Autism genetics: emerging data from genome-wide copy-number and single nucleotide polymorphism scans

Autism and related traits are highly heritable but cannot be explained by currently known genetic risk factors. Therefore, the advent of genome-wide single nucleotide polymorphism (SNP) and copy number variant (CNV) microarray technologies heralded identification of additional autism loci. CNVs associated with autism seem to show variable expressivity, also leading to other phenotypes, such as schizophrenia, mental retardation/developmental delay and epilepsy. Initial genome-wide SNP-association studies have each identified a single novel associated locus with modest effect. Based on the lessons from other complex common disease, larger sample sizes and meta-analyses are likely to identify additional SNP loci, and the genes implicated may act on multiple related disorders. Even if common alleles or rare variants hold little predictive value, neurodevelopmental pathways disrupted in autism may be identified. Future research might yet uncover common CNV risk loci and rare single nucleotide risk alleles, which are currently difficult to detect. The genetic architecture and phenotypic heterogeneity identified so far suggest additional approaches, such as population-based research and study of relevant neurobiological endophenotypes.