​The stem cells of our body can generate specialized, “differentiated” daughter cells to repair a damaged tissue. The Stem Cells and Development unit1 (Institut Pasteur/CNRS) is interested in the adult stem cells of muscle in mice. These can be divided in a “symmetrical” way, resulting in either two stem cells or two differentiated cells; they can also be divided in an “asymmetrical” way, creating one cell of each type. In the latter case, the DNA of the mother stem cell can end up entirely within the daughter stem cell, whereas the other (differentiated) daughter cell inherits one copy. The DNA segregation is therefore called “biased”. The mechanisms controlling these phenomena however remain unknown.

The researchers studied the influence of the mechanical tension acting upon a cell in the tissues of the body. For this, the CEA-IRTSV designed small plates containing thousands of patterns with varied shapes, the size of one or two cells (300 square micrometers). Each stem cell was placed on a pattern guiding its division, with its daughter cells remaining on the “micropattern”. Result: an asymmetrical pattern provokes four times as many asymmetric divisions as a symmetrical pattern. It also promotes “biased” DNA segregation. The fate of the stem cells is thus not only based on internal signals but also on external conditions, especially the tensions perceived during division.

This work opens up important therapeutic perspectives, suggesting the possibility of controlling the type of cells produced for a transplant.

[1] directed by Shahragim Tajbakhsh