Researchers have discovered a gene mutation that causes a deadly heart defect in Newfoundland dogs. They hope the findings will lead to better breeding practices.
Newfoundlands—those massive, furry, black dogs—are all too often afflicted with a potentially lethal congenital disease called subvalvular aortic stenosis, or SAS, which also affects other dog breeds, including the golden retriever.
Although rare, SAS sometimes affects children, but when it is diagnosed, surgical removal of the ridge or ring below the aortic valve is one option for improving the child’s health. In dogs, however, such a surgical procedure has not increased survival. And open-heart surgery for dogs is only available at a few centers around the world.
“Our hope now is that breeders will be able to make informed breeding decisions and avoid breeding dogs that harbor this mutation, thus gradually eliminating the disease from the Newfoundland breed,” says Joshua Stern, a veterinary cardiologist at the University of California, Davis, who led the study.
“In addition, now that we know one gene responsible for SAS and more about which proteins are involved, we can move forward to consider novel therapies that may help treat this devastating condition.”
The researchers conducted a “whole genome” analysis, scanning thousands of genes, which revealed that the mutation associated with SAS resides in a gene called PICALM. This same gene mutation has been associated with the formation of plaque-like lesions in the brains of people with Alzheimer’s disease, Stern says.
The researchers also conducted a pedigree analysis in a family of 45 Newfoundland dogs to examine the inheritance pattern of the SAS mutation. This analysis confirmed that the inheritance follows a certain pattern, by which only one parent needs to be carrying the gene mutation in order for the offspring to inherit the disease, and that not all dogs carrying the mutation will develop the disease.
Symptoms and life expectancy
SAS shows up in the dog’s heart as abnormal tissue growth—often forming a ridge or ring below the aortic valve, which restricts blood flow from the heart into the aorta.
Diagnosing and treating SAS, however, is particularly challenging because the disease may appear in mild to severe forms. The first sign that a dog has SAS may be a collapse, fainting spell, irregular heart rate, or even sudden death. Veterinarians sometimes discover the disease when they detect a heart murmur and conduct further diagnostic tests such as chest X-rays, an echocardiogram, or an electrocardiogram.
Dogs with the mild form of SAS may have a normal lifespan. Those with the severe form, however, often die by the time they turn four years old, even with therapeutic drugs.
Researchers are now beginning to study why SAS is less severe in some dogs while causing severe symptoms in others. They also are examining the genetic basis of SAS in the golden retriever, Rottweiler, and other dog breeds.
Genetic tests for determining whether a dog carries the PICALM mutation are now available through North Carolina State University’s College of Veterinary Medicine and will soon be available through the Veterinary Genetics Laboratory at the UC Davis School of Veterinary Medicine.
The Morris Animal Foundation, Pfizer Animal Health training grant, and the Newfoundland Club of America supported the research, which appears online in the journal Human Genetics.
Source: University of California, Davis