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Osteochondrodysplasia         OC Test        Code 364

For breeds: Miniature, Dwarf, Moyen (Klein) and Toy Poodles

Clinical signs/Disease description:
A form of severe dwarfism was first described in the Miniature Poodle in Great Britain almost 60 years ago (1). Also known as osteochondrodysplasia (OC), it involves abnormalities in cartilage and bone development. The initial clinical signs of the disorder appear at 3 weeks of age when affected puppies show stunted growth and abnormal movements. Later, deformity in limbs, jaws and the rib cage become apparent, causing difficulties in breathing and feeding. Affected puppies are typically euthanized. Dogs with less pronounced symptoms of OC can survive into adulthood but the majority have significant physical abnormalities and increased incidence of osteoarthritis.

Combined efforts of the dedicated Miniature Poodle breeders and the research team led by Dr. Mark Neff at the Van Andel Research Institute culminated in the discovery of a partial deletion of the sulfate transporter gene, SLC13A1, as a cause of the osteochondrodysplasia in this breed (2,3). In Miniature Poodles OC is inherited as an autosomal recessive disease. Affected dogs of both sexes develop this form of OC, apparently due to abnormalities in sulfate metabolism, when they receive two copies of the truncated gene, one from each parent.

Prevalence of the SLC13a1 mutation:
The frequency of the SLC13a1 mutation has been estimated in the U.S. subpopulation of the Miniature Poodle, with an average of 9.7 percent of tested dogs being carriers of the mutation (2). Cases of the OC disease have been described in European subpopulation of the breed but the frequency of the mutation has not yet been reported.

DNA test for OC in the Miniature Poodle:

The mutation based test for OC is designed to detect the presence/absence of the SLC13a1 deletion and to clearly distinguish three groups of dogs corresponding to three genotypes:

NORMAL/CLEAR homozygotes with two normal copies of the gene do not develop OC and can only transmit the normal gene to its offspring.

CARRIERS heterozygotes with one copy of the mutation and one copy of the normal gene do not develop OC but they can transmit the SLC13a1 deletion to progeny.

AFFECTED homozygotes with two copies of the truncated SLC13a1 gene develop clinical signs of OC and they can only pass the mutated gene on to their offspring.

Recommendations for breeding strategies:

 Because of the recessive nature of OC inheritance, the mutation can exist in breeding lines without detection for many generations until two carriers of the mutation produce an affected pup. On average, 25 percent of the offspring from a mating between carriers will be affected. Due to random (chance) assortment of gametes and the relatively small litter size, the actual percentage of puppies affected with OC produced in Carrier to Carrier mating often deviates from the expected 25%. It is recommended to test dogs prior to mating to ensure that at least one parent is Normal/Clear of the OC mutation to avoid production of affected progeny.

 Expected results for breeding strategies using the mutation test for Osteochondrodysplasia (OC)

Parent 1
Status

Parent 2 Status

Normal/Clear

Carrier

Affected

Normal/Clear

All = Normal/Clear

1/2 = Normal/Clear
1/2 = Carrier

All = Carrier

Carrier

1/2 = Normal/Clear
1/2 = Carrier

1/4 = Normal/Clear
1/2 = Carrier
1/4 = Affected

1/2 = Carrier
1/2 = Affected

Affected

All = Carrier

1/2 = Carrier
1/2 = Affected

All = Affected


References:
  1. Cotchin E, Dyce K. 1956. A case of epiphyseal dysplasia in a dog. Veterinary Record 68: 427-428.

  2. Neff MW, Beck JS, Koeman JM, Boguslawski E, Kefene L, Borgman A, Ruhe AL. Partial deletion of the Sulfate Transporter SLC13a1 is associated with an osteochondrodysplasia in the Miniature Poodle breed. PLoS ONE, 2012. V. 7(12), e51917.

  3. Collaboration aids discovery of SLC13a1 mutation for dwarfism in Miniatures. Pro Club Update Newsletter, 2013. V.12.

 

 

 


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