Image Glossary > Reprogramming Factors

In 2006, the Yamanaka lab identified four factors that, when co-transfected and expressed in mouse adult fibroblast cells, caused those fibroblasts to revert back to a pluripotent like state.  One year later, the same four factors were used to successfully reprogram human adult fibroblast cells into induced pluripotent stem cells.  These four factors are:

Octamer-4 (Oct-4) encoded by the gene POU5F1 is a transcription factor that is highly expressed in undifferentiated embryonic stem cells compared to other somatic cells.  Oct-4 expression in embryonic stem cells is critical to maintain them in an undifferentiated, pluripotent state.  In fact, if Oct-4 experession is experimentally knocked out, this causes embryonic stem cells to spontaneously differentiate. 

SOX2 is a transcription factor critical for the maintenance of pluripotency in embryonic stem cells. SOX2 and Oct-4 work in parallel to co-regulate expression of target genes involved in the maintenance of pluripotency.

c-Myc is a well known proto-oncogene. The c-Myc gene codes for a transcription factor that regulates the expression of many genes involved in the control of cell proliferation, growth, differentiation and apoptosis. Abberant expression of c-Myc on the other hand is associated with tumor formation and cancer.  Recent studies have demonstated that c-Myc is a dispensable reprograming factor; however, the transcription factor has been shown to greatly improve reprogramming efficiency. 

Kruppel-like factor 4 (Klf-4) is a transcription factor that is highly expressed in undifferentiated ES cells and is also expressed elsewhere in the adult organism including the gut, testis and lungs and functions to regulate proliferation, differentiation and cell survival.

Chromatin The complex of DNA and DNA-binding protein that makes up a eukaryotic chromosome. The DNA is wrapped around histone proteins... Read More

Retrovirus An RNA virus that fuses to surface receptors located within the host cell's plasma membrane. After binding, the membrane of the... Read More

Reverse Transcriptase A DNA polymerase enzyme that transcribes single-stranded RNA into double-stranded DNA which is then integrated into the host ... Read More

Transcription Factor A regulatory protein that binds to DNA and affects the transcription of specific genes. The four reprogramming factors, Oct-4, SOX2, Klf-4... Read More

Cellular Reprogramming Cellular reprogramming describes the process where a fully differentiated, specialized cell type is induced to transform into a different... Read More

Stem Cell There are many different types of stem cells within our body. Each type of stem cell is defined by the group of specialized cells it give ... Read More

Induced Pluripotent Stem Cell A somatic cell that has been reprogrammed to exhibit pluripotent stem cell properties. Many somatic cells have been... Read More

iPS Colony Refers to the tightly packed homogenous cluster of induced pluripotent cells. Undifferentiated embryonic stem cells and... Read More

Fibroblast A type of cell in loose connective tissue that secretes the protein ingredients of the extracellular matrix. Many somatic cells have been ... Read More