Dilute coat color with neurological defects in Miniature Dachshunds

The disease, known as CDN, is the equivalent of human Griscelli Syndrome Type I (GST1). The striking feature is a coat colour dilution caused by disruption of melanosome transport in melanocytes. However, this condition is accompanied by severe neurological abnormalities that are evident in puppies as young as 4 weeks of age. Affected puppies are unable to maintain an upright head position or to hold a normal prone position on their belly for an extended period. They are almost unresponsive to environmental stimuli.

The cause of the disease is mutation c.4973_4974insA in the MYO5A gene, which encodes the motor protein myosin VA. The lack of function of this protein reduces synaptic plasticity and leads to neurological deficits.

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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Reference:

Christen, M., de le Roi, M., Jagannathan, V., Becker, K., Leeb, T. : MYO5A Frameshift Variant in a Miniature Dachshund with Coat Color Dilution and Neurological Defects Resembling Human Griscelli Syndrome Type 1. Genes (Basel) 12:1479, 2021. Pubmed reference: 34680875.