Sharpening Boundaries

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Science  06 Feb 2009:
Vol. 323, Issue 5915, pp. 688
DOI: 10.1126/science.323.5915.688a

Gradients of morphogen concentration have been postulated to inform cells of their relative positions within a developing organism in order to adopt the appropriate fates, but do they offer enough information to support a robust formation of developmental patterns? Piddini and Vincent explored the development of the wing in Drosophila, which depends on a gradient of the morphogen Wingless (Wg). They progressively depleted Wg-expressing cells in the developing wing and found that the wings looked nearly normal and that expression of the distalless (dll) and vestigial (vg) genes (enhanced by low concentrations of Wg) persisted. In flies in which small patches of mutant cells that could not transduce Wg signals were interspersed with normal cells, the expression of dll and vg did require continuous signaling by Wg. Apparently, cells only needed the continued presence of Wg when surrounded by wild-type cells, indicating that cells receiving Wg signals were themselves producing a signal that inhibited Wg signaling in their neighbors—a process known as lateral inhibition, which can enhance contrast at the edges of regions of cells immersed in a signal gradient. The inhibitory effect required the presence of Notum (also called Wingful), an inhibitor of Wg signaling that is known to be produced in cells near the source of Wg production. — LBR

Cell 136, 296 (2009).

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