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 Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>