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Skeletal Dysplasia Type 2      SD2 Test     Code 

Test Pricing

For breeds: Labrador Retrievers

Clinical signs/Disease description: Several hereditary forms of disproportionate dwarfism or “short-legged” phenotype have been recognized by breeders of Labrador Retrievers over the years. A distinct form of a mild skeletal dysplasia type 2, termed SD2, is characterized by short legs with normal body length and width. In contrast to more severe conditions such as Oculoskeletal Dysplasia (OSD) or radius curvus deformity, SD2 has a very subtle phenotype without any obvious ocular or auditory defects and without known secondary joint problems. Still, this form of disproportionate dwarfism is not a desirable trait and can result in Labrador Retrievers failing to reach  the international height standard for the breed.  

SD2 mutation test: A mutation in collagen gene COL11A2 has been identified as a causative genetic defect associated with the skeletal dysplasia type 2 [1]. Genetically, SD2 is inherited as a monogenic autosomal recessive trait. Dogs of both sexes with two copies of the mutation usually display disproportional dwarfism and they are classified as affected homozygotes. Carriers of one copy of the mutation have normal appearance. Because height is controlled by multiple factors, the impact of the COL11A2 mutation on a dog’s stature can be less obvious in Labradors that are at the taller edge of the spectrum for the breed.

Testing/Breeding recommendations: The DNA-based SD2 test offered by Optigen determines the genetic status of a dog as having 2, 1 or 0 copies of the COL11A2 mutation and thus being Affected, Carrier or Normal/Clear for SD2, respectively. It is of particular importance for breeders of Labrador Retriever whose dogs produced progeny with short-legged phenotype in the past to check their breeding animals for the presence of mutations that have been identified in this breed as being associated with skeletal dysplasia and for which genetic tests are available. In addition to the SD2 test for the newly identified mutation in COL11A2, Optigen offers RD/OSD test.

 

Expected results for breeding strategies using the
Skeletal Dysplasia SD2 Test

Parent 1
Genotype
Parent 2 Genotype
Normal/ClearCarrierAffected
Normal/ClearAll = Normal/Clear1/2 = Normal/Clear
1/2 = Carrier
All = Carrier
Carrier1/2 = Normal
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.  Frischknecht M., Niehof-Oellers H. et al., 2013. A COL11A2 mutation in Labrador Retrievers with Mild Disproportionate Dwarfism. PLOS One, 8 (3), e60149.


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