Thread: HCM gene testing- are we wasting our time?

The most recent study is out of France:

Prevalence of the MYBPC3-A31P mutation in a large ... [J Vet Cardiol. 2010] - PubMed result

Abstract

OBJECTIVES: The MYBPC3-A31P mutation has been identified in the USA in a colony of Maine Coon cats with an autosomal dominant hypertrophic cardiomyopathy (HCM). The objectives of this prospective study were: 1) to evaluate the prevalence of this mutation in a large feline population from Europe; 2) to compare these data with the prevalence of HCM in the Maine Coon breed.

ANIMALS AND METHODS: 1) 3757 cats from different breeds including 2744 Maine Coon cats were screened for the mutation. 2) 164/2744 Maine Coon cats were subjected to echocardiography (Echo-Group, mean age = 2.6 years [0.3-11.5]).

RESULTS: 1) In the whole study population, the mutation was only found in Maine Coon cats (prevalence = 41.5%), except for one British Longhair cat. 2) 55/164 (34%) cats from the Echo-Group carried the mutation while only 12/164 (7%; 5/48 heterozygous, 5/7 homozygous mutated, 2/109 homozygous wild-type cats) showed HCM. MYBPC3-A31P was associated with a significant increased risk of HCM (relative risk = 9.91).

CONCLUSION: The MYBPC3-A31P mutation is highly prevalent in Maine Coon cats in Europe and appears to be breed specific with potential marginal events. Young unaffected mutated cats and affected homozygous wild-type cats illustrate the phenotypic and etiological heterogeneity of feline HCM, as demonstrated in humans.
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There was an extremely elevated incidence of HCM in Maine Coons homozygous for the mutation - 71%.

Thanks Ekimmel for taking the time to post. Unfortunately I'm finding it hard to decipher this information. What is a 'marginal event'? How do I know if my cat is mutated, or does that not matter? Could you explain the conclusion? Sorry for being a bit thick... but, help!

Nice to see some new research, and thanks for the post.

Originally Posted by Howlinbob

Unfortunately I'm finding it hard to decipher this information. What is a 'marginal event'? How do I know if my cat is mutated, or does that not matter? Could you explain the conclusion? Sorry for being a bit thick... but, help!

Let me take a shot at the above questions from reading the abstract...

The researchers assembled a population of 3757 European cats of which 2744 were Maine Coons.

They screened these cats for the known HCM mutation and found only one non-MC cat that tested positive. 41.5% of the MCs had the mutation (abstract does not say fraction with one copy, heterozygous, vs. two copies, homozygous). So this is largely a MC-specific health issue.

164 of the MCs were screened by echocardiogram to look for evidence of heart changes indicative of HCM. 55 (34%) of the echoed MCs had the mutation. Only 12 of the 164 cats showed evidence of HCM changes, broken down as follows: 5/48 heterozygous, 5/7 homozygous mutated, 2/109 homozygous wild-type cats (wild-type means free of the mutation).

So here the probability of MCs free of the mutation showing HCM changes was less than 2%, while the probability for hetero MCs was 10%, but for homo mutated cats it was 71%!

So again we see that homozygous MCs--those with two copies of the MYBPC3 mutation--are virtually certain to undergo structural changes of the heart consistent with HCM. How many of these will show symptoms and how many will die prematurely was not addressed by this study.

Hetero MCs fared much better, though I note that the median age of the echoed population of cats was stated as 2.6, which is quite young. If it was more like 5, we might have seen the hetero percentage be much higher (and the homo group be much smaller due to them having died!).

What does this tell a person thinking of buying a MC? In my opinion it tells them quite clearly that if they want to buy a MC that has the best chance to live a long and healthy life, they should absolutely avoid getting a kitten that was homozygous for the mutation, and most likely also avoid a hetero kitten.

The only thing I found surprising here was the claim that over 40% of European MCs carry the mutation. That makes buying from breeders that do not do HCM testing pretty risky.

As for how you can find out about your own cat, well ideally your breeder could tell you. However it is possible to have your cats tested with a simple mouth swab. Here is the original lab that does it (run by the person that discovered the mutation):
Cat DNA Tests from the VCGL at the College of Veterinary Medicine

Other labs now do the testing as well, though whether they are as reliable is probably an open question.