Valproic acid induces transcription of specific Hoxb genes in undifferentiated embryonic stem cells. Two mouse embryonic stem (ES) cell lines CCE/R (panel A, feeder-independent) and J1 (panel B, feeder-dependent and the parent line of the Eed/Ring1b double knockout (dKO) cells) were treated with valproic acid (VPA) (1 mM, 8 h) and harvested, along with untreated controls, for preparation of RNA and cDNA. Transcript levels from Hoxb1-9 were determined by real time-quantitative (RT-q)PCR. Error bars show the standard error of the mean of independent experiments (n = 3). Two-tailed unpaired t-tests were used to assess significance of changes; *P <0.05, **P <0.01.