Sci. Signal., 6 October 2009
No Gradient RequiredMorphogens are molecules that both specify cells to form tissues and stimulate the cells in the tissues to proliferate, allowing tissues to grow. The graded distribution of proteins called morphogens is required for the appropriate patterning of cells in developing tissues, with the different morphogen concentrations differentially affecting the expression of their target genes. Whether the contribution of morphogens to tissue growth depends on their graded distribution is unclear. In Drosophila, Wingless is one of the morphogens that is critical for pattern formation in the wing imaginal disc, an epithelial sac of cells that ultimately develops into the wing of the adult fly. Baena-Lopez et al. found that although intense Wingless signaling inhibited cellular proliferation, moderate Wingless signaling supported proliferation. Indeed, ectopic expression of a weakened variant of Wingless (WinglessS239A) promoted wing growth. In addition, when uniformly distributed throughout a Wingless-deficient imaginal disc at the third instar stage, WinglessS239A rescued the proliferative defect caused by the absence of endogenous Wingless. Together, these data suggest that, at least in the Drosophila wing imaginal disc, the graded distribution of Wingless is not required to stimulate cellular proliferation, at least during the main period of growth.
Citation: L. A. Baena-Lopez, X. Franch-Marro, J.-P. Vincent, Wingless Promotes Proliferative Growth in a Gradient-Independent Manner. Sci. Signal. 2, ra60 (2009).
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