Genetic testing and dog gender predict risk of disease with 75% accuracy-ScienceDaily

German shepherds are predisposed to congenital idiopathic megaesophagus (CIM). It is a hereditary disease in which puppies develop an enlarged esophagus and cannot move food to the stomach. Puppies in this state are unable to breed due to backflow of food, often leading to euthanasia.

While German Shepherds have the highest incidence of this disease, other varieties such as Labrador Retrievers, Great Dane, Dachshunds and Miniature Schnauzers are also susceptible. Researchers do not yet know if the same genetic variation is involved in the development of diseases of other varieties.

Researcher Lee Ann Clark, an associate professor of genetics and biochemistry, and her collaborators used German Shepherd dog breeders to reduce the risk of future littermate puppies developing illness. We have developed a genetic test for possible diseases.

journal PLOS Genetics The survey results were released on March 10.

CIM is often found when puppies wean from breast milk to solid foods about 4 weeks old.

“They are not swallowing. When a puppy swallows food, it only sits in the esophagus and does not cause those continuous contractions that normally occur to help push food into the stomach.” Said Sarabel, a graduate research assistant, the first author of genetics and research. “Gravity does not help transport food to the stomach because the dog’s esophagus is horizontal rather than vertical like we do.”

Puppies with megaesophagus need to eat and drink while sitting upright in the dog’s high chair to get food and water into their stomachs, and then stay there for up to 30 minutes. Some may exacerbate the condition, but often require an upright diet, a small liquid diet multiple times daily, gelatin cubes, and lifelong symptomatic treatment with medication.

In this study, Clark and Bell performed a genome-wide scan to identify genes associated with the disorder. Scanning revealed an association between canine chromosome 12 and mutants within melanin-concentrating hormone receptor 2 (MCHR2). This affects appetite, weight, and how food travels through the gastrointestinal tract. Clark and her team believe that an imbalance in melanin-concentrated hormones is involved in CIM.

The study also found that male puppies are twice as likely to be affected by the disease as females. Researchers believe that higher estrogen levels allow food to pass through the stomach more effectively, thereby preventing the onset of the disease.

“What they found in people is that estrogen has the effect of relaxing the sphincter muscles that connect the esophagus to the stomach. Having more estrogen makes it easier for smooth muscles to open naturally. It increases your motility. Stomach, “Bell said. “In dogs with megaesophagus, a drug called sildenafil has shown good results. It relaxes the sphincter that connects the esophagus to the stomach.”

Sildenafil is a general term for the active ingredients of Viagra. Sildenafil will increase the proportion of dogs that overcome the disease and eliminate the need to use a high chair when eating, Clark said.

The MCHR2 variant, along with the dog’s gender, can predict whether a dog will develop megaesophagus with 75% accuracy. Owners can wipe the dog’s gums and submit a sample to a genetic testing company to find out which mutants the dog has inherited.

This test is a tool that breeders can use to reduce the incidence of disease while maintaining genetic diversity.

“One of the things I emphasize about any disease of any breed is that it’s okay if you don’t have the disease. If you’ve been breeding German Shepherds for 20 years and haven’t had a puppy with megaesophagus. Do not breed. Use this test, “she said. “But if you are a breeder and have a megaesophagus puppy, you may benefit from the test.”

This work was partially supported by funding from the Collie Health Foundation, the American Kennel Club Dog Health Foundation, the Upright Dog Brigade, the Animal Orthopedic Foundation, and the National Institute of Health’s National Institute of Medical Sciences.