Not a day without mutation

How many mutations do we get with age?

Kirill Stasevich, "Science and Life"

Mutations constantly appear in our cells, that is, defects in DNA: somewhere a genetic "letter" will fall out altogether, somewhere one "letter" will be replaced by another, etc. Of course, there are special repair proteins in cells that try to correct such errors. However, over time, repair (repair) systems begin to work poorly, and uncorrected mutations in cells occur more and more.

Researchers from the Sanger Institute decided to calculate how many mutations in human cells appear at different times of life (Mutant cells colonize our tissues over our lifetime). To do this, esophageal cells were taken from nine volunteers aged 20 to 75 years to read their DNA. It turned out that if a twenty-year-old can find several hundred mutations per cell, then with age they become more than two thousand.

Wellcome Sanger Institute,
Genome Research Limited

It should be emphasized that all the participants in the experiment were healthy and no one in the family had cases of esophageal cancer – that is, they could not have inherited cancer mutations.

Many of the DNA defects are quite harmless, but there were also those that usually accompany oncological problems. For example, mutations in the TP53 gene: they are found in almost all malignant tumors of the esophagus, but besides they are in 5-10% of completely normal cells. And mutations in the NOTCH1 gene, which controls cell division, were in almost half of the cells taken from middle-aged people. The results of the study are described in detail in Science (Martincorena et al., Somatic mutant clones colonize the human esophagus with age).

It should be emphasized that all the cells in which these hundreds and thousands of mutations were found were not malignant. Of course, it is not a fact that they would continue to remain so, and it is quite possible that someone from those who participated in the study would be nice to be regularly checked for esophageal cancer. On the other hand, the presence of cancer mutations in normal cells makes us take a closer look at how a malignant tumor arises: it is obvious that a bad mutation alone is not enough here, and it is necessary to take into account the entire spectrum of DNA defects - among them, some can help or hinder others, and the fate of the cell and the organism as a whole will depend on this.

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