TWIST - A MYOGENIC SWITCH IN DROSOPHILA

Somatic muscle is derived from a subset of embryonic mesoderm. In Dros ophila, Twist (Twi), a basic helix-loop-helix transcription factor, is a candidate regulator of mesodermal differentiation and myogenesis. A ltering amounts of Twist after gastrulation revealed that high levels of Twist are required for somatic myogenesis and block the formation o f other mesodermal derivatives. Expression of twist in the ectoderm dr ives these cells into myogenesis. Thus, after an initial role in gastr ulation, twist regulates mesodermal differentiation and propels a spec ific subset of mesodermal cells into somatic myogenesis. Vertebrate ho mologs of twist may also participate in the subdivision of mesoderm.