A long-term study of identical twins reveals that an individual’s DNA may change over the course of a lifetime.
Researchers discovered cases where large or small DNA segments change direction, are duplicated, or become completely lost. The changes were mainly discovered in older twins.
This finding may help to explain why the immune system is often impaired in older age.
Uppsala University researchers explain that during a person’s life, continuous alterations in the cells’ DNA occur. The alterations can be changes to the individual building blocks of the DNA but more common are rearrangements where large DNA segments change place or direction, or are duplicated or completely lost.
In the current study, scientists examined normal blood cells from identical (monozygotic) twins in different age groups and looked for large or smaller DNA rearrangements.
The results showed that large rearrangements were only present in the group older than 60 years.
The most common rearrangement was that a DNA region, for instance a part of a chromosome, had been lost in some of the blood cells. Certain, almost identical, rearrangements were found in several individuals and some of these could be associated with a known blood disease in which the bone marrow’s capacity to produce new blood cells is disturbed.
Rearrangements were also found in the younger age group. The changes were smaller and less complex but the researchers could also in this case show that the number of rearrangements correlated with age.
Investigators were surprised to find that as many as 3.5 percent of healthy individuals older than 60 years carry such large genetic alterations.
The discovery sets the stage for a better understanding of disease development in older age.
Scientists believe that this type of acquired genetic variation might be much more common, says Jan Dumanski, professor at the Department of Immunology, Genetics and Pathology and one of the authors of the paper.
A key to the potential association between DNA changes and alterations to our immune system is the understanding that although we possess a variety of blood cell types, only white blood cells contain DNA.
This distinction is important as researchers believe an increased number of WBC cells with DNA alterations can damage or alter the immune system.
Specifically, the genetic alterations lead to an increased growth of the cells that have acquired them; these cells will increase in number in relation to other white blood cells.
The consequence might be a reduced diversity among the white blood cells and thereby an impaired immune system.
Researchers have published the findings online in the American Journal of Human Genetics.
Source: Uppsala University