Variants of the CLOCK gene affect the risk of idiopathic male infertility in the Han-Chinese population

Abstract

Recent experimental animal studies suggested that the circadian locomotor output cycles kaput protein gene (CLOCK) has been reported to play a critical role in sperm function and male fertility. The aim of this study was to determine whether variants of the CLOCK gene are involved in idiopathic male infertility. The study included 478 idiopathic infertile men and 194 fertile controls who completed physical examinations. Each subject donated 5 ml of peripheral blood and a sample of semen in the ejaculate. An aliquot of each blood sample was used to separate the serum for the measurement of testosterone as well as follicular stimulating hormone (FSH) using the standard radioimmunoassay. The rest of the blood samples was used to extract the DNA for the assay of three tagging single-nucleotide polymorphisms of CLOCK gene, viz., rs1801260, rs3817444 and rs3749474, using the real-time fluorescence quantitative PCR. The ejaculate of each subject was used for semen analysis by computer-assisted semen analysis system. The results indicated: (a) the variant rs1801260 associated with normal semen parameters was linked to a significant increase in the risk of idiopathic infertility, (b) the variant rs3817444 associated with both normal and abnormal semen parameters also indicated an increased risk of idiopathic infertility, and (c) the variants rs3749474 associated with both normal and abnormal semen parameters, on the other hand, conferred no significant risk for male infertility. Furthermore, elevated serum testosterone and FSH levels were correlated with the three variants of CLOCK gene in idiopathic infertility. The findings demonstrate that the human subjects with variants of the CLOCK gene are associated with idiopathic male infertility and therefore may be applied as a risk factor of male infertility.