The genetic specification of pattern in a Drosophila muscle.

During development of Drosophila the bithorax complex of genes is responsible for diversification of segments in the ectoderm. The muscles derive from the mesoderm and their pattern also varies from segment to segment--a variation that could be determined directly through deployment of the bithorax complex in the muscle cells themselves. Alternatively, the muscle pattern could be determined indirectly, either by the epidermal cells to which the muscles attach, or by the nerves which contact developing muscles. Using a segment-specific muscle found only in males and a new mutation in the bithorax complex, we show that the development of this muscle is independent of the sex and segmental identity of the epidermis. The development of the muscle therefore depends on the sex and state of the bithorax complex in the muscle nuclei themselves or in part of the central nervous system.