A group of University of Washington researchers has devised a method that combines DNA sampling and mathematical modeling to find out how accurately methylation patterns are copied during DNA replication. That could pave the way for understanding the role methylation plays in normal gene expression and how it factors in the development of human disease.
In methylation, a methyl group (made up of a carbon atom and three hydrogen atoms) is attached to a specific gene sequence in one part of DNA. The density of methyl saturation determines how the gene is expressed. The densest saturation turns the gene off so that it is not expressed at all, and less-dense saturation allows the gene to be expressed at different levels.
The result can be obvious, for instance, in a calico cat and its multicolored coat, said Diane Genereux, a visiting UW biology graduate student and lead author of a paper describing the new measuring technique in the April 19 edition of the Proceedings of the National Academy of Sciences.
"In a calico cat, different genes that express coat color are on and off in different parts of the cat's coat, so you get patches of different-colored fur," Genereux said.
Methylation typically passes from genes in a DNA strand to the same genes in a daughter strand created during DNA replication. The new technique allows researchers to examine how faithfully this "maintenance" methylation is carried out across generations and how consistently it occurs on the same gene sequence, said Brooks Miner, a UW research scientist in biology and a co-author of the paper.