The Role of Protamine 2 Gene Expression and Caspase 9 Activity in Male Infertility

Approximately 15% of couples are affected by infertility with the man responsible in almost half of the cases. PRMs (protamines) confer a higher order of DNA packaging in sperm than that in somatic cells. Because of the critical roles of PRMs in spermatid differentiation, aberrations in PRM expression or changes in protein structure could be causes of certain types of idiopathic human male infertility. The aim of this study was to give insight into the role of PRM2 gene expression and caspase 9 activity in the pathogenesis of male infertility.

The current study included 70 men with idiopathic infertility and 64 fertile men who attended the andrology outpatient clinic at Mansoura University Hospital. Semen sample analyses were done according to WHO recommendations. The acrosome reaction of spermatozoa recovered from each sample was assessed. Samples were separated using discontinuous gradient separation. From each semen sample mature sperm were separated from immature sperm. The resulting samples were divided into 2 parts, including one to determine caspase 9 activity and the other for RNA extraction and reverse transcriptase-polymerase chain reaction of PRM2 gene expression. The polymerase chain reaction product was electrophoresed on 2% agarose gel.

PRM2 gene expression was significantly decreased in immature sperm extracted from the fertile and infertile groups. Caspase 9 activity was significantly increased in immature sperm extracted from both groups.

Low levels of PRM2 may be associated with morphological abnormalities, initiation of the apoptotic pathway and decreasing sperm motility. PRM2 may be an important marker to better understand the key regulatory pathway of spermatogenesis and it may act as a crucial part of fertilization.