Imagine listening to your favorite song on a streaming service. Then, right in the middle of the song, the lyrics and music are replaced by those from your least favorite tune. It’s as if a portion of this unwanted ditty had vaulted across an invisible barrier, hijacked the soundtrack, and transformed it into something unexpected.
Believe it or not, this kind of leaping and bounding also occurs within our DNA. Genes, known as mobile elements, are capable of hopping from place to place within our genome—occasionally smack dab into the middle of another gene, altering its function. These so-called “jumping genes” can spark remarkable evolutionary changes in plants and animals. However, they can also muddle up other genes so much that they stop working, triggering a host of genetic diseases and conditions. Yet, until recently, scientists had remarkably little idea how often these jumps occurred, particularly in developing reproductive cells.
Now, in what is believed to be a first-of-its kind discovery, researchers at University of Utah Health who studied family members across three generations have determined that these genetic leaps typically occur in about 5% of live births. They say knowing the baseline rate of jumping genes could lead to better understanding of the onset of at least 130 genetic diseases, including cancer, that are linked to insertion of mobile elements into various parts of the human genome.
Their study appears in Genome Research.
Knowing the baseline rate of jumping genes could lead to better understanding of the onset of at least 130 genetic diseases, including cancer.
“For a long time, these jumping genes were considered junk DNA, a sort of flotsam and jetsam of the genome,” says Lynn B. Jorde, Ph.D., chair of U of U Health’s Department of Human Genetics and the senior author of the study. “But we now know that these elements have some important consequences for our genome. Having a baseline understanding of how often these jumps occur will help us better evaluate the process as well as predict and, in time, possibly prevent genetic changes that occur in diseases like breast cancer.”
First detected by Nobel Laureate Barbara McClintock more than 60 years ago, jumping genes or mobile elements occur in virtually every living thing and appear to make up about half of the human genome. These genes can copy themselves, then transpose or move elsewhere in the genome. Once at a new site, the mobile elements insert themselves into genetic sequences, disrupting or deleting vital genetic material. In all, Jorde says, about 10% of all deletions and duplications in the genome, which often can lead to genetic disease, are due to jumping genes.
To determine how often these genes typically jump, Jorde, doctoral student Julie Feusier, and colleagues used whole genome sequencing to measure the rate of gene transposition in 599 members of 33 Utah families who had participated in the Centre d’Etudes du Polymorphisme Humain (CEPH) study. This international study included genetic information gathered from families from around the world beginning in the 1980s. These genetic profiles are considered instrumental in mapping the human genome and detecting new mutations.
Although there were slight deviations in the transposition rates for individual mobile elements, ranging from one in 40 to one in 63, Jorde’s team found, on average, jumping genes normally occur in about one in 20 births. Being able to study grandparents, parents, and grandchildren over time was a key factor in this result, Jorde says, allowing the researchers to follow the flow of jumps from egg fertilization through early embryonic development in multiple generations.