WJ Brad Hanna, DVM, PhD
Ontario Veterinary College
University of Guelph
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The following article appeared on
the University of Guelph website on May 14, 2007:

Researchers Find Cause of Muscle-Stiffness Disease

Imagine a dog running after a ball, only to stiffen up and fall over because of a genetic muscle cell disorder. It may sound almost comical, but this disorder, called Myotonia congenita, affects dogs, cats, horses, water buffalo, and even people.

Two University of Guelph professors have found the cause of the disease that temporarily prevents an animal’s muscles from relaxing after they contract. The research by Andrew Bendall and Brad Hanna is published today in the Journal of Veterinary Internal Medicine .

In humans, so far more than 80 mutations of the skeletal muscle chloride channel gene (called CLCN1) - which temporarily prevents muscles from relaxing after they contract - have been found. In animals, scientists have barely begun to scratch the surface of finding the causes of the muscle disease. Bendall and Hanna of the Department of Molecular and Cellular Biology have discovered the mutation associated with Myotonia congenital in Australian Cattle Dogs and in a Maltese-cross dog.

"There are probably eight breeds of dogs known to have Myotonia, but up until our study, the Miniature Schnauzer was the only breed for which a specific genetic mutation had been found," says Bendall.

Adds Hanna: "I think there’s a misunderstanding among some veterinary practitioners that once you find a mutation that causes the disease, that’s it. The human example shows us clearly that, no, in different families there may be different mutations."

That means that even though a blood test has been established to detect Myotonia in the Miniature Schnauzer, it’s unlikely that it will detect the disease in any other breed of dog. Because Bendall and Hanna found the mutation in the Australian Cattle Dog, they were able to develop a blood test to detect the disease in that breed which is now offered at the provincial diagnostic Animal Health Lab at U of G.

"We found that in the Australian Cattle Dog it’s a truncation mutation, so there’s actually a portion of the skeletal muscle chloride channel that’s missing," says Hanna. "Eighty-eight amino acids are missing at one end of the channel."

Bendall and Hanna’s research will not only benefit the owners of Australian Cattle Dogs, but "by identifying the kinds of mutations that affect the function of the protein, you can lean something about how the normal protein works," says Bendall.

The fact that Bendall and Hanna have successfully cloned the CLCN1 gene in the Australian Cattle Dog and found the mutation means that they are now able to find mutations in other breeds more quickly.

Since their success in Australian cattle dogs, they’ve also discovered the mutation in a Maltese-cross with a severe case of Myotonia. "We have found a missense mutation, which results in the substitution of one amino acid for another in the protein," says Hanna. "That amino acid has not been found to be mutated in this way in humans, so we’re in the process of doing the functional work to determine the significance of this change."

When veterinarians diagnose Myotonia in animals, since there’s no known treatment for the disease, they often don’t refer clients to Bendall and Hanna for testing.

"We would be interested in hearing from veterinarians who have identified animals of any breed or any species with a similar disorder,"says Hanna. "It’s possible, especially with purebred animals, for this type of disease to become widely disseminated, so by developing blood tests we can help breeders eliminate these disorders."



The following article appeared in
"Veterinary Practice News" 18(10):6, Oct 2006:

Myotonia Test Available for Australian Cattle Dogs

The Animal Health Laboratory at the Ontario Veterinary College, University of Guelph, now offers a diagnostic restriction fragment length polymorphism-based genetic test for whole blood that can identify myotonia congenita in Australian cattle dogs.

The test can detect the defective allele in those that are affected or a carrier.

All proceeds from the test will be used to help W.J. Brad Hanna, DVM, Ph.D., assistant professor in the Department of Biomedical Sciences, and colleagues continue research to identify other ion channel diseases of animals and to develop blood tests to detect them.

For more information visit www.ahl.uoguelph.ca.


The following article appeared in
the "Guelph Mercury", Apr 8, 2005, and "At Guelph", May 4, 2005:

Searching for a Calming Effect
Researchers tackle disease that causes muscle spasms in animals

BY ALYSSA CALDER
SPARK PROGRAM


Prof. Andrew Bendall, left, graduate student Dan Finnigan, centre, and Prof. Brad Hanna are studying a muscle cell disease that can cause animals such as their canine companion, Ally, to shake in place uncontrollably. Photo by Vince Filby

A disorder that causes muscular spasms in many animal species is under the microscope of Guelph researchers who want to find the genes behind the disorder and methods to test for them. Knowing its causes, they believe, will help eliminate the disease through selective breeding.

Prof. Brad Hanna and graduate student Dan Finnigan of the Department of Biomedical Studies and Prof. Andrew Bendall, Molecular and Cellular Biology, are looking at domesticated animals such as cats, dogs, horses and Brazilian water buffalo (a food animal in its native country) to shed more light on myotonia congenita, a genetic muscle cell disorder that temporarily prevents muscles from relaxing after they contract. During these episodes, which usually last less than a minute, the animal shakes or shivers in place, unable to move.

