The behavior of various signaling components during NANOG fluctuations. a: Expression levels, as determined by rt-pcr, of NANOG, SOX2, OCT4, ESRRB and the FGFs active within mouse ESCs. Data show fold change differences in expression normalized to Gapdh transcript levels. Each expression value is the average of values obtained from three independent experiments. b: ERK activity in cell populations with various extent of NANOG expression. As a positive control, we also include pERK western blot data from mouse embryonic fibroblasts (MEF). c: Western analysis of dox-inducible Nanog ES cell line. Note reduction of pERK levels in response to increasing amounts of NANOG.