Human embryonic stem cellsWIKIMEDIA, NISSIM BENVENITSKYPluripotent stem cells are capable of generating all embryonic cell lineages but, until now, scientists could seldom manipulate induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) to generate extra-embryonic cell types, such as placental cells. A study published this week (January 12) in Science has now shown that removing one particular microRNA—miR-34a—from a stem cell can kick off a molecular pathway that induces endogenous retroviruses and, at the same time, enables iPSCs and ESCs to consistently form extra-embryonic cells in a dish.
The results suggest that a particular class of noncoding RNA works in concert with the latent viral elements of the genome work to limit stem cell potential, and that removing a key miRNA can lift this limitation—at least in vitro.
“At first we were a bit dubious about our findings,” said coauthor Lin He, an associate professor of developmental biology at the University of California, Berkeley. “In this experiment, we definitively show that the progeny [of embryonic stem cells] can go to both embryonic and extra-embryonic lineages. That was a pretty incredible moment for us, because we actually convinced ourselves that this finding was real.”
Although stem cells can give rise to virtually any cell type inside the embryo, they have limited potential to give ...
