Deficits in social cognition are present in autism and 9% of otherwise normal males. An X-linked gene, EFHC2, has been mapped in women with Turner Syndrome, 30% of whom show autism-like deficits. Nothing is known about the function of EFHC2. We will first resolve the allelic, spatial, and temporal expression pattern of EFHC2. Our next aim will determine the normal properties of EFHC2. We will resolve the subcellular location of EFHC2 in neurons and assay Ca2+ binding. Our final aim is to determine which natural variation in EFHC2 has functional consequences. We will sequence the EFHC2 locus and narrow down functional SNPs by genotyping and analyzing association in Turner Syndrome patients. We will assess the molecular consequences of EFHC2 variation on expression or calcium binding. Our ultimate goals would be to evaluate whether neurotransmitter release is influenced by the genetic variation in EFHC2 associated with fear recognition. Functional analysis of a gene influencing social cognition could contribute to understanding autism, revealing normal social physiology, and developing methods for the dissection of complex traits. [unreadable] [unreadable] [unreadable]