Nanog protein detection in PUC isolations. Nanog protein was found in the nuclei of PUC cells (n = 5) (A). Comparison to TO-PRO-3 nuclear counterstain (B) revealed positive staining in virtually every cell (see superimposed image in C), although faint labeling was detected in the cytoplasm of some cells (arrowheads). Superimposing primary antibody-omitted controls with the nuclear counterstain image revealed no protein detection (D). Nuclear labeling was detected, but reduced, in porcine fibroblasts (E). Superimposition of E with nuclear counterstain (F) with faint cytoplasmic labeling in some cells (G). Primary antibody-omitted control and nuclear counterstain revealed no labeling (H). Bar = 50 μM.