eLife Assessment: Primordial cardiomyocytes orchestrate myocardial morphogenesis and vascularization but are dispensable for regeneration

This important work identifies phlda2 as a specific marker for primordial cardiomyocytes in the adult zebrafish heart and demonstrates their essential role in myocardial morphogenesis and coronary vascularization, but not in heart regeneration.The conclusions are well supported by single-cell transcriptomics, new genetic tools, and cellspecific ablation experiments.The revised version strengthens these findings with analyses of the epicardium, long-term time points showing that the developmental defects persist, and a control confirming that loss of primordial cardiomyocytes alone does not trigger a regenerative response.Overall, the evidence is solid and provides insight into the difference between developmental and regenerative cardiac programs, and this work will be of interest for those studying cardiac development and regeneration.