TWIST AND NOTCH NEGATIVELY REGULATE ADULT MUSCLE DIFFERENTIATION IN DROSOPHILA

Twist is required in Drosophila embryogenesis for mesodermal specifica tion and cell-fate choice. We have examined the role of Twist and Notc h during adult indirect flight muscle development. Reduction in levels of Twist leads to abnormal myogenesis, Notch reduction causes a simil ar mutant phenotype and reduces Twist levels. Conversely, persistent e xpression, in myoblasts, of activated Notch causes continued twist exp ression and failure of differentiation as assayed by myosin expression . The gain-of-function phenotype of Notch is very similar to that seen upon persistent twist expression. These results point to a relationsh ip between Notch function and twist regulation during indirect flight muscle development and show that decline in Twist levels is a requirem ent for the differentiation of these muscles, unlike the somatic muscl es of the embryo.