Epigenetic marks on DNA change over a person's lifetime to a degree that is similar among family members, according to an international group of researchers. The team suggests that while overall genome health is heritable, epigenetic changes through a person’s lifetime may explain why disease susceptibility increases with age.
“We're beginning to see that epigenetics stands at the center of modern medicine, because epigenetic changes unlike DNA sequence, which is the same in every cell, can occur as a result of dietary and other environmental exposure,” comments Andrew P. Feinberg, M.D., study investigator and professor of molecular biology and genetics and director of the Epigenetics Center at the Johns Hopkins School of Medicine.
If epigenetics does contribute to diseases through interaction with environment or aging, Dr. Feinberg says, a person's epigenetic marks would change over time. To investigate this hypothesis, his team focused on methylation.
“Methylation levels can vary subtly from one person to the next, so the best way to get a handle on significant changes is to study the same individuals over time,” points out Vilmundur Gudnason, M.D., Ph.D., another investigator on the study and professor of cardiovascular genetics at the University of Iceland.
The researchers used DNA samples collected from people involved in the AGES Reykjavik Study. The research team measured the total amount of DNA methylation in each of 111 samples and compared total methylation from DNA collected in 2002 to 2005 to that person's DNA collected in 1991.
They found that in almost one-third of individuals, methylation changed over the 11-year span but not all in the same direction. Some individuals gained total methylation in their DNA, while others lost.
The team then measured total methylation changes in a different set of DNA samples collected from Utah residents of northern and western European descent. These DNA samples were collected over a 16-year period from 126 individuals.
Similar to the Icelandic population, the Utah family members also showed varied methylation changes over time. They found, though, that family members tended to have the same kind of change; if one individual lost methylation over time, they saw similar loss in other family members.
The research team comprised scientists from Hjartavernd, Reykjavik in Iceland, NIA, University of Utah, Salt Lake City, and Temple University Medical School. The study is published in the June 25 issue of the Journal of the American Medical Association.