Researchers at the Pasteur Institute show for the first time the mechanism which adult skeletal muscle stem cells can use to protect their genome from mutations. Before cell division, DNA is duplicated, and each daughter cell inherits one copy. During DNA synthesis, however, errors can arise from this imperfect process. Over time, repeated rounds of cell divisions result in the accumulation of these mutations which can perturb normal cellular processes, and provoke cancers. In an Article published in Nature Cell Biology, researchers provide convincing evidence that muscle stem cells retain the original DNA strands which have not been copied. By doing so, the stem cells can avoid accumulating mutations in their DNA, which may provoke carcinogenesis. This mechanism which preserves the "immortal" DNA involves complex molecular and cellular regulation which remains to be explored.

RStem cells represent a promising tool for the development of therapeutic strategies. To regulate their numbers correctly in the organism, stem cells can self-renew by asymmetric cells divisions. In other words, they can give rise to two different daughter cells: one daughter which retains the properties of the stem cell, and another daughter which will contribute to the tissue. A key question is how stem cells retain their original state without being altered, as well as their potent capacity to regenerate the tissue over extended periods, often decades.

The research laboratory Stem Cells & Development directed by Shahragim Tajbakhsh at the Pasteur Institute, has taken a significant step in validating a controversial hypothesis proposed 3 decades ago (Cairns, Nature, 1975), that of immortal DNA. This theory suggested that only the differentiating cells will inherit the newly "photocopied" DNA strands, which contain errors. The stem cells retain the unmodified original DNA strands, which consequently remain "immortal" after repeated cell divisions.

The researchers used sophisticated experimental approaches including ...