MyoblastSCS

Skeletal muscles display remarkable morphological diversity, but the developmental mechanisms specifying distinct muscle morphology remain poorly understood. Using Drosophila leg muscles as a model, myoblast identities were inferred at several development stages using both Seurat v.4.1.1 and Scanpy v.1.9.1. Initially, multipotent mesodermal precursors become spatially and transcriptionally restricted into two broad lineages - proximal and distal - under the combined influence of Wg/Wnt1 and Dpp/BMP signals from the overlying epithelium. By tracing mesodermal precursors that eventually give rise to distal leg muscles, we reveal a second sequence of fate bifurcations that generate distinct muscle subtypes prior to myoblast fusion, as well as a separate lineage producing neuronal lamella cells. Focusing on a single muscle lineage, the single-cell analysis suggested that Wg and Dpp act again during a second phase to control the spatial and temporal deployment of specific transcription factors, ultimately specifying a unique muscle identity. RNAi experiments and spatial imaging was used to confirmed this hypothesis.