Autism Spectrum Disorders (ASDs) are likely caused by interactions between genetic and environmental factors which result in changes in neural development and activity. These changes might be associated with differences in the levels of expression of multiple different genes in both the nervous system and in peripheral blood cells. Identifying reproducible changes in gene expression levels in individuals with ASDs would be a valuable tool both for understanding the molecular basis of these disorders and in developing earlier and more accurate diagnostic tests. In the proposed study, Dr. Collins will examine gene expression profiles in individuals with ASDs using microarray technology, a technique used to measure the levels of expression of thousands of genes simultaneously. Gene expression in peripheral blood from ASD patients will be compared to that of healthy controls, and genes expressed at either higher or lower levels in the ASD patients will be identified. This approach may identify novel genes which are misregulated in autism, as well as provide the basis for the development of newer, more sensitive diagnostic tools for this disorder.