09-P053 Systematic analysis of adult muscle formation and function in Drosophila

The muscle system is a complex network of highly specialised syncytial cells, the myofibers. These form by fusion of undifferentiated migratory myoblasts and subsequent organisation of contractile myofibrils. Many aspects of this complex, multi-step process remain poorly understood. With the development of genome-wide transgenic RNAi libraries in Drosophila, it is now possible to conduct a systematic genetic dissection of any cell or tissue type at any stage of the lifespan. We applied this approach to muscles and used flight as a simple and sensitive assay to test for adult muscle function. The muscle-specific knockdown of about 300 genes results in viable but completely flightless animals, indicating an essential role of these genes in flight muscles. We classified these genes by examining flight muscle fiber and myofibril morphology in detail. These analyses revealed anatomical defects in almost 200 genes with flightless phenotype and we assigned each of these genes to a specific function in the formation or maintenance of muscle fiber, myofibril or sarcomere structure. Many of the identified genes had no functional annotation so far or have not been implicated in muscle biology. This illustrates the power of inducible RNAi for systematic dissection of organogenesis, in particular for such complex tissues as muscles.