Autism may be caused by an interaction between genetic and environmental factors. This interaction may take place at the level of gene expression, which is the process by which genes are turned on and made into proteins. While much research into the genetic basis of autism has focused on finding mutations within genes, researchers also appreciate that even normal genes can play a role in causing autism if they are inappropriately turned on or off. Gene expression is tightly controlled within a cell, and disruption of this process can lead to pathological conditions. Thus, it is crucial to understand the “epigenetic” mechanisms controlling gene expression and how they may be influenced by environmental factors. This study is looking for abnormal gene expression patterns in the brains of individuals with autism. One way that genes are turned off is through DNA methylation: an enzyme places a methyl group onto certain sequences of DNA, thus flagging those genes for silencing. Thus, by examining the methylation status of genes, one can tell whether the gene is turned off or not. Dr. Beaudet's fellow will examine the methylation patterns of genes taken from post-mortem brain tissue of autistic individuals, and compare them to tissue from controls. The primary tool for analysis will be DNA microarrays (“gene chips”), which allow a genome-wide scan. What this means for people with autism: Finding genes that are abnormally expressed in autism will advance understanding of the genetic basis of autism, and may indicate a role for gene-environment interactions in the cause of autism.