You are here:
REGULATION OF SPERM NUCLEAR REACTIVATION DURING FERTILIZATION
Citation:
Darney, S. REGULATION OF SPERM NUCLEAR REACTIVATION DURING FERTILIZATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-89/142 (NTIS PB90113200).
Description:
Upon fusion of sperm and oocyte at fertilization, a series of events is initiated whereby the highly compacted sperm nucleus expands and is transformed into a male pronucleus capable of DNA synthesis. The regulation of these early post-fusion fertilization events has been studied using in vitro fertilization and sperm microinjection methods. We have learned that the first step in reactivation of the mammalian sperm nucleus is reduction of sperm protamine disulfide bonds by the oocyte. his step is modulated by glutathione, the levels of which increase during oocyte maturation and correlate with the relative sperm decondensing activity of oocytes at different developmental stages. Once sufficient protamine disulfide bonds have been released, the sperm chromatin becomes accessible to oocyte factors that induce its decondensation. his event is dependent upon the type of protamine present, a species specific characteristic. Next, protamine is removed and replaced by somatic histones, and a new nuclear envelope forms. These steps, while poorly understood, are essential prerequisites for pronuclear DNA synthesis. Taken together, these findings indicate that the oocyte plays a major role in the regulation of sperm nuclear remodelling and subsequent reactivation during fertilization.