Gene discovery in truffle dogs sheds new light on mechanisms of childhood epilepsy

ScienceDaily (July 29, 2011) — A new epilepsy gene, LGI2, has been found in the Lagotto Romagnolo dogs, known from their gift for truffle hunting. The gene discovery made by Professor Hannes Lohi and his research group at the University of Helsinki and the Folkhälsan Rsearch Center offers a new candidate gene for human benign childhood epilepsies characterized by seizure remission.

The research is published in the online journal PLoS Genetics.

Epilepsy is the most common neurological disease in children. It occurs in 0.5 percent of all 2-10 year-old children -- during the ages when the development of the nerves in the brain is at its strongest. Childhood epilepsies are characterized by remission: the seizures set in and last for a while before they disappear completely. The mechanisms related to the remission have remained unknown. The new gene discovery made by the research group of Professor Lohi and colleagues in the Lagotto Romagnolo breed gives us new perspectives into the development of a child's brain and the remission mechanisms in childhood epilepsies. In addition, the identified gene has enabled the development of a DNA test for the Lagotto Romagnolo breed.

"This gene discovery is significant for both dogs and humans. Every third Lagotto Romagnolo carries the gene mutation in its genome and we have now developed a gene test to be used by breeders to eliminate the disease from the breed. Furthermore, the gene has not previously been linked to human epilepsies, which makes it a new candidate gene for especially childhood epilepsies," explains Hannes Lohi.

An epileptic seizure is caused by an electronic disturbance in brain function. Epilepsies form a heterogeneous group of syndromes of the nervous system in which the causes, the age of onset and the treatment vary significantly. Epilepsy is most common in the ends of the age spectrum -- childhood and old age.

"With this study we gain crucial insight into the pathways and mechanisms that control the development of a child's brain, optimizing its structure for electrical stability and seizure-freedom in the rest of adult life. This study will open vast avenues of research in uncovering the molecular bases of the transformation of the brain from its immature state in infancy to its maximal abilities in adolescence and early adulthood," says Dr. Berge Minassian, senior co-author of the study and a senior scientist and pediatric epileptologist at The Hospital for Sick Children in Toronto, Canada.

Epilepsy is the most common disease of the nervous system in dogs, and different types of hereditary epilepsy exist in many breeds. Lohi has previously identified the first canine epilepsy gene, EPM2B, in the Miniature Dachshund. The newly identified mutation in the LGI2 gene is the first idiopathic epilepsy gene in dogs.

Previous clinical studies have demonstrated the focal remitting epilepsy in Lagotto Romagnolo puppies. Seizures causing tremor, trembling, shaking and wheezing set in at around four weeks of age and last for one to two months before a complete cease. The seizure frequency varies significantly even within the same litter and severity can vary from very mild to attacks of unconsciousness. The mildest seizures may even go unnoticed. Between seizures some dogs may experience ataxic episodes with difficulties in movement coordination and motor function. Lagotto's epilepsy resembles human benign childhood epilepsies with remission.

"We tested the mutation in about 40 different breeds and in dogs with a very early age of onset of epilepsy, but it was present only in Lagottos. On the other hand, the study revealed another form of epilepsy in the breed, unconnected with this mutation and with an age of onset in adulthood. In addition, the breed has a progressive juvenile ataxia (lack of motor coordination) with similar onset and symptoms to juvenile epilepsy except that it does not remit -- ataxic puppies have to be euthanized usually by the first year of life. More samples are needed for both adult-onset epilepsy and ataxia to enable us to investigate their genetics further," says a primary author of the study, Eija Seppälä, PhD.

Together with his research group Lohi has built a large canine DNA bank in Finland with over 35 000 samples from 250 breeds. The DNA bank has played an important role in the present and ongoing studies.

"We also study the epilepsies in other breeds, and several new epilepsy loci have been discovered recently. I believe that there will be more similar success stories such as the case of the truffle dogs in future. Canine epilepsies are natural, spontaneous and resemble human epilepsies, offering us a great opportunity to advance the epilepsy research for the benefit of both humans and dogs," Lohi asserts.

