Stem cells without virus infection

Recently there has been a lot of new studies showing how to reprogram adult cells into stem cells. Just a few months ago researchers showed that only four genes (c-Myc, Klf4, Oct4, and Sox2) were needed to obtain stem cells, and a few weeks ago Oct4 was shown to be the only gene needed to reprogram cells into stem cells.
All these studies required the use of viruses to reprogram cells into stem cells. The typical experiment was basically as follows: introduce your genes (Oct4, etc) into a retrovirus and then infect a cell with it. The retrovirus integrates into the cell's genome, expresses its genes (Oct4, etc) and the cell becomes a stem cell.
Now two studies, both published in the latest issue of Nature, have shown how to get around using a virus. One approach cloned the now called Yamanaka factors (c-Myc, Klf4, Oct4, and Sox2) into a vector and introduced it into cells. After the cells were reprogrammed the vector was digested using a restriction enzyme, only leaving a small trace of DNA. The other approached used a transposable element called piggyBac (from the cabbage looper moth). As with the vector, all four Yamanaka factors were cloned into piggyBac and then introduced into cells, which lead to reprograming into stem cells. The beauty of this new method is that this transposable element can be removed entirely with the use of a transposase (an enzyme that makes the transposable element completely excise itself from DNA, not leaving any trace of its existence). The transposase experiments remain to be performed, as well as a complete characterization of the pluripotent nature of these reprogrammed stem cells (there are a lot of experiments that need to be performed to fully characterize a cells as a stem cell).
These new techniques have great potential for genetic therapy. Up until now in order to introduce genetic modifications into cells to turn them into stem cell you had to infect them with a retrovirus (not the nicest thing and potentially dangerous). By getting rid of viruses altogether, these new techniques made genetic therapy and stem cell research significantly safer and easier.


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