Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Double-teaming a whole-genome hunt

13.07.2010
Scientists combine new and classic approaches to discover rare disease gene

By inspecting the sequence of all 3 billion "letters" that make up the genome of a single person affected with a rare, inherited disorder, a Johns Hopkins and Duke University team ferreted out the single genetic mutation that accounts for the disease.

Reporting their results in the June 17 issue of PLoS Genetics, the team says an altered version of the gene PTPN11 is the cause of metachondromatosis, a disorder characterized by bony growths, often on the hands and feet.

The study, the scientists say, demonstrates that new, whole-genome sequencing technology can efficiently and accurately lead investigators to the identification genes that cause Mendelian diseases — those caused by mutations in a single gene and passed on according to classic genetic patterns.

The traditional way of collaring a Mendelian disease-causing gene entails time-consuming and labor-intensive genetic analyses of numerous related individuals across generations. Known as "linkage," this approach depends on collecting families, especially large families with multiple affected members. This can be difficult and time consuming and often does not have sufficient resolution to identify the responsible gene. In fact, the definitive catalog of genes and disorders maintained at Johns Hopkins, Online Mendelian Inheritance in Man (OMIM), lists more than 1,500 disorders for which linkage studies have identified a large genomic region but have failed to pinpoint the responsible gene.

The failures were often due to the absence of enough related and affected individuals to provide linkage evidence of sufficient strength and resolution to identify the genes responsible for rare inherited diseases. Another weakness of linkage studies is that an affected individual may be so mildly affected that they are erroneously classified as unaffected, thereby skewing study results.

Success for metachondromatosis came when researchers combined a linkage study of 11 family members (five affected with metachondromatosis and six unaffected) with the whole-genome sequencing of one affected member. The linkage study identified likely regions of the genome where the suspect mutation could be found, considerably reducing the fraction of the genome that could contain the disease. Focusing on these regions, the team identified a mutation in PTPN11 that was sure to cause loss of function of the gene product.

"This whole-genome study, which took only two months, got us to a place where otherwise we wouldn't have arrived very quickly, if ever," says David Valle, M.D., Henry J. Knott Professor and director of the Institute of Genetic Medicine, Johns Hopkins University School of Medicine. "It's a great example of the power of a broad, agnostic approach."

By comparing the one whole genome of the affected individual with eight non-affected control genomes as well as to a database of single-letter variations known to occur in more than one percent of the population, and to other sequencing data, the researchers came up with a list of 100 possible candidate genes. These were analyzed in light of the linkage evidence which, although modest, allowed the team to narrow its search for variants to just a fraction of the genome and narrowed the list to half a dozen genes. Then they combed the literature to understand what was known of the biological function of these candidates, looking for any that might be involved in bone development.

Nara Sobreira, a graduate student in human genetics at Johns Hopkins and a lead author of the study, found that lots had been published about one of the six genes, PTPN11. Mutations in this gene made it hyperactive, causing Noonan syndrome, a genetic disorder that prevents normal development in various parts of the body, including the skeleton.

This newly discovered mutation or altered version involved a so-called "deletion" in which a piece of the genetic code is missing and likely to cause a loss of function of the gene, disabling its ability to manufacture normal protein, Sobreira explains. She said that gave credibility to the possibility that PTPN11 was responsible for metachondromatosis, which gives rise to different physical characteristics.

To confirm their suspicions, the team first checked to see if all affected members of the family in the linkage studies had the mutation and if all unaffected members didn't. The answer was yes.

The next and final assurance needed to prove that this gene was responsible for metachondromatosis was to find the same mutation of the same gene in an affected person unrelated to the family originally studied. The Hopkins team located a second family already seeking treatment at the Greenburg Center for Skeletal Dysplasias and confirmed that mutations, causing a loss of function of the PTPN11 gene, caused metachondromatosis.

"This discovery has given us clues about the molecular basis of other genetic diseases for which a cause remains unknown and that are not benign like this one," Sobreira says.

Johns Hopkins authors on the paper, in addition to Sobreira and Valle, are Dimitrios Avramopoulos, Elizabeth Wohler, Gretchen L. Oswald, Eric L. Stevens, Jonathan Pevsner, George Thomas and Julie E. Hoover-Fong. Authors from Duke University are Elizabeth T. Cirulli, Dongliang Ge, Kevin V. Shianna, Jason P. Smith, Jessica M. Maia, Curtis E. Gumbs and David B. Goldstein.

On the Web:

Valle lab:
http://www.hopkinsmedicine.org/geneticmedicine/People/Faculty/valle.html
PLoS Genetics:
http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000991

Maryalice Yakutchik | EurekAlert!
Further information:
http://www.jhmi.edu

More articles from Life Sciences:

nachricht More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>