Factor VII deficiency

Factor VII (FVII) is a vitamin K-dependent glycoprotein that is synthesized in the liver and secreted into the circulation as a single-chain zymogen that, once activated, plays a pivotal role in the initiation of coagulation. Following vascular injury, FVII, in combination with tissue factor (TF) and in presence of calcium, cleaves the factor IX and the factor X to their active forms leading to the generation of thrombin. The deficiency of factor VII affects the blood coagulation and causes excessive bleeding in case of an injury or other intervention in the organism (e.g. during a planned operation of a dog).

In 2007, Callan et al. described a mutation causing FVII deficiency in Beagles. It is a substitution c.407G>A (previous nomenclature c.6385G>A) in EGF-2 domain causing glycine substitution for glutamic acid at position 96. Further researches have shown that the same mutation is responsible for deficiency of FVII in dog breeds such as Airedale Terrier, Alaskan Klee Kai (Miniature Alaskan Husky), Giant Schnautzer and Scottish Deerhound.

F VII deficiency is an autosomal recessive disorder. The disease affects dogs with P/P (positive / positive) genotype only. Dogs with P/N (positive /negative) genotype are clinically without any symptoms. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

Carriers of the mutated allele having no clinical signs can be reliably identified with a molecular genetic test. We recommend that all dogs intended for breeding are tested. With regard to the high risk of disease occurrence in offsprings, when two carriers are mated, we recommend that a carrier is mated with a dog having a wild type genotype (N/N, negative/negative, i.e. a dog with no gene mutation).

References:
Callan MB et al.: A novel missense mutation responsible for factor VII deficiency in research Beagle colonies. J Thromb Haemost 2006; 4: 2616-22.