Congenital myasthenic syndrome in Old Danish Pointing Dogs

Congenital myasthenic syndrome is an inherited disease that affects neuromuscular transmission. In the Old Danish Pointer, the disease is manifested by transient muscle paralysis after physical exercise. After a few minutes of running, affected dogs begin to shorten their strides until they eventually remain lying down with their legs bent. The symptoms disappear after a few minutes of rest but if physical activity continues symptoms will recur.

The disease is caused by a missense mutation c.85G>A in the CHAT gene, which causes reduced presynaptic synthesis of acetylcholine.

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

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to avoid unintentional breeding of affected puppies.

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Reference:

Proschowsky, HF., Flagstad, A., Cirera, S., Joergensen, CB., Fredholm, M. : Identification of a mutation in the CHAT gene of Old Danish Pointing Dogs affected with congenital myasthenic syndrome. J Hered 98:539-43, 2007. Pubmed reference: 17586598