Germband shortening in Drosophila is mediated by cell-matrix interactions. F. Schöck , E. Noll , N. Perrimon. Department of Genetics, Harvard Medical School, Boston, MA.

   Large-scale movements of epithelial sheets are the hallmark of most embryonic and regenerative morphogenetic events. Here, we have used the process of germband shortening (GBS) of the Drosophila embryo as a model system to study epithelial sheet movements. During GBS, the caudal end of the embryo retracts to its final posterior position. Time-lapse recordings reveal that cells within the germband and the extra-embryonic amnioserosa move as a coherent sheet and are tightly linked to each other. Disruption of the amnioserosa cytoskeleton is shown to cause GBS failure. In addition, mutations in the laminin gene wing blister affect GBS, implicating cell-matrix adhesion in GBS. We find that the amnioserosa adheres to the underlying yolk sac during GBS. This adhesion can be perturbed by overexpression of activated Src64 in the amnioserosa resulting in GBS failure. Our data indicate that the amnioserosa is a major mechanical force driving GBS, both through cell-cell and cell-matrix interactions.