HAND2 (heart and neural crest derivatives expressed 2) is a basic helix-loop-helix (bHLH) transcription factor essential for multiple developmental processes 1. The protein functions as a DNA-binding transcription factor that forms heterodimers with Twist1 and binds to E-box consensus sequences to regulate gene expression 1. HAND2 plays critical roles in cardiac morphogenesis, particularly right ventricle formation and aortic arch development, as well as limb development through regulation of sonic hedgehog signaling 1. The gene demonstrates significant dosage sensitivity, where overexpression causes developmental defects in limbs, craniofacial structures, and vertebrae, directly contributing to human congenital disorders like partial trisomy distal 4q 1. In neuroblastoma, HAND2 participates in core regulatory circuitries that define sympathetic noradrenergic cell identity alongside PHOX2B and GATA3 2. The protein also contributes to super-enhancer formation with MYCN and MEIS2, regulating neuroblastoma cell proliferation networks 3. In cardiac pathology, HAND2 overexpression as part of cardiac reprogramming (MGTH) improves heart failure with preserved ejection fraction by reducing fibrosis and improving diastolic function 4. Additionally, HAND2 expression can be disrupted by environmental toxins like bisphenol A, potentially contributing to developmental abnormalities 5.