Credit: Kaisa Wickström.
Hereditary retinal atrophy is a common cause of blindness, with up to 2 million people experiencing the disorder globally. There is no effective treatment available for retinal atrophy. Gene therapy is expected to offer a solution, but the development of such treatments is only possible when the genetic cause of the disease is known. Related mutations have been identified in more than 70 genes to date, but the genetic background for the disease remains unknown in up to half of the patients.
“Retinal atrophy has been described in more than 100 dog breeds, with related investigations helping to identify new genes associated and pathogenic mechanisms with blindness across different breeds. IFT122 is a good example, providing a potential explanation for unresolved human issues as well.” Professor Hannes Lohey says.
Data involving over a thousand Finnish Lapponian and Lapphund Shepherds from a Dog DNA Bank were used in the study. Previously, several genes for retinal dystrophy were described in both strains.
Among other discoveries, two eye disease genes were previously identified in Lapponian Herders, but they did not take into account all cases. In some dogs, the disease is caused by the IFT122 gene. This finding is important because gene tests can now distinguish retinal dystrophies associated with different genes in the lineages, making a difference in monitoring disease progression, prognosis and developing new treatments. Maria Coconen, MD, MD, explains that the prognosis improves and makes veterinarians easier to work.
The discovery of the gene also facilitates understanding of the biology of the retina. IFT122 is part of a protein complex associated with the ciliary function of the retina.
The age of onset varies, and the disease progresses slowly in some dogs. IFT122 is known to contribute to the transport of opsin in photoreceptor cells. This gene variant impedes this transfer and results in gradual blinding. Because IFT122 is related to the function of cilia, which is important to the body, we have studied some dogs more closely in relation to other issues potentially related to disorders associated with cilia, such as renal abnormalities or serious developmental disorders of the internal organs. We found that the damage appears to be limited to the retina alone. This information helps us understand the mechanisms of the gene’s action, ”Cocoonen adds.
The results are also important for further plans to remove the disease from different strains. In the Finnish Lapponian Herders and Lapphunds, the proportion of individuals carrying the gene variant was 28% and 12%, respectively.
“This is a recessive genetic disease, which means that a dog who will go blind inherits the variant from both parents, both of whom carry the type. Gene testing can help avoid carrier groups, which easily prevent the birth of sick dogs,” Luohe says. For concrete based on the study for the benefit of breeders. “
The new study is part of a broader research project on the genetic background of inherited diseases by Professor Luohi’s research group. Kaukonen recently moved to an active research group at the University of Oxford, focusing on developing gene therapies for retinal dystrophy. Meanwhile, Kaukonen and Lohi continue to collaborate closely to clear a range of eye diseases along with University Hospital of Helsinki and other operators.
There are a lot of genetic findings linked to eye disease on the way in canine research. We are only at the beginning. Among other things, we are currently investigating the genetic background of glaucoma as well as corneal and retinal dystrophies in nearly 30 strains. “The initial results are promising,” Luhei says.