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Oculoskeletal dysplasia 1 (COL9A3 gene, Labrador Retriever)

Oculoskeletal dysplasia 1 (COL9A3 gene, Labrador Retriever)

Oculoskeletal dysplasia type 1 is a rare condition that affects collagen, manifesting itself through ocular abnormalities and bone dysplasia, often resulting in the development of dwarfism.

Symptoms

The first clinical signs are visible from the first 4 to 6 weeks of life. Visual disturbances include cataracts, vitreous syneresis and retinal detachment. Retinal dysplasia, retinal degeneration or lens coloboma may also occur. The clinical expression of the disease varies from asymptomatic cases to total loss of vision. At the skeletal level, it is common to observe limb dwarfism, ulnar shortening, radial curvature, osteoarthritis and hip and elbow dysplasia in affected dogs.

Disease Management

There are no preventive measures or a specific cure for this condition. Suggested strategies focus on improving the quality of life of affected dogs, so regular ophthalmic care and consideration of surgical interventions in particular cases are recommended. In addition, it is crucial to ensure a nutritionally adequate diet and to adapt the environment to possible skeletal and mobility problems.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, however, some carriers have shown mild signs of eye damage and may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that may cause disease is not recommended, even if they do not show symptoms.

Technical report

Oculoskeletal dysplasia type 1 is a genetic disorder characterized by ocular and skeletal defects resulting from genetic variations affecting the COL9A3 gene, which encodes type IX collagen. This type of collagen interacts with other fibers to provide joint strength and flexibility. In the Labrador Retriever breed, a variant has been identified in the COL9A3 gene that consists of the insertion of a guanine residue (c.10_11insG) in exon 1 of the COL3 domain, causing the incorporation of a premature stop codon and giving rise to a truncated protein. It appears that this defect causes collagen deficiency at the cartilage and ocular level, which would explain the underlying symptomatology. Oculoskeletal dysplasia has also been described in the Samoyed and Northern Inuit breeds.

Most affected breeds

Labrador Retriever

Bibliography

Goldstein O, Guyon R, Kukekova A, et al. COL9A2 and COL9A3 mutations in canine autosomal recessive oculoskeletal dysplasia. Mamm Genome. 2010 Aug;21(7-8):398-408.

Sebbag L, Riggs A, Carnevale J. Oculo-skeletal dysplasia in five Labrador Retrievers. Vet Ophthalmol. 2020 Mar;23(2):386-393.