In this project, researchers will directly investigate relationships between co-occurring gastrointestinal dysfunction (GID) and autism spectrum disorders (ASD), testing a biological hypothesis regarding disruption of the tyrosine kinase receptor MET receptor and its associated intracellular signaling events as a common theme in ASD. Genetic polymorphisms in MET have been implicated in ASD, and MET plays a role in brain wiring and gastrointestinal epithelial cell repair. Researchers will follow a pediatric group with and without ASD, characterizing their GI function and genotyping for sequence alterations in the MET gene to connect the genetic risk findings with biological changes. The studies will provide unique epidemiological descriptions of the study population giving insight into stratification of the ASD subgroup that is characterized by the presence of GID. Identification of biomarkers such as pan-MET and phospho-MET protein levels may also benefit diagnosis and treatment for ASD.