An ambitious hunt by Johns Hopkins scientists for actively "jumping genes" in humans has yielded compelling new evidence that the genome, anything but static, contains numerous pesky mobile elements that may help to explain why people have such a variety of physical traits and disease risks.
Using bioinformatics to compare the standard assembly of genetic elements as outlined in the reference human genome to raw whole-genome data from 310 individuals recently made available by the 1000 Genomes Project, the team revealed 1,016 new insertions of RIPs, or retrotransposon insertion polymorphisms, thereby expanding the catalog of insertions that are present in some individuals and absent in others. Their results appeared online October 27 in Genome Research.
Retrotransposons are travelling bits of DNA that replicate by copying and pasting themselves at new locations in the genome. Having duplicated themselves and accumulated over evolutionary history, transposable elements now make up about half of the human genome. However, only a tiny subfamily of these insertions known as LINE-1 (L1) is still active in humans. Line 1 insertions are able to mobilize not only themselves but also other pieces of DNA.
"In any individual, only between 80 to 100 retrotransposons are actively copying and inserting into new sites," says Haig Kazazian, M.D., professor of human genetics, McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine. "We're not only discovering where they are and who has which ones, but also finding out that they insert with a remarkable frequency: On the order of one in every 50 individuals has a brand-new insertion that wasn't in their parents."
The researchers recognized L1 retrotransposons distinguishing them from the vast amount of fixed "fossil" transposable elements that litter the genome because these actively jumping genes are human specific and almost exactly the same in sequenc
|Contact: Maryalice Yakutchik|
Johns Hopkins Medical Institutions