PLK1 and thanatophoric dysplasia: In hematoxylin and eosin (H&E) and Ki-67 staining, the relative intensities of H&E and Ki-67-positive cells in lung tissue expressing TD were higher than those expressing mock, WT, or FA, evidence of TD’s tumorigenic properties in the in vivo metastatic mouse model (Fig. 4c, d), suggesting that catalytically active PLK1 promotes metastasis and tumorigenicity in vivo and that non-functional mutants of PLK1 lose those tumorigenic properties.