Lohi's research group operates in two campuses at the Faculties of Veterinary Medicine and Medicine at the University of Helsinki and also at the Folkhälsan Research Center. His research is funded by several sources including the Academy of Finland, the European Union, the Sigfrid Jusélius Foundation, the Finnish Cultural Foundation, the Jane and Aatos Erkko Foundation, Biocentrum Helsinki, University of Helsinki Research Funds and Folkhälsan.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Helsingin yliopisto (University of Helsinki), via AlphaGalileo.

Journal Reference:

Eija H. Seppälä, Tarja S. Jokinen, Masaki Fukata, Yuko Fukata, Matthew T. Webster, Elinor K. Karlsson, Sami K. Kilpinen, Frank Steffen, Elisabeth Dietschi, Tosso Leeb, Ranja Eklund, Xiaochu Zhao, Jennifer J. Rilstone, Kerstin Lindblad-Toh, Berge A. Minassian, Hannes Lohi. LGI2 Truncation Causes a Remitting Focal Epilepsy in Dogs. PLoS Genetics, 2011; 7 (7): e1002194 DOI: 10.1371/journal.pgen.1002194

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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Bioengineers identify the cellular mechanisms of traumatic brain injury; New hope for treatment of TBI in veterans wounded by explosions

ScienceDaily (July 25, 2011) — Bioengineers at Harvard have identified, for the very first time, the mechanism for diffuse axonal injury and explained why cerebral vasospasm is more common in blast-induced brain injuries than in brain injuries typically suffered by civilians.

The research addresses two major aspects of traumatic brain injury (TBI), with significant implications for the medical treatment of soldiers wounded by explosions.

Two papers, published in the journals Proceedings of the National Academy of Sciences (PNAS) and PLoS ONE, provide the most comprehensive explanation to date of how mechanical forces can be translated into subtly disastrous physiological changes within the brain's neurons and vasculature.

"These results have been a long time coming," says principal investigator Kevin Kit Parker, a Professor of Bioengineering at Harvard's School of Engineering and Applied Sciences (SEAS) and a major in the U.S. Army. "So many young men and women are returning from military service with brain injuries, and we just don't know how to help them."

When the brain encounters a jarring force, such as an exploding roadside bomb, the delicate tissue slams against the skull. The result, if the patient survives, can be a temporary concussion, a more dangerous hemorrhage, or long-term TBI, which can even lead to the early onset of Parkinson's or Alzheimer's diseases.

Inspired by Parker's own military experience, the Disease Biophysics Group (based at SEAS and at the Wyss Institute for Biologically Inspired Engineering at Harvard) has taken up the cause. Using cutting-edge tissue engineering techniques -- essentially creating a living brain on a chip -- biologists, physicists, engineers, and materials scientists collaborate to study brain injury and potential targets for treatment.

Now, researchers in his group have identified the cellular mechanism that initiates diffuse axonal injury, offering urgently needed direction for research in therapeutic treatments.

Their studies show that integrins, receptor proteins embedded in the cell membrane, provide the crucial link between external forces and internal physiological changes.

Integrins connect the structural components within the cell (such as actin and other cytoskeletal proteins) with the extracellular matrix that binds cells together into tissue. Collectively, this network of structural and signaling components is referred to as the focal adhesion complex.

Parker's research has demonstrated that the forces unleashed by an explosion physically disrupt the structure of the focal adhesion complex, setting off a chain reaction of destructive molecular signals within the nerve cells of the brain.

Inside the neuron, integrins normally mediate the activation of the proteins RhoA and Rho kinase (ROCK). When the focal adhesion complex is disturbed, the Rho-ROCK signaling pathway goes haywire: it directs the motor protein actin to retract the cell's arm-like axons, disconnecting the neurons from each other and collapsing the cellular networks that constitute the brain.

"Our research has shown that abrupt mechanical forces, such as those from a blast wave and transduced by integrins, can result in neural injury," says Matthew A. Hemphill, who with Borna Dabiri (S.B. '07) and Sylvain Gabriele, is a lead author of the paper in PLoS One. Dabiri and Hemphill are currently graduate students at SEAS, and Gabriele is a former postdoctoral fellow in Parker's lab.

