The Homeobox Transcription Factor CUX1 Coordinates Postnatal Epithelial Developmental Timing but Is Dispensable for Lung Organogenesis and Regeneration.

Lung epithelial progenitors use a complex network of known and predicted transcriptional regulators to influence early lung development. In this study, we evaluated the function of one predicted regulator, CUX1, that we identified from transcriptional regulatory analysis of the SOX9 distal lung progenitor network. We generated a new -floxed mouse model and created an epithelium-specific knockout of CUX1 using (Cux1). Postnatal Cux1 animals recapitulated key skin phenotypic features found in prior constitutive CUX1 knockout animals, confirming the functionality of our new floxed model. Postnatal Cux1 mice displayed subtle alveolar simplification and a transient delay in alveologenesis and alveolar type 1 cell development without persistent lung phenotypes. Cux1 mice developed failure to thrive in their second and third weeks of life because of delayed ileal maturation, which similarly resolves by Postnatal Day 35. Finally, we challenged Cux1 with influenza-mediated lung injury to demonstrate that Cux1 mice undergo productive alveolar regeneration that is indistinguishable from that in wild-type animals. Together, these findings indicate that epithelium-specific loss of CUX1 leads to transient developmental delays in the skin, lung, and intestine without defects in definitive organogenesis. We conclude that CUX1 function is required for temporal optimization of developmental maturation in multiple organs with implications for susceptibility windows in developmental disease pathogenesis.