Migration and ultrastructural localiziation of the c-kit receptor protein in spermatogenic cells and spermatozoa of the mouse

Purpose: The c-kit receptor is a proto-oncogene important in germ cell migr ation and maturation and has also been demonstrated on the acrosomal region of mature sperm. The purpose of the present study was to examine the ultra structural location of the c-kit receptor in mouse testis and sperm. Materials and Methods: Testis and sperm from mature male mice were examined for the c-kit receptor utilizing electron microscopy and Western blot anal ysis techniques. Thin sections of mouse testis and sperm were stained with immunogold-labeled anti-c-kit antibodies. The protein from these testes and sperm was also utilized for Western blot analysis. Results: The c-kit protein was localized within the mouse testes to the typ e A spermatogonia, the round spermatids, and the mature testicular spermato zoa. The c-kit receptor was noted to migrate from the lumen of the acrosoma l vesicles in the early spermatids to the plasma membrane of the late sperm atids. It was also noted in the acrosomal region of the testicular spermato zoa, as well as the sperm from the epididymis. Sperm undergoing the acrosom e reaction demonstrated association of the c-Kif receptor with the plasma m embrane of the acrosome, but not on the acrosomal membrane itself. Western blot analysis demonstrated protein bands of 150 kDa in testis and intact sp erm. Conclusions: The present study confirms the presence of the c-Kit receptor in mouse testis and sperm. It also demonstrates that this receptor is local ized to the region of the developing acrosome.