Fig. 2.

Heart and limb develop from neighboring LPM populations with shared transcription factors. The heart and the forelimb progenitors emerge within the anterior LPM in close proximity to each other, as depicted in a schematic representing the vertebrate embryo (left). On the right, we depict heart and limb/fin development in the mammalian and zebrafish embryo; the developmental process in zebrafish is similar to that in mammals. The heart forms by medial progenitor migration and leftward jog, resulting in the primitive heart tube that then undergoes complex remodeling to form a multi-chambered heart (top). The limb buds for both forelimbs and hindlimbs emerge from dedicated territories within the LPM via a conserved cascade of signaling events; interaction with the apical ectodermal ridge through Fgf ligand secretion supports limb bud outgrowth followed by LPM-based formation of connective tissue and skeletal structures (bottom).