Andrés-Delgado L Ernst A Galardi-Castilla M Bazaga D Peralta M Münch J González-Rosa JM Marques I Tessadori F de la Pompa JL Vermot J Mercader N 2019 The epicardium, the outer mesothelial layer enclosing the myocardium, plays key roles in heart development and regeneration. During embryogenesis, the epicardium arises from the proepicardium (PE), a cell cluster that appears in the dorsal pericardium (DP) close to the venous pole of the heart. Little is known about how the PE emerges from the pericardial mesothelium. Using a zebrafish model and a combination of genetic tools, pharmacological agents and quantitative in vivo imaging, we reveal that a coordinated collective movement of DP cells drives PE formation. We found that Bmp signaling and the actomyosin cytoskeleton promote constriction of the DP, which enables PE cells to extrude apically. We provide evidence that cell extrusion, which has been described in the elimination of unfit cells from epithelia and the emergence of hematopoietic stem cells, is also a mechanism for PE cells to exit an organized mesothelium and fulfil their developmental fate to form a new tissue layer, the epicardium. application/pdf https://sonar.ch/global/documents/170305 eng info:eu-repo/semantics/altIdentifier/doi/10.1242/dev.174961 info:eu-repo/semantics/altIdentifier/pmid/31175121 info:eu-repo/semantics/openAccess Development (Cambridge, England). - 2019 Actomyosin Bmp Cell extrusion Heart development Proepicardium Zebrafish Actins Animals Animals, Genetically Modified Body Patterning Bone Morphogenetic Proteins Carrier Proteins Cell Movement Embryo, Nonmammalian Heart Myocardium Organogenesis Pericardium Signal Transduction Stem Cells Zebrafish Zebrafish Proteins Actin dynamics and the Bmp pathway drive apical extrusion of proepicardial cells. http://purl.org/coar/resource_type/c_6501