A, ESC and EB morphology of p38α+/+ESCs (α+), p38α−/−/siCON ESCs (α-/siCON), and p38α−/− siδ ESCs (α-/siδ). A representative of ESC colony (200x magnification) or a 10 day EB (100x magnification) formed from each genotype of ESCs were photographed under a phase contrast microscope. B, expression levels of ESC pluripotency markers, Oct4, Rex1 and Sox2, was determined by RT-PCR and analyzed by agarose gel electrophoresis. Actin was analyzed in parallel and was used as an internal control. The similar expression levels of ESC pluripotency markers among different ESCs were conformed by RT-qPCR (data not shown).