A novel signalling mechanism for generating Ca2+ oscillations at fertilization in mammals.
At fertilization in mammals the sperm activates the egg by triggering a series of oscillations in the intracellular free Ca2+ concentration. The precise sequence of events that occur between sperm-egg contact and the increases in intracellular Ca2+ remains unknown. Here, we discuss recent evidence supporting the hypothesis that a cytosolic sperm protein enters the egg after gamete membrane fusion and triggers Ca2+ oscillations from within the egg cytoplasm. Biochemical studies suggest that there exists a novel sperm protein, named oscillin, that specifically comigrates with Ca2+ oscillation-inducing activity. Oscillin has been immunolocalised to the region of the sperm that first fuses with the egg. The concept of a specific protein that triggers Ca2+ oscillations may have wider physiological significance since sperm oscillin can induce Ca2+ oscillations in somatic cells, such as neurons and hepatocytes. Unravelling the novel signalling system involved in mammalian fertilization may help reveal some fundamental molecular mechanisms responsible for triggering cytoplasmic Ca2+ oscillations.
Swann
K
K
Department of Anatomy and Developmental Biology, University College, London. k.swann@ucl.ac.uk
Lai
F A
FA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D005260:Female; D005306:Fertilization / Q000502:physiology*; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D008322:Mammals; D008954:Models, Biological; D010063:Ovum / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction; D013094:Spermatozoa / Q000378:metabolism
D002135:Calcium-Binding Proteins; D011506:Proteins; C097705:oscillin; D002118:Calcium