Ancient roots: A Cambrian explosion of autism susceptibility genes

Functional gene groups often share unique evolutionary patterns. The present study addresses whether autism susceptibility genes, which frequently share functional overlap, display unusual gene age and conservation patterns compared to other gene groups. Using phylostratigraphically-derived and other genetic data, the investigator explores average gene age, Ohnolog status, evolutionary rate, variation intolerance, and numbers of protein-protein (PPI) interactions across autism susceptibility, nervous system, developmental regulatory, immune, housekeeping, and luxury gene groups. Autism susceptibility genes are unusually old compared to controls, many genes having radiated in the Cambrian period in early vertebrates from whole genome duplication events. They are also tightly conserved across the animal kingdom, are highly variation intolerant, and have more PPI than other genes-all features suggesting extreme dosage sensitivity. The results of the current study indicate that autism susceptibility genes display unique radiation and conservation patterns, which may be a reflection of the major transitions in nervous system evolution that were occurring in early animals and which are still foundational in brain development today.