Drosophila morphogenesis: Tissue force laws and the modeling of dorsal closure

Dorsal closure, a stage of Drosophila development, is a model system for cell sheet morphogenesis and wound healing. During closure, two flanks of epidermal tissue progressively advance to reduce the area of the eye‐shaped opening in the dorsal surface, which contains amnioserosa tissue. To simulate the time evolution of the overall shape of the dorsal opening, we developed a mathematical model, in which contractility and elasticity are manifest in model force‐producing elements that satisfy force‐velocity relationships similar to muscle. The action of the elements is consistent with the force‐producing behavior of actin and myosin in cells. The parameters that characterize the simulated embryos were optimized by reference to experimental observations on wild‐type embryos and, to a lesser extent, on embryos whose amnioserosa was removed by laser surgery and on myospheroid mutant embryos. Simulations failed to reproduce the amnioserosa‐removal protocol in either the elastic or the contractile limit, indicating that both elastic and contractile dynamics are essential components of the biological force‐producing elements. We found it was necessary to actively upregulate forces to recapitulate both the double and single‐canthus nick protocols, which did not participate in the optimization of parameters, suggesting the existence of additional key feedback mechanisms.