WINGLESS SIGNALING INDUCES NAUTILUS EXPRESSION IN THE VENTRAL MESODERM OF THE DROSOPHILA EMBRYO

The segregation of founder cells from the somatic mesoderm is a prereq uisite for the formation of body wall muscles in the Drosophila embryo . The myogenic basic helix-loop-helix protein, Nautilus (Nau), is expr essed in a subset of these founder cells in medial and lateral positio ns in the somatic mesoderm. Mutations in the wingless (wg) gene, which encodes a secreted growth factor, lead to the complete loss of Nau-ex pressing medial muscle precursor cell clusters, but not lateral cluste rs. Using the GAL4/UAS system, we demonstrate that the wg-derived sign al can originate from either ectoderm or mesoderm to influence nan exp ression. By using a temperature-sensitive wg allele, we also show that wg function is required during and after gastrulation for the formati on of Nau-expressing medial muscle precursor cell clusters. Our result s, combined with recent studies from chick, suggest a conserved role f or Wg signaling pathways during muscle development. (C) 1996 Academic Press, Inc.