A minimal model predicts cell shapes and tissue mechanics in the amnioserosa during dorsal closure

Dorsal closure is a process that occurs late in embryogenesis of Drosophila melanogaster. During dorsal closure, a one-cell thick epithelial tissue, the amnioserosa (AS) which fills a dorsal opening, gradually shrinks while lateral epidermis sheets converge and eventually merge. AS cells shrink and eventually ingress out of the layer into the interior of the embryo. Throughout the process, the amnioserosa remains rigid, in the sense that cells do not exchange neighbors, although they undergo vigorous shape fluctuations.