This spontaneous and progressive development of pulmonary fibrosis in conditional Nedd4-2−/− mice is strikingly different from most other mouse models of IPF, which are based on exogenous administration of toxic substances such as bleomycin that induce acute injury and repair resulting in a transient fibrotic response that does not recapitulate the evolution of IPF in patients11,38,39. The gene discussed is NEDD4L; the disease is pulmonary fibrosis.