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									                                                             Julia Gill and Kristen Kilroy
                                                                          March 9th, 2010
Induction of Pluripotent Stem Cells from Adult Human Fibroblasts by Defined
  Takahashi, K., Tanabe, K., Ohnuki, M., Narita, M., Ichisaka, T., Tomoda, K. and S.
                      Yamanaka. (2007). Cell 131: 861-872.

Key Terms:
 Embryonic Stem Cell: cell derived from the inner cell mass of a mammalian
   blastocyst that can be indefinitely maintained in a pluripotent state in culture
   (Wolpert et al. 2007; Takahashi et al. 2007).

   Pluripotent Cell: a cell that has the potential to differentiate into any cell type.

   iPS cells: induced pluripotent stem cells, are adult somatic cells that have been
    reprogrammed to a pluripotent state through the over-expression of four
    essential transcription factors: Sox2, Oct 3/4, Klf4 and c-Myc. Yamanaka and
    Takahashi developed this method in 2006 using mice.

   Oct3/4: A transcription factor found in embryonic carcinoma cells, early
    embryos and germ lines that has a role in cell differentiation (Yamanaka 2007).

   Sox2: A transcription factor expressed in the inner cell mass, epiblast and germ
    cells. It forms heterodimers with Oct3/4 to regulate gene expression (Yamanaka

   Klf4: A transcription factor expressed in epithelial and fibroblast cells. May play
    an important role in the transition from proliferation to differentiation in cell
    development (Yamanaka 2007).

   c-Myc: An important transcription factor involved in apoptosis, biological
    processing and cell differentiation. May modify chromatin structures by histone
    acetylation and be active in tumor formation (Yamanaka 2007).

   NANOG: A transcription factor that stops differentiation in ES cells and is a
    marker of pluripotency (Vallier et al. 2009).

   Retroviral Transduction: A process in which retroviral vectors containing the
    genes of interest are introduced into packaging cells that will produce
    retroviruses that may in turn be used to infect cells of interest (Morita et al.

   Fibroblasts: “connective tissue cells” (Wolpert et al. 2007, p 471).

   hES Markers: protein markers that characterize human embryonic stem cells.
    These may include: stage specific embryonic antigens (SSEA), Tumor related
    antigens (TRA) or developmental genes (ie. NANOG) (Takahashi et al. 2007).
                                                             Julia Gill and Kristen Kilroy
                                                                          March 9th, 2010

       Teratoma: Tumors that contain a variety of differentiated cell types (Wolpert et
        al. 2007).

This paper shows that it is possible to reprogram differentiated adult human
fibroblast cells to a pluripotent state, using the four essential transcription factors
(Oct3/4, Sox2, Klf4 and c-Myc). These induced pluripotent stem (iPS) cells very
closely resemble human embryonic stem cells. The differentiation of the iPS cells
generated into cardiac and neural cells was achieved, as was teratoma formation.
The efficiency of iPS cell generation was low, however Takahashi et al. (2007)
deemed it acceptable. Possible reasons for low the low efficiency were the
requirement of specific integration sites, possibility of integration in only certain
cells and the possible presence of undifferentiated cells in the experiment. Overall
the success shown with the creation of human iPS cells may be promising for future
medical research.

Future Applications (Lee and Studer 2010):
    Modeling disease
    Individualized drug therapy and assessment of disease risk factors
    Gene therapy

                                                                   (Yamanaka 2009)

Useful Links for Review and Further Information:

        Nature Methods: This website contains great videos, commentaries and
         reviews that explain iPS and its applications.
        Takahashi, K., and Yamanaka, S. (2006). Induction of pluripotent stem
         cells from mouse embryonic and adult fibroblast cultures by defined
         factors. Cell 126: 663–676.
                                                                     Julia Gill and Kristen Kilroy
                                                                                  March 9th, 2010
Please Note: All references given in this handout may be found on the reference slides of the
associated PowerPoint

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