Ovo/svb integrates Wingless and DER pathways to control epidermis differentiation

In Drosophila, as in mammals, epidermal differentiation is controlled by si gnalling cascades' that include Wnt proteins(2,3) and the ovo/shavenbaby (s vb) family of zinc-finger transcription factor(4-6) Ovo/svb is a complex ge ne with two genetic functions corresponding to separate control regions: ov o is required for female germline development and svb for epidermal morphog enesis(7,8). In the Drosophila embryo, the ventral epidermis consists of th e segmental alternance of two major cell types that produce either naked cu ticle or cytoplasmic extrusions known as denticles. Wingless signalling spe cifies smooth cells that produce naked cuticle(9), whereas the activation o f the Drosophila epidermal growth factor (EGF) receptor (DER) leads to the production of denticles(10). Here we show that expression of the ovo/svb ge ne controls the choice between these cell fates. We find that svb is a key selector gene that, cell autonomously, directs cytoskeletal modifications p roducing the denticle. The DER pathway promotes denticle formation by activ ating svb expression. Conversely, Wingless promotes the smooth cell fate th rough the transcriptional repression of svb by the bipartite nuclear factor Armadillo/dTcf. Ou data indicate that transcriptional regulation of svb in tegrates inputs fi om the Wingless and DER pathways and controls epidermal differentiation.