Although the condition may be disturbing to a pet owner, it doesn't seem to do any damage to the muscle, says Hanna, so it often goes undiagnosed. But the problem is more serious in large animals. Prolonged muscular rigidity causes the animals to fall over as they try to move, which increases the risk of injury to both the animals and the people working around them. And it's undesirable in animal athletes such as race horses.

“Imagine a race horse that is unable to move out of the starting gate or cattle that stiffen and collapse when they're herded,” says Hanna.

He and Finnigan are focusing on how myotonia congenita works at the cellular level. In healthy animals, passageways in muscle cell membranes called chloride ion channels act as conduits for electrical nerve signals, which enter muscle cells and tell them to contract or relax. But animals afflicted with myotonia congenita have defective channels, causing muscles to contract but not relax right away.

That's where Hanna comes in. He's studying the ion channel function in animal patients suspected of having myotonia congenita. Currently, Finnigan and Bendall are using molecular biology techniques to look for mutations in the chloride ion channel genes. If a mutation is found, the genes responsible for the mutation are incorporated into cell cultures.

From there, Hanna can measure electrical currents in these cells to see whether the chloride ion channels are functioning properly. If they aren't, that means he and his colleagues may have found the mutation that causes myotonia congenita, which is the first step toward stopping the disease.

Hanna and Finnigan hope their research will lead to the development of blood tests for myotonia congenita, so breeders of cats, dogs, horses and livestock can eliminate the disease from their animals through selective breeding. As an added benefit, the researchers can also learn more about the relationship between structure and function of chloride ion channels in normal muscle, which could be of use to other muscle research in the future, Hanna says.

Also involved in this work are Profs. Joane Parent, Roberto Poma and Henry Staempfli and graduate student Ronaldo da Costa, Biomedical Sciences. This research is funded by the Morris Animal Foundation.

 

The following article appeared in
"At Guelph", Aug 11, 1999:

 

Light at the End of the Channel


Scientists study malfunctioning ion channels to gain information useful to pharmaceutical companies, geneticists 

BY ANDREW VOWLES
U of G scientists are studing ion channel defects causing various human and animal diseases. Pictured with Smokey, an OVC research horse, are clockwise from left: Prof. Henry Staempfli, Prof. Saul Goldman, Prof. Brad Hanna, Prof. Chris Gray, Igor Tolokh, George White and Hank DeHann.
PHOTO BY DEAN PALMER/SCENARIO IMAGING
Glance at the computer monitor in Prof. Chris Gray's biophysics laboratory and you might be hard-pressed to see the connection to studies of heart diseases in a Toronto medical lab. But Gray and Prof. Saul Goldman, Chemistry and Biochemistry, hope to see their computer simulations help medical - and veterinary - researchers develop treatments for several diseases caused by ion channels gone awry. 

That colourful tableau on Gray's computer screen simulates the workings of tiny passages in cell membranes that serve as gatekeepers, passing ions such as sodium and potassium into and out of cells. By studying malfunctioning ion channels, they hope to gain information useful to pharmaceutical companies developing drugs for treating various diseases or to gene doctors aiming to correct the underlying hereditary defects. 

In cystic fibrosis patients, for example, defective chloride channels interfere with the transport of water across cell membranes, causing the lungs to become clogged with mucous. And heart disease is connected with malfunctioning sodium and potassium ion channels. "Drug companies are interested in developing drugs to fix the problem," says Goldman. 

Peter Backx, a Guelph graduate in biophysics and veterinary medicine who is now a faculty member at the University of Toronto, says his research group wants to learn more about the role of malfunctioning potassium channels in heart disease. He hopes to help pharmaceutical companies develop selective drugs, especially compounds to treat heart arrythmia. About 40 per cent of all heart disease patients who die suddenly are believed to suffer from abnormal heart rhythms. 

Backx, a former student of Goldman's, says the Guelph computer model is currently the only way to simulate the workings of ion channel proteins and the effects of altering their structure and function. Noting that he recently received funding from the Medical Research Council for his research program, Backx says: "It's early, but I think this has incredible promise. We believe we're the first ones to try to combine experimental approaches with the theoretical approach developed by Guelph." 

Over the long term, learning more about the genetic underpinnings of ion channel diseases such as cystic fibrosis might allow scientists to repair the rogue DNA itself, says Gray. "Perhaps you could put a vector into the lung with DNA to generate properly functioning ion channels. You could go in and fix the genes responsible for constructing these bad channels." 

He and Goldman have spent four years studying how one type of ion channel permits the passage of potassium ions. The pair relies on theoretical physics and chemistry and the use of computer simulations to model the flow of ions through channels and to study the microscopic workings of ion channel proteins. Also involved in their work are research associate Igor Tolokh and graduate students Hank DeHann and George White. 

