pdf abstract:
Wingless Promotes Proliferative Growth in a Gradient-Independent Manner
Luis Alberto Baena-Lopez1*, Xavier Franch-Marro2,3*, and Jean-Paul Vincent1{dagger}
1 Department of Developmental Neurobiology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
2 Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, Parc Científic de Barcelona, 08028 Barcelona, Spain.
3 Institut de Recerca Biomèdica, Parc Científic de Barcelona, 08028 Barcelona, Spain.
* These authors contributed equally to this work.
Abstract: Morphogens form concentration gradients that organize patterns of cells and control growth. It has been suggested that, rather than the intensity of morphogen signaling, it is its gradation that is the relevant modulator of cell proliferation. According to this view, the ability of morphogens to regulate growth during development depends on their graded distributions. Here, we describe an experimental test of this model for Wingless, one of the key organizers of wing development in Drosophila. Maximal Wingless signaling suppresses cellular proliferation. In contrast, we found that moderate and uniform amounts of exogenous Wingless, even in the absence of endogenous Wingless, stimulated proliferative growth. Beyond a few cell diameters from the source, Wingless was relatively constant in abundance and thus provided a homogeneous growth-promoting signal. Although morphogen signaling may act in combination with as yet uncharacterized graded growth-promoting pathways, we suggest that the graded nature of morphogen signaling is not required for proliferation, at least in the developing Drosophila wing, during the main period of growth.
