Abstract: Objective To compare the expression of OCT4 isoforms in human embryonic stem cells (hESCs) and human mesenchymal stem cells (hMSCs). Methods The characterizations of hESCs and hMSCs were confirmed by RT-PCR, immunofluorescence staining, flow cytometry and in vivo/vitro differentiation assays. The expressions of OCT4 isoforms and regulators that control their transcription (NANOG, SOX2) and translation (LIN28) were quantified by real-time PCR, flow cytometry and Western blot. Results Three OCT4 isoforms mRNA were expressed in both hESC and hMSC. However, their expressions were significantly higher in hESC than in hMSC, especially for OCT4A (p<0.01). At protein level, OCT4A and OCT4B-265aa were translated in hESC while no OCT4 protein could be detected in hMSC. NANOG, SOX2 and LIN28 were highly translated in hESCs while hMSCs were weak positive for SOX2 expression but negative for NANOG and LIN28. Conclusion NANOG, SOX2 and LIN28 regulate the expression of OCT4. The different expression profile of OCT4 isoforms in hESC and hMSC indicates that OCT4 may be one of the important factors resulting in the differences of self-renewal and differentiation potentials of stem cells at different developmental stages.

Key words: Human embryonic stem cells, human mesenchymal stem cells, OCT4, alternative splicing