A small number of growth factors are sufficient to reprogram somatic cells into pluripotent stem cells.OBJECTIVE:
To explore the epigenetic mechanism in cellular reprogramming and regulating, and to reveal epigenetic alterations, the stability of epigenetic modifications and their effects on genome expression.METHODS:
Pubmed database and CNKI database from 1990 to 2008 were retrieved by computer with the keywords of “DNA methylation; cell reprogramming; stem cells”.RESULTS AND CONCLUSION:
Though cellular differentiation is unidirectional and irreversible, this process can be changed by reprogramming. Some growth factors are sufficient to reprogram somatic cells into pluripotent stem cells. So far, the introduction of transcription factors, DNA demethylation and the apparent genetic modification have been used to induce reprogramming. By understanding the molecular mechanism, the apparent changes in genetic regulation, the stability of epigenetic marks and their effects on expression of the genome are significant in the development of gene therapy. However, many issues still need further studies, such as: Is AID or DNA demethylation enzyme plays an important role in DNA demethylation? What are the requirements for DNA demethylation? Can demethylation take place in CpG fragments of tumor cells? Are cancer cells more difficult to re-programming?