What is it?
It is a newly identified gene found in sphynx that is contributory to HCM.
It is an autosomal dominant gene with incomplete penetrance.
Autosommal means that it affects both male and female.
Dominant means that only one copy of the gene is required to potentially cause clinical HCM.
Incomplete penetrance means this gene doesn’t always penetrate enough to cause disease. The penetrance percentage is the percentage of cats with one or two copies of this gene that actually develop HCM.
What does Heterozygous, Homozygous and Negative mean in regards to this gene test?
Heterozygous means the cat has one copy of the gene. Homozygous means the cat has two copies of this gene, and Negative means the cat has no copies of this gene.
If my cat has one or two copies of this gene, will they get HCM?
No, not every cat with this gene will develop HCM. This gene is epigenetic, which means that outside factors (not genetic in nature) can affect the gene and how it expresses. Diet, lifestyle, viruses, weight, hydration, stress etc can all impact how this gene expresses itself.
If my cat does not have this gene does it mean they will never develop HCM?
Unfortunately, no. A Sphynx that is negative for this gene can still develop HCM caused by other unidentified mutations. This gene accounts for approximately 60% of the cases of HCM in the breed, so there remains 40% of cases without an identified genetic cause.
Does this DNA test replace the need for yearly Echocardiograms?
No, echocardiograms are still our most valuable tool against HCM. This DNA test is an additional tool to use in conjunction with yearly echocardiograms, that helps us evaluate a cat’s risk of developing HCM, but it is not a way to diagnose heart disease in any way. Echocardiograms remain the gold standard.
Why aren’t breeders spavinq and neutering all Sphvnx with one or two copies of this gene?
So far, we are seeing about 50% of the gene pool being heterozygous (one copy), 25% homozygous (two copies) and 25% negative. If we were to remove all sphynx with this gene from breeding programs, we would cripple the breed population and destroy our genetic diversity. Genetic diversity is critical to a breed’s over all health, and when it decreases, we see an inevitable increase in diseases and health issues within that breed. Most heterozygous cats are very healthy, and have valuable genes to contribute to the breed’s future health.
What are the breeding guidelines in regards to this gene?
Dr. Kate Meurs, the geneticist who discovered this gene, recommends a slow and careful approach. A heterozygous cat with a history of clear HCM scans, no familial HCM, and healthy offspring, might have better over all health and beneficial genetic material to pass on than a cat that is negative for the gene. So every breeder must carefully assess each of their cats and make the best decisions moving forward, balancing diversity in their programs as well as slowly weeding out this gene over several generations. Moving too quickly can even be more disastrous than doing nothing at all. This test only represents a risk. Age, pedigree and HCM scanning can help us determine which cats with this gene have likely dodged that risk or not. Cats with this gene who do not have HCM might have other factors causing that low gene penetrance that could potentially be inherited, which could prove very valuable to pass on.
Should I refrain from adopting a sphvnx that is heterozygous or homozygous for this gene?
No, provided this breeder is also taking all other steps to ensure they are breeding heart healthy cats. I would still be more concerned about the HCM scanning history. We do not yet know how significant or benign this gene is in causing HCM in our breed. We can look to other breeds with breed specific HCM genes to get a rough idea of what our penetrance percentage might be. In one study of Maine Coons, 8% of heterozygous developed HCM, and 58% of homozygous developed HCM. We might find out that our penetrance is much lower than that as well.
Should my kitten be tested for this new gene?
Yes, unless the results of the parents can unequivocally determine the results of the offspring. For instance, if both parents are negative for this gene then all of their offspring will also be negative. While this test is not diagnostic, it might be valuable to know wether or not your cat has a higher risk for developing disease.
Support Breeders who are actively participating in disease mitigation, and improving the over all health of the breed for future generations. This tireless effort protects our beloved breed.
-Shauntay Burris