Fate-Mapping of Yolk Sac-Derived Macrophages

To better understand the distinct functions of yolk-sac-derived tissue-resident macrophagesTissue resident macrophages (TRMsTissue-resident macrophages (TRMs)) and bone-marrow-derived macrophages in homeostasis and disease, it is important to trace the ontogeny of these cells. The majority of TRMsTissue-resident macrophages (TRMs) originate from erythro-myeloid progenitors (EMPs)Erythro-myeloid progenitors (EMPs). EMPs develop into pre-macrophages (pMacsPre-macrophage (pMacs)), which can be detected starting at embryonic developmental day (E)9.0, and which give rise to all TRMTissue-resident macrophage (TRM) during early developmentDevelopment. pMacsPre-macrophage (pMacs) start expressing the gene Cx3cr1, allowing us to genetically target the early yolk-sacYolk sac wave of pMacsPre-macrophage (pMacs) and their progeny. Here, we describe the protocol for the identification of yolk sac-derived TRMsTissue-resident macrophages (TRMs) utilizing in utero labelling of the inducible fate mapping Cx3cr1CreERT; Rosa26LSL-eYFP mouse model.