A gene mutation responsible for a devastating heart disease in cats — which is also a leading cause of sudden death in young athletes — has been identified by a team of researchers at UC Davis, Ohio State University, and the Baylor College of Medicine.

This is the first report of a spontaneous genetic mutation causing any type of heart disease in a cat or dog and the first to identify a mutation in a non-human species causing hypertrophic cardiomyopathy. The discovery of the mutation in Maine coon cats was reported Oct. 19 online in the journal Human Molecular Genetics.

The human form of hypertrophic cardiomyopathy was responsible for the deaths of Boston Celtics basketball player Reggie Lewis in 1993 and Loyola Marymount University basketball player Hank Gathers in 1990. The disease causes an excessive thickening of the muscle of the left ventricle, the lower left chamber of the heart.

"This finding paves the way for development of a screening test that will identify those Maine coon cats carrying this genetic mutation so that they can be identified before they are bred, thus reducing the incidence of the disease and, we hope, ridding this breed of the disease," said Mark Kittleson, a veterinary cardiologist at UC Davis and a co-author on the study.

"We also are hopeful that this discovery will provide a valuable model for investigators in both veterinary and human medicine who are studying the disease," he said.

Kittleson noted that the findings of this study should equip scientists to further investigate the mechanism by which this mutation leads to thickening of the muscle and potentially to pursue novel treatments for the disease, based on this knowledge.

Hypertrophic cardiomyopathy occurs in one out of every 500 humans and is the most common heart disease in domestic cats. It is characterized by progressive thickening of the left ventricular myocardium (heart muscle) — most commonly during adolescence and young adulthood in both humans and cats — a defect that can be detected if the heart is examined using an ultrasound procedure known as echocardiography.

The disease, however, is highly variable, and in some cases ultrasound evidence is not present until much later in life. Sudden death from abnormal electrical activity in the heart can occur at any stage. At some age, the disease reaches its maximum severity, ranging from mild to severe. In cats, if the disease is severe, it causes heart failure.

When viewed at the microscopic level, hypertrophic cardiomyopathy in humans and Maine coon cats appears as poorly aligned muscle fibers. The fibers are aligned in an orderly parallel fashion in normal heart muscle but are scattered erratically in a heart affected by the disease. This abnormality is thought to interfere with the electrical activity of the heart, resulting in rapid or irregular heart rhythms.

Cats with hypertrophic cardiomyopathy often develop severe disease, which may lead to heart failure, or a clot in the left atrium that most commonly breaks loose and lodges in the terminal aorta, resulting in acute pain and paralysis. Sudden death often occurs.

"Veterinary therapies for this condition in domestic cats cannot halt the progression of the disease," Kittleson said.

"These therapies are only able to provide limited relief when the disease is severe, so the prognosis for severely affected cats is often poor," he added. "Consequently, preventing the disease from occurring by identifying affected cats can save a lot of heartache."

Since the early 1990s, Kittleson and colleagues, primarily Kathryn Meurs, formerly of Ohio State University and lead author on this paper, have been studying the genetic basis of the disease in a research colony of Maine coon cats at UC Davis. Meurs is now at Washington State University.

Previous research in humans with hypertrophic cardiomyopathy has identified more than 200 mutations in 11 genes involved with the production of certain muscle proteins known as sarcomeric proteins, which are responsible for the heart's contraction.