FIGURE 1.

Schematic diagram of the development of heart cells in vivo. (A) Mutual regulation between epiblast and distal visceral endoderm (DVE) through Nodal, Cerberus, Lefty1, and DRP1 signals leads to a gradient distribution of the concentrations of Nodal and WNT, which results in the formation of primitive streak. During primitive streak migration, a small number of cells express mesoderm posterior protein 1 (MESP1), marking the beginning of heart development. MESP1⁺ cells finally differentiate into various cells that form the heart, such as endothelium, smooth muscle, and myocardium. (B) The migration of the primitive streak from posterior to anterior also marks the beginning of gastrulation, a crucial event in embryonic development. During this period, the embryo becomes a trilaminar embryonic disk, and the heart develops from the mesoderm.