Development of diagnosis and therapy for male infertility ; The infertility-related gene approach including seminal plasma motility inhibitor

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Our aim was to determine the effect of Sg on capacitation, which is the series of transformations that spermatozoa must undergo to become fertile. We induced capacitation by ultrafiltrates of fetal cord blood. It was observed that hyperactivation of the human spermatozoa was suppressed by the existence of Sg. But the dose dependence on the concentration of Sg could not be found because the analysis on the motility pattern of spermatozoa by CASA was very unstable. Using the acrosome reaction as an index, we revealed that Sg suppressed capacitation of the human spermatozoa in the dose dependent manner. By the measurement of chemiluminescence using Xantine oxidase, one mechanism of suppressed capacitation by Sg was interference with O_2 generation during this process. We also found that Sg was degraded by the incubation with the washed spermatozoa and the degradation products also inhibited capacitation of the human spermatozoa. These data suggest that Sg and/or its degradation products may be natural regulators of sperm capacitation.We investigated whether the mutation of the Sg I causes infertility. We have previously reported a deletion of 180 bp in the second exon of the Sg I in 5 infertile men and 8 fertile men, and we also found the smaller products of deleted Sg I(than normal one)in one of these fertile men. The mutation form protein is currently being purified and analyzed to determine the difference in the protein function. Though the SNP analysis of the Sg gene is carried out by the DNA two-dimensional electrophoretic method, presently, it has not been confirmed. It succeeded in the expression of the r-Sg protein with much high activity and high-purity. The antibody that produced this r-Sg as an antigen peculiarly reacted with native Sg and SPMI.