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nuclear reprogramming
The transformation of one somatic cell type into another somatic cell type or a stem cell would be beneficial for, in the long term, producing isogenic replacement cells for therapeutic use (Collas and Håkelien, 2003). Our approach to nuclear reprogramming involves a reversible permeabilization of the cell to be reprogrammed, treatment of the permeabilized cell with a nuclear and cytoplasmic extract derived from the ‘target’ cell type, and resealing of the cell membrane. Our nuclear reprogramming protocol can be found here. Large numbers of cells can be treated with extracts, and extracts can be manipulated, so the system constitutes a powerful tool to examine the molecular mechanisms of reprogramming.
Transdifferentiation – Using this approach, we have initially shown that epithelial cells treated with an extract of Jurkat cells down-regulate epithelial cell genes and take on various T cell properties, (Håkelien et al., 2002; Håkelien et al., 2005; Landsverk et al., 2002).
Figure: Epithelial cells treated with a "target" cell extract can take on properties of, here, T cells, cardiomyocytes, pancreatic beta cells or ES cells.
Dedifferentiation – Extracts of undifferentiated human carcinoma cells can reprogram the epigenome and the transcriptome of epithelial cells to elicit embryonic stem (ES) cell functions (Taranger et al., 2005). Using bisulfite sequencing analysis of DNA methylation and a Q2ChIP assay, we have shown that extracts elicit DNA demethylation and changes in histone modifications on ES cell-specific promoters, promoting their reactivation (Freberg et al., 2007). Reprogrammed cells can be induced to differentiate toward mesodermal and ectodermal lineages using classical differentiation cocktails. We are currently elucidating the series of epigenetic events leading to nuclear reprogramming.
Persons involved: Christel T. Freberg, Sanna Timoskainen
Figure: Phenotypic changes of epithelial cells reprogrammed in extract of embryonal carcinoma cells.
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