Penetrance of missense mutation of OR2AT4 and OR9G1/9 gene polymorphism increases risk factor in azoospermic patients

Abstract

Objectives: In human, olfactory receptor (ORs) gene polymorphism regulate testicular development and physiological functions during spermatogenesis. However, the etiopathology of OR gene in male infertility is still restricted that required further studies. Basic mechanism involves the identification of peripheral signals based on specific chemoreceptors site that are expressed on the surface of mature spermatozoa inside the female reproductive tract. These receptors belong to G-protein couple receptors (GPCR) of superfamily and the roles of ORs gene linked to sperm chemotaxis through chemokinesis. In the present study, we have studied the role of Olfactory receptor family 2 subfamilies AT member 4 (OR2AT4) and Olfactory receptor family 9 subfamily G member 1/9 (OR9G1/9) genes polymorphism in clinically diagnosed azoospermic patients. Materials and Methods: Systematically, GTG banded karyotypes were developed using short term lymphocyte cultures, fluorescence in situ hybridization using SRY probe and PCR based microdeletion of Y-chromosome was characterized using STS marker (SY255). Whole exome sequencing (WES) based analysis was performed in azoospermic patients to identify the involvement of de-novo mutation in OR2AT4 and OR9G1/OR9G9 genes mutation followed by bioinformatics tools used for the analysis to identify changes in respective amino acids. Results: OR2AT4 showing missense mutation after substitution of nucleotide (G→A) followed by lack of change in amino acid (Gln→Gln), but in OR9G1/G9 gene showing changes of substitution of nucleotide thymidine into adenine (T→A), whereas valine is replaced by glutamine (Val→ Glu), similarly thymidine is substituted by cysteine (T→C), after decode phenylalanine is replaced by leucine (Phe→Leu). Further, 3D protein helical structure was developed with the help of bioinformatics on the basis of amino acids coded protein and compare with mutated amino acid or truncated protein residues with the help of iTASSER server. Conclusion: Present study demonstrate the role of OR2AT4 and OR9G1/9 gene polymorphism elucidates the functional role of protamine in ectopic receptors followed by increasing “risk” of developing male infertility that leads the clinical condition defined as non-obstructive azoospermia.