BIRMINGHAM, Ala. (Ivanhoe Newswire) James D. Watson, Frances Crick, and Maurice Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962 for their discovery of the structure of DNA. Using x-ray diffraction data, they found that the structure of the DNA molecule was shaped like a double helix or spiral staircase. Today, researchers continue their efforts in understanding DNA.
Researchers at Uppsala University collaborated with others, from Hudson Alpha Institute for Biotechnology, as well as Karolinska Institutet and other research centers found in the United States, Poland, the Netherlands, and Norway, to compare the DNA of identical twins. Their goal was to better understand the mechanics behind why the immune system becomes impaired with age.
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 this study, led by Uppsala University, the scientists examined normal blood cells from identical (monozygotic) twins in different age groups and looked for large or smaller DNA rearrangements. They discovered 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 correlated 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 show that the number of rearrangements correlated with age.
Out of the cell types in blood only white blood cells contain DNA. The researchers believe that the increased number of cells with DNA alterations among elderly can have a role in the senescence of the immune system. If 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.
“We were surprised to find that as many as 3.5 percent of healthy individuals older than 60 years carry such large genetic alterations,” said Jan Dumanski, professor at the Department of Immunology, Genetics and Pathology at Uppsala University. “We believe that what we see today is only the tip of the iceberg and that this type of acquired genetic variation might be much more common.”
SOURCE: Uppsala University, February, 2012
