Research

Sex chromosomes and Autism

The number of children diagnosed with autism has surged to 1 in 36 in the past decade. Accurate diagnosis and adequate support will require a thorough understanding of autism's genetic basis. Even though autism affects men and women differently, previous genome-wide association studies (GWAS) have focused on the 22 chromosomes shared by males and females, neglecting the sex chromosomes. We are ramping up an effort to remedy this in collaboration with the Danish iPSYCH consortium. In addition to GWAS tailored to human sex chromosomes, we pursue hypotheses that link sex bias in autism to the unique evolutionary forces acting on sex chromosomes. Recent research from our group has revealed uniquely strong natural selection on the human X chromosome, best explained by selfish X-genes promoting their natural selection in spermatogenesis by killing sperm cells that carry the Y chromosome. Such selfish advantage in spermatogenesis easily trumps modest deleterious effects such gene variants may have on brain development. One in four neuron genes is also expressed in spermatids. We hypothesize that selfish selection for transmission to live sperm promotes gene variants despite a mildly detrimental impact on neuro-development and that female fitness is favored in the subsequent resolution of these collateral effects.