Forces driven by morphogenesis modulate Twist Expression to determine Anterior Mid-gut Differentiation in \textit{ Drosophila} embryos

By combining magnetic tweezers to \textit{in vivo} laser ablation, we locally manipulate \textit{Drosophila} embryonic tissues with physiologically relevant forces. We demonstrate that high level of \textit{Twist} expression in the stomodeal primordium is mechanically induced in response to compression by the 60$\pm $20 nN force developed during germ-band extension (GBE). We find that this force triggers the junctional release and nuclear translocation of Armadillo involved in Twist mechanical induction in the stomodeum in a Src42A dependent way. Finally, stomodeal-specific RNAi-mediated silencing of Twist during compression impairs the differentiation of midgut cells, as revealed by strong defects in Dve expression and abnormal larval lethality. Thus, mechanical induction of Twist overexpression in stomodeal cells is necessary for subsequent midgut differentiation. \newline \newline In collaboration with Nicolas Desprat, Willy Supatto, and Philippe-Alexandre Pouille, MGDET, UMR168 CNRS, Institut Curie11 rue Pierre et Marie Curie, F-75005, Paris, France; and Emmanuel Beaurepaire, LOB, Ecole Polytechnique, CNRS and INSERM U 696, 91128 Palaiseau, France.