Comparison of Protamine 1 to Protamine 2 mRNA Ratio and YBX2 gene mRNA Content in Testicular Tissue of Fertile and Azoospermic Men

Abstract

Background Although aberrant protamine (PRM) ratios have been observed in infertile men, the mechanisms that implicit the uncoupling of PRM1 and PRM2 expression remain unclear. To uncover these mechanisms, in this observational study we have compared the PRM1/PRM2 mRNA ratio and mRNA contents of two regulatory factors of these genes. Materials and Methods In this experimental study, sampling was performed by a multi-step method from 50 non-obstructive azoospermic and 12 normal men. After RNA extraction and cDNA synthesis, real-time quantitative polymerase chain reaction (RT- QPCR) was used to analyze the PRM1, PRM2, Y box binding protein 2 (YBX2) and JmjC-containing histone demethylase 2a (JHDM2A) genes in testicular biopsies of the studied samples. Results The PRM1/PRM2 mRNA ratio differed significantly among studied groups, namely 0.21 ± 0.13 in azoospermic samples and -0.8 ± 0.22 in fertile samples. The amount of PRM2 mRNA, significantly reduced in azoospermic patients. Azoospermic men exhibited significant under expression of YBX2 gene compared to controls (P < 0.001). mRNA content of this gene showed a positive correlation with PRM mRNA ratio (R=0.6, P=0.007). JHDM2A gene expression ratio did not show any significant difference between the studied groups (P=0.3). We also observed no correlation between JHDM2A mRNA content and the PRM mRNA ratio (R=0.2, P=0.3). Conclusion We found significant correlation between the aberrant PRM ratio (PRM2 under expression) and lower YBX2 mRNA content in testicular biopsies of azoospermic men compared to controls, which suggested that downregulation of the YBX2 gene might be involved in PRM2 under expression. These molecules could be useful biomarkers for predicting male infertility.

Keywords

• protamines
• azoospermia