LETHAL OF SCUTE, A PRONEURAL GENE, PARTICIPATES IN THE SPECIFICATION OF MUSCLE PROGENITORS DURING DROSOPHILA EMBRYOGENESIS

The mechanisms that underlie the segregation of muscle founder cells i n the Drosophila embryo are undefined. We show that the proneural gene lethal of scute (l'sc) is expressed in clusters of cells in the somat ic mesoderm, from which individual muscle progenitors are singled out by progressive restriction of l'sc expression. Coexpression of l'sc an d S59 (a putative muscle identity gene) in a subset of muscle progenit ors shows that muscle founders are produced by division of muscle prog enitors. In neurogenic mutant embryos the restriction of l'sc expressi on fails and all cells in a cluster coexpress l'sc and S59. Loss-of-fu nction and overexpression phenotypes indicate a role for l'sc in the s egregation of muscle progenitors and the formation of the muscle patte rn.