Grb2 promotes reinitiation of meiosis in Xenopus oocytes

The adaptor protein Grb2 plays a central role in cell proliferation and/or cell cycle progression. In this study, we investigate the role of Grb2 in s ignalling pathways involved in meiotic reinitiation. For that purpose, Xeno pus Grb2 cRNA and its mutated forms or human Grb2 protein was microinjected into immature Xenopus oocytes. Reinitiation of meiosis was seen in unstimu lated oocytes. Induction of the meiosis was time dependent and Ras dependen t, and the presence in Grb2 of SH2 and SH3 domains was required. Several ty rosine phosphorylated proteins were solely detected in oocytes responsive t o Grb2 injection. Our results are in favour of an unusual recruitment and i nitiation of the Grb2 transduction cascade independent of a receptor tyrosi ne kinase (RTK) stimulation. (C) 2001 Elsevier Science Inc. All rights rese rved.