Severely Reduced Female Fertility in CD9-Deficient Mice

TLDR

CD9 is a widely expressed tetraspanin involved in metastasis suppression, possibly through interactions with β1 integrins. The authors generated CD9 knockout mice to evaluate CD9’s physiological importance. The study assessed CD9’s role by creating and analyzing CD9‑deficient mice. CD9−/− females exhibited severely reduced fertility because sperm failed to fuse with their oocytes, demonstrating that CD9 is essential for sperm‑egg fusion via integrin α6β1.

Abstract

CD9 is a widely expressed cell surface molecule that belongs to the tetraspanin superfamily of proteins. The tetraspanins CD9, KAI-1/CD82, and CD63 are involved in metastasis suppression, an effect that may be related to their association with β1 integrins. Knockout mice lacking CD9 were created to evaluate the physiological importance of CD9. CD9 −/− females displayed a severe reduction of fertility. Oocytes were ovulated but were not successfully fertilized because sperm did not fuse with the oocytes from CD9 −/− females. Thus, CD9 appears to be essential for sperm-egg fusion, a process involving the CD9-associated integrin α6β1.