The supplementary figures and movies provide detailed experimental protocols and results supporting the main findings of the study. Key points include: 1. **Generation of Cardiomyocyte-Specific Reporter Mouse Line**: - Transgenic mice with an α-MHC-GFP transgene were used to generate adult tail-tip or cardiac fibroblasts, which were infected with retroviruses encoding candidate cardiac transcription factors. - Flow cytometry and imaging confirmed the specific expression of the transgene in cardiomyocytes. 2. **Generation of Retroviruses Encoding Individual Cardiac Transcription Factors**: - Mouse 10T1/2 fibroblasts were infected with retroviruses encoding various cardiac transcription factors, and protein expression was confirmed by Western blot analysis. 3. **Screening for Transcription Factors to Reprogram Adult TTFs**: - Flow cytometry plots and summary data showed the percentage of α-MHC-GFP+ cells after transduction with different combinations of cardiac transcription factors. 4. **Analysis of Cardiac Markers in Adult TTFs and CFs**: - Flow cytometry and immunofluorescence staining confirmed the induction of cardiac markers in adult TTFs and CFs transduced with cardiac transcription factors. 5. **Time Course of Cardiac Gene Activation**: - Flow cytometry plots and summary data showed the activation of cardiac genes over time in adult TTFs and CFs transduced with GHMT. 6. **Induction of Cardiomyocyte Markers in Adult TTFs and CFs**: - Immunofluorescence staining and sarcomere-like structures were observed in adult TTFs and CFs transduced with GHMT. 7. **Gene Expression Profiles in Adult CFs Transduced with GHMT**: - Microarray data and gene ontology analysis showed that GHMT transduced CFs expressed genes characteristic of adult cardiomyocytes. 8. **Analysis of Cardiac and Fibroblast Gene Expression in TTFs**: - Real-time PCR quantified the expression of cardiac and fibroblast markers in TTFs. 9. **Tracing of Membrane Potentials in Spontaneously Beating iCLMs**: - Membrane potential tracing showed the spontaneous beating of iCLMs reprogrammed from adult CFs and TTFs. 10. **Induction of iCLMs from CFs by Inducible Lentivirus Expression of GHMT**: - Lentiviral vectors expressing cardiac transcription factors were used to induce iCLMs in adult CFs. 11. **GHMT Induction of iCLMs is Cell-Autonomous**: - Immunostaining and quantification confirmed that the induction of iCLMs is cell-autonomous. 12. **Retrovirus Infected Non-Cardiomyocytes in the Ischemic Area of the Injured Heart**: - H&EThe supplementary figures and movies provide detailed experimental protocols and results supporting the main findings of the study. Key points include: 1. **Generation of Cardiomyocyte-Specific Reporter Mouse Line**: - Transgenic mice with an α-MHC-GFP transgene were used to generate adult tail-tip or cardiac fibroblasts, which were infected with retroviruses encoding candidate cardiac transcription factors. - Flow cytometry and imaging confirmed the specific expression of the transgene in cardiomyocytes. 2. **Generation of Retroviruses Encoding Individual Cardiac Transcription Factors**: - Mouse 10T1/2 fibroblasts were infected with retroviruses encoding various cardiac transcription factors, and protein expression was confirmed by Western blot analysis. 3. **Screening for Transcription Factors to Reprogram Adult TTFs**: - Flow cytometry plots and summary data showed the percentage of α-MHC-GFP+ cells after transduction with different combinations of cardiac transcription factors. 4. **Analysis of Cardiac Markers in Adult TTFs and CFs**: - Flow cytometry and immunofluorescence staining confirmed the induction of cardiac markers in adult TTFs and CFs transduced with cardiac transcription factors. 5. **Time Course of Cardiac Gene Activation**: - Flow cytometry plots and summary data showed the activation of cardiac genes over time in adult TTFs and CFs transduced with GHMT. 6. **Induction of Cardiomyocyte Markers in Adult TTFs and CFs**: - Immunofluorescence staining and sarcomere-like structures were observed in adult TTFs and CFs transduced with GHMT. 7. **Gene Expression Profiles in Adult CFs Transduced with GHMT**: - Microarray data and gene ontology analysis showed that GHMT transduced CFs expressed genes characteristic of adult cardiomyocytes. 8. **Analysis of Cardiac and Fibroblast Gene Expression in TTFs**: - Real-time PCR quantified the expression of cardiac and fibroblast markers in TTFs. 9. **Tracing of Membrane Potentials in Spontaneously Beating iCLMs**: - Membrane potential tracing showed the spontaneous beating of iCLMs reprogrammed from adult CFs and TTFs. 10. **Induction of iCLMs from CFs by Inducible Lentivirus Expression of GHMT**: - Lentiviral vectors expressing cardiac transcription factors were used to induce iCLMs in adult CFs. 11. **GHMT Induction of iCLMs is Cell-Autonomous**: - Immunostaining and quantification confirmed that the induction of iCLMs is cell-autonomous. 12. **Retrovirus Infected Non-Cardiomyocytes in the Ischemic Area of the Injured Heart**: - H&E