These results demonstrate that eppin can modulate intracellular calcium concentrations and subsequently affect the calcium ionophore A23187-induced acrosome reaction.

No abstract

To investigate the expression pattern of rat Eppin (epididymal protease inhibitor; official symbol Spinlw1), we detected mRNA transcripts and subsequent protein translation of Eppin in several sorts of tissues by RT-PCR and western blotting. Then immunohistochemistry was performed for more detailed observation. The testicular transcription level was monitored by real-time PCR throughout postnatal development. We found that rat Eppin was specifically expressed in the testis and epididymis. The testicular transcription was slight in neonatal (1-day) and infantile stages (5-, 7- and 10-day). It increased sharply thereafter, with maximum expression level (about 38-fold compared with that of 1-day old rat) detected in prepubertal stage (15-day). Then a slightly declined but stable level (about 20-fold compared with that of 1-day old rat) was kept in pubertal-early adult (30-day) and adult (60-day) stages of postnatal maturation. In the adult rat, EPPIN protein was mainly localized in the elongated spermatids and epididymal epithelial cells. Sperm in the epididymal duct were all covered with EPPIN and its level kept constant during incubation under conditions used to achieve capacitation. Its stage-specific expression in the testis suggests that EPPIN may be important during spermatogenesis especially for the spermatid elongation. The abundant production of epididymal EPPIN indicated indirectly that it might play a role in the function of the epididymis.

These results suggest that different variants in the EPPIN gene may have different relationships with idiopathic male infertility and men carrying these variants have a decreased or increased risk of abnormal semen parameters associated with male infertility.

The human epididymal protease inhibitor (Eppin) gene is specifically expressed in testis and epididymis and is important in male reproduction. However, to date, there is no report on variants of this gene, particularly in relation to male fertility. To investigate the association between Eppin genetic variants and semen quality, variant genotyping and semen analysis was performed in 473 males with definite idiopathic infertility by polymerase chain reaction-restriction fragment length polymorphism and computer-assisted semen analysis. It was found that rs6124715 GG/CG genotypes were associated with a significantly higher curvilinear velocity (VCL) (P=0.029 and 0.021 respectively) and average path velocity (VAP) (P=0.043 and 0.016 respectively) compared with the CC genotype. The straight line velocity (VSL) between rs6124715 CG and CC genotype was also significantly different (P=0.019). Regarding variant rs11594, subjects with C allele (CC or AC) had significantly lower VCL (P=0.011 and 0.046 respectively), VSL (P=0.025 and 0.041 respectively) and VAP (P=0.026 and 0.030 respectively) in comparison with AA homozygote. The sperm number per ejaculate was also significantly different between rs2231829 TT and CC genotype (P=0.042). These findings indicate, for the first time, that the genetic variants in the Eppin gene may be associated with semen quality.