CAG repeat variation in the mtDNA polymerase gamma is not associated with oligoasthenozoospermia

Variations in the trinucleotide-CAG repeat number of the catalytic subunit of the mitochondrial DNA polymerase gamma (POLG) have been speculated to be associated with male infertility. The ten CAG repeats (10/10) were found to be the most common allele (88%), absence of which was found to be associated with male infertility. As no study on Indian population was conducted so far to support this view, we investigated the distribution of the POLG-CAG repeats in 509 oligoasthenozoospermic and 241 normozoospermic control Indian men from the same ethnic background. Our study suggested that the distribution of common allele (10/10) was almost similar in both infertile (75%) and normozoospermic (75.5%) men. Further, we had analysed the CAG repeat number in as many as 1306 Indian men belonging to different ethnic, geographical and linguistic backgrounds and found the common allele 10/10 at a frequency of 78.4%. Our study, therefore, suggests that the 10-CAG repeat is the most common allele present in Indian populations, but its absence and the occurrence of the other mutant homozygous (non 10/non 10) genotype should not be understood as being specific to infertility. It, thus, suggests that the POLG-CAG repeat variation is not associated with male infertility in Indian populations, and hence is not a useful marker for screening infertile men.