Exclusive Q&A with GenSol Diagnostics

We're thrilled to work with GenSol Diagnostics to bring our community a special Q&A series featuring Dr. Micah Halpern, Principal Scientist and Owner of GenSol Diagnostics. Every week for a month, Dr. Halpern will answer a breeder-submitted question. Check out all the questions and answers here!

Q: Can genetic testing predict all health problems?

A: Genetic testing has become a great tool for breeders and pet parents to gain deeper insight into their dogs and make more informed breeding and health care decisions. For breeders, it gives you knowledge of DNA mutations that exist in your line that may not be apparent by looking at the dam and sire but can lead to genetic disease in the puppies. Some diseases caused by genetic mutations also may not exhibit symptoms until later in the dog’s life.

By knowing the genetic status of your dog, pet parents can plan ahead for their dog’s health knowing what could be coming. We are not currently able to predict all health problems that can arise from genetic mutations primarily due to the fact that not all mutations for all health problems are currently known. As basic research continues to discover the location of these mutations, we will be able to better test and predict disease for an ever growing list of genetic diseases. It is important to know that there are also other types of health issues that are not impacted by a dog’s DNA. These can include bacterial and viral infections, issues during development, and environmental issues like diet or exposure to toxins. For these types of health problems, please consult your veterinarian.

Q: Is there a test for goniodysgenesis and what is the genetic transmission?

A: Goniodysgenesis is a condition that affects the ability of the eye to drain fluid known as aqueous humor. The inability to properly drain this fluid can eventually lead to a condition known as glaucoma. Glaucoma is characterized as an increased pressure in the eye which can be painful and eventually lead to blindness. An eye exam by a veterinarian can measure the pressure in the eye for a definitive glaucoma diagnosis. With an early diagnosis, glaucoma can be managed with different medical and surgical options.

There is a genetic test for Border Collies that can identify a dog’s risk of developing glaucoma by detecting a known mutation associated with goniodysgenesis. This genetic test allows breeders to make informed decisions about breeding pairs that reduces the risk of passing the mutation and potentially leading to affected puppies. This mutation is inherited in a recessive manner which means the puppy must inherit two copies of the mutation to be impacted by the disease. A dog that inherits one copy of the mutation is unlikely to show signs of the disease but can pass the mutation to their offspring.

The Border Collie glaucoma mutation that has been identified is very strongly associated with severe goniodysgenesis. This means that most dogs that inherit two copies of the mutation will eventually develop goniodysgenesis that will likely progress to glaucoma. Although this strong association means it is very likely that the identified mutation is the cause of this disorder, it is important to note that the condition may be more complex and require additional research to better determine disease progression.At this point in time, this DNA test is considered valuable in making breeding decisions to prevent puppies with the disease.

Q: Is Addison’s or Cushing’s disease a genetic disorder? