Severely reduced female fertility in CD9-deficient mice

CD9 is a widely expressed cell surface molecule that belongs to the tetrasp anin superfamily of proteins. The tetraspanins CD9, KAI-1/CD82, and CD63 ar e involved in metastasis suppression, an effect that may be related to thei r association with beta 1 integrins. Knockout mice lacking CD9 were created to evaluate the physiological importance of CD9. CD9(-/-) females displaye d a severe reduction of fertility. Oocytes were ovulated but were not succe ssfully fertilized because sperm did not fuse with the oocytes from CD9(-/- ) females. Thus, CD9 appears to be essential for sperm-egg fusion, a proces s involving the CD9-associated integrin alpha 6 beta 1.