EPILEPSY DNA RESEARCH QUESTIONS AND ANSWERS

Is epilepsy the same in all breeds? Probably not. There have been over 15 genes defined so far which cause epilepsy in humans and a similar number in mice, and it is likely that many additional epilepsy-causing genes will be found in the future. This same assortment of genes may be responsible for epilepsy in dogs. Within some breeds, all the dogs with epilepsy appear to follow the same basic pattern. In other breeds there may be several different patterns, or no discernable pattern at all. It is possible that each breed and each different pattern has a different genetic mutation. It is also possible that several breeds who all follow the same pattern may all have the same or very similar mutations. Research is only just beginning to search for these answers.

What are DNA researchers looking for? DNA researchers attempt to find the genes responsible for various traits, both detrimental and beneficial. Like the human genome and mouse genome project, the canine genome project is trying to determine how the genes are arranged on the various chromosomes and what they do. While good progress has been made mapping the human and mouse genome, the canine gene map until recently has been very rudimentary, which makes genetic research much slower and more challenging. The goals of DNA researchers working on canine epilepsy are: (1) to identify the gene or genes responsible for the various forms of canine epilepsy; (2) to characterize the responsible mutations within the epilepsy genes; and, (3) to devise and validate DNA marker assays that can detect the epilepsy-causing mutations. These DNA marker assays should enable breeders to produce epilepsy-free puppies.

Will a DNA test be valid for all dogs within a breed or only for a limited group within that breed? Each epilepsy-causing mutation stems from a particular mutation event that has occurred in a specific ancestor. If several mutation events are contributing to the epilepsy in a breed it will take several DNA tests to completely eliminate epilepsy from the breed. Nonetheless it is likely that one or a few mutations are responsible for most of the epilepsy in a particular breed so one or a few tests would go a long way toward eliminating epilepsy in these breeds.

Has an "epilepsy gene" been found in any other breed yet? How close are researchers to finding one? Although several research groups are looking for epilepsy genes in a variety of dog breeds, we are not aware of any successes as yet. Predicting how long it will take to find the mutation(s) and develop a test is like trying to predict how long it will take to catch a fish - some days you catch a fish on the first cast, other days you may fish all day to finally catch one, and still other days you go home sunburned and try again another day. Preliminary work does look encouraging, but more research needs to be done, and more families are needed for testing. We do believe that with time and access to informative families, markers will be identified in many breeds.

Suppose the genetic test shows my dog is a carrier. Does that mean the end of his/her breeding career? If epilepsy is a recessive trait or a polygenic (2 or more genes controlling) trait, then carriers can be bred to DNA-tested normal dogs without producing offspring that will develop clinical signs of epilepsy. However, such a breeding will produce some puppies who are clear, and some who are carriers. Therefore, it is critical that the offspring from such a breeding also be DNA tested before they are bred. The key is to know the genetic status of BOTH dogs involved in any breeding. Selection of a carrier in a breeding program should be done very carefully and the breeder ethically must share this information with the buyers of the puppies from that breeding.

I have an affected dog. Can one dog be helpful? YES! The best information for research comes from families - affected, littermates, parents, and grandparents - but single affected dogs are also useful. Participation in the research is confidential - the identity of dogs and owners participating will NOT be revealed. Information sheets and sample submission forms are available to download at www.canine-epilepsy.net, or you may email your request to HansenL@missouri.edu, or call 573-884-3712.

When the mutation(s) or marker(s) are defined for epilepsy in our breed, how much will it cost to have a dog tested for the defective gene? How old must a dog be to have this test performed? It depends on who finds the defective gene. If the gene is found at a research institution and the results go into the public domain, the test will probably cost about $35-$50 per dog. If a private organization finds the gene and patents the test, it will probably add an additional $50 to $100 to the cost of the test. The tests can be done on DNA from any age dog. Docked tails (in breeds where this is customary) are a good source of DNA if breeders keep careful track of which pup goes with which tail. Blood samples are difficult to draw from young puppies - your vet would probably recommend you wait until the pups are over 7 weeks of age.

The Canine Epilepsy Network web site was launched December 1999 to provide a resource for owners and breeders dealing with canine epilepsy. You may view the site at www.canine-epilepsy.net. If you have specific questions about the research, please ask!

Liz Hansen
Coordinator of Veterinary Information
Animal Molecular Genetics Lab - Dept. of Vet. Path.
321 Connaway Hall - College of Vet. Med.
University of Missouri
Columbia, MO 65211
573-884-3712 (office phone)
573-884-5414 (department fax)
HansenL@missouri.edu (email)