THE POLYGENETIC ARCHITECTURE OF AUTISM

Abstract

Autism is highly heritable and has been associated with multiple classes of genetic variation. Common genetic variation contributes substantially to autism. Previously, with 18,381 autistic individuals and 27,969 non-autistic individuals, five genome-wide significant loci were identified. Now with 38,717 autistic individuals and 232,725 non-autistic individuals, we report an updated genome-wide association study (GWAS) of autism with 12 genome-wide significant loci. We observe a moderate genetic correlation (0.675, SE=0.0434) between Europe-based (Nautistic=22,643; Nnon-autistic=204,389) and United States-based (Nautistic =16,074; Nnon-autistic=28,346) autism cohorts, which contributes to the decline of the estimated single nucleotide polymorphism (SNP) heritability (from 0.118 (SE=0.010) to 0.068 (SE=0.003)). The genetic correlation between autism with intellectual disability (ID) (Nautistic=6,590; Nnon-autistic= 43,071; h2=0.062; SE=0.012) and autism without ID (Nautistic=23,173; Nnon-autistic= 204,679; h2=0.089; SE=0.005) is 0.658 (SE=0.086). In the United States family-based cohorts, the genetic correlation between autism with ID (Nfamily=3,993; h2=0.159; SE=0.033) and autism without ID (Nfamily=4,357; h2=0.171; SE=0.031) is 0.812 (SE=0.157). Autism without ID was positively genetically correlated with educational attainment (0.163; P=4.84 × 10-11) and intelligence (0.233; P=1.95 × 10-11). Autism with ID genetically correlated with neither educational attainment (0.036; P=0.409) nor intelligence (-0.072; P=0.235). As ID alone is negatively genetically correlated with intelligence, the lack of correlation between autism with ID and intelligence strongly suggests that autism with ID is genetically different from ID alone. This difference has implications for both research and clinical nosology. Rare and de novo variants contribute substantially to autism in some individuals. Through rare variant analyses, 72 genes have been associated with autism at a genome-wide significant level to date. While de novo protein truncating variants (PTVs) and copy number deletions have been associated with autism, we report preliminary findings that the burden of inherited PTVs and copy number deletions among autistic individuals was elevated compared to their non-autistic siblings (P=4.00 × 10-5). Integration of multiple genetic factors will help us better understand the etiology of autism.