This is an individual National Research Service Award for pre-doctoral research training, which provides support for promising doctoral candidates who will be performing dissertation research and training in a scientific health-related field. Continued identification of genes associated with ASDs has advanced understanding of the role of genetics in ASDs, but the skewed sex ratio in prevalence remains unexplained. To this end, studying a candidate gene that shows sex differences in expression patterns or associated neural phenotypes may provide unique insights into ASD pathophysiology. Data from the Geschwind lab show that cytoplasmic FMRP-interacting protein 1 (CYFIP1) expression patterns differ by sex and that neuropathological phenotypes associated with Cyfip1 over-expression may also show sex differences. CYFIP1 has also been implicated in neural development and function, making this candidate gene a unique target for study. A transgenic mouse model that over-expresses Cyfip1 will be used to better understand the implications of the sex differences in Cyfip1 expression in neural development and ASD pathophysiology. Continued investigation along these lines will accelerate identification of those factors that cause males to be vulnerable to, or females to be protected from, ASDs, thereby facilitating the development of pharmaceutical treatments and preventive measures for ASDs.