Fertilization signalling and protein-tyrosine kinases

Fertilization is initiated by species-specific gamete cell recognition, i.e . sperm-egg interaction, followed by a rapid and sustained activation of mu ltiple cellular and biochemical events, collectively called 'egg activation ': which is indispensable for successful formation of zygotic nucleus and l ater embryogenesis. It is well known that sperm-induced egg activation is m ediated by a transient release of calcium ions that originates from the spe rm entry point and propagates through the entire egg cytoplasm. It is uncle ar, however, what kind of upstream events prelude to the calcium transient after sperm-egg interaction. Recently, much attention has been paid to the role of protein-tyrosine phosphorylation in egg activation process by a num ber of studies on some well-established model organisms. These includes mar ine invertebrates, frogs, and mammals. In this review, we will summarize th e recent findings that begin to uncover a 'missing link' between sperm-egg interaction and egg activation with emphasis on the role of egg protein-tyr osine kinases (PTKs) in Xenopus egg fertilization. (C) 2000 Published by El sevier Science Inc. All rights reserved.