Tissue Engineering

Lecture 5Paper Review

Discovery of Induced Pluripotent Stem Cells

Kazutoshi Takahashi and Shinya Yamanaka

Our group will use molecular and cell biological techniques to gain a better understanding of mechanisms underlying the pluripotent state. We expect to pursue crucial issues in this work, not only the reprogramming phenomenon itself, and are particularly intrigued by the variations between cell lines that arise from differences between individuals.

The goal of our laboratory is to generate pluripotent stem cells from human somatic cells. Somatic cells can be reprogrammed either by nuclear transfer into oocytes or by fusion with embryonic stem (ES) cells. These results suggest that oocytes and ES cells contain factors that induce reprogramming. By identifying these factors, it should be possible to induce pluripotency in somatic cells without using embryos or oocytes.

Why do we need a new source of stem cells?

• Prior to this study, others had shown that you could re-program adult cells by transferring nuclear contents into oocytes, or by fusing with ES cells. These are really difficult – is there an easier way?

• Ethical difficulties with using ES cells

Figure 1: Akarawin Hongdusit

Figure 1: Akarawin Hongdusit

Figure 2: Hiu Yeung

Figure 3: Alpha Bamba

Figure 3: Alpha Bamba

Figure 4:Michael Mulroy

Figure 5: Brittany Shepler

Figure 5: Brittany Shepler

Figure 6: Kyle

Pariseau

Figure 7: Christine Davis

Figure 7: Christine Davis

Stem Cell Genes• Oct3/4: marker for stem cells. Tightly controlled. Is a

transcription factor.• Sox2: marker for stem cells. Is a transcription factor.

Overexpression can cause cancer.• C-Myc – Transcription factor. later shown to be

tumorigenic. Originally discovered in lymphoma. Follow up studies show that this gene is dispensable.

• Klf4 – transcription factor. Regulates cell growth. Stem cell marker.

• Nanog (dispensable). Transcription factor. Stem cell marker. Critical for ES cells but seems to be dispensable for iPSC creation.

Conclusions, Perspectives

• Generation of iPSCs, as shown in mouse cells here, is now being routinely done in human cells.

• This has been repeated also with protein delivery and non-integrating plasmids.

• This is still an inefficient process, and there are big differences in efficiency between different starting cell populations.