Adds Dabiri: "Encouragingly, we also found that treating the neural tissue with HA-1077, which is a ROCK inhibitor, within the first 10 minutes of injury, reduced the number of focal swellings. We think that further study of ROCK inhibition could lead to viable treatments within the near future."

A second direction of research in Parker's lab has solved another mystery in TBI, explaining why cerebral vasospasm, a dangerous remodeling of the brain's blood vessels, occurs more commonly in TBI caused by explosions than in other types of brain trauma.

"Until now, other researchers looking at TBI focused on ion channels and membrane poration, and it was generally accepted that cerebralvasospasm was only caused by hemorrhaging. It turns out that it's much morecomplicated than that," says Patrick W. Alford, a former postdoctoral fellow in Parker's lab and lead author of the paper in PNAS. "Integrins and Rho-ROCK signaling appear to be players in both diffuse axonal injury and cerebral vasospasm."

As reported in PNAS, the forces exerted on arteries are different during an explosive blast than during blunt force trauma. Subarachnoid hemorrhage, which can occur in very severe head injuries, is known to cause vasospasm, but Parker's new research shows that the unique force of an explosion can also cause vasospasm by itself.

The blast from an explosion creates a surge in blood pressure, which stretches the walls of the blood vessels in the brain. To study this, Parker's team of bioengineers built artificial arteries, made of living vascular cells, and used a specialized machine to rapidly stretch them, simulating an explosion. While this stretching did not overtly damage the cellular structure, it did cause an immediate hypersensitivity to the protein endothelin-1.

Endothelin-1 is known to stimulate vascular cells to absorb calcium ions, which affect actin -- the same protein involved in the retraction of axons.

In the 24 hours following the simulated blast, the vascular tissues hypercontract and undergo a complete phenotypic switch, disrupting the overall function of the tissue. Both of these behaviors are characteristic of cerebral vasospasm.

Most importantly, as in the neural tissue, the Rho-ROCK signaling pathway plays an important role in the behavior of actin and the cells' contraction. Parker's team found that inhibition of Rho soon after the injury can mitigate the harmful effects of the blast on the brain's vascular system.

"We have established a toe-hold as we try to climb up on top of this problem," says Parker. "In many ways, this work is just the beginning."

Parker's coauthors on the paper in PLoS One are Hemphill, currently at the University of Mons in Belgium; Dabiri, who beganworking in Parker's lab as an undergraduate; Gabriele, who is now at the University of Mons; Lucas Kerscher, a visiting student; Christian Franck, formerly a postdoctoral fellow at SEAS and now at Brown University; Josue A. Goss, a staff engineer at SEAS; and Alford, who is now at the University ofMinnesota.

Parker's coauthors on the paper in PNAS are Alford; Dabiri; Goss; Hemphill; and Mark D. Brigham, a graduate student at SEAS.

The Disease Biophysics Group received financial support from the Defense Advanced Research Projects Agency (DARPA) Preventing Violent Explosive Neurologic Trauma (PREVENT) Program, the Department of Defense, and the Harvard School of Engineering and Applied Sciences (SEAS).

The researchers also gratefully acknowledge the use of facilities at the Harvard Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network (NNIN), which is funded by the National Science Foundation (NSF).

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Harvard University, via EurekAlert!, a service of AAAS.

Journal References:

P. W. Alford, B. E. Dabiri, J. A. Goss, M. A. Hemphill, M. D. Brigham, K. K. Parker. Blast-induced phenotypic switching in cerebral vasospasm. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1105860108Matthew A. Hemphill, Borna E. Dabiri, Sylvain Gabriele, Lucas Kerscher, Christian Franck, Josue A. Goss, Patrick W. Alford, Kevin Kit Parker. A Possible Role for Integrin Signaling in Diffuse Axonal Injury. PLoS ONE, 2011; 6 (7): e22899 DOI: 10.1371/journal.pone.0022899

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

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