Testing of dogs: Mucopolysaccharidosis VII in German Shepherds
Related tests
- Combination German Shepherd Dog 2 ACHM1 + Ectodermal dysplasia + MSP VII + MTM1 + Ichthyosis + RCND + Scott syndrom
Mucopolysaccharidosis VII in German Shepherds
Mucopolysaccharidosis VII is a lysosomal storage disease in which mucopolysaccharides (glycosaminoglycans - dermatan, heparan and chondroitin sulphates) accumulate in lysosomes. The accumulation results from a deficiency of the lysosomal enzyme beta-glucuronidase hydrolase. Clinical signs include facial dysmorphia (noticeable shortening and widening of the muzzle and low-set ears as early as 4 weeks of age in puppies), diffuse corneal opacity, presence of glycosaminoglycans in the urine, bone lesions, lack of body growth relative to the head, later joint problems, and even inability to stand. Various cardiac abnormalities may also occur. Affected dogs have very low beta-glucuronidase activity, while the carriers have 40-60% activity of this enzyme compared to normal healthy dogs.
The causal mutation is a substitution of G for A (c.497G>A) in the gene encoding the hydrolase, beta-glucuronidase (GUSB). The base substitution causes the substitution of arginine for histidine and alters the properties of the resulting protein.
The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.
The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.
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References:
Ray, J., Haskins, M.E., Ray, K. : Molecular diagnostic tests for ascertainment of genotype at the mucopolysaccharidosis type VII locus in dogs American Journal of Veterinary Research 59:1092-1095, 1998. Pubmed reference: 9736382.