Clinical and Genetic Advances - Canine Epilepsy
by George J. Brewer, MD
University of Michigan Medical School
Inherited canine epilepsy is a major health problem in many breeds
because of its high frequency and it potentially serious effects on pet ownership and
breeder reputation. A preliminary examination of published data indicate that over 20
breeds have a serious health problem with canine epilepsy.
In the AKC Molecular Genetics Conference that preceded this
conference, experts discussed canine epilepsy form the standpoint of separating a
diagnosis, separating inherited from non-inherited epilepsy, and the sub-types of
epilepsies that may indicate different genetic types: One talk was from the perspective of
a breeder/breed club (Standard Poodle) and what they are doing about the problem in their
breed. The pertinent information from this session will be summarized.
There is likely to be a large amount of genetic heterogeneity in
canine epilepsy. By that, it is meant that several different genes are involved. The
strongest reason for believing that is the demonstration, by crude mapping techniques, of
seven different regions of human chromosomes that contain epilepsy genes. Genetic
heterogeneity is not to be confused with polygenic inheritance, in which more than one
genetic defect contributes to the presence of the disease in a single patient or animal.
In epilepsy, in any one patient, or animal, the disease is likely to be due to a defect in
a single gene. But in the next patient, or animal, the epilepsy may be due to a defect in
an entirely different gene.
The fact that each breed is a genetic isolate gives the dog world a
great advantage over the human world, where the adonexture in the population mixes up all
the genetic types, making it difficult to map and isolate the gene. It is expected that
the cause of epilepsy in any particular breed will be due to a single genetic defect. This
provides@great advantages because pedigrees collected within a breed will be pure for a
single gene causation of epilepsy. This concept is no longer theory. It is borne out by
VetGen's extensive experience with canine von Willebrand's disease (VWD), which is also,
genetically heterogenous. We find that within a breed VWD is due to precisely the same
mutation. Using pure canine pedigrees the epilepsy gene in any breed can be mapped as the
dog map unfolds, and the gene identified and cloned. Developing a DNA test to allow breed-
ers to reduce the disease gene frequency then becomes a simple,.task. In turn, such newly
identified canine epilepsy disease genes become candidates for being one of the
undiscovered human epilepsy genes. In this way, purebred dogs can power not only canine
gene discovery, but human gene discovery.
In this session we will hear from experts on canine epilepsy who
will help us understand the problems of diagnosis, better understand how inherited and
non-inherited epilepsies can be separated, and who will tell us what is known about the
sub-types of canine epilepsies that may guide us in beginning to identify different
genetic types. We will also hear about the disease from a breeder's perspective, and what
one group of determined people, and a committed breed club, are doing about the problem in
their breed.
In summary, there is reason to be optimistic that within the next
five years, DNA tests will be available for the inherited epilepsies in many breeds.
Biographical Profile
George Brewer, M.D. earned his Bachelors Degree with highest honors
from Purdue University and his M.D. with honors from the University of Chicago, where he
also pursued his postdoctoral research studies. His study, of genetics was continued with
an NIH research fellowship at the University of Michigan, Department of Human Genetics. He
currently serves on the Editorial Advisory Board of Biochemical 'Genetics, is Associate
Editor of the American Journal of Hematology, and Editor of Progress in Clinical and
Biological Research. He is currently the Chairman, of the Interdepartmental Genetics
Training Program at the University of Michigan and adjunct Professor of Veterinary
Medicine, Small Animal Clinic Science Department at Michigan State, and is one of the
founders of VetGen, the company, offering vWD DNA testing. Dr. Brewer is also a devoted
owner of Labrador Retrievers.
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