Gene-environment interactions and epigenetic pathways in autism: the importance of one-carbon metabolism.

Both genetic and epigenetic factors play important roles in the rate and severity of classic autism and autism spectrum disorders (ASDs). This review focuses on DNA methylation as a key epigenetic mechanism in autism. The critical role that one-carbon (C1) metabolism plays in establishing and maintaining DNA methylation patterns makes it a likely candidate pathway to regulate epigenetic processes in ASDs. This review is the first, to our knowledge, to examine how altering C1 metabolic function through genetic and environmental factors (focusing on diet) may lead to aberrant DNA methylation and increase susceptibility to ASDs. Additionally, the critical time windows for sensitivity to genetic and dietary factors both during the development of cortical networks implicated in ASDs and in regard to potential treatments are discussed. One thing is clear, if C1 metabolism plays a critical role in ASDs, it provides a potential avenue for treatment and perhaps, ultimately, prevention.