Discovery of Gene Defect Linked to Heart Disease in Cats
Written by Steve Dale   
August, 2005

You can’t help but wonder if Dr. Kathryn Meurs hollered “Bingo!” when she found a gene mutation in Maine Coon cats that is clearly associated with feline hypertrophic cardiomyopathy, the most common form of heart disease in cats.

You can’t help but wonder if Dr. Kathryn Meurs hollered “Bingo!” when she found a gene mutation in Maine Coon cats that is clearly associated with feline hypertrophic cardiomyopathy, the most common form of heart disease in cats. After years of scratching for research dollars and laboriously sequencing genes, she finally discovered the genes that were linked to sarcomeric proteins in the heart and was recently able to publish the findings.

Dr. Mark Kittleson, a cardiac veterinary specialist at the School of Veterinary Medicine at the University of California, Davis has partnered with Meurs. “First we’ll confirm this finding is really true of Maine Coon cats in the general population (outside a lab setting), and then we look for other mutations in other breeds. Meanwhile, we’re able to identify individual Main Coon cats with the mutation. So, yes, this discovery is potentially important for saving lives.”

Feline hypertrophic cardiomyopathy (HCM) is by far the most common heart disease in cats. According to several studies, it is also the number one cause of spontaneous death in all indoor adult cats.

Just as the rare football star who drops suddenly and dies on the field – the same thing occurs in cats. Except, in cats, sudden death due to HCM is surprisingly common, and often the first – and only - symptom. In people HCM is generally diagnosed. In cats, when diagnosed, one symptom may be a clot, causing debilitating stroke-like symptoms, which can be treated. The problem is that these stroke-like events continue and typically worsen.

“This is very difficult to deal with emotionally and also financially,” says Dr. Susan Little, executive director of the Winn Feline Foundation, a not for profit organization that helped to fund the ground-breaking research. “Sudden death though is especially traumatic to witness – you’re just not prepared for it.”

Kittleson explains that HCM is a thickening of the left chamber of the heart, causing the heart to over-work. Sometimes vets can diagnose HCM hearing a murmur or an exceedingly rapid heartbeat (though neither is always necessarily indicative of HCM). Cardiac vets can identify HCM using an ultra-sound.

While any cat, including mixed breeds, can have HCM, it was Kittleson who learned years ago, there is a genetic and also a breed tendency, among the American Shorthair, Devon Rex, Ragdoll, Persian and the Maine Coon.

Since HCM often isn’t found until cats are young adults or older, breeding out genetic carriers is challenging if not downright impossible. A male cat, for example, can sire several litters before he reaches, say 5 years, and then is unexpectedly diagnosed with HCM – even if there is no immediate family history. Kittleson says naturally that cat is neutered, but gene mutations – which ‘till now have remained a mystery - have already been potentially passed on.

Kittleson says the hopes now that the mystery is unraveled – at least for Maine Coons – the hope is HCM carriers can be identified as kittens.

Meurs, who was at Ohio State University College of Veterinary Medicine – Columbus, has been sniffing for the HCM gene abnormality since 1995. Several years of research focused on sarcomeric proteins associated with the thickening of the heart that occurs in HCM in people. The “Bingo” winner and breakthrough came when Meurs discovered cardiac myosin binding protein C doesn’t get properly incorporated into the muscle of the Maine Coon cats with HCM. Meurs then traced the gene responsible for this abnormality.

Little, who is in Ottawa, Ontario, Canada says, “By identifying the gene and the protein the gene produces, it’s more likely a drug may be created to intervene.”

While there are drugs currently used to hopefully control HCM (in the cats who are lucky enough to be diagnosed), the reviews on their effectiveness are mixed at best.

Kittleson is now researching the potential efficacy of two medications that would successfully treat HCM. To determine the impact of these meds, Kittleson is looking at the hearts of the cats using MRI imaging, a first for revealing changes in cats’ hearts.

Generating Funds for Feline Research

The research conducted by Meurs and Kittleson was financed through the Ricky Fund of the Winn Feline Foundation, private donations to Ohio State and the University of California, Davis.

The Morris Animal Foundation is another funder of animal health studies, and executive director Dr. Patricia Olson says there’s actually a shortage of proposals on feline health.

“With so much to learn, and so much to do it’s shocking and it’s inexcusable there’s money (for funding research) that isn’t being used,” says veterinary cardiologist Dr. Paul Pion, co-founder and president of the Davis, CA-based Veterinary Information Network.

“I’m grateful for the dollars I’ve received, but it’s a struggle,” says Kittleson. “I assume my colleagues see a lot more money being thrown at the problem of HCM in humans without a significant breakthrough – so they figure, how can we ever solve the problem in cats?”

Pion, isn’t as diplomatic, “With the progress Kate (Meurs) has made, it’s flabbergasting there aren’t more investigators interested.”

Meurs, who is in the process of setting up a new lab at Washington State University College of Veterinary Medicine – Pullman, as the Dr. Richard L. Ott Endowed Chair in Small Animal Medicine & Research points out there are many mutations in human HCM, so it’s likely the mutations will vary as she investigates other breeds. “The prospects are exciting, but we have a long ways to go,” she says.

Kittleson – who with Pion – helped to solve the mystery of a related heart disease in cats several years ago says, “I just think about all the cats who suffer with this disease or die early. My hope is that one day we can do something about it.”