23 & MEow

October 26, 2019

Genetic testing has become all the rage in humans, and now pets. Unfortunately, very little is known about cat genetics. At this moment in time, it is difficult to know if a “positive” test will translate into an increased risk for a specific disease. It appears the goals of these genetic test companies is to acquire a massive amount of data (and money) with the hope of continuing research and potentially “linking” genetic markers with risk factors for disease. It is unclear if this process will be fruitful or not as these companies are in their infancy. Currently, genetic testing is not regulated and extreme caution must be taken when interpreting any results, especially related to your cat’s health.

It is extremely difficult to determine cause and effect.

There are many factors that determine gene expression. A gene is a part of DNA that has specific instructions to make a molecule (usually a protein). Gene expression is the process of taking that specific information and making that molecule. This expression is tightly regulated and influenced by a number of factors, environment being one of them. Epigenetics is the study of how the environment affects gene expression, essentially turning on or off genes in the body, without changing the gene (or DNA) itself. We humans have a lot of factors that affect gene expression such as diet, exercise, smoking, drugs, air and water quality, chemicals, and stress (i.e. post-traumatic stress disorder or PTSD). Even gender can affect gene expression. Cats do not have as many environmental components that may affect gene expression as we humans. However, there are environmental triggers that may alter gene expression in your cat. Therefore, simply having a gene, especially associated with a disease process as far as we know, does not guarantee your cat will develop that disease. Another way of thinking of this is with identical twins whose DNA is the same. If the twins grow up in different environments (i.e. different households, different schools, different social networks), each twin will act and behave differently. The reason for this difference is because the different environments resulted in different gene expression of the same DNA resulting in two different people.

One example I use is the genetic marker for a heart condition known as HCM (hypertorphic cardiomyopathy) in Maine Coon cats. UC Davis provides a genetic test that detects the A31P gene. Studies have shown that Maine Coon cats with one copy of the gene are 1.8 times for likely to develop HCM while cats with 2 copies of the gene are 18 times more likely to develop HCM. This seems pretty straight forward and this genetic test might be useful in Maine Coon cats. However, the body is complex and a condition like heart disease is not solely determined by the presence of one gene. Many genes interact within the body and there are probably many factors that lead to the development of HCM. This particular gene is not dominant which means the presence of the gene does not definitely determine if a Maine Coon will develop HCM. Some Maine Coon cats do not have the A31P gene and still have HCM. This information is useful to breeders as cats with the A31P genes should not be bred. If your cat has two copies of the A31P gene, a cardiologist consultation early in life will be recommended, but there is no guarantee your cat will develop HCM.

The presence of a gene in your cat

does not equate to a disease.

The above example is for a very specific gene in a specific cat breed from a veterinary school. I feel pretty comfortable that UC Davis is conducting accurate tests and giving realistic expectations about what the results mean. I do not have the same confidence with these new, cat DNA companies that have popped up in the past few years. Where UC Davis gives the very specific gene they are detecting and the scientific studies that reference the gene, it is difficult to determine what exactly these new companies are testing for as their websites do not list the exact markers they are testing. How are the results from these companies validated? Are these results accurate? How do we interpret these results? What recommendations should we give based on positive results?

We do not know how feline genetic data

translates to your cat’s health.

These DNA tests simply give information. One cannot definitely say that your cat will have health consequences based on these tests results. Positive results may lead to unnecessary testing. In time and with enough data, this data may be useful and allow preventative measures to take place before a disease process occurs. Currently, I would not use this information for anything other than entertainment. An extreme concern is that cat owners may elect to euthanize their cat based on this information instead of properly working up their cat with your veterinarian. You are better served by spending your money on annual examination, vaccines, preventatives and wellness screening.

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