A feed-forward circuit linking wingless,Fat-Dachsous signaling,and the warts-hippo pathway to drosophila wing growth

During development,the drosophila wing primordium undergoes a dramatic increase in cell number and mass under the control of the long-range morphogens wingless (wg,a wnt) and decapentaplegic (dpp,a bmp). this process depends in part on the capacity of wing cells to recruit neighboring,non-wing cells into the wing primordium. wing cells are defined by activity of the selector gene vestigial (vg) and recruitment entails the production of a vg-dependent ''feed-forward signal'' that acts together with morphogen to induce vg expression in neighboring non-wing cells. here,we identify the protocadherins fat (ft) and dachsous (ds),the warts-hippo tumor suppressor pathway,and the transcriptional co-activator yorkie (yki,a yes associated protein,or yap) as components of the feed-forward signaling mechanism,and we show how this mechanism promotes wing growth in response to wg. we find that vg generates the feed-forward signal by creating a steep differential in ft-ds signaling between wing and non-wing cells. this differential down-regulates warts-hippo pathway activity in non-wing cells,leading to a burst of yki activity and the induction of vg in response to wg. we posit that wg propels wing growth at least in part by fueling a wave front of ft-ds signaling that propagates vg expression from one cell to the next. © 2010 zecca,struhl.