Cats don’t have perfect genes – our furry feline friends can inherit devastating genetic diseases. Major disease-causing versions of genes have been discovered with the advent of feline genome sequencing. And pedigree breeding can exacerbate the genetic problems faced by cat breeds. Now the largest genetic study of domestic cats ever reveals the frequency with which the known disease-causing versions of genes, or gene variants, show up in purebred cat breeds and their unpedigree cousins.
More than 11,000 cats were screened for established disease-causing gene variants, said lead study author Heidi Anderson, a senior scientist at Kinship, a company specializing in genetic testing kits for pets. ldquo;If you screen the cat more extensively, yoursquo;ll sort of find out; and keep cherry picking for anticipated illnesses to a minimum, she says. This approach led the team to identify 13 disease-related gene variants in 47 breeds in which they had not been previously found and three variants that were unique to non-pedigree cats. The researchers published their findings in PLOS Genetics.
The commercial test they used to sample the cats is similar to tests available to humans, Anderson says. Owners have wiped their petsrsquo; mouth to collect a DNA sample and then send it to be analyzed. Anderson and her team screened 10,419 pedigree and 617 non-pedigree cats for 87 different gene variants. Not all variants were associated with disease; a compromised appearance or blood type.
Identifying blood type is important for cats undergoing surgery and may need a blood transfusion, Anderson says. It is also helpful for breeders wishing to avoid neonatal isoerythrolysis, a condition that is particularly common in domestic cats and horses and occurs when a mother has a different blood type than her babies. In cats, the motherrsquo;s antibodies can travel to her kitten through her milk and attack his red blood cells, Anderson explains. If not diagnosed within the first few hours after birth, the condition can be fatal. Testing for compatible blood groups before breeding can completely bypass the risk of neonatal isoerythrolysis.
Screening for disease-causing gene variants can help prevent them from being inherited. Of the 90 different breeds represented by the participating purebred cats, Maine Coons had the highest number of disease-related gene variants. One of the nine variants detected was associated with polycystic kidney disease, which is unexpected in Maine Coons. Cats suffering from this disease form fluid-filled cysts on their kidneys that affect the organs; natural function. Surprisingly, none of the Persian cats — a breed known to suffer from polycystic kidney disease — tested positive for the disease-causing variant, Anderson says. Breeders of Persian cats know their animals are at risk for this devastating disease and often choose to screen them before breeding, she says.
ldquo;This is such a great example of seeing the [variant] frequencies of some of these devastating diseases drop in breeds where they were traditionally very high, rdquo; said Christopher Kaelin, a senior scientist and feline geneticist at HudsonAlpha Institute for Biotechnology, who was not involved in the study. ldquo;It shows me that breeders are really really interested in breeding healthier cats and that theyrsquo;re taking steps to do it.rdquo; Awareness of the prevalence of this disease in Persian cats helped breeders make the best decisions when breeding individual cats, which likely led to a decrease in disease frequency.
These kinds of large-scale studies highlight the frequency of various genetic diseases in all races, not just those previously known to have a disease. In fact, 13 disease-related variants were found in the non-pedigree cats that participated in the study, indicating that this technology is not only useful for breeders.
ldquo;I think the real strength of this research is the ability of these commercial sequencing platforms to collect really large amounts of data, rdquo; says Kaelin. The genetic variants tested in the study were based on academic research examining dozens or perhaps hundreds of cats. It would be difficult for an individual research lab to process thousands of samples per year, says Kaelin. But common inherited diseases, such as diabetes, are genetically more complex than those screened for by Anderson and her colleagues, and are much harder to understand, Kaelin explains. If researchers supplemented this larger platform with comprehensive veterinary information, it could serve as a framework for figuring out the genetic risk of those more common diseases — which require large sample sizes to uncover genetic causes and consequences. ldquo;From that perspective I think this is a really exciting paper, rdquo; he says.
The study also had some direct implications for the feline participants. Anderson says that when a disease-associated variant was discovered in a sample, her team would contact the catrsquo;s owner to talk about what that meant for their pet. ldquo;Therersquo;s a [nonpedigreed] cat who had very strange symptoms and had visited several vets, rdquo; she says. ldquo;We were able to confirm that it was suffering from myotonia congenitardquo; – a musculoskeletal condition for which symptoms can be treated, although there is no known cure. Anderson hopes these types of genetic testing can help other cats in the future, providing an accessible tool for vets treating our feline companions.
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