MUTATIONS IN A NOVEL GENE, MYOBLAST CITY, PROVIDE EVIDENCE IN SUPPORTOF THE FOUNDER CELL HYPOTHESIS FOR DROSOPHILA MUSCLE DEVELOPMENT

We have used mutations in the newly identified gene myoblast city to i nvestigate the founder cell hypothesis of muscle development in Drosop hila melanogaster. In embryos mutant for myoblast city the fusion of m yoblasts into multinucleate muscles is virtually abolished. Neverthele ss, a subset of the myoblasts develop specific musclelike characterist ics, including gene expression appropriate to particular muscles, migr ation to the appropriate part of the segment, correct position and ori entation, and contact by motor neurons. We suggest that this subset of myoblasts represents the proposed muscle founder cells and we draw an analogy between these founder cells and the muscle pioneers described for grasshopper muscle development.