Autism spectrum disorders (ASD) are the fastest growing neurodevelopmental disorders in the United States, affecting as many as one in 100 children. Despite the immense etiological heterogeneity in ASD, with more than 100 associated genetic mutations and variants, affected individuals have common behavioral manifestations that may arise due to perturbation of common neurodevelopmental processes. In the long term, identification of common cell- and molecular-level elements underlying the ASDs will require sampling of individuals throughout the spectrum, including both idiopathic cases and cases associated with a genetic abnormality. Of the known genetic causes of ASD, mutations in the FMR1 gene in fragile X syndrome are the most common. In fact, fragile X is the most common form of inherited mental retardation. This project aims to the study the causes of this disease using cutting edge stem cell technologies and state of the art molecular profiling techniques that provide a global view of gene activity and regulation in any given sample. With this approach, the research team hopes to identify genomic and developmental abnormalities associated with fragile X and potentially other forms of ASD.