Homeobox protein Nkx-2.1 (NKX2-1),also named Thyroid nuclear factor 1,Thyroid transcription factor 1(TTF1). It is a transcription factor that binds and activates the promoter of thyroid specific genes such as thyroglobulin, thyroperoxidase,and thyrotropin receptor. Crucial in the maintenance of the thyroid differentiation phenotype. May play a role in lung development and surfactant homeostasis. Defects in NKX2-1 are the cause of benign hereditary chorea (BHC),choreoathetosis,hypothyroidism,and neonatal respiratory distress (CHNRD).