NKX2-1 and interstitial lung disease: In mouse lungs, Nkx2.1 is essential for alveolar differentiation and maintenance and binds to promoters of alveolar type 1 (AT1)- and alveolar type 2 (AT2)-cell-specific genes.8 Heterozygous missense mutations in the NKX2.1 homeodomain cause brain-lung-thyroid syndrome, which includes disrupted surfactant gene expression and interstitial lung disease.9,10 However, whether NKX2.1 simply promotes surfactant synthesis,10 or has additional roles in human lung alveolar differentiation is unknown.