MUSCLE DEVELOPMENT IS INDEPENDENT OF INNERVATION DURING DROSOPHILA EMBRYOGENESIS

We have examined the role of innervation in directing embryonic myogen esis, using a mutant (prospero), which delays the pioneering of periph eral motor nerves of the Drosophila embryo. In the absence of motor ne rves, myoblasts fuse normally to form syncytial myotubes, myotubes for m normal attachments to the epidermis, and a larval musculature compar able to the wild-type pattern is generated and maintained. Likewise, t he twist-expressing myoblasts that prefigure the adult musculature seg regate normally in the absence of motor nerves, migrate to their final embryonic positions and continue to express twist until the end of em bryonic development. In the absence of motor nerves, myotubes uncouple at the correct developmental stage to form single cells. Subsequently , uninnervated myotubes develop the mature electrical and contractile properties of larval muscles with a time course indistinguishable from normally innervated myotubes. We conclude that innervation plays no r ole in the patterning, morphogenesis, maintenance or physiological dev elopment of the somatic muscles in the Drosophila embryo.