Discovery
of Gene Defect Linked to Heart Disease in Cats
By
Steve Dale
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.”
