POT1 and idiopathic pulmonary fibrosis: From analysis of 40 and 30 cells for control and IPF-derived fibroblasts, respectively, we found that although only 7.5% of control POT1(WT) fibroblasts had at least two TIFs, this percentage rose to 58% for POT1(L259S)-containing patient fibroblast cells (P < 0.0001; Fig. 8).