NKX2-6 is a homeodomain-containing transcription factor that acts as a transcriptional activator 1 and plays critical roles in embryonic cardiovascular and pharyngeal development. In conjunction with NKX2-5, NKX2-6 is essential for proper pharyngeal endoderm differentiation, proliferation, and survival, with double mutants showing marked pharyngeal hypoplasia and enhanced apoptosis 2. NKX2-6 functions downstream of TBX1 in the cardiac developmental pathway 3. Loss-of-function mutations in NKX2-6 are associated with congenital heart disease (CHD), particularly conotruncal malformations and truncus arteriosus. Biallelic nonsense and frameshift variants disrupting the homeodomain cause truncus arteriosus 3, while heterozygous missense mutations reduce transcriptional activity and increase susceptibility to tetralogy of Fallot, double outlet right ventricle with ventricular septal defect 4, and familial atrial fibrillation 5. A homozygous deleterious NKX2-6 mutation causes conotruncal malformations with absent thymus 6. These findings confirm NKX2-6's essential role in human cardiogenesis and establish loss-of-function mutations as a rare but significant genetic etiology for CHD.