Variants in the Eppin gene show association with semen quality in Han-Chinese population

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.