Association Study Between Single Nucleotide Polymorphisms Of PARP-1 Gene With Spermatogenesis Impairment

Infertility is a polygenic disease. According to the data from WHO, there are about 10—15% of couples can not reproduce the offspring at their reproductive age. Of these infertile couples, about half are due to male infertility. In male infertile patients, spermatogenesis impairment is the most common type. Spermatogenesis is a complex process mainly including three stages, namely spermatogonia cells proliferation and differentiation, meiosis and sperm cells to differentiate into sperm,in which many genes are involved. Abnormality of each gene related to spermatogenesis may lead to spermatogenesis impairment. Hence, the inherited pathogenic factor of spermatogenesis impairment is very complex. In recent year, extensive studies have been carried out in order to find genetic defects of spermatogenesis impairment, and some genetics factors leading to spermatogenesis impairment have been identified, such as chromosome abnormalities, microdeletions of Y chromosome and some gene mutations. However, the majority genetic factors of spermatogenesis impairment remain to be clarified. At presently, many genes playing roles in spermatogenesis have been found and these genes are been taken for the important candidate for male infertility. It is important for exploring the genetic causes of male infertility to investigated the relationship between these candidate genes and spermatogenesisPoly(ADP-ribose) polymerases(PARP) gene family is closely associated with spermatogenesis. The gene family consists of 18 members. Among these members, PARP-1 is an important one and has been the most studied. It plays an important part in many cell activities. PARP-1 gene widely exists in testicular tissue. It is expressed highly in testicular germ cell and involved in DNA damage repair. PARP-1 is able to quickly combine with DNA cracked site caused by exogenous stimulation such as ionizing radiation, ultraviolet rays,strong oxidant and catalyze poly ADP-ribosylation. When poly ADP-ribose chain reach at a certain length, PARP-1 can recognize and repair DNA damage, which indicate that PARP-1 plays an important role in DNA damage repair and keeping genome integrity in spermatogenesis process. In addition, PARP-1 is also involved in chromatin remodeling, cell apoptosis and oxidative stress in spermatogenesis. It has been demonstrated the abnormal expression level of PARP-1 can affect spermatogenesis in mouse. These results suggested that PARP-1 gene is essential for spermatogenesis and its variation may lead to abnormal spermatogenesis. It is interesting for elucidating the role of PARP-1 in spermatogenesis impairment to investigate the association of variations of PARP-1 gene with spermatogenesis impairment.So far, there is death of the data about the effect of PARP-1 gene on human spermatogenesis and male infertility. To redress the deficiencies in this field, we investigated the allele and genotype frequency distribution of two single nucleotide polymorphism loci(rs1136410 and rs1805405) in PARP-1 gene using PCR(polymerase chain reaction), RFLP(restriction fragment length polymorphism) analysis and DNA sequencing in fertile men and patients with azoospermia or oligospermia in Chinese population to explore the possible the role of PARP-1 gene in spermatogenesis impairment and male infertility. The results of the study are following: 1.This study indicated that allele frequency and genotype frequency of rs1136410 locus of PARP-1 existed significant difference in oligospermia patients and controls. The frequencies of allele C(46.3% versus 36.4% P=0.003, OR=1.510, 95%CI=1.159-1.964) and genotype CC(22.6% versus 13.4%, P=0.014, OR=1.890, 95%CI=1.156-3.072) of rs1136410 in patients with oligospermia were significantly higher than those in controls. This indicates that allele C and genotype CC were associated with oligospermia. Genotype CC may increase the risk of oligosoermia. Whereas, genotype TT of SNP rs1136410 locus of PARP-1(30% vs. 40.7%, P=0.021, OR=0.625, 95%CI=0.425-0.918) significantly decreased in patients with oligospermia compared with controls, which is suggested that there is a negative correlation between genotype TT and oligospermia and Genotype TT may have some protective effect from oligospermia. These findings suggested that SNP rs1136410 in PARP1 gene may modify the susceptibility to male infertility with oligospermia. SNP rs1136410 locus is a T to C change, which is a missense mutation leading to the substitution of alanin for valine in the catalytic domain. Compared with allele T, allele C reduces the activity of PARP-1. The activity of PARP-1 in individuals with genotype TT is higher than that in individuals with genotype CC. So, the changed activity related to the polymorphism of SNP rs1136410 may affect the role of PARP-1 in the process of spermatogenesis. This may be a possible reason that the polymorphism of SNP rs1136410 affects the susceptibility to oligospermia. 2. There is no significant difference in frequencies of allele and genotype of SNP rs1805405 in PARP-1 between patients with spermatogenesis impairment, which indicated that this SNP is not associated with spermatogenesis impairment.In summary, this study indicates that the polymorphism of rs1136410 in PARP-1 was associated with male infertility with oligospermia, suggesting that PARP-1 gene may play a role in oligospermia in Chinese population.