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. The gene discussed is NKX2-1; the disease is brain-lung-thyroid syndrome.