Ear position and osteochondrodysplasia

The study of osteochondrodysplasia, a disorder of bone and cartilage growth, has been linked to a mutation in the TRPV4 gene, which also helps explain the genetic predisposition to having an erect or drooping ear position.

Symptoms

Feline osteochondrodysplasia is a genetic disease that mainly affects the distal extremities of the forelimbs and hind limbs, as well as the tail, causing bone malformations and progressive joint destruction. Symptoms include signs of lameness, stiffness and avoidance of jumping. Heterozygous cats, which carry only one copy of the mutated allele, usually show less severe clinical signs. Affected cats are born with erect ears, but at around three to four weeks of age, the pinnae begin to fold forward.

Disease Management

Feline osteochondrodysplasia has no curative treatment, and management focuses on alleviating symptoms and improving the quality of life of the affected cat. Nonsteroidal anti-inflammatory drugs (NSAIDs), glycosaminoglycans or a combination of these may have a palliative effect. In severe situations, surgery to correct joint deformities or dislocations is considered.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the cat, 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 cat 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, but may pass the mutation on to future generations. Breeding between cats carrying genetic variants that may cause disease, even if they do not show symptoms, is not recommended.

Technical report

Osteochondrodysplasia is a heterogeneous group of diseases that affect cartilage and bone development, leading to a deformed skeleton. In Scottish Fold cats, the disease is associated with a mutation in the TRPV4 gene, which encodes a protein involved in cell differentiation and tissue homeostasis, including chondrocytes and osteoblasts. This gene plays a crucial role as a mechanosensor in chondrocytes, regulating intracellular responses to mechanical stimuli. The variant responsible for this disease is a missense mutation, c.1024G>T, which causes an amino acid change p.V342F in the ankyrin repeat domain region of the TRPV4 protein. This change affects mechanical signal transduction and alters the intracellular responses of chondrocytes, leading to bone deformities and progressive joint degeneration, which are characteristic features of affected cats.

Most affected breeds

Fold Scottish

Bibliography

Chang J, Jung J, Oh S, et al. Osteochondrodysplasia in three Scottish Fold cats. J Vet Sci. 2007 Sep