Recent studies have suggested that autism may be associated with perturbations in cellular energy metabolism. The brain is a highly energy-dependent tissue, and is very sensitive to changes in energy metabolism. The underlying cause of the changes in energy metabolism seen in autism is not known; however, it is hypothesized that it involves a dysfunction in mitochondria, the cellular structures which are responsible for metabolizing nutrients to energy that can be used by the cell. Dr. Giulivi and colleagues will test the hypothesis that mitochondrial dysfunction is associated with altered expression of the gene PTEN. This gene has been connected to autism-like symptoms and neurodevelopmental disorders, and may also be involved in mitochondrial function. In the present study, mitochondria will be systematically examined in mice engineered to lack the PTEN gene. This research will clarify the aspects of mitochondrial function and energy metabolism which are disrupted in the absence of this gene. Results from these experiments should enhance the understanding of the connection between energy metabolism, mitochondrial dysfunction, and autism, and may lead to new diagnostic or treatment methods.