I will describe a chemo-mechanical model for dorsal closure, a morphogenetic process during the embryonic development of Drosophila. The model accounts for the dynamic interaction among signaling proteins and how they direct mechanical deformation and movement. More specifically, I will discuss how the Par-family proteins aPKC and Bazooka induce the cyclic assembly and disassembly of a medial actomyosin network in the apical surface of the amnioserosa cells, and how this causes oscillation of the cells and subsequently constriction of their surface area, culminating in the closure of the entire tissue. This is joint work with Tony Harris' lab at the University of Toronto.