The diagram depicts the interplay between calcium and RGS2 during egg development and fertilization. RGS2 suppresses calcium signaling long enough for the sperm to travel and fuse with the egg.
“These findings show the critical role that the protein RGS2 plays in preserving the fertilizability of the ovulated egg,” said Carmen Williams, M.D., Ph.D., lead researcher at the National Institute of Environmental Health Sciences, part of the NIH. “Other researchers have shown that RGS2 plays an important role in regulating heart function and blood pressure, but this is the first demonstration of the protein’s significant role in fertilization.”
Dr. Williams explained that the immature egg found in the ovary is not very good at rallying the necessary calcium signaling that is needed to respond to sperm. However, during the maturation process, the egg stores calcium, preparing it for fertilization. At fertilization, the sperm causes calcium to release within the egg, turning it into a developing embryo.
The mouse study, published online in the journal Development, shows that during maturation the egg synthesizes RGS2, which suppresses calcium signaling. This safety mechanism ensures that the egg does not begin releasing calcium and start developing before the sperm arrives. Beginning development too early prevents the egg from merging with the sperm.
The RGS2 protein is being looked at as a therapeutic target for hypertension and other heart ailments. “Understanding the role RGS2 plays in reproduction is important when considering the possible benefits and side effects of any new treatments, as well as understanding the impact that toxins might have on human fertility,” said Linda Birnbaum, Ph.D., director of NIEHS and the National Toxicology Program.
NIEHS collaborated with the University of Connecticut Health Center, Farmington; University of Western Ontario, London, Ontario; and the University of South Florida, Tampa, to conduct this research.
Grant Number: Z01ES102985
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Bernhardt ML, Lowther KM, Padilla-Banks E, McDonough CE, Lee KN, Evsikov AV, Uliasz TF, Chidiac P, Williams CJ, Mehlmann LM. Regulator of G-protein signaling 2 (RGS2) suppresses premature calcium release in mouse eggs. Development; doi: 10.1242/dev.121707 [Online 9 July 2015].