Expression of Sperm-specific Cation Channel CatSper in Human Spermatozoa

PURPOSE: We aimed to elucidate the expression and intracellular localization of sperm-specific cation channel CatSper in human spermatozoa. Moreover, the relationship between the expression of CatSper mRNA and the motility of ejaculated human spermatozoa were investigated. MATERIALS AND METHODS: Using cDNAs extracted from the ejaculated sperm of patients (n=39), the expression of CatSper mRNA was observed by RT-PCR. Semi-quantitative analysis of the CatSper mRNA expression was performed by comparing with the expression of GAPDH mRNA. To elucidate the expression and intracellular localization of CatSper protein, double fluorescent immunocytochemistry for CatSper and beta-tubulin was performed. RESULTS: The CatSper mRNA was expressed in all of the sperm samples. Using semi-quantitative analysis for the amount of CatSper mRNA expression, no significant difference was found between the normozoospermia and asthenozoospermia groups (1.5+/-0.6 vs. 1.4+/-0.6, p=0.623). Polyclonal antiserum, generated against a recombinant protein of the N-terminal 160 amino acids of human CatSper, was used. In double fluorescent immunocytochemistry, CatSper protein was found to be expressed in the flagellum of the ejaculated human spermatozoa, and localized in the connecting piece, mid-piece and principal piece, with the exception of the end piece of the flagellum. Moreover, the proportion of CatSper-positive sperm was similar in both the normozoospermia and asthenozoospermia groups. CONCLUSIONS: To the best of our knowledge, this is the first time ejaculated human spermatozoa have been shown to express the mRNA and protein of CatSper. The results of our RT-PCR and immunocytochemistry suggest that CatSper may play a role in the motility of ejaculated human spermatozoa.ope