Homeostatic response to blocking cell division in Drosophila imaginal discs: Role of the Fat/Dachsous (Ft/Ds) pathway

- Blocking growth in large domains of Drosophila imaginal discs triggers a response mechanism.
- Cells are recruited from adjoining regions and incorporated into the growth-arrested domain.
- Triggering of this mechanism is provoked by alterations in the expression of planar polarity genes.

One major problem in developmental biology is the identification of the mechanisms that control the final size of tissues and organs. We are addressing this issue in the imaginal discs of Drosophila by analysing the response to blocking cell division in large domains in the wing and leg discs. The affected domains may be zones of restricted lineage like compartments, or zones of open lineage that may integrate cells from the surrounding territory. Our results reveal the existence of a powerful homeostatic mechanism that can compensate for gross differences in growth rates and builds structures of normal size. This mechanism functions at the level of whole discs, inducing additional cell proliferation to generate the cells that populate the cell division-arrested territory and generating an active recruitment process to integrate those cells. The activation of this response mechanism is mediated by alterations in the normal activity of PCP genes of the Fat/Ds system: in discs mutant for dachs, ds or four jointed the response mechanism is not activated.