Cerebellar hypoplasia

Cerebellar hypoplasia in Eurasier dogs is characterized by malformation or consistent absence of the posterior parts of the cerebellum – the caudal portions of the cerebellar vermis and caudal portions of the cerebellar hemispheres, together with enlargement of the fourth cerebellar ventricle. Hydrocephalus is an additional feature in some dogs. The main clinical sign is non-progressive ataxia (loss of coordination of movements), which is already evident in puppies at the age of 5-6 weeks. The severity of ataxia can vary from mild truncal sway and dysmetric gait to severe ataxia characterised by frequent falls. Epileptic seizures may occur in some dogs.

The causative mutation is deletion c.1713del in the VLDLR lipoprotein receptor gene, which results in a shift in the reading frame, premature introduction of the stop codon and truncation of the resulting protein by more than one-third.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. 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 prevent unintentional breeding of affected puppies.

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References:

Gerber, M., Fischer, A., Jagannathan, V., Drögemüller, M., Drögemüller, C., Schmidt, M.J., Bernardino, F., Manz, E., Matiasek, K., Rentmeister, K., Leeb, T.: A deletion in the VLDLR gene in Eurasier dogs with cerebellar hypoplasia resembling a Dandy-Walker-like malformation (DWLM). PLoS One 10:e0108917, 2015. Pubmed reference: 25668033