Executive Summary : | Among different DNA damages, DNA double-strand breaks (DSBs) are considered as the most deleterious to a cell and thus an organism. It is speculated that the number of DSBs progressively increase in germ cells during biological aging. The major sources of DSBs include ROS generated during oxidative exposure, incomplete apoptotic process, defective DNA compaction, DNA replication, meiosis and defects in the DSB repair pathways during gametogenesis etc. Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are two main pathways for repairing DSBs. Recently, a backup NHEJ called microhomology mediated endjoining (MMEJ) has also been reported. Previous studies have helped in characterizing these DNA repair pathways in terms of proteins associated with it and by delineating the mechanism. Although there are multiple studies for understanding the repair process and mechanism in germ cells, impact of DSB repair during aging in germ cells is not well understood. Previous studies suggested that while NHEJ may operate throughout different stages of spermatogenesis, HR is mostly restricted to Zygotene and Pachytene stages of prophase I during gametogenesis. Although, some of these aspects are investigated during spermatogenesis in mammals, it is mostly unclear during oogenesis. Interesting questions to address will be whether DNA DSBs increases during aging, whether the efficacy of DSB repair is affected during aging, etc. If efficacy is affected, what are the factors contributing to that, whether the proteins responsible for DSBs repair is regulated during DSB repair, what is the role of P53, ATM, CTIP in the regulation of DSB repair during aging process in germ cells. Further, if NHEJ is mutated what will be the impact of DSB repair in the aging germ cells in males and females. Another important question would be, whether deregulated DSB repair during aging could contribute towards reduced fertility. In summary, the present proposal will help in addressing whether there is an accumulation of DNA breaks in male and female germ cells during aging and whether that contribute towards reduced fertility in older animals. Further, this will also help in dissecting out whether the reduced fertility is due to reduction in the expression of critical DSB repair genes or there are other factors that regulate transcription of DSB repair genes during aging. Besides, the contribution of mutations in some of the important DSB repair associated genes in germ cell development and fertility will also be unraveled. The information generated from the project could be extrapolated to human, when infertility related problems are considered, particularly if there are mutations in DSB repair genes in such patients with infertility. |