Dorso-ventral patterning of the embryonic epidermis. Francois Payre^1,2, Ahmad Alsawadi^1,2, Robin Vuilleumier³, Philippe Valenti^1,2, Jennifer Zanet^1,2, Giorgos Pyrowolakis³, Serge Plaza^1,2. 1) Developmental Biology, University of Toulouse, Toulouse, France; 2) CNRS, UMR5547, Toulouse, France; 3) Institute for Biology I, University of Freiburg, Freiburg, Germany.

   BMP signalling is broadly conserved across bilateral animals in setting up the Dorso-Ventral (DV) axis and patterning of the neuroectoderm. Although many works have deciphered the network of factors underpinning BMP signalling, how these DV cues influence programs of terminal differentiation remains not fully understood. The fly embryonic epidermis ultimately produces cuticle extensions called trichomes, which display various organization and morphologies along the body plan therefore providing an exquisite readout of terminal differentiation. Combining large-scale genetic and molecular screenings, we identified transcription factors and cis-regulatory elements that implement the DV patterning of epidermal trichomes in response to BMP (Dpp) signalling. We found that DV cues modify transcriptional outputs at different levels of the developmental program of trichome differentiation, from upstream regulatory factors to terminal effectors. These results further reveal an unexpected prevalence of seemingly redundant regulatory interactions, showing that both enhancers and transcription factors of similar activities are used during terminal differentiation to achieve a robust phenotype.