From Scientific American, news of another step towards the control - and possibly creation - of embryonic stem cells: scientists used short hairpin RNA (shRNA) "to sequentially turn on and off various genes within embryonic stem cells from a mouse. The shRNA, delivered by a virus, allowed the researchers to determine whether a given gene helped control stem cell differentiation. ... the scientists found 10 likely candidates [and] engineered versions of these genes that could be turned on and off by the presence of the drug doxycycline to uncover their specific effects. Seven of the identified genes proved to be potent regulators of a stem cell's ability to split and then renew itself. Without them, the cell rapidly became specialized, losing its unique pluripotent status."