Induced pluripotent stem cell
Induced pluripotent stem cells are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka and Kazutoshi Takahashi in Kyoto, Japan, who together showed in 2006 that the introduction of four specific genes, collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. Shinya Yamanaka was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent."
Confocal microscopic image of a colony of human induced pluripotent stem cells derived from a patient with oculocutaneous albinism. Red indicates transcription factor Oct-4, green the protein SSEA4, and blue the nuclei of the cells.
In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.
Transmission electron micrograph of a mesenchymal stem cell displaying typical ultrastructural characteristics
Mouse embryonic stem cells with fluorescent marker
Human embryonic stem cell colony on mouse embryonic fibroblast feeder layer