Sperm extract injection into ascidian eggs signals Ca(2+) release by the same pathway as fertilization.
Injection of eggs of various species with an extract of sperm cytoplasm stimulates intracellular Ca(2+) release that is spatially and temporally like that occurring at fertilization, suggesting that Ca(2+) release at fertilization may be initiated by a soluble factor from the sperm. Here we investigate whether the signalling pathway that leads to Ca(2+) release in response to sperm extract injection requires the same signal transduction molecules as are required at fertilization. Eggs of the ascidian Ciona intestinalis were injected with the Src-homology 2 domains of phospholipase C gamma or of the Src family kinase Fyn (which act as specific dominant negative inhibitors of the activation of these enzymes), and the effects on Ca(2+) release at fertilization or in response to injection of a sperm extract were compared. Our findings indicate that both fertilization and sperm extract injection initiate Ca(2+) release by a pathway requiring phospholipase C gamma and a Src family kinase. These results support the hypothesis that, in ascidians, a soluble factor from the sperm cytoplasm initiates Ca(2+) release at fertilization, and indicate that the activating factor from the sperm may be a regulator, directly or indirectly, of a Src family kinase in the egg.
Runft
L L
LL
Department of Physiology, University of Connecticut Health Center, Farmington, CT 06032, USA.
Jaffe
L A
LA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002457:Cell Extracts; D002938:Ciona intestinalis / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology; D005260:Female; D005306:Fertilization; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D010063:Ovum / Q000378:metabolism*; D051966:Phospholipase C gamma; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051076:Proto-Oncogene Proteins c-fyn; D015398:Signal Transduction; D013094:Spermatozoa / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology; D018909:src Homology Domains
D002457:Cell Extracts; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D051076:Proto-Oncogene Proteins c-fyn; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium