Howard Hughes Medical Institute (HHMI) reports that an international team of scientists has captured pictures of sperm-oocyte fusion events on the molecular level and hence deciphered the microscopic mystery with serious reproductive health implications (i.e. improvement of fertilization techniques or new ways to provide birth control). The research was conducted by Luis Mayorga, an HHMI researcher, and colleagues at the National University of Cuyo School of Medicine in Mendoza, Argentina:
“If the sperm doesn’t respond right on time, it won’t get through the egg’s coating.” And since fertilization is one-way and all-or-nothing, so too is the fusion event that releases the sperm’s enzymes. This tight control enabled Mayorga’s laboratory to capture a molecular movie of fusion as it unfolded. Their findings are published in the September issue of the journal Public Library of Science Biology.
Inside the sperm, the enzymes are contained in a small bag known as the acrosome. During fertilization, as the acrosome membrane meets the sperm’s outer membrane, the two fuse together, and the enzymes are released outside the cell – much the same way a bubble rises to the surface of a soda and releases its gas into the air.
Mayorga, who has studied membrane fusion for more than 15 years, recognized an unexplored potential in this simple secretion event, called acrosomal exocytosis (AE). Preliminary experiments showed that AE uses the same basic fusion molecules as neuronal and endocrine cells. However, AE is much less complicated than fusion in these other cell types because it only happens once…