The Partial Reprogramming of Mammalian Somatic Cells by Pluripotent Cell and Oocyte Extracts

During mammalian development pluripotent stem cells produce a myriad of structurally and functionally distinct somatic cells. The reprogramming of somatic into pluripotent cells is fundamental to the development of patient-specific cell sources applicable to biomedical science and regenerative medicine. Different experimental approaches can reprogram somatic into pluripotent cells: the induced pluripotent stem cell (iPSC) technique, somatic cell nuclear transfer (SCNT), and cell-cell fusion. However, the factors and mechanism underlying somatic cell reprogramming remain elusive. Extract cell reprogramming is a suitable system to identify factors and mechanisms responsible for somatic cell reprogramming because it is amenable to biochemical assays and manipulations that can identify factors and therefore mechanisms involved in the reprogramming process. One prerequisite for the biochemical dissection of cell reprogramming is the development of a large scale reprogramming system, which uses potent but inexpensive extract sources to reprogram large numbers of somatic cells. Here, I describe the development of a cell extract-based reprogramming system, which uses protein extract isolated from the oocytes of salmon (Oncorhynchus tshawytscha). The developed system supports the digitonin-mediated permeabilization and survival of somatic cells as well as the uptake and retention of large molecules such as proteins within somatic cells. Salmon oocyte extract can at least partially reprogram mouse somatic cells into pluripotent cells. The established extract-based reprogramming system provides evidence that salmon oocytes are a suitable cell source for the identification of factors and the dissection of mechanisms involved in somatic cell reprogramming.