Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A subtle tool to study mankind’s diseases

25.03.2003


One of the most powerful tools in today’s biological and medical science is the ability to artificially remove and add bits of DNA to an organism’s genome. This has helped scientists to understand problems caused by defective genes, for example, which have now been linked to thousands of human diseases. So far the technology has been limited to small segments of DNA. But four years ago, Francis Stewart and his colleagues at the European Molecular Biology Laboratory (Heidelberg) developed a new technique to engineer greater stretches of DNA in bacteria. The researchers, now working at the Biotec-Technical University in Dresden, have just used this method to engineer a complex set of changes in a mouse gene, in hopes of shedding light on human leukemias. Their work appears in the current edition of the journal Nature Biotechnology.

Over two decades ago, researchers learned to use bacteria as "copy machines" for DNA taken from other organisms. This was a huge step for biotechnology, because most types of research require billions of copies of a molecule under investigation. However, there was a limitation: researchers need to change the DNA molecules in precise ways and for large molecules, such as whole genes, this was tremendously difficult.

Stewart and his colleagues thought that bacteria could be taught to do better, so they "borrowed" a strategy that organisms such as mice and yeast use to repair breaks in DNA. Proteins called recombinases circulate through their cells, looking for loose DNA fragments that have familiar sequences.



"Recombinases assume that the fragments have been cut out of the DNA by mistake, so they try to glue them back into the genome in the right place," says Giuseppe Testa, who headed the current study. "Sometimes they’re a bit over-industrious; they put in pieces that look right, such as variations of a gene that have been put into the cell by a researcher."

Called homologous recombination, this process works a bit like a "find-and-replace" command in your word processor. Imagine you have typed "Stephen Q. Gould" everywhere, and suddenly discover that the middle initial should be "J". The computer can be told to look for "Stephen" and "Gould" and replace what comes between them. In the same way, recombinases find recognizable sequences of DNA to the left and right of a target and replace what comes in between with the new sequence.

Homologous recombination was known to occur in bacteria, but it hadn’t been possible to use it to engineer DNA, as was the case in yeast and mouse stem cells. Stewart?s team decided to try to find a strain that could do it. "We ordered as many types of E. coli as we could, looking for defects in the way they repair their DNA," he says. "After five months of work, Youming Zhang, a postdoc in the lab, found the strain."

The group quickly identified the bacterial factors involved and turned them into a new tool called Red/ET recombination that is now being adopted by biologists all over the world. It’s one of the mainstays of Gene Bridges GmbH, a company that Stewart and his colleagues founded with EMBL to develop the commercial implications of the breakthrough.

"We have been pushing it to work with larger and larger bits of DNA," Testa says, "and our latest project has been to engineer an entire artificial chromosome in bacteria. We’ve constructed a large, complex ’cassette’ that we’ve now inserted into a mouse in place of its normal gene."

The gene that they chose is called mixed-lineage leukemia (Mll), and is known to become defective in childhood leukemias in humans. By inserting the artificial version into the mouse, researchers hope to understand how the defects lead to disease. "There are many things that can go wrong in this gene," Testa says, "and we wanted to construct a version of it that would allow us to test as many aspects of the problem as possible."

The artificial Mll that they have put into the mouse will permit a variety of experiments. It contains two defects in the genetic sequence that have been linked to leukemias. The cassette also contains control switches that allow each defect to be "switched on" whenever the researchers choose; they can also be left off. "We can study each mutation independently, or watch how they act together, or control the time at which each one acts," Testa says. "This will give us a new look at subtle relationships between multiple defects."

Many diseases are linked to single mutations; however, disease susceptibility also often relies on other sequence variations, known as polymorphisms, in the human population. "The Mll cassette shows, in principle, a simple way to study both a mutation and a related polymorphism in the gene of interest," Testa says. "This aspect of making mouse models will become increasingly more important for authentic modeling of human disease susceptibility and the way organisms respond to drugs and we think that our work shows the way to set up these models".

The new work also heralds a new era for genomic engineering in many living systems. "The Mll cassette is a first demonstration of what can be done with large DNA molecules," Stewart says. "Red/ET recombination increases the size of DNA that can be comfortably engineered by more than ten times and opens up new possibilities for genomic engineering that will filter into standard practice in the next few years."

Russ Hodge | EurekAlert!
Further information:
http://www.embl-heidelberg.de/

More articles from Life Sciences:

nachricht New switch decides between genome repair and death of cells
27.09.2016 | University of Cologne - Universität zu Köln

nachricht A blue stoplight to prevent runaway photosynthesis
27.09.2016 | National Institute for Basic Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

New imaging technique in Alzheimer’s disease - opens up possibilities for new drug development

28.09.2016 | Medical Engineering

Innovate coating extends the life of materials for industrial use

28.09.2016 | Materials Sciences

Blockchain Set to Transform the Financial Services Market

28.09.2016 | Business and Finance

VideoLinks
B2B-VideoLinks
More VideoLinks >>>