Stage-specific localization of basigin, a member of the immunoglobulin superfamily, during mouse spermatogenesis

Ablation of the transmembrane glycoprotein basigin leads to azoospermic mic e, indicating that this gene is essential for spermatogenesis. To examine t he functions of basigin in the testis, the precise localization of basigin during spermatogenesis was examined immunohistochemically. In the adult mou se testis, basigin immunoreactivity appeared on the cell surface of leptote ne spermatocytes and gradually increased in intensity during the meiotic pr ophase. Cytoplasmic staining, as well as cell surface staining, was detecte d in spermatids. The most conspicuous reactivity was found in the spermatid s at steps 9-11 and in the flagella of spermatids. Immuno-electron microsco pic analysis demonstrated that basigin was localized not only on the plasma membranes of spermatocytes and spermatids, but also on the plasma membrane of the Sertoli cell processes which contact the spermatocytes and spermati ds. Basigin immunoreactivity was also detected during postnatal development in spermatocytes and spermatids but not in spermatogonia. Experimental cry ptorchid testes which contain only spermatogonia and Sertoli cells in the s eminiferous epithelium showed no basigin immunoreactivity. Seven days after surgical reversal of the cryptorchid testis, spermatocytes reappeared in t he tubules, along with basigin immunoreactivity. Furthermore, in sterile mu tant mice, in which neither spermatocytes nor spermatids were generated, no basigin immunoreactivity was detected in the seminiferous tubules. These f indings indicate that expression of basigin is concomitant with appearance of spermatocytes in the seminiferous tubule, and suggest that basigin is in volved in the interaction between Sertoli cells and germ cells at specific stages of spermatogenesis.