Gain of function of Antp in developing flight muscle prevents determination of the fibriallar muscle fate

Muscle development and diversity require a large number of spatially and temporally regulated events controlled by transcription factors (TFs). Drosophila has long stood as a model organism to study myogenesis due to the highly conserved key TFs involved at all stages of muscle development, from specification to differentiation. While many studies focused on the diversification of Drosophila larval musculature, how distinct adult muscle types are generated is much less characterised. Here, we identify a novel essential regulator of Drosophila thoracic flight muscle development, the Hox TF Antennapedia (Antp). Correcting a long standing misconception that flight muscle development occurs without the input of Hox TFs, we show that Antp intervenes at several stages of adult flight muscle development, from the establishment of the progenitor pool in the embryo to myoblast differentiation in the early pupa. Furthermore, the precisely regulated clearance of Hox at the pupal stage in the developing indirect flight muscle fibers is required to allow for stretch-activated fibrillar muscle fate diversification that sets these flight muscles apart from all other adult tubular muscle types. For the role of Antp in developing IFM once normal Antp expression is lost, Act88F-Gal4 flies were crossed to either UAS-GFP or UAS-Antp. IFM were then dissected at 72h APF, RNA prepared and sequenced. Samples represent triplicate independent replicates of each condition (WT and Antp GOF)