Oculoskeletal dysplasia (OSD)

Oculoskeletal dysplasia (OSD) is an autosomal recessive disease affecting two canine breeds – the Labrador retriever and the Samoyed. Affected dogs have shorter forelimbs and their radius and ulna forelimb bones exhibit morphological abnormalities. Other severe symptoms include ocular defects such as cataracts, retinal detachment or vitreous dysplasia. Beside the recessive homozygotes (dogs carrying two affected alleles of the mutated gene), this disease affects even heterozygotes (dogs carrying only one affected allele of the mutated gene), however the homozygotes do not exhibit any skeletal malformations. They may suffer from slight ocular defects such as extensive retinal folds causing retinal dysplasia. Dogs affected by oculoskeletal dysplasia are usually recognized at the age of 4 to 6 weeks when the morphological features distinguishing the affected dogs from the healthy ones become apparent.  Ocular defects are detected on the basis of an ophthalmological examination.

OSD in Labrador retrievers (osd1; drd1) is caused by an insertional mutation c.10_11insG in exon 1 of COL9A3-gene.  Both types of oculoskeletal dysplasia occur in dogs that obtain the mutant gene from the both parents. These dogs are designated as P/P (positive/positive).

OSD is autosomal recessive inherited disease. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive / negative) genotype are mostly clinically without any symptom - nevertheless in some cases dogs can have eye defects. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

OSD can be found also in Samoyeds (osd2; drd2) - there is a deletion of 1,267 base pair in the 5' end of COL9A2-gene. Genomia does not offers the test for Samoyeds.

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Reference:

Goldstein, Orly et al. “COL9A2 and COL9A3 mutations in canine autosomal recessive oculoskeletal dysplasia” Mammalian genome : official journal of the International Mammalian Genome Society vol. 21,7-8 (2010): 398-408.

Miyadera, K., Acland, G. M., & Aguirre, G. D. (2011). Genetic and phenotypic variations of inherited retinal diseases in dogs: the power of within- and across-breed studies. Mammalian genome : official journal of the International Mammalian Genome Society, 23(1-2), 40-61.