Mitochondrial DNA mutations in Autism Spectrum Disorder

Mitochondrial dysfunction is frequently observed in Autism Spectrum Disorders (ASD). Thus, variations in the mitochondrial DNA (mtDNA) sequences may contribute to increased ASD risks. In the current study, we evaluated mtDNA variations, including homoplasmy and heteroplasmy, in 903 ASD individuals along with their mothers and non-ASD siblings by using off-target reads from whole-exome sequencing data sets of Simons Foundation Autism Research Initiative (SFARI) Simons Collection available on NDAR. We found that heteroplasmic mutations in ASD individuals were enriched at non-polymorphic mtDNA sites (P = 0.0015) compared to their non-ASD siblings, which were more likely to confer deleterious effects than heteroplasmies at polymorphic mtDNA sites. Accordingly, we observed a ~1.5-fold enrichment of nonsynonymous mutations as well as a ~2.2-fold enrichment of predicted pathogenic mutations (P < 0.003) in ASD individuals compared to their non-ASD siblings. Our genetic findings substantiate pathogenic mtDNA mutations as a potential cause for ASD and synergize with recent work calling attention to their unique metabolic phenotypes for diagnosis and treatment of ASD.