MESP1 is a basic helix-loop-helix transcription factor that functions as a key regulator of cardiovascular lineage commitment 1. As one of the earliest markers of nascent mesoderm, MESP1 drives cardiovascular system onset through cell-autonomous and cell non-autonomous mechanisms 2. During embryonic development, MESP1 marks the earliest population of cardiovascular progenitor cells and traces almost all heart cell derivatives from primary and secondary heart fields 1. Mechanistically, MESP1 interacts with RING1A, a core component of polycomb repressive complex 1, to activate cardiogenic genes through promoter-enhancer interactions regulated by cohesin and CTCF, alongside p300-mediated histone acetylation 3. MESP1 activation depends on canonical Wnt signaling strength, with MESP1 subsequently binding the WNT5A promoter to suppress this pathway during cardiomyocyte differentiation 4. Clinically, MESP1 mutations cause congenital heart diseases including ventricular septal defects 5, with mutations in this developmental transcription factor representing frequent findings in VSD patients 5. MESP1 shows therapeutic potential: MESP1+ cardiovascular progenitor cells effectively differentiate into cardiomyocytes, endothelial cells, and smooth muscle cells, and their engraftment repairs myocardial infarction in animal models 4. Additionally, forced coexpression of ETS2 and MESP1 reprograms human dermal fibroblasts into cardiac progenitors for regenerative applications 6. Notably, MESP1 exhibits aberrant expression in hepatocellular carcinoma associated with poor prognosis, suggesting broader roles beyond cardiac development 7.