The long-term objective of the current application is to study the regulation of meiosis in mice. Abnormality in meiosis is a leading cause of birth defects and infertility in humans. Genomics studies in mice showed that the X chromosome is enriched for genes involved in early spermatogenesis. The current application is to study the role of a mouse X-linked testis-specific gene product, TEX11, in meiosis of both sexes. The TEX11 protein is conserved in mice and humans. Our specific aims are: 1) To characterize defects in meiotic recombination and chromosomal synapsis in TEX11-deficient males;2) To investigate the role of TEX11 in oocyte aneuploidy and embryo death;3) To study the role of TEX11 in linking meiotic recombination with the synaptonemal complex. Our proposed genetic, cell and molecular biological studies will help to uncover the mechanism underlying the regulation of meiosis in both sexes by TEX11. Our research will also provide insight into the molecular etiology of X-linked male infertility and birth defects (trisomy and monosomy) in humans.