Results . KLF4 forms nuclear condensates at modest expression levels . We used expression tags to monitor the distribution of KLF4 by fluorescence microscopy in HEK 293T cells or BJ fibroblasts, the somatic cells most widely used for reprogramming 28 . KLF4 fused to mTurquoise2 (KLF4-mTurq) localizes to the nucleus and forms small puncta or round droplets, whereas mTurquoise2 alone is diffusely distributed throughout the nucleus and the cytoplasm (Fig.? 1a ). Transfection produces cel...