Expression and localization of CMTM 2 in human testis and sperm

Purpose: To examine the expression and localization of transmembrane protein CMTM2 in human testis and sperm, and to approach the potential function of the protein in the male reproductive system. Methods: With testicular tissues obtained from obstructive azoospermia patients via biopsy and semen from healthy male volunteers, Western blot and immunohistochemistry were performed on human testis and sperm to explore the expression of CMTM2 on protein level, and immunofluorescence analysis was also used to examine the localization of CMTM2 in human testis and sperm before and after the acrosome reaction. Results: CMTM2 represented high expression in both human testis and sperm. In the testis, CMTM2 immunoreactive particles were observed mainly in the membranes of spermatogenic cells at different stages. In human sperm, CMTM2 was restrictively localized in the posterior head of sperm where sperm-egg fusion occurred, and the localization remained identical before and after sperm acrosome reaction. Conclusion: Expression of CMTM2 in human testis and sperm exhibits celland region-specific patterns, which suggests that they may play a pivotal role in spermatogenesis and sperm-egg fusion.