Progressive retinal atrophy (PRA) in Lapponian Herder

Progressive retinal atrophy is a large group of inherited diseases that are the leading cause of blindness in various breeds of dogs. Individuals affected by PRA show a similar sequence of clinical abnormalities during the disease. Symptoms begin with night blindness followed by progressive loss of daytime vision and eventual blindness in all light conditions. Routine eye examinations reveal a progressive loss of the retinal lens cells (retina) due to their degeneration or retinal atrophy, which gives the name to the disease.

The Lapinporokoira breed is affected by several types of inherited retinal atrophies. Variants in the PRCD and BEST1 genes have been identified. A new candidate gene associated with this disease is the IFT122 gene. It is a missense mutation c.3176G>A. Progression of the disease is slower in this variant than in others and usually does not result in complete loss of vision.

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:

Kaukonen, M., Pettinen, I.T., Wickström, K., Arumilli, M., Donner, J., Juhola, I.J., Holopainen, S., Turunen, J.A., Yoshihara, M., Kere, J., Lohi, H. : A missense variant in IFT122 associated with a canine model of retinitis pigmentosa. Hum Genet 140:1569-1579, 2021. Pubmed reference: 33606121