Objective: To study the expression of transmembrane protein CMTM2 in the testis and sperm of adult males and to approach the potential function of the protein in the male reproductive system.Methods: The expression of CMTM2 in human testis and sperm was confirmed by Western blot.Immunohistochemical staining was used for detecting CMTM2 localization in the testis tissue, TRITC-CMTM2 and FITC-Hoechst double immunofluorescence staining was performed to examine the subcellular localization of CMTM2 in the human sperm before and after acrosome reaction, that is, immunofluorescent staining was used for detecting CMTM2 localization in both the testis and sperm before and after the acrosome reaction.Results: CMTM2 was presented in both human testis and sperm.In the testis, CMTM2 immunoreactive particles were observed mainly in the membrane of the different stages of spermatogenic cells.In the human sperm, its immunoreactivity was restrictively localized to the posterior head where sperm-egg fusion occurred, and the CMTM2 localization was not affected by sperm acrosome reaction.CMTM2 was widely expressed in seminiferous tubules of the human testis, mainly in the cell membranes of spermatogenic cells, which was consistent with the previous reports.The immunofluorescence performed on frozen human testis slides showed similar findings with immunohistochemistry, which gave weight to the localization of CMTM2 in the cell membranes of spermatogenic cells at different stages.TRITC-CMTM2 and FITC-Hoechst double immunofluorescence staining was performed to examine the subcellular localization of CMTM2 in the human sperm before and after acrosome reaction.CMTM2 was localized at the posterior head of sperm before and after acrosome reaction.The localization and expression of CMTM2 were not affected by sperm acrosome reaction.Conclusion: Expression of CMTM2 in the male reproductive system of the adult human exhibits cell-and region-specific patterns, which suggests that they may play an important role in spermatogenesis and sperm-egg fusion.The expression of CMTM2 in the male reproductive system of the adult human exhibits cell-and region-specific patterns, which suggests that they may play an important role in spermatogenesis and sperm-egg fusion.However, it still remains to be further elucidated about the definite role of CMTM2 in male reproductive system and the process of spermatogenesis.And in vitro fertilization experiments are needed to confirm the role of CMTM2 in fertilization in future.

OBJECTIVE: To investigate whether CKLF-like MARVEL transmembrane domain-containing protein 2 (CMTM2) is involved in spermatogenesis in mice. CMTM2 is highly expressed in testis, and could possibly be a potential spermagogenesis specific gene. METHODS: CMTM2-deficient mouse model was generated. Northern, RT-PCR and Western blotting analysis were performed on total RNA derived from wild-type (WT, CMTM2+/+) and CMTM2+/- (heterozygote) and CMTM2-/-(homozygote) mice to examine the CMTM2 level. The number of litters and the number of pups were counted and pregnancy rates calculated. The motility and morphology of the sperm and the histology of testes were analyzed. Serum testosterone and FSH concentrations were also measured. Standard t-tests were used and standard error of means were calculated. RESULTS: CMTM2 was highly expressed in a finely regulated pattern in the mouse testis during spermatogenesis. The body weight of adult mice with CMTM2 deficiency was not significantly different from that of wild type mice. No obvious anatomical or behavioral abnormalities were observed. The testis of CMTM2-/- was smaller than that of CMTM2+/+ mice. The testis diameter in wild mice and CMTM2 null mice were (11.32±1.21) mm vs. (8.29±1.92) mm (P<0.05), and the weights were (101.63±2.33) mg vs. (85.22±2.84) mg (P<0.05), respectively. Female CMTM2 null mice were fertile, indicating that CMTM2 was not required for female gametogenesis. The CMTM2-/- mice produced virtually no sperm, and CMTM2+/- mice sperm count showed a significant decline. In terms of sperm morphorlogy study, more round spermatids could be observed in the heterozygote group, compared with the wild type group; while in the homozygote group, a large amount of round spermatids could be observed because of complete arrest of spermiogenesis. The hormone levels were not significantly different. The CMTM2-/- male mice were sterile due to a late, complete arrest of spermiogenesis. The organized architecture of the seminiferous epithelium of the seminiferous tubules seen in CMTM2+/+ mice was lost in CMTM2-/- mice. CONCLUSION This study suggests CMTM2 is not required for embryonic development in the mouse but is essential for spermiogenesis, however, further studies are required for more detailed mechanism study.
Animals ; Chemokines/metabolism* ; Female ; Heterozygote ; MARVEL Domain-Containing Proteins/metabolism* ; Male ; Mice ; Mice, Knockout ; Pregnancy ; Spermatogenesis ; Spermatozoa ; Testis