Egg activation at fertilization: where it all begins

Dev Biol. 2002 May 15;245(2):237-54. doi: 10.1006/dbio.2002.0600.


A centrally important factor in initiating egg activation at fertilization is a rise in free Ca(2+) in the egg cytosol. In echinoderm, ascidian, and vertebrate eggs, the Ca(2+) rise occurs as a result of inositol trisphosphate-mediated release of Ca(2+) from the endoplasmic reticulum. The release of Ca(2+) at fertilization in echinoderm and ascidian eggs requires SH2 domain-mediated activation of a Src family kinase (SFK) and phospholipase C (PLC)gamma. Though some evidence indicates that a SFK and PLC may also function at fertilization in vertebrate eggs, SH2 domain-mediated activation of PLC gamma appears not to be required. Much work has focused on identifying factors from sperm that initiate egg activation at fertilization, either as a result of sperm-egg contact or sperm-egg fusion. Current evidence from studies of ascidian and mammalian fertilization favors a fusion-mediated mechanism; this is supported by experiments indicating that injection of sperm extracts into eggs causes Ca(2+) release by the same pathway as fertilization.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Calcium Signaling*
  • Echinodermata / embryology
  • Echinodermata / metabolism
  • Fertilization*
  • Protein-Tyrosine Kinases / metabolism
  • Sperm-Ovum Interactions
  • Type C Phospholipases / metabolism
  • Urochordata / embryology
  • Urochordata / metabolism
  • Zygote / cytology*
  • Zygote / metabolism*


  • Protein-Tyrosine Kinases
  • Type C Phospholipases