SMRT-RID mutation linked to Type I Pneumocyte Associated Respiratory Distress Syndrome via TR repression. Mus musculus

We show that knock-in mutations of the nuclear corepressor SMRT in C57Bl6 mice (SMRTmRID) produces a novel respiratory distress syndrome (RDS) due to prematurity of the type I pneumocyte. Treatment with the anti-thyroid hormone drug, propylthiouracil (PTU), completely rescues the SMRT-induced RDS, suggesting an unrecognized and essential role for the thyroid hormone receptor (TR) in lung development. We show that TR and SMRT control type I pneumocyte differentiation through Klf2, which in turn appears to directly activate the type I pneumocyte gene program. Conversely, mice without lung Klf2 lack mature type I pneumocytes and die shortly after birth, closely recapitulating the SMRTmRID phenotype. These results identify a second nuclear receptor, the TR, in type I pneumocyte differentiation and suggest a new type of therapeutic option in the treatment of glucocorticoid non-responsive RDS. Overall design: Total RNA was obtained from WT and SMRT-RID E18.5 lungs of embryos from mothers treated with Diet containing 0.15% PTU or control chow for 2 days (from E16.5).