Association of single nucleotide polymorphisms(SNPs) in Pygo2 coding gene with idiopathic oligospermia and azoospermia

Male infertility is often associated with a decreased sperm count. Pygo2 gene is expressed in the elongating spermatid when chromatin remodeling occurs, thus it is possible that impairment of Pygo2 function could lead to spermatogenic arrest, reduction of sperm count and subsequent infertility. The aim of this study was to detect mutations in Pygo2 that lead to idiopathic oligospermia and azoospermia in human. DNA was isolated from venous blood from 77 fertile and 195 idiopathic oligospermic or azoospermic men. PCR-sequencing analysis was performed for the 3 coding regions of Pygo2. Non-synonymous single nucleotide polymorphisms (SNPs) were detected and analyzed using SIFT, Polyphen-2 and Mutation Taster software to determine possible changes in protein structure that could affect phenotype. Of the 195 patients analyzed, sufficient gene sequencing was accomplished for 178 men (30 mild or moderate oligospermic, 57 severe oligospermic and 91 azoospermic men). Three previously reported non-synonymous SNPs were identified in azoospermic and severe oligospermic patients and not in mild and moderate oligozoopermic or normozoospermic men. SNP rs61758740 (M141I) causes the replacement of a hydrophobic amino acid with another hydrophobic amino acid, rs61758741 (K261E) causes the replacement of a basic amino acid with an acidic amino acid and rs141722381 (N261I) causes the replacement of a hydrophilic amino acid with another hydrophobic amino acid. The data predicted by three different software programs showed that SNP rs141722381 results in the damage of tertiary protein structure and thus could be involved in relevant diseases. The study demonstrates that SNPs in the coding region of Pygo2 gene may be one of the causative factors in idiopathic oligospermia and azoospermia, resulting in male infertility.