New Epilepsy Gene Discovered in Dogs May Help Humans
Dogs are not only man’s best friend, they also suffer many of the same diseases as their human companions, and what we learn about a condition in one species often can help the other. Such may be the case with a new epilepsy gene discovered in dogs.
Epilepsy is common in some dog breeds
Epilepsy syndrome can be divided into genetic (idiopathic) epilepsies, structural/metabolic (symptomatic) epilepsies, and epilepsies of unknown cause. Idiopathic epilepsy occurs in up to 3% of dogs, according to the Dog Owner’s Home Veterinary Handbook, and is responsible for up to 80% of recurrent seizures.
The common thread among the three main types of epilepsy is recurring seizures, which can appear in various forms and are divided into two main types: focal and generalized. Focal (partial) seizures are electrical disturbances that occur in a limited area of the brain, while generalized seizures affect the entire brain.
Both dogs and people can experience either type of seizure, and both types can occur in Belgian Shepherds, the dog breed that was the focus of a recent study by Professor Hannes Lohi and his team from the University of Helsinki and the Folkhalsan Research Center. Their discovery of a chromosome region associated with the most common form of epilepsy in dogs is a major breakthrough.
Although previous research had uncovered several genes involved in the development of symptomatic epilepsies, the genetic foundation of idiopathic epilepsies was unknown. Lohi and his colleagues compared the genome of dogs with epilepsy and healthy controls and found a gene region in chromosome 37 which, if homozygous, increases the risk of developing epilepsy by sevenfold. (Homozygous means having identical DNA coding on a specific location on a chromosome for a single trait.)
The discovery is exciting because this is the first time epilepsy genes have been identified in this chromosome region, so this new find will reveal a new epilepsy gene in dogs and perhaps also in humans. “I believe that the ongoing analyses will help us to discover the specific epilepsy gene,” noted Lohi.
In addition, Lohi explained that their discovery will “give us a better understanding of the disease mechanisms and provide us with new diagnostic tools for the disease.” Continuing research into epilepsy is important for all dogs, and especially those that tend to inherit the condition, including Beagles, Dachshunds, Keeshonden German Shepherds, Belgian Shepherds, and others.
Eija Seppala, PhD, first author of the new research article, explained they are trying to “identify the specific mutation for genetic testing” at chromosome 37 and possibly other chromosomes. Seppala described the need for a gene test as “urgent” because up to 20% of Belgian Shepherds are believed to have epilepsy.
Epilepsy in dogs
Epileptic seizures in dogs usually occur in three phases: aura, grand mal seizures, and postseizure state. During the aura, dogs typically become restless, cry, demand affection, or try to be alone. The seizure itself usually causes the dog to collapse and the legs to become rigid. Dogs become unconscious, may stop breathing for 10 to 30 seconds, and may have jerking legs, chewing or drooling behavior, and loss of bladder and bowel control.
As the dog regains consciousness, he or she enters the postseizure stage, characterized by staring, stumbling while walking, and confusion, which may last several minutes or up to several hours.
Epilepsy is the most common nervous system disorder in dogs, and different types of genetic epilepsies are seen in dozens of dog breeds. According to the Dog Owner’s Home Veterinary Handbook, it’s important to identify which dogs are carriers of genes for epilepsy before they are bred, as “no dog known to seizure from suspected epilepsy should be bred.”
Thus the discovery of a new gene for epilepsy in dogs is an important step in identifying which dogs have the seizure disorder, and it may also prove helpful in better understanding the more than 50 million people in the world who also have epilepsy.
Eldredge DM et al. Dog Owner’s Home Veterinary Handbook. Wiley, 2007
Seppala EH et al. Identification of a novel idiopathic epilepsy ocus in Belgian Shepherds. PLoS ONE 2012. DOI:10.1371/journal.pone.0033549
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