Round up of the genetic mutations causing HCM in Maine Coons

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I have decided to do what I would call a 'round up' of the mutated genes behind the disastrous inherited heart disease of hypertrophic cardiomyopathy (HCM) in this very popular domestic cat breed which is in top three most popular breeds on some polls. 

Mutated genes cause HCM in Maine Coons
Mutated genes cause HCM in Maine Coons, but the problem is fixable by removing studs and queens with the mutation from breeding lines. Why isn't this happening? Image: MikeB

By 'round up' I mean pulling together the strands of information that I have discovered about the causes of this disease from research conducted over many years. I have endeavoured to use plain English at all times as this is a very technical topic.

A round up is needed because different research projects have come to apparently different findings, but they are overlapping as in all cases the genetic mutation responsible has a negative impact on the creation of heart muscle such that HCM is programmed to occur at some stage in the affected cat's life and this disease can affect young Maine Coons and old.

HCM

Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle becomes thickened (hypertrophied). This impairs the functioning of the heart to the point where it causes death.

On my research there are two recorded mutated genes involved.

Troponin-T (TNNT2)

This is a mutation in a gene named Troponin-T.  It is a mutation found in humans and for the first time was revealed to be associated with heart disease in cats. This is a non-sex-linked (autosomal) recessive gene.
"The gene is involved in regulating calcium in the heart which regulates pumping action of the heart. If you know this, you can treat this cat and other carriers of this gene differently when addressing heart disease. You can consider calcium blockers, channel blockers or other types of drugs. This type of diagnosis can be essential in heart treatment." - Sakthivel Sadayappan, Ph.D., professor in the UC College of Medicine.

Read more. 

 Genetic mutation of MYBPC3-A31P

This mutation is linked to HCM in 41.4% of European Maine Coons. It instructs the developing body to make cardiac myosin protein which is one of the building blocks of heart muscle cells. The way the gene causes HCM is very complicated and for specialist scientists but in summary this is the finding of a study: "the A31P mutation causes HCM through a poison polypeptide mechanism that disrupts cMyBP-C or myocyte function." Read more.

What is a gene mutation?

"Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection" (genome.gov). The mutated gene is passed from parent to offspring as a recessive gene, which means both parents have it.

Bad instructions

These mutated genes send bad instructions in the building of heart muscle. 

Cull breeding Maine Coons carrying with gene?

Why don't the breeders cull (remove from their breeding programs) the studs and queens that have the genetic mutation and start again with clean, healthy cats? Answer: the stud cats with the disease which they pass on to kittens are great looking Maine Coons that are showstoppers, and their kittens sell well. The breeders compromise. 

But they shouldn't because it is unethical and against the principles of animal welfare and the rules of cat associations who do nothing about it. Wrong? Tell me.

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