Reverse transcription polymerase chain reaction analysis of embryonic stem (ES) cell marker genes in transplanted 10T1/2 cell nuclei and mouse ES cell nuclei. 10T1/2 cell nuclei (a) or differentiated mouse ES cell nuclei (b) were injected into Xenopus oocyte germinal vesicles and incubated at 14°C for the times indicated. Expression of Sox2, Oct4 and Sall4 were analysed as pluripotency genes. Expression of β-globin was tested as a non-reprogrammed gene. GAPDH expression was examined as a reference gene.