C3 deficiency in Brittany Spaniels

C3 is a key complement protein that is a part of the immune system and helps the body fight bacterial infections. Its deficiency leads to increased susceptibility to bacterial infections and sometimes to kidney diseases such as membranoproliferative glomerulonephritis. Affected dogs have overall weakened immunity and slower wound healing.

In Brittany Spaniels, C3 deficiency is caused by a c.2136del mutation in the C3 gene, which causes a shift in the reading frame and the production of a non-functional protein.

The mutation is inherited in an autosomal recessive manner. This means that the disease only develops in individuals who inherit the mutated gene from both parents. Carriers of the mutated gene are clinically healthy, but they pass the mutation on to their offspring. In the case of mating two heterozygous individuals, theoretically 25% of offspring will be completely healthy, 50% will be carriers, and 25% will inherit the mutated gene from both parents and will therefore be affected by the disease.

Genetic testing can clearly reveal an animal's genotype and is a useful tool for breeders to prevent the unintentional breeding of affected puppies.

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Reference:

Ameratunga, R., Winkelstein, J.A., Brody, L., Binns, M., Cork, L.C., Colombani, P., Valle, D. : Molecular analysis of the third component of canine complement (C3) and identification of the mutation responsible for hereditary canine C3 deficiency. J Immunol 160:2824-30, 1998. Pubmed reference: 9510185