Transposons, or "jumping genes," make up roughly half of the human genome. Geneticists previously estimated that they replicate and insert themselves into new locations roughly one in every 20 live births.
New results, published in the June 25, 2010 issue of Cell, suggest that every newborn is likely to have a new transposon somewhere in his or her genome.
"Now it looks like every person might have a new insertion somewhere," says senior author Scott Devine, PhD, associate professor of medicine at the University of Maryland School of Medicine's Institute for Genome Sciences. "This is an under-appreciated mechanism for continuing mutation of the human genome."
The research was initiated at Emory University School of Medicine, where Devine was in the Department of Biochemistry. First author Rebecca Iskow, PhD (now a postdoctoral fellow at Brigham & Women's Hospital in Boston) was a graduate student at Emory. Two other papers on human transposons appear in the same issue of Cell.
Transposons resemble e-mail spam: short repeated sequences that have no obvious function other than making more of themselves. The full name for the type of transposon that is most abundant in the human genome is retrotransposon. The "retro" term comes from how they replicate: first, the DNA is transcribed (copied) into RNA, and the RNA is reverse-transcribed into DNA again. This process normally only happens during very early in development, when the cells that will become eggs and sperm have not turned down a separate path of differentiation.
"Transposons are the original selfish genes, and this strategy makes sense for them, because it makes sure new copies will get carried into the next generation," Devine says.
While working in Devine's lab as a graduate student, Iskow devised a technique for "amplifying" the stretches of individual genomes that border transposons and reading thousands of the junctions with advanced sequencing techniques, then comparing them to the reference human genome.
"The basic problem was that a new insertion can be anywhere within three billion base pairs – how do you find it compared to all the other ones?" Devine says.
Ninety-seven percent of genomes the team surveyed had at least one rare insertion of the L1 variety of transposon that was present in only a single human in the study, and some genomes had several. Since the study surveyed 76 genomes, "rare" insertions could still be shared by large groups consisting of thousands of people. Rare insertions corresponded to the most recent transposons, which are less likely to have their jumping abilities impaired by other types of mutations.
Devine's team also showed that transposons frequently jump to new locations during the process of tumor formation. Surveying 20 lung tumors and comparing their genomes against the normal tissues they came from, the team found that six tumors had new transposon insertions that were not present in the normal adjacent tissues.
"This indicates that transposons are jumping in tumors and are generating a new kind of genomic instability," Devine says.
Transposons can inactivate tumor suppressor genes and can facilitate rearrangements that involve large stretches of chromosomes. Geneticists have already identified many transposons that interrupt genes and cause human diseases, including neurofibromatosis, hemophilia and breast cancer.
Scientists believe a process called methylation, which silences genes during differentiationalso shuts off transposons' ability to jump. Analyzing the patterns of mutations in the lung tumors suggested that during tumor formation, modified methylation patterns may be allowing transposons to re-awaken, Devine says.
Several scientists from the Biomolecular Computing core facility and the Winship Cancer Institute of Emory University were involved in the research.
The research was supported by grants from the National Human Genome Research Institute, the American Cancer Society and Sun Microsystems.Reference:
Writer: Quinn Eastman
The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service. Its components include the Emory University School of Medicine, Nell Hodgson Woodruff School of Nursing, and Rollins School of Public Health; Yerkes National Primate Research Center; Winship Cancer Institute of Emory University; and Emory Healthcare, the largest, most comprehensive health system in Georgia. Emory Healthcare includes: The Emory Clinic, Emory-Children's Center, Emory University Hospital, Emory University Hospital Midtown, Wesley Woods Center, and Emory University Orthopaedics & Spine Hospital. The Woodruff Health Sciences Center has a $2.5 billion budget, 17,600 employees, 2,500 full-time and 1,500 affiliated faculty, 4,700 students and trainees, and a $5.7 billion economic impact on metro Atlanta.
Learn more about Emory's health sciences: http://emoryhealthblog.com - @emoryhealthsci (Twitter) - http://emoryhealthsciences.org
Vince Dollard | EurekAlert!
Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München
Second research flight into zero gravity
21.10.2016 | Universität Zürich
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences