Reprogramming of somatic cells and nuclei by Xenopus oocyte and egg extracts.

Differentiated somatic cells and nuclei can be reprogrammed to a pluripotent undifferentiated state in the cytoplasm of oocytes and eggs. The ability of the gamete cells to induce reprogramming is not species-specific, so the extracts prepared from the oocytes and eggs of the African clawed frog Xenopus laevis can reprogram somatic mammalian cells. Thus, Xenopus egg extract-mediated reprogramming may constitute an alternative or complement other experimental reprogramming approaches, such as nuclear transfer, cell fusion, and transcription factor transduction. Here, we discuss the major reprogramming events induced by the extracts in somatic nuclei and cells, including remodeling of nuclear structure, replacement of somatic proteins with their embryonic counterparts, epigenetic modification of DNA and histones, transcriptional reprogramming, and initiation of DNA replication. We also address the advantages and limitations of the extract-based reprogramming approach.