Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Engineered flies spill secret of seizures

12.10.2012
Scientists have observed the neurological mechanism behind temperature-dependent — febrile — seizures by genetically engineering fruit flies to harbor a mutation analogous to one that causes epileptic seizures in people. In addition to contributing the insight on epilepsy, their new study also highlights the first use of genetic engineering to swap a human genetic disease mutation into a directly analogous gene in a fly.

In a newly reported set of experiments that show the value of a particularly precise but difficult genetic engineering technique, researchers at Brown University and the University of California–Irvine have created a Drosophila fruit fly model of epilepsy to discern the mechanism by which temperature-dependent seizures happen.

The researchers used a technique called homologous recombination — a more precise and sophisticated technique than transgenic gene engineering — to give flies a disease-causing mutation that is a direct analogue of the mutation that leads to febrile epileptic seizures in humans. They observed the temperature-dependent seizures in whole flies and also observed the process in their brains. What they discovered is that the mutation leads to a breakdown in the ability of certain cells that normally inhibit brain overactivity to properly regulate their electrochemical behavior.

In addition to providing insight into the neurology of febrile seizures, said Robert Reenan, professor of biology at Brown and a co-corresponding author of the paper in the Journal of Neuroscience, the study establishes

“This is the first time anyone has introduced a human disease-causing mutation overtly into the same gene that flies possess,” Reenan said.

Engineering seizures

Homologous recombination (HR) starts with the transgenic technique of harnessing a transposable element (jumping gene) to insert a specially mutated gene just anywhere into the fly’s DNA, but then goes beyond that to ultimately place the mutated gene into exactly the same position as the natural gene on the X chromosome. HR does this by outfitting the gene to be handled by the cell’s own DNA repair mechanisms, essentially tricking the cell into putting the mutant copy into exactly the right place. Reenan’s success with the technique allowed him to win a special grant from the National Institutes of Health last year.

The new paper is a result of that grant and Reenan’s collaboration with neurobiologist Diane O’Dowd at UC–Irvine. Reenan and undergraduate Jeff Gilligan used HR to insert a mutated version of the para gene in fruit flies that is a direct parallel of the mutation in the human gene SCN1A that causes febrile seizures in people.

When the researchers placed flies in tubes and bathed the tubes in 104-degree F water, the mutant fruit flies had seizures after 20 seconds in which their legs would begin twitching followed by wing flapping, abdominal curling, and an inability to remain standing. After that, they remained motionless for as long as half an hour before recovering. Unaltered flies, meanwhile, exhibited no temperature-dependent seizures.

The researchers also found that seizure susceptibility was dose-dependent. Female flies with mutant strains of both copies of the para gene (females have two copies of the X chromosome) were the most susceptible to seizures. Those in whom only one copy of the gene was a mutant were less likely than those with two to seize, but more likely than the controls.

While the researchers at Brown compared the seizure susceptibility of whole flies, O’Dowd, lead author Lei Sun, and colleagues at Irvine studied individual fly neurons implicated in seizure activity to see how they behaved as the brains were heated. What their measurements revealed in the mutant flies were flaws in how “GABAergic” neurons take in sodium through channels in the cell membrane. Under normal circumstances, the neurons inhibit brain overactivity. But the mutants’ mishandling of sodium led them to fail electrically.

“When [O’Dowd’s team] isolates those currents due to the sodium channel, which is what’s mutated in this case, and she compares the normal animals to the disease-model animals, what happens is the mutant channels pass too much current,” Reenan said. “The channels open too easily and they take more effort to close. They open too soon and they close too late. That effect is magnified at higher temperature. Then the neuron can’t send any [inhibitory] signals.”

Searching for therapies

With a useful genetic model of epilepsy in fruit flies, Reenan said he is optimistic that researchers can now look for potential treatments for the disease. The next step, he said, is to use the practice of “forward genetics” to look for further mutations that might counter febrile seizures.

Given thousands of flies with model of the disease, scientists can purposely subject them to different DNA-altering conditions and then look to see if any flies lose their propensity for seizures. Among those that do, the researchers can then identify the specific genetic alteration responsible and determine whether that could ever be clinically applied. For example, if it turns out that a mutation proves therapeutic because it causes a certain protein to be overexpressed, then perhaps that protein could be refined into some kind of biologic pharmaceutical.

Reenan said he’d expect to see researchers follow a similar roadmap for other diseases as well.

“Knock-in of specific disease-causing mutations into the fly genome has the potential to provide a rapid and low-cost platform for studying the cellular mechanisms of heritable human diseases,” the authors wrote. “In addition, knock-in flies can be used in combination with forward genetic screens to identify suppressor and/or enhancer mutations, a strategy that is challenging in humans and rodent models but well established in Drosophila.”

In addition to Reenan, Gilligan, O’Dowd and Sun, other authors are Cynthia Staber of Brown and Ryan Schutte and Vivian Nguyen of UC Irvine.

In addition to the National Institutes of Health, the Howard Hughes Medical Institue and the Ellison Medical Foundation funded the research.

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

David Orenstein | EurekAlert!
Further information:
http://www.brown.edu

More articles from Life Sciences:

nachricht Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel

nachricht The Nagoya Protocol Creates Disadvantages for Many Countries when Applied to Microorganisms
05.12.2016 | Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

Construction of practical quantum computers radically simplified

05.12.2016 | Information Technology

NASA's AIM observes early noctilucent ice clouds over Antarctica

05.12.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>