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Scottish Fold Osteochondrodysplasia (Osteodystrophy)
| Acronym: | OCD |
| Gene: | TRPV4 |
| Mutation: | c.1024G>T |
| Inheritance: | Autosomal incompletely dominant |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Scottish Fold osteochondrodysplasia is an inherited bone and cartilage disorder specific to this cat breed. It belongs to a wider group of disorders, generally known as osteochondrodysplasia, but the form occurring in the Scottish Fold breed is specific by its causative mutation. Osteochondrodysplasia is a disorder (”dysplasia”) of bones (”osteo”) and cartilage (”chondro”). It can be characterized into a group of musculoskeletal disorders, a broad category of diseases that affects the muscles or bones.
The Scottish Fold is a breed of domestic cat, specific by its ”folded” ears, which are bending forward and down towards the front of their head. This phenotype is caused by a dominant gene mutation that affects the cartilage throughout the body. Although it causes an appealing look for the cat because of its folded ears, it also causes severe cartilage abnormalities which lead to severe and painful arthritis. The evident deformities caused this breed to be excluded from the list of recognized breeds in 1974, also by the Fédération Internationale Féline, an international cat fancy society. However, the breed is still being maintained by breeders in the USA and elsewhere in the world.
Affected cats show painful bone deformity, appearing as short wide limbs and short, inflexible tails. They exhibit lameness, swollen wrist and ankle joints, abnormal gait, and are reluctant to move and jump. In more severe cases, the cat is completely unable to walk. The disorder can be diagnosed based on history and examination. The examination includes imaging of limbs, by the usage of radiology, bone scan, MRI, and spiral CT. As the Scottish Fold osteochondrodysplasia is caused by a dominant gene, homozygous cats appear to be more severely affected than the heterozygous. Homozygous cats can be identified on x-ray already from 7 weeks of age, while in heterozygous cats it can be evident from 6 months of age. Currently, there is no treatment for Scottish Fold osteochondrodysplasia.
Scottish Fold osteochondrodysplasia is caused by a substitution mutation in the TRPV4 gene (transient receptor potential cation channel, subfamily V, member 4). This gene is encoding a calcium-permeable ion channel and is expressed in various tissues, including chondrocytes, osteoblasts, and osteoclasts. TRPV4 gene-correct activity is important for cell differentiation and tissue homeostasis. Various mutations within this gene have been associated with different human skeletal dysplasias. Scottish Fold osteochondrodysplasia is inherited in an autosomal dominant pattern and both homozygous and heterozygous for the mutation cats will develop symptoms. Homozygous cats appear to develop symptoms earlier than heterozygous cats and their symptoms appear to be more severe.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
AFFECTED HETEROZYGOTE |
Tested mutation was detected in animal with „affected heterozygote“ result. Animal tested as affected heterozygote has one wild-type and one mutation allele, it is in heterozygous state. It is likely to develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
**Penetrance of tested mutation, and potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Gandolfi, B. Et al. (2016): A dominant TRPV4 variant underlies osteochondrodysplasia in Scottish fold cats. Osteoarthritis Cartilage. 2016 Aug;24(8):1441-50. doi: 10.1016/j.joca.2016.03.019. Epub 2016 Apr 6.