The researchers expect to benefit from a group grant approved last month by the Medical Research Council for the U of T-based Membrane Biology Group, to which they belong as co-investigators. 

Brad Hanna, another OVC and biophysics graduate who worked with Backx in Toronto, says that kind of basic research is central not just to studies of human disease but also to certain veterinary disorders. He points to his work with Prof. Henry Staempfli, Clinical Studies, on a particular genetic disease that results in defective sodium channels in the skeletal muscles of horses. 

Called hyperkalemic periodic paralysis (HPP), the rare condition causes muscular weakness that can lead to collapse, paralysis or even death. Paradoxically, it increases muscle mass in quarter horses, the very trait that makes them prize candidates for the show ring (the disease is also called Impressive Syndrome after an award-winning stallion whose descendants have also been afflicted with it). HPP also occurs in humans. 

"In selecting for the most muscular quarter horses, breeders were unwittingly selecting for the sodium channel mutation causing HPP," says Hanna, who first pinpointed the cause of the disease in a paper written three years ago while completing his PhD with Prof. George Renninger, Physics. 

A chance meeting had brought together the graduate student's expertise in studying sodium channels with Staempfli's puzzlement over abnormal electrical activity in the skeletal muscles of quarter horses. Hanna suggested that sodium channels were failing to inactivate properly, which was subsequently proven by his and Backx's research. "I'll never forget, three o'clock in the morning, looking at the oscilloscope and thinking: 'This is the first time anyone has ever seen evidence for a sodium channel disease.'" 

When Hanna began his doctorate, only one ion channel disease - a disorder in a calcium channel in people and pigs - had been found. Since then, scientists have uncovered dozens of human ion channel mutations that underlie diseases in heart, brain, muscle and other tissues. 

"Interest in ion channel diseases has exploded over the last decade," says Hanna, who spent a year in private practice but has recently returned to Guelph hoping to study possible links between sodium channel defects and "tying-up," the most common form of muscle disorder found in horses.

The following article appeared in
the "Guelph Mercury", Jan 9, 1997:

Periodic paralysis -- a mystery no more
by Corina Brdar

The mystery of a potentially fatal equine disease has been solved by researchers at the University of Guelph. 

Dr. Brad Hanna, Biophysics, and his colleagues have discovered the exact cause of hyperkalemic periodic paralysis (HPP) or "Impressive Syndrome" (named after an award-winning Quarter Horse which first displayed signs of the disease). Hanna made the discovery while fulfilling his Ph.D. with the help of researchers in several departments, including OVC and physics.

"I got involved with this project because I wanted to combine the knowledge I've gained from previous degrees in biophysics and veterinary medicine by relating a clinical disease to its physical causes at the molecular level," Hanna explains. 

HPP is a genetic disorder which affects both humans and horses. Since first showing up in Impressive, it’s been passed through his lineage to thousands of other horses. Impressive and his descendants are prized for their excellent musculature...but ironically, that's a signature of the disease. 

HPP is a problem because the skeletal muscles of afflicted horses often stiffen or relax involuntarily. The nerve cells of an HPP horse send a signal to the muscle cell telling it to contract... but the cell tries to contract many times.

According to Hanna, HPP foils the mechanism by which a normal muscle cell keeps messages from repeating themselves. This can cause muscle stiffness, sudden paralysis, weakness, collapse and even death in horses. 

Hanna thought the problem might be related to sodium channels. All muscle cells have sodium channels in their membranes which let sodium in and out of the cell. When an electrical signal arrives at the muscle cell from a nerve, the change in voltage opens the sodium channel, and sodium flows into the cell. This is part of the chain of events which cause the muscle cell to contract. In normal cells, the channel immediately shuts. Hanna wanted to find out what was happening in the sodium channels of horses with HPP. 

Using cell cultures and recombinant DNA, he found that in cells with this genetic defect, the sodium channel's ability to shut itself off is impaired. Since it doesn’t shut immediately like a normal channel, it results in the production of many electrical signals when there should be only one. Hanna worked closely with Dr. P.H. Backx of the Toronto General Hospital, another graduate of biophysics and veterinary medicine at Guelph. 

Hanna also used cell cultures to determine if drugs like anaesthetics and anti-epilepsy medications could make the sodium channels work normally and prevent the symptoms of the disease. So far, it seems that these drugs are able to restore the functioning of the channels almost to normal. 

"Horse owners currently depend on indirect methods to treat HPP," says Hanna. "Now that we know the exact cause of the problem, we hope that people may be able to treat the disease more directly." 

Hanna had the financial, laboratory, and intellectual support of several researchers: Profs. George Renninger of Biophysics, Henry Staempfli of Clinical Studies and Jill McCutcheon of OVC. 

This research was sponsored by the Medical Research Council, the Natural Sciences and Engineering Research Council, Dynasty Equine Trust, and the Muscular Dystrophy Association of Canada.

 

 

Last updated May 14, 2007