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The genetics of autism
The causes of autism are not well understood. Identification of the genes responsible currently remains a major research direction with the objective of developing sound understanding of the underlying pathophysiological mechanisms.
Research has identified a number of genetic causes likely to lead to cases of autism but none of them on their own can explain more than a few cases per thousand or ten thousand.
The identification of high-penetrance mutations in certain patients confirmed the existence of a genetic predisposition.
Studies conducted on monozygotic twins suffering from autism showed a phenotype concordance of 60 to 90%.
The incidence of autism in the younger brothers or sisters in a family with an autistic child is 25 to 50 times higher than it is in the general population.
In the vast majority of cases, autism seems to be a multi-gene disease, involving variations of several genes in variable proportions and architectures.
Thanks to new technologies and the support of parents’ associations, we have learned more about the molecular genetics of autism in the last three years than in the last three decades.
These advances have made it possible to assess the role of rare genetic variations more accurately and identify the first common variants (SNP) via GWS (Genome-Wide Scan).
Recent reference to the literature* revealed that between 30 and 40 genes have been associated with autism and can be targeted via SNP-type markers.
In the vast majority of cases, the direct physiopathological impact of the gene in autism is not demonstrated.
Association studies on cohorts of affected children serve to identify the high-risk alleles in the common variants (SNP).
Complementary tools, such as the study of RNA expression or animal models, will give a global view of the mechanism of autism where genetic and non-genetic factors may intervene in the origin of the disease.
The genetics of autism, like its phenotype, are not unequivocal. The use of biomarkers, such as SNPs marking associated genes, serves to take into account the multi-gene concept of the pathology.
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*Abrahams et Geschwind 2010. M. Speicher et al. (eds.), Vogel and Motulsky’s Human Genetics: Problems and Approaches, © Springer-Verlag Berlin Heidelberg 2010.
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