John C. Fyfe, D.V.M, Ph.D. Associate Professor D.V.M., 1984, Washington-Oregon-Idaho Regional Program in Veterinary Medicine Ph.D., 1994, University of Pennsylvania Department of Microbiology and Molecular Genetics 5169 Biomedical Physical Sciences Michigan State University East Lansing, MI 48824 Email: fyfe@cvm.msu.edu Glycogen storage disease type IIIa (GSDIIIa) is an inherited metabolic disorder that causes liver and skeletal muscle disease due to deficiency of the glycogen debranching enzyme (GDE) and tissue storage of abnormally structured glycogen. This disorder was discovered in an extended family of curly coated retrievers (CCR), with representatives from USA, Canada, and New Zealand, and is due to a single based deletion in the GDE gene. This disease, too, is an autosomal recessive trait, and so the laboratory provides carrier testing for GSD IIIa in curly coated retrievers . CCR GSDIIIa Database An autosomal recessive trait means that the gene is located on of of the autosomes (Chromosome pairs) Males and females can be equally affected. Recessive means that two copies of the gene are necessary to have the trait, or in this case the disease. One inherited from the mother and one from the father. Both parents must be carriers in order for a pup to have the symptoms of the disease. A pup that inherits the gene from only one parent will be a carrier. This pup will have a recessive gene for GSDIIIa, and not show any health problems, but the pup will have to potential to pass the gene on to its offspring. A quick explanation is shown in the tables below. BB being a dog that does not have the disease and does not carry the recessive gene for GSDIIIa. Bb demonstrates a dog that does not have the disease, but does carry the recessive gene. bb represents a dog that is affected with the disease. Dogs that are carriers need not be eliminated from breeding. Carriers bred to clear, non carriers, will produce some carriers and some non-carriers. These offspring may then be tested and used as valuable animals in a breeding program. To illustrate this, we will use the following colors: Think in terms of a stop light. Green means go... a non carrier dog, you can breed. Orange means caution... a dog that is a carrier, can be bred, but only to non-carriers. Red means STOP! this is a dog with the disease. Even if it could be bred, all pups will be carriers. Clear dog, not carrying the GSD recessive trait BB Dog carrying the GSD recessive trait Bb Dog that has Glycogen storage disease bb

A non affected, not carrier dog (BB) A non affected, not carrier bitch (BB) B B B BB BB B BB BB produces all clear, not carrier offspring(BB) The offspring af a breeding like this would all be clear of GSD based on the absence of the GSD mutation in both parents. At this time, the resulting offspring need not be individually tested.

A non affected, not carrier dog (BB) A non affected carrier bitch (Bb). B B B BB BB b Bb Bb produces all non affected pups, two of which would carry the GSDIIIa gene as a recessive trait (Bb) No dogs would have the disease, but all offspring should be tested prior to breeding

A non affected carrier dog (Bb) A non affected carrier bitch(Bb) B b B BB Bb b Bb bb produces one non affected, non carrier (BB) one GSDIIIa affected pup(bb) and 2 pups that are carriers(Bb) There is the potential for pups that will have Glycogen storage disease, and some will be carriers. All dogs from this litter should be tested prior to breeding

A non affected carrier dog (BB) Bred to a GSDIIIa affected bitch (bb) B B b Bb Bb b Bb Bb produces all pups that are carriers of GSDIIIa(Bb) All pups are carriers, and should be only bred to non-carriers.

Male carrier of GSDIIIa (Bb) Bitch who is affected with GSDIIIa(bb) B b b Bb bb b Bb bb produces 2 Carriers (Bb) and 2 GSDIIIa affected pups (bb) Some of the pups will have Glycogen storage disease, and some will be carriers. Carriers can be bred to non-carriers

Affected dog (bb) bred to an affected bitch (bb) b b b bb bb b bb bb Produces all GSDIIIa affected pups (bb) pups These are just examples. I do not think anyone would breed two affected dogs.

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