Hypomyelination in Weimaraners leads to tremors during puppyhood that often resolve by 3-4 months of age.
Phenotype: Hypomyelination leads to tremors during puppyhood. Affected puppies have tremors when awake as early as 2 weeks of age. Clinical signs resolve in most cases by 3-4 months of age, though some of the dogs may have a mild persistent tremor of the hind legs.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, HYM = Hypomyelination
Breeds appropriate for testing: Weimaraner
Explanation of Results:
Dogs with N/N genotype will not have hypomyelination and cannot transmit this variant to their offspring.
Dogs with N/HYM genotype will not be affected by hypomyelination, but are carriers. They will transmit this variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% hypomyelination-affected puppies.
Dogs with HYM/HYM genotype will have hypomyelination and will transmit this variant to all of their offspring.
Researchers from the University of Wisconsin, Madison, lead by Dr. Ian Duncan, in collaboration with researchers from Dr. Patel’s Laboratory at University of Southern California and Dr. Bannasch’s Laboratory at University of California, Davis have identified the genetic basis for hypomyelination (HYM) in the Weimaraner. This condition leads to tremors during puppyhood. The disease is inherited as a simple autosomal recessive disorder and the carrier frequency has been estimated to be 4.29% within the breed. Hypomyelination is also called "tremors" and "shaking puppies" by dog breeders based on the fact that affected puppies have tremors when awake as early as 2 weeks of age. Clinical signs resolve in most cases by 3-4 months of age. Some of the dogs may have a mild persistent tremor of the hind legs.
Testing for hypomyelination assists owners and breeders in identifying affected and carrier dogs. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.
Dogs that have only one mutant copy of HYM (N/HYM genotype) are normal but they are carriers of the disease. When two carriers are bred to each other the resulting puppies can be affected. At the time that this test was released, approximately 4.3% of Weimaraners were carriers of HYM; however, the number of carriers can change with each generation. Dogs that are carriers of HYM are completely normal and they can be safely bred to dogs that are non-carriers of HYM (N/N) in order to maintain diversity within the breed and to select for other positive attributes in carrier dogs.