Male infertility could be due to abnormal sperm shape, blockages that prevent sperm delivery due to illnesses and injuries, chronic health problems, lifestyle choices and others coupled with genetic factors play a major role in most of these causes.
Scientists at the Centre for Cellular and Molecular Biology (CCMB) led by K. Thangaraj, who have been studying genetic causes for male infertility for the last two decades, said the ‘Y’ chromosome consisting of several genes are responsible for the production of sperms, i.e. spermatogenesis, and deletion of these causes severe diseases of testes and spermatogenic defects leading to male infertility.
“We had earlier identified that the large deletion of ‘Y’ chromosome was responsible for male infertility in 8.5% of the cases. Now, we have studied micro to macro deletions of ‘Y’ chromosome and the molecular mechanisms behind the deletion events,” said Dr. Thangaraj, chief scientist and senior author of the study published in Scientific Reports on April 18 this year.
Approximately, one out of every seven couples is infertile worldwide, of which the male factors account for about 50% of the cases. The AZoospermia Factor (AZF) regions consist of three genetic domains in the long arm of the human ‘Y’ chromosome referred to as AZFa, AZFb and AZFc, and they are home to genes required for spermatogenesis.
“We screened 973 infertile men along with 587 fertile men with normal sperm count and the motility for AZF regions deletions using several AZF-specific DNA markers and detected a total of 29.4% of infertile Indian men carrying deletions,” said Deepa Selvi Rani, the lead author of the study.
She further said, “We observed a few unique combinations of deletion events exclusively in Indian infertile men”. The present study highlights that genetic isolation and endogamy, which is widespread in Indian population, can play a major role in introducing novel causal variations. Hence, the authors undertook the study and found various deletion events of AFZ regions on the ‘Y’ chromosome in diverse Indian population and their association with male infertility.
“Since Indian population is genetically unique, the novel causal deletion events of AFZ regions are not surprising,” pointed out CCMB Director Rakesh Mishra, adding that the worldwide data without Indian data was incomplete and the findings have potential applications in the infertility clinic. Dr. Thangaraj said now that it is known that the sperm carrying ‘Y’ chromosome deletion often leads to failure in assisted reproduction, it could be worthwhile to check for the deletion to screen infertile men prior to adapting any assisted reproductive methods. The Institute of Reproductive Medicine, Kolkata; Institute and Research Centre, Hyderabad; Central Drug Research Institute, Lucknow, and Banaras Hindu University, Varanasi, also took part in the study.
