Polioencephalopathy (PE) Eurasier

Polioencephalopathy (PE) in Eurasiers is a rare hereditary disease in which the grey matter of the brain is damaged. In this form of PE, the causative mutation (c.823A>G) in the MECR gene was identified following abnormalities in a single litter. (Publikation).

If both MECR genes have the mutation, the symptoms occur, heterozygous animals are healthy, so that an autosomal recessive inheritance can be assumed according to the current status.

The clinical picture of PE is not indicative of the presence of the mutation, but is generally observed when the grey matter of the brain, i.e. the bodies of the nerve cells, are affected. These are generally sensitive to external disturbances, e.g. nutritional deficiencies and poisoning, but congenital metabolic disorders also play a role. In human medicine, disorders in the mitochondria are increasingly being identified as the cause of PE.

PE in Eurasians is also caused by a disorder of mitochondrial metabolism. The MECR gene, in which the isolated mutation was found, stands for mitochondrial trans-2-enoyl-CoA reductase. It encodes an enzyme that catalyses the final step of mitochondrial fatty acid synthesis. It is understandable that a disruption of this function severely impairs the mitochondria.

The heterogeneity of clinical manifestations in mitochondrial encephalopathies is a major challenge and genetic testing is considered crucial for the identification of carriers and early detection of the disease.

Affected newborns show early onset movement disorders that worsen as the disease progresses. Typical symptoms are

• persistent divergent strabismus
• episodes of generalised ataxia
• wide-spreading gait with the front legs and their uncontrolled bending and stretching movements.
• Consciousness and behaviour remain intact in all dogs.

Dogs of the Eurasier breed and mixed breeds in which Eurasiers are involved.

As long as the origin of the mutation hasn’t been clarified, the breeds from which the Eurasier breed was formed (Samoyed, Chow-Chow, Wolfspitz) are also potentially segregating the mutation.

The test is based on a PCR-based amplification of the DNA section in which the mutation is located. It involves the exchange of a single base pair (c.823A>G), which can be recognized by sequencing the PCR product or other diagnostic methods.

Please order at: Polioencephalopathy (PE) Eurasier

Result: N/N

Short statement: homozygous normal - healthy

Explanation: The tested animal does not have the mutation in any allele of the MECR gene and therefore cannot pass it on to offspring. When mated with a heterozygous carrier, 50% of the offspring are heterozygous, 50% are homozygous wildtype.

Result: N/mecr

Short statement: heterozygous - healthy

Explanation: The animal carries the mutant allele in one of the two copies of the MECR gene and will transmit it to 50% of its offspring. The tested animal is healthy; in breeding, it must be ensured that mating is only carried out with N/N-tested animals.

Result: mecr/mecr

Short statement: homozygous for the mutation - affected

Explanation: The animal has the analysed mutation in both MECR genes. Animals with this genetic status show the symptoms typical of Polioencephalopathy and are not able to live. The animal should be euthanised to avoid unnecessary suffering.

1. Rawson F, Christen M, Rose J, Paran E, Leeb T, Fadda A. Polioencephalopathy in Eurasier dogs. J Vet Intern Med. 2024 Jan-Feb;38(1):277-284. doi: 10.1111/jvim.16945. Epub 2023 Dec 2. PMID: 38041431; PMCID: PMC10800227.
   https://onlinelibrary.wiley.com/share/6TDKDJJVIRKPXERQXBDC?target=10.1111/jvim.16945
    
2. Online Mendelian Inheritance in Animals