Deficient spermiogenesis in mice lacking Rlim

The X-linked gene plays major roles in female mouse development and reproduction, where it is crucial for the maintenance of imprinted X chromosome inactivation in extraembryonic tissues of embryos. However, while females carrying a systemic knockout (KO) die around implantation, male KO mice appear healthy and are fertile. Here, we report an important role for in testis where it is highly expressed in post-meiotic round spermatids as well as in Sertoli cells. Systemic deletion of the gene results in lower numbers of mature sperm that contains excess cytoplasm, leading to decreased sperm motility and in vitro fertilization rates. Targeting the conditional cKO specifically to the spermatogenic cell lineage largely recapitulates this phenotype. These results reveal functions of in male reproduction specifically in round spermatids during spermiogenesis.