Spatially and temporally regulated expression of myosin heavy chain alternative exons during Drosophila embryogenesis

We used alternative exon-specific probes to determine the accumulation of t ranscripts encoding myosin heavy chain (MHC) isoforms in Drosophila melanog aster embryos. Six isoforms accumulate in body wall muscles. Transverse (ex ternal) muscles express a different major form than intermediate and intern al muscles, suggesting different physiological properties. Cardioblasts exp ress one of the somatic muscle transcripts: visceral muscles express at lea st two transcript types. The pharyngeal muscle accumulates a unique Mhc tra nscript, suggesting unique contractile abilities. Mhc transcription begins in stage 12 in visceral and somatic muscles, but as late as stage 15 in car dioblasts. This is the first study of myosin isoform localization during in sect embryogenesis, and forms the basis for transgenic and biochemical expe riments designed to determine how MHC domains regulate muscle physiology. ( C) 2001 Elsevier Science Ireland Ltd. All rights reserved.