For the first time, researchers at Cornell University have identified a human gene that retains the ability to move around the genome while still serving an important biological role. Published Sept. 24 in Science, the discovery centers on a genetic element known as BC200, which scientists found tucked inside a poxvirus.
How BC200 Combines Mobility With Cellular Function
BC200 is expressed mainly in neurons and traces its evolutionary history back millions of years to a transposon, often called a jumping gene. Transposons are non-coding genetic elements that can relocate and insert themselves into new spots within a genome. While about half of the human genome consists of transposon-derived DNA, the vast majority of these elements are no longer active. Only a tiny fraction retains the capacity to copy and move themselves.
Genes that come from transposable elements and that are repurposed for cellular functions are typically no longer transposable,
said Cedric Feschotte, a senior author of the study. BC200 was itself created from a mobile element but has retained its mobility and yet it is also clearly serving a cellular function. Somehow evolution hasn’t been able to untangle these two things.
While the exact physiological role of BC200 remains uncertain, current evidence suggests it helps regulate how neuronal messenger RNAs translate into proteins. Researchers also detected the gene at low levels in germ cells, including sperm and eggs, pointing to a potential mechanism for creating new, heritable insertions.
Tracking the Genetic Jump Into a Molluscum Contagiosum Virus
The Cornell team think that BC200 may have made its way into the molluscum contagiosum virus (MCV) while the virus was infecting skin cells, which are the only cells known to be infected by MCV. Documenting a transposon jumping into a virus is rare. In the late 1980s, researchers observing cultured moth cells noted a similar event involving a baculovirus, but equivalent instances involving human genes and viruses have remained elusive until now.
Beyond its presence in normal neuronal tissue, BC200 has drawn scrutiny for abnormal expression patterns in some tumors and elevated levels in the brains of Alzheimer’s disease patients. These observations suggest that the gene’s ability to move could be tied to disease. Feschotte and his colleagues plan to study whether MCV uses BC200 to manipulate human host cells, while also examining whether active jumping in breast cancer and other tumors creates mutations.
Questions About the BC200 Gene
Where is the BC200 gene primarily found in the human body?
BC200 is expressed mainly in neurons, though researchers have also detected low levels in germ cells such as sperm and eggs.
What makes the discovery of BC200 unusual compared to other human genes?
While previous studies showed that genes derived from transposable elements typically lose their mobility once repurposed for cellular tasks, BC200 simultaneously retains the ability to move around the genome and perform a biological function.
Which virus carried the human genetic element analyzed by Cornell researchers?
The researchers found the human genetic element inside the molluscum contagiosum virus, which infects human skin cells.