ABSTRACT Cellular syncytium to cells: Novel regulatory mechanisms observed in Drosophila embryos

Abstract

RESUME Abstracts / Resumes 641s / Resumes 641 © 2000 NRC Canada Cellular syncytium to cells: Novel regulatory mechanisms observed in Drosophila embryos S. D. Campbell, D. Price, S. Rabinovitch, and Z. Jin Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada The Drosophila embryo provides an ideal model system for investigating developmental controls of the cell cycle as it undergoes a temporal progression of four distinct kinds of cycle. We have been studying nuclear cleavage divisions 1–13, which occur in a common cellular syncytium. A regulatory transition then occurs in cycle 14, during which nuclei become cellularized prior to gastrulation. The syncytial divisions are regulated by maternal factors, including the gene products of grp, mei-41, and Dwee1. These genes all have fission yeast homologs that are known to participate in a signaling pathway which is activated in response to DNA damage or delays in DNA replication. This pathway activates a cell cycle checkpoint that delays mitosis by inhibitory phosphorylation of Cdk1. The mechanism by which these gene products act in the early Drosophila embryo is not understood, since Cdk1 inhibitory phosphorylation is not normally observed until cycle 14. Apparently the Drosophila embryo has adapted this regulatory pathway, which usually serves a genome surveillance function, to employ it in an essential developmental process. We are undertaking genetic and biochemical approaches to dissect this problem.