Paper detailing PRA modifier frequencies published

The Canine Genetics Centre has had an important study published, in collaboration with Wisdom Panel, on the genetics of progressive retinal atrophy in dogs. The paper describes the frequency of two genetics variants, called RPGRIP1ins44 and MAP9del, in 132 different breeds of dog. Both the variants were originally identified in Miniature Longhaired Dachshunds, and both are known to modify the development and progression of PRA.

The new paper shows that both variants are probably ancient, as both are carried by multiple breeds of dog, and in fact both are individually quite common within largely non-overlapping subsets of breeds. But only a single breed, the Miniature Longhaired Dachshund (MLHDs), has a relatively high frequency of both variants, with about 1 in approximately 1,100 MLHDs estimated to be homozygous for both variants, according to the data analysed in the new paper. This is important – extensive research carried out on both variants over many years shows that only dogs that are homozygous for both variants typically go blind early in life, with dogs that are only homozygous for the RPGRIP1ins44 variant unlikely to develop significant visual problems.

The RPGRIP1ins44 variant was identified in 2006 whereas the MAP9del variant wasn’t identified until a decade later, in 2016. The paper is a very good illustration of how our understanding of the genetics of some inherited canine diseases develops over time, with a full understanding of some only being made possible with many years of continued research.

The paper, which was co-authored by Cathryn Mellersh and Jonas Donner, analysed data from 242,665 dogs submitted for commercial genetic testing by Wisdom Panel (Portland, OR, USA) in the years 2019–2021and and is available here:

https://onlinelibrary.wiley.com/doi/pdf/10.1111/age.13443