MYOMEDUSA

Most animal movements are powered by contractile muscle cells, whose organization varies across species and cell types. Striated muscles consist of periodic myofibrils built by sarcomeres, while smooth muscles lack this regular organization. The evolutionary origins of these contractile structures remain poorly understood. Cnidarian medusae use both smooth and striated muscles to power their movements, with their sarcomeres displaying ultrastructural similarities to those found in vertebrates and insects. Despite the crucial phylogenetic position of medusae for understanding muscle evolution, the molecular organization and development of medusa muscles remain unclear. We recently introduced the scyphozoan medusa Pelagia noctiluca as a model organism for studying muscle formation, and ultrastructure. Its unique life cycle and characteristics make it an ideal candidate for molecular, structural and developmental research of muscle evolution. In this proposal, we aim to leverage the advantages offered by the Pelagia system to achieve three objectives: Aim 1: Identify proteins expressed in smooth and striated muscles across cnidarians by comparing single-cell datasets and proteomic analyses. Aim 2: Explore the ultrastructural features of the medusa myofibrils with super-resolution imaging, electron microscopy, and cryo-electron tomography. Aim 3: Unravel the molecular mechanisms and interactions that govern myofibrillogenesis in medusae by conducting functional studies in Pelagia, Nematostella, and Drosophila. This comprehensive comparative work will significantly advance our understanding of muscle biology and enable us to uniquely probe the conservation and differences of the molecular mechanisms responsible for myofibril formation across animals.