Genomic medicine: gone to the dogs?

Genomic medicine: gone to the dogs?

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By: Jennifer Rilstone

Paula Ballak travelled to France in 2010 to pick up the puppy of her dreams—a black-and-white, wavy-haired Barbet (French water dog) named Rocket. Like other Barbet breeders, Ballak is dedicated to reviving this rare, historical, working breed—persecuted in WWII as the national dog of France—which is no small feat considering its limited numbers and genetic diversity. Rocket represented a distinct genetic line to breed with her own dogs, and in the first year, he excelled as a retriever. However, just after his first birthday, Rocket began to have seizures. The seizure disorder progressed quickly, affecting his behaviour and quality of life, and was determined to probably have a genetic cause. Recently—at just over the age of 2—Rocket had to be put down after having no response to antiepileptic medications.

Canine epilepsy is not rare, occurring in as many as 1 –5% of purebred dogs (compared with 1% of the general human population), and up to 20% of some breeds. Considered a side effect of selective breeding, the insidious condition occurs in multiple forms and with multiple genetic causes. The insight of veterinary neurologists has shown that these many varieties of canine epilepsy are remarkably similar to the many forms of human epilepsy. Beyond epilepsy, dogs and humans are physiologically similar and many canine diseases mimic human conditions. Researchers, therefore, have begun to study canine genetic diseases with two hopes—improving the health of purebred dogs, and gaining insights about related diseases that afflict humans.

The study of canine epilepsy to aid human health has a proud history in Toronto. Drs. Hannes Lohi and Berge Minassian at the Hospital for Sick Children discovered the first canine epilepsy gene in 2005. Mutations in this gene caused myoclonic epilepsy in the miniature wire-haired dachshund (MWHD) breed (1). Mutations in the same gene were concurrently discovered to cause Lafora progressive myoclonic epilepsy in children. While research into the human disease continues, breeders of the MWHD dogs are now able to identify carriers of the epilepsy mutation by genetic testing. As a result of this testing and responsible breeding practices, the incidence of epilepsy has decreased and the health of the breed has improved. Dr. Lohi has since moved on to establish a canine genetic research laboratory at the University of Helsinki, where more canine disease genes have since been identified—including the gene causing epilepsy in the Barbet’s close relative, Lagotto Romagnolo (Italian water dog) (2). Ballak hopes that Rocket’s DNA will lead to similar success for the imperiled Barbet breed.

Amid growing controversy about the declining health of purebred dogs, Lohi hopes to harness advancing genomic technologies to address health concerns and genetic diversity in all breeds. With a worldwide network of collaborating scientists, breed clubs who are passionate about the health of their dogs, and tireless veterinarians (including Dr. Fiona James, the veterinary neurologist at Ontario Veterinary College who cared for Rocket), Lohi collects health records and generates genetic data for vast pedigrees of purebred dogs. The age of genomic medicine has come not only to people, but also to the veterinary clinic. And with the promise of new insights into our own health that can be gleaned by studying canine diseases, we are again indebted to man’s best friend.

References:

1. Lohi H, Young EJ, Fitzmaurice SN, et al. Expanded Repeat in Canine Epilepsy. Science 2005;307(5706):81.
2. Seppälä EH, Jokinen TS, Fukata M, et al. LGI2 truncation causes a remitting focal epilepsy in dogs. PLoS Genet 2011;7(7):e1002194.