Activation of development in mammals. Is there a role for a sperm cytosolic factor?

In mammalian oocytes, fertilization-associated calcium [Ca2+](i) oscillations are responsible for the activation of development. The mechanism(s) by which the sperm triggers the initial [Ca2+](i) rise and supports long-lasting oscillations is not resolved. It has been proposed that the sperm may interact with receptors in the oocyte's plasma membrane and engage intracellular signaling pathways that result in Ca2+ release. A different line of investigation suggests that upon sperm-oocyte fusion, a sperm cytosolic factor is released into the oocyte which interacts with unknown cytosolic targets, and generates [Ca2+](i) oscillations. We will discuss the most recent evidence for both lines of thought and demonstrate that injections of sperm crude extracts (SF) into mammalian oocytes trigger [Ca2+](i) oscillations that support in vitro parthenogenetic development to the blastocyst stage. (C) 1998 by Elsevier Science Inc.