We report in this study that the longitudinal visceral muscle founder cells (LVMFs), a population of cells that migrate along the midgut primordium and visceral mesoderm, require the function of the Drosophila fibroblast growth factor receptor (FGFR) homolog, Heartless (Htl). Htl is expressed in LVMFs before and during their migration, and mitogen-activated protein K (MAPK) activity is present at the same stage. Embryos deficient for htl show an almost complete absence of longitudinal visceral fibers at late stages. In line with previous studies implicating FGFR signaling in morphogenetic movements, we conclude that the defect we observe in htl mutant embryos indicates a role of this signaling pathway in cell migration and/or differentiation of the LVMFs. Given that, in addition to hemocytes, LVMFs are the only cells of the Drosophila embryo that migrate over large distances, we propose that these cells represent a highly suitable system to dissect the role of signaling pathways in cell migration in Drosophila.
2004 Wiley-Liss, Inc.