NKX6-1 is a homeodomain transcription factor that functions as a master regulator of pancreatic β cell identity and development. It binds to A/T-rich DNA sequences in promoter regions to control gene expression through RNA polymerase II 1. NKX6-1 is both necessary and sufficient for β cell specification; its expression in endocrine progenitors is sufficient to reprogram non-β cells toward the β cell lineage, while its loss causes β cells to adopt alternative endocrine fates 2. Mechanistically, NKX6-1 establishes β cell identity by repressing the alpha cell determinant Arx through direct binding, competing antagonistically with the Isl1 activator to determine alpha versus beta cell fate 2. During in vitro differentiation, PDX1+/NKX6.1+ pancreatic progenitors represent the critical precursor population that matures into functional, glucose-responsive insulin-secreting cells 345. In human pancreatic islets, NKX6-1 expression is exclusive to β cells and absent in other islet cell types, making it a definitive β cell marker 1. Clinical relevance extends to diabetes pathogenesis, as NKX6-1 dysregulation impairs β cell development and function. Additionally, NKX6-1 hypermethylation serves as a biomarker for predicting metachronous gastric lesions in cancer surveillance 6.