Article

Genetics of autistic disorders: Review and clinical implications

Department of Child and Adolescent Psychiatry, Psychosomatics, and Psychotherapy, Johann Wolfgang Goethe-University, Deutschordenstrasse 50, Frankfurt am Main, Germany.
European Child & Adolescent Psychiatry (Impact Factor: 3.34). 11/2009; 19(3):169-78. DOI: 10.1007/s00787-009-0076-x
Source: PubMed

ABSTRACT

Twin and family studies in autistic disorders (AD) have elucidated a high heritability of AD. In this literature review, we will present an overview on molecular genetic studies in AD and highlight the most recent findings of an increased rate of copy number variations in AD. An extensive literature search in the PubMed database was performed to obtain English published articles on genetic findings in autism. Results of linkage, (genome wide) association and cytogenetic studies are presented, and putative aetiopathological pathways are discussed. Implications of the different genetic findings for genetic counselling and genetic testing at present will be described. The article ends with a prospectus on future directions.

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Available from: Christine M. Freitag, Sep 24, 2014
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    • "According to multiple family and twin studies reporting a substantial heritable component ranging between 70 and 90 % of autism etiology (Bailey et al. 1995; Freitag 2011; Folstein and Rosen-Sheidley 2001), ASD is considered to be one of the most strongly genetically influenced multifactorial childhood psychiatric disorders (Hallmayer et al. 2011). Despite the high heritability, the genetics are inferred to be complex and no major gene has been identified to be relevant for the majority of ASD diagnoses (Freitag et al. 2010). In the past decades, various studies have implicated a small amount of genes with either rare highly penetrant mutations, lowpenetrant common variants or copy-number variants (CNV) that together explain only about 15–30 % of the population prevalence (Sampath et al. 2013; Anney et al. 2010; Klei et al. 2012). "
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    ABSTRACT: The Contactin Associated Protein-like 2 (CNTNAP2) gene has been discussed to be associated with different symptoms of autism spectrum disorders (ASDs) and other neurodevelopmental disorders. We aimed to elucidate the genetic association of CNTNAP2 within high functioning ASD (HFA), focusing on autism specific symptoms and reducing intelligence related factors. Furthermore, we compared our findings conducting a meta-analysis in patients with ASD and HFA only. A case-control association study was performed for HFA (HFA, n = 105; controls, n = 133). Moreover, we performed a family-based association study (DFAM) analysis (HFA, n = 44; siblings, n = 57). Individuals were genotyped for the two most frequently reported single nucleotide polymorphisms (SNPs) in the CNTNAP2 gene (rs2710102, rs7794745). Furthermore, a meta-analysis using the MIX2 software integrated our results with previously published data. A significant association for the carriers of the T-allele of the rs7794745 with HFA was found in the case-control sample [OR = 1.547; (95 % CI 1.056-2.266); p = 0.025]. No association could be found by DFAM with any of the CNTNAP2 SNPs with HFA. The meta-analysis of both SNPs did not show a significant association with either ASD or with HFA. Overall, including case-control, sibs, and meta-analysis, we could not detect any significant association with the CNTNAP2 gene and HFA. Our results point in the direction that CNTNAP2 may not play a major role in HFA, but rather seems to have a significance in neurodevelopmental disorders or in individuals displaying intellectual delays.
    Full-text · Article · Nov 2015 · Journal of Neural Transmission
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    • "Although there is strong evidence for genetic factors in ASD, it appears to be a polygenic condition (Betancur 2011), and also responsive to a range of environmental events. Although, its precise etiology is unknown , ASD is clearly a complex human genetic disorder that involves interactions between genes and environment (Freitag et al. 2010; Li et al. 2014). Future integrative epigenomic analyses of genetic risk factors for environmental exposures and methylome analyses are expected to be important for understanding the complex etiology of ASD (LaSalle 2014). "
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    ABSTRACT: Autism research continues to receive considerable attention as the options for successful management are limited. The understanding of the autism spectrum disorder (ASD) etiology has now progressed to encompass genetic, epigenetic, neurological, hormonal, and environmental factors that affect outcomes for patients with ASD. Glycosaminoglycans (GAGs) are a family of linear, sulfated polysaccharides that are associated with central nervous system (CNS) development, maintenance, and disorders. Proteoglycans (PG) regulate diverse functions in the central nervous system. Heparan sulfate (HS) and chondroitin sulfate (CS) are two major GAGs present in the PGs of the CNS. As neuroscience advances, biochemical treatments to correct brain chemistry become better defined. Nutrient therapy can be very potent and has minimal to no side effects, since no molecules foreign to the body are needed. Given GAGs are involved in several neurological functions, and that its level can be somewhat modulated by the diet, the present study aimed to evaluate the role of GAGs levels in ASD symptoms. Both tGAG and its different fractions were evaluated in the urine of ASD and healthy control childrens. As levels differed between groups, a second trial was conduted evaluating if diet could reduce tGAG levels and if this in turn decrease ASD symptoms. The present study found that tGAG concentration was significantly higher in the urine of children with ASD compared to healthy control children and this was also evident in all GAG fractions. Within groups (controls and ASD), no gender differences in GAG excretion were found. The use of a 90 days elimination diet (casein-free, special carbohydrates, multivitamin/mineral supplement), had major effects in reducing urinary tGAG excretion in children with ASD.
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    • "The studies mainly identified regions in chromosomes 2 and 7, and also other regions in chromosomes 1, 5, 16, and 17 (Gupta and State 2006). More recently, other studies have indicated positive results in different regions in chromosomes 4, 6, 11, 15, 20, and 22 (Freitag et al. 2010; Fradin et al. 2010; Liu et al. 2008; Weiss et al. 2009). The 7q region is an area of particular interest, since many chromosomal rearrangements have been identified and some genes have been related to brain expression and other known physiological functions, possibly involved in the pathology of ASD (Gupta and State 2006). "
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    ABSTRACT: Autism spectrum disorder (ASD) is multifactorial and complex condition, with a marked genetic influence, as evidenced by the high heritability (around 80—90%). Additionally, both common and rare genetic variants have an influence on the etiology and development. Several genetic syndromes are described in ASD, and they are present in approximately 10% of cases. Different genetic approaches are described in studies with ASD samples. Linkage studies mainly identify regions in chromosomes 2 and 7 which are involved in ASD. Genetic association studies, which aim to identify genes or genomic regions influencing ASD, involve the analysis of candidate genes or genome scan. The genes analyzed in these studies encode components related to neurotransmitter metabolism, neural migration, neuronal cell adhesion, apoptosis, and cell proliferation. Other methodologies have been used to complement genetic investigations, for example, exome and copy number variation (CNV) studies. Epigenetic studies indicate an important environmental influence on these disorders. The genetic evaluation of all patients with ASD is now required due to recent advances in knowledge regarding the genetic factors involved in the etiology of autism. Definitions of key terms and concepts used throughout this chapter are presented in Fig.3.1.
    No preview · Chapter · Jun 2015
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