly heritable ( approximately 90%), the underlying genetic determinants are still largely unknown. Here we analysed the genome-wide characteristics of rare (<1% frequency) copy number variation in ASD using dense genotyping arrays. When comparing 996 ASD individuals of European ancestry to 1,287 matched controls, cases were found to carry a higher global burden of rare, genic copy number variants (CNVs) (1.19 fold, P = 0.012), especially so for loci previously implicated in either ASD and/or intellectual disability (1.69 fold, P = 3.4 x 10(-4)). Among the CNVs there were numerous de novo and inherited events, sometimes in combination in a given family, implicating many novel ASD genes such as SHANK2, SYNGAP1, DLGAP2 and the X-linked DDX53-PTCHD1 locus. We also discovered an enrichment of CNVs disrupting functional gene sets involved in cellular proliferation, projection and motility, and GTPase/Ras signalling. Our results reveal many new genetic and functional targets in ASD that may lead to final connected pathways.

/pdf/functional-impact-of-global-rare-copy-number-variation-in-xg6aybceyo.pdf

Functional impact of global rare copy number variation in autism spectrum disorders

Brain development and function depend on the precise regulation of gene expression. However, our understanding of the complexity and dynamics of the transcriptome of the human brain is incomplete. Here we report the generation and analysis of exon-level transcriptome and associated genotyping data, representing males and females of different ethnicities, from multiple brain regions and neocortical areas of developing and adult post-mortem human brains. We found that 86 per cent of the genes analysed were expressed, and that 90 per cent of these were differentially regulated at the whole-transcript or exon level across brain regions and/or time. The majority of these spatio-temporal differences were detected before birth, with subsequent increases in the similarity among regional transcriptomes. The transcriptome is organized into distinct co-expression networks, and shows sex-biased gene expression and exon usage. We also profiled trajectories of genes associated with neurobiological categories and diseases, and identified associations between single nucleotide polymorphisms and gene expression. This study provides a comprehensive data set on the human brain transcriptome and insights into the transcriptional foundations of human neurodevelopment.

/pdf/spatio-temporal-transcriptome-of-the-human-brain-4lesb40ibj.pdf

Spatio-temporal transcriptome of the human brain

Autism is a heterogeneous syndrome defined by impairments in three core domains: social interaction, language and range of interests. Recent work has led to the identification of several autism susceptibility genes and an increased appreciation of the contribution of de novo and inherited copy number variation. Promising strategies are also being applied to identify common genetic risk variants. Systems biology approaches, including array-based expression profiling, are poised to provide additional insights into this group of disorders, in which heterogeneity, both genetic and phenotypic, is emerging as a dominant theme.

/pdf/advances-in-autism-genetics-on-the-threshold-of-a-new-1vbpm6dbmd.pdf

Advances in autism genetics: on the threshold of a new neurobiology

Many studies have supported a genetic etiology for autism. Here we report mutations in two X-linked genes encoding neuroligins NLGN3 and NLGN4 in siblings with autism-spectrum disorders. These mutations affect cell-adhesion molecules localized at the synapse and suggest that a defect of synaptogenesis may predispose to autism.

https://www.hal.inserm.fr/inserm-00124744/document

Mutations of the X-linked genes encoding neuroligins NLGN3 and NLGN4 are associated with autism.

Background It is only recently that comorbidity in ADHD has come to the forefront as one of the most important aspects of the disorder. It is agreed that, often, these problems are at least as important as ADHD in contributing to the longer term outcome in the individual child. Objective To provide the reader with basic information about clinics and treatment of comorbidity in ADHD. Method Review of the empirically based literature. Results ADHD exists in a surprisingly high frequency together with a broad range of child neuropsychiatric disorders. This is accompanied with many still unresolved treatment problems. Conclusion It would not be appropriate to develop ADHD–services where clinicians would only have expertise in ADHD as such. Anyone working with children, adolescents and adults with ADHD would need to have training in general neuropsychiatry. Further research in this field is urgently needed. (Less)

Co-existing disorders in ADHD -- implications for diagnosis and intervention.

Individuals with attention-deficit/hyperactivity disorder (AD/HD) and autism spectrum disorders (ASD) often display symptoms from other diagnostic categories. Exclusion criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and the International Statistical Classification of Diseases and Related Health Problems (ICD-10) impede the use of categorical diagnoses to describe the particular problem constellation in a patient. In this study, we describe the prevalence and patterns of comorbid bipolar and psychotic disorders in 241 consecutively referred adult patients with AD/HD and/or ASD. Thirty per cent of patients with AD/HD had comorbid ASD and 38% of patients with ASD had comorbid AD/HD. Of the subjects with ASD, 7% had bipolar disorder with psychotic features, and 7.8% had schizophrenia or another psychotic disorder. The corresponding figures for the patients with AD/HD were 5.0% and 5.0%, respectively. Current diagnostic criteria have to be revised to acknowledge the comorbidity of bipolar and/or psychotic disorders in AD/HD and ASD.

Bipolar disorder, schizophrenia, and other psychotic disorders in adults with childhood onset AD/HD and/or autism spectrum disorders

Several brain-imaging studies have found associations between aberrant functioning in the frontal and temporal lobes and violent offending. We have previously reported decreased frontotemporal perfusion unrelated to psychosis, substance abuse, or current medication in 21 violent offenders. In the present study, we compared the regional cerebral blood flow (rCBF) in a new group of 32 violent offenders to scores on the Psychopathy Checklist-Revised (PCL-R), which rates two aspects of psychopathy: disturbed interpersonal attitudes (Factor 1) and impulsive antisocial behavior (Factor 2). A recently proposed model has split Factor 1 into a new Factor 1 (deceitful interpersonal style), a new Factor 2 (affective unresponsiveness), and a Factor 3, which approximately corresponds to the old Factor 2. The rCBF was assessed by single-photon emission computed tomography (SPECT) with technetium-99m-d,l-hexamethylpropyleneamine oxime (HMPAO) in regions of interest (ROIs) placed in accordance with fusioned magnetic resonance images (MRI) and SPECT scans. Significant negative correlations were found between interpersonal features of psychopathy (the old and especially the new Factor 1) and the frontal and temporal perfusion. The two most clearly associated ROIs were the head of the caudate nuclei and the hippocampi. These findings in a group of violent offenders living under the same conditions, which reduced the number of state-related confounders, add to the evidence indicating that aberrant frontotemporal activity may be a factor in violent behavior.

http://www.the-brights.net/morality/statement_1_studies/DOI/10.1016_s0925-4927(02)00006-9.pdf

Reduced frontotemporal perfusion in psychopathic personality.

To study the personality characteristics of adults with Asperger syndrome, and investigate the value of self-rating personality inventories, we administered the Temperament and Character Inventory (TCI) to 31 outpatients with Asperger syndrome.The TCI is a self-rating personality inventory that has been validated in the Swedish general population. The results were compared with age- and sex-matched norm groups. Participants with Asperger syndrome scored significantly higher on harm avoidance and lower on self-directedness and cooperativeness. Reward dependence and novelty seeking tended to be low. They also had significantly higher rarity scores, reflecting idiosyncratic perspectives. The most common temperament configurations were 'obsessional', 'passive-dependent' and'explosive'. Character, reflecting conceptual maturity, was poorly developed in the majority of our subjects. The self-ratings of persons with Asperger syndrome thus indicated anxious personalities with coping difficulties in the areas of social interaction and self-directedness, a picture corresponding to the clinical descriptions of Asperger syndrome.

Henrik Soderstrom

Papers

Mutations of the X-linked genes encoding neuroligins NLGN3 and NLGN4 are associated with autism.

Co-existing disorders in ADHD -- implications for diagnosis and intervention.

Bipolar disorder, schizophrenia, and other psychotic disorders in adults with childhood onset AD/HD and/or autism spectrum disorders

Reduced frontotemporal perfusion in psychopathic personality.

Temperament and Character in Adults with Asperger Syndrome