Researchers from UC Berkeley (CA, USA) have discovered a way to make embryonic stem cells (ESCs) from mice totipotent, similar to a fertilized egg. They were able to generate all cell types found in a developing embryo, as well as those that allow nutrient exchange between the embryo and its mother.
Although it was hoped that the pluripotency of ESCs and could soon be translated into therapies, these cell lines can be restricted in their developmental potential as they have already committed to a cell lineage by the time they are harvested. By contrast, the original fertilized egg can form embryonic tissues as well as extra-embryonic tissues
“What is quite amazing is that manipulating just a single microRNA was able to greatly expand cell fate decisions of embryonic stem cells,” Lin He, Associate Professor of Molecular and Cell Biology (UC Berkeley), said. “This finding not only identifies a new mechanism that regulates totipotent stem cells, but also reveals the importance of non-coding RNAs in stem cell fate.”
The team, led by He, found that a microRNA called miR-34a appeared to be the obstacle preventing ESCs and induced pluripotent stem cells (iPSCs) from producing extra-embryonic tissue. When miR-34a was removed, both ESCs and iPSCs were able to produce all embryonic cells types as well as placenta and yolk sac cells. In the study, approximately 20% of the cells without miR-34a exhibited expanded cell fate potential, maintaining this for up to a month in cell culture.