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Phenotype: Cats with the severe form of mucopolysaccharidosis VI show signs at 6-8 weeks of age that include wide faces, shortened noses, small ears, reduced flexibility, and retarded growth. By 8 months of age, severe hind-limb mobility issues or paralysis and signs of degenerative joint disease may be observed. Additional effects of the disease include corneal clouding and heart valve thickening. Clinically, urine samples show increased levels of dermatan sulfate (DS) and an increase in white blood cell granules.
Cats with two copies of the mild form disease (MPSVIm) have less 4S enzyme and form granules in the white blood cells but otherwise appear healthy.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, MPSVIm = mucopolysaccharidosis VI (mild form), MPSVIs = mucopolysaccharidosis VI (severe form)
Breeds appropriate for testing: Domestic Shorthair, Birman, Oriental Longhair, Oriental Shorthair, Ragdoll, Siamese and related breeds
Explanation of Results:
- Cats with N/N genotype will not have either form of mucopolysaccharidosis VI. They cannot transmit these MPSVI variants to their offspring.
- Cats with N/MPSVIm genotype will not have mucopolysaccharidosis VI, but are carriers of the mild form of the disease. They will transmit this MPSVIm variant to 50% of their offspring. Matings between two carriers of the mild form are predicted to produce 25% kittens affected by the mild form of mucopolysaccharidosis VI.
- Cats with N/MPSVIs genotype will not have mucopolysaccharidosis VI, but are carriers of the severe form of the disease. They will transmit this MPSVIs variant to 50% of their offspring. Matings between two carriers of the severe form are predicted to produce 25% kittens affected by the severe form of mucopolysaccharidosis VI.
- Cats with MPSVIs/MPSVIm genotype will have the mild form of mucopolysaccharidosis VI but may appear healthy. They will transmit this MPSVIm variant to 50% of their offspring and this MPSVIs variant to 50% of their offspring.
- Cats with MPSVIm/MPSVIm genotype will have the mild form of mucopolysaccharidosis VI but may appear healthy. They will transmit this MPSVIm variant to all of their offspring.
- Cats with MPSVIs/MPSVIs genotype will have the severe form of mucopolysaccharidosis VI, a degenerative disease.
Mucopolysaccharidosis VI severe (MPSVIs) and mild (MPSVIm) are lysosomal storage diseases resulting from two independent mutations in the gene for enzyme N-acetylgalactosamine 4-sulfatase (4S). Both are inherited as autosomal recessives, thus males and females can be equally affected if they carry 2 copies of the defective gene. Cats with 2 copies of the severe form show signs at 6-8 weeks of age that include wide faces, shortened noses, small ears, reduced flexibility, and retarded growth compared to unaffected littermates. By 8 months of age, problems of severe hind-limb mobility or paralysis, and signs of degenerative joint disease can be observed. Clinically, urine samples show increased levels of dermatan sulfate (DS) and an increase in white blood cell granules. Organs and tissues can also be compromised by accumulation of intercellular DS. Additional effects of the disease include corneal clouding and heart valve thickening.
Cats with two copies of the mild form disease (MPSVIm) have less 4S enzyme and form granules in the white blood cells but otherwise appear healthy. The same is true of cats with one copy of the mild form and one copy of the severe form. Cats with only one copy (carrier) of either mutation and one copy of the normal gene appear healthy. Breeding two carriers together is predicted to produce 25% affected offspring and 50% carriers of the disease.
Testing for MPSVIs and MPSVIm assists owners and breeders in identifying affected and carrier cats.
Species
Breed
|
Result Name on Report Mucopolysaccharidosis VI (MPS VI) |
Report Interpretation |
|---|---|
| N/N | Normal. No copies of either allele associated with MPSVIs or MPSVIm detected. |
| N/MPSVIs | Carrier. One copy of the allele associated with MPSVIs detected. |
| N/MPSVIm | Carrier. One copy of the allele associated with MPSVIm detected. |
| MPSVIs/MPSVIm | Carrier. One copy of the allele associated with MPSVIm and one copy of the allele associated with MPSVIs detected. |
| MPSVIs/MPSVIs | Affected. Two copies of the allele associated with MPSVIs detected. Cat will likely develop the severe form of the disease. |
| MPSVIm/MPSVIm | Affected. Two copies of the allele associated with MPSVIm detected. Cat will likely develop the mild form of the disease. |
Yogalingam, G., Litjens, T., Bielicki, J., Crawley, A.C., Muller, V., Anson, D.S., & Hopwood, J.J. (1996). Feline mucopolysaccharidosis type VI. Characterization of recombinant N-acetylgalactosamine 4-sulfatase and identification of a mutation causing the disease. Journal of Biological Chemistry, 271(44), 27259-27265. doi: 10.1074/jbc.271.44.27259
Crawley, A.C., Yogalingam, G., Muller, V.J. & Hopwood, J.J. (1998). Two mutations within a feline mucopolysaccharidosis Type VI colony cause three different clinical phenotypes. Journal of Clinical Investigation, 101(1), 109-119. doi: 10.1172/JCI935
Yogalingam, G., Hopwood, J.J., Crawley, A. & Anson, D.S. (1998). Mild feline mucopolysaccharidosis type VI. Identification of an N-acetylgalactosamine 4-sulfatase mutation causing instability and increased specific activity. Journal of Biological Chemistry, 273(22), 13421-13429. doi: 10.1074/jbc.273.22.13421
