The EGF receptor and notch signaling pathways control the initiation of the morphogenetic furrow during Drosophila eye development

The onset of pattern formation in the developing Drosophila retina begins w ith the initiation of the morphogenetic furrow, the leading edge of a wave of retinal development that transforms a uniform epithelium, the eye imagin al disc into a near crystalline array of ommatidial elements. The initiatio n of this wave of morphogenesis is under the control of the secreted morpho gens Hedgehog (Hh), Decapentaplegic (Dpp) and Wingless (Wg). We show that t he Epidermal Growth Factor Receptor and Notch signaling cascades are crucia l components that are also required to initiate retinal development. We als o show that the initiation of the morphogenetic furrow is the sum of two ge netically separable processes: (1) the 'birth' of pattern formation at the posterior margin of the eye imaginal disc; and (2) the subsequent 'reincarn ation' of retinal development across the epithelium.