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Canine Dominant Macrothrombocytopenia
| Acronym: | MTC-D |
| Gene: | TUBB1 |
| Mutation: | c.745G>A |
| Inheritance: | Autosomal dominant |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Canine Dominant Macrothrombocytopenia, also known as Giant platelet disorders, is a genetic disorder characterized by abnormally large platelets that cannot stick adequately to an injured blood vessel walls, resulting in abnormal bleeding when injured. Macrothrombocytopenia has been reported in several animals, including dogs, and is similar to that observed in people. The signs and symptoms are similar to other bleeding disorders and include nose bleeds, bruising, and/or gum bleeding. However, most of the affected individuals are asymptomatic with a low platelet count and increased mean platelet volume. The molecular basis of macrothrombocytopenia is a mutation in the b1-tubulin (TUBB1) gene that causes impaired microtubule assembly, affecting proplatelet formation and platelet production by megakaryocytes.
Macrothrombocytopenia in dogs is inherited as an autosomal dominant trait meaning even individuals with only one copy of the mutated gene will develop the disease, not only those with two mutated genes. The prevalence of asymptomatic macrothrombocytopenia in some dog breeds is very high with more than 90% of dogs being either carriers or affected. Early genetic testing can help identify dogs that carry the gene with the specific mutation and prevent their further breeding by proper selection of 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:
Gelain, M. E., Tutino, G. F., Pogliani, E., Bertazzolo, W. (2010). Macrothrombocytopenia in a group of related Norfolk terriers. The Veterinary record, 167(13), 493–494. https://doi.org/10.1136/vr.c4782
Davis, B., Toivio-Kinnucan, M., Schuller, S., Boudreaux, M. K. (2008). Mutation in beta1-tubulin correlates with macrothrombocytopenia in Cavalier King Charles Spaniels. Journal of veterinary internal medicine, 22(3), 540–545. https://doi.org/10.1111/j.1939-1676.2008.0085.x
Gelain, M. E., Bertazzolo, W., Tutino, G., Pogliani, E., Cian, F., Boudreaux, M. K. (2014). A novel point mutation in the β1-tubulin gene in asymptomatic macrothrombocytopenic Norfolk and Cairn Terriers. Veterinary clinical pathology, 43(3), 317–321. https://doi.org/10.1111/vcp.12168