Deutsch
Hrvatski
Русский
Português
Osteogenesis Imperfecta (OI) – Chow Chow Type
| Acronym: | OI |
| Gene: | COL1A2 |
| Mutation: | c.936+1G>A |
| Inheritance: | Autosomal Dominant |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Osteogenesis Imperfecta (OI) is a genetic disorder also known as „brittle bone disease“ and it is characterized by a loss of bone mineral density and extreme bone fragility. OI is the most common connective tissue disorder in humans and other animals including dogs and it is classified into 9 types based on the specific mutation that causes it, the mode of inheritance it shows, and the phenotype in the affected individuals. All types of OI are caused by a mutation in COL1A1 or COL1A2, the two genes encoding type I collagen, and cause similar signs such as joint laxity, dwarfism, fragile teeth, and skeletal deformities. In dogs, OI most closely resembles human OI types I–IV and it has been reported in Golden Retriever, Collie, Poodle, Beagle, and other dog breeds, including Chow Chow dogs. The type of OI found in Chow Chow dogs is caused by a mutation in the COL1A2 gene that encodes the pro-alpha2 chain of type I collagen that is crucial for the formation of collagen I found in connective tissues and is abundant in bone, cornea, dermis, and tendons.
This type of connective tissue disorder specific to Chow Chow dogs is inherited as an autosomal dominant trait. That means not only dogs with both mutated COL1A2 genes but also dogs carrying only one mutated gene will develop and show signs of the disease. Also, in both cases, dogs may act as carriers and potentially pass the mutation to their offspring. Early genetic testing can help identify carriers of the specific mutation and help breeders in selecting future mating pairs.
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:
Quist, E. M., Doan, R., Pool, R. R., Porter, B. F., Bannasch, D. L., Dindot, S. V. (2018). Identification of a Candidate Mutation in the COL1A2 Gene of a Chow Chow With Osteogenesis Imperfecta. The Journal of heredity, 109(3), 308–314. https://doi.org/10.1093/jhered/esx074
Campbell, B. G., Wootton, J. A., Macleod, J. N., Minor, R. R. (2001). Canine COL1A2 mutation resulting in C-terminal truncation of pro-alpha2(I) and severe osteogenesis imperfecta. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 16(6), 1147–1153. https://doi.org/10.1359/jbmr.2001.16.6.1147