Approaches to identifying nuclear reprogramming factors from embryonic stem cell biology and somatic cell nuclear cloning

Undifferentiated cells, such as embryonic stem cells (ES cells) and vertebrate eggs, contain powerful nuclear reprogramming factors that can erase previous cell memory and induce dedifferentiation of various somatic cells. The existence of these nuclear reprogramming factors has been most clearly demonstrated by somatic cell nuclear cloning and cell fusion between ES cells and differentiated somatic cells. This chapter will discuss several examples of the reprogramming factors identified from cell fusion, somatic cell nuclear cloning, and comparisons of mRNA and chromatin structure between ES cells and differentiated cells. Further analyses of the molecular mechanisms underlying the nuclear reprogramming by undifferentiated cells will significantly contribute to the development of novel cell-based therapy in regenerative medicine.