Fig. 1

GMTMy overexpression directly reprograms cardiac fibroblasts into iCMPs. a Schematic outline of the protocol used to convert cardiac fibroblasts (CFs) toward CM lineage. b Immunofluorescent staining for CM marker cTnT (magenta) in combination with eGFP (cyan) 14 days after lentiviral GMTMy delivery reveals the coinduction of two subpopulations: (1) clusters of immature, proliferating cTnT-positive cells (left panel, white arrows point to mitotic nuclei); and (2) isolated, more mature, nonproliferative cTnT-positive cells (right panel). DAPI (yellow) marks cell nuclei. Scale bars, 100 µm. Single channel images are provided in Additional file 1: Fig. S3c. c Analysis of cTnT protein expression by flow cytometry on day 14 in selected experiments (in total n > 15 biologically independent experiments). Shown are contour plots (contour level 5%). d Quantification of cTnT expression. Stacked bar graph presents the proportion of cTnT- and eGFP-positive cells in (C) as mean ± SD (n = 2). e CPC marker expression in GMTMy-transduced cells on day 14 as determined by immunocytology and subsequent image-based quantification. Scatter plot with bar graph shows replicates and mean ± SD (n = 2–5). f Immunofluorescent staining for CPC markers (magenta) NKX2-5, MESP1, KDR, and CXCR4 in combination with eGFP (cyan) on day 14 indicates that GMTMy induces a cardiac progenitor signatures. DAPI (yellow) marks cell nuclei. Scale bars, 50 µm Figure 2