Generation of multipotent induced cardiac progenitor cells from mouse fibroblasts and potency testing in ex vivo mouse embryos. Lalit Pratik A,Rodriguez Adriana M,Downs Karen M,Kamp Timothy J Nature protocols Here we describe a protocol to generate expandable and multipotent induced cardiac progenitor cells (iCPCs) from mouse adult fibroblasts using forced expression of Mesp1, Tbx5, Gata4, Nkx2.5 and Baf60c (MTGNB) along with activation of Wnt and JAK/STAT signaling. This method does not use iPS cell factors and thus differs from cell activation and signaling-directed (CASD) reprogramming to cardiac progenitors. Our method is specific to direct CPC reprogramming, whereas CASD reprogramming can generate various cell types depending on culture conditions and raises the possibility of transitioning through a pluripotent cell state. The protocol describes how to isolate and infect primary fibroblasts; induce reprogramming and observe iCPC colonies; expand and characterize reprogrammed iCPCs by immunostaining, flow cytometry and gene expression; differentiate iCPCs in vitro into cardiac-lineage cells; and test the embryonic potency of iCPCs via injection into the cardiac crescent of mouse embryos. A scientist experienced in molecular cell biology and embryology can reproduce this protocol in 12-16 weeks. iCPCs can be used for studying cardiac biology, drug discovery and regenerative medicine. 10.1038/nprot.2017.021