Since the characterization of the transitional AEC state by scRNA-Seq studies in mice and human IPF, keratins have been used as marker genes, since they are highly upregulated in the transitional state (51, 54, 58, 62) (although we found that Krt8 was also expressed in mature AEC2s and AEC1s; Figure 6C and Supplemental Figure 1C). Here, KRT8 is linked to idiopathic pulmonary fibrosis.