Characterization of signaling pathways enabling coordinated morphogenesis of tissues during Drosophila dorsal closure

Drosophila dorsal closure (DC) is the best-characterized model system for studying wound healing. During DC, a hole in the dorsal epidermis, covered by an epithelium called the amnioserosa (AS), is sealed by migration of the epidermal flanks. Seamless closure is achieved through coordinated morphogenesis of the AS and epidermis, which is facilitated by communication between the two tissues via bidirectional signaling networks. To better understand this crosstalk, three diffusible signals present during DC were analyzed, and their signaling roles were identified: 1.) Folded gastrulation (Fog), which may act as an upstream activator of a JNK pathway in the epidermis; 2.) the TGF-β ligand, Decapentaplegic (Dpp), which regulates production of the steroid hormone, 20- hydroxyecdysone (ecdysone) in the AS; 3.) ecdysone, which interacts with the transcription factor AP-1 to regulate gene transcription in the AS. Signaling via these molecules ultimately regulates myosin contractility necessary for morphogenesis of both tissues during DC.