Cellular and Molecular Mechanisms of Myotube Guidance

项目总结

PROJECT SUMMARY The mechanisms that regulate skeletal muscle topography and perfectly align muscle morphology with the overall body plan remain poorly understood. During embryonic development, muscle precursors known as myotubes undergo a dramatic morphogenesis in which the myotube leading edges elongate, navigate to tendons, and then choose pre-determined sites for muscle attachment. Myotube guidance refers to the combined cellular processes of leading edge navigation and targeting decisions that connect muscles with the correct tendons. We have used myogenesis in the Drosophila embryo as an entry point to identify the cellular and molecular mechanisms of myotube guidance. Using forward genetic screens and genomics-based reverse genetics, we identified multiple navigational signals that direct myotube leading edge migration, and uncovered transcription factors that direct muscle morphogenesis. Our live imaging approaches revealed that myotubes actively choose the correct muscle attachment site through a putative contact-dependent mechanism with tendon cells. We hypothesize that the integrated actions of short-range navigational signals, morphogenetic gene regulatory networks, and contact-dependent cell recognition programs direct myotube guidance to ensure muscle topography perfectly complements the body plan. To achieve a comprehensive understanding of myotube guidance, we will investigate the interplay between navigation, cell recognition, and gene regulatory modules. We propose (1) to investigate how multiple navigational signals co-regulate the cytoskeleton to direct myotube leading edge migration, (2) to use functional genomics to understand how a morphogenetic gene regulatory network modulates responses to navigational signals and directs contact-dependent cell recognition, and (3) to uncover the heterophilic protein- protein interactions between myotubes and tendon cells that establish a myotendinuos code. We expect the foundational work proposed in this study will be a necessary first step toward understanding how navigational, cell recognition, and gene regulatory modules cooperate to direct myogenesis in more complex systems and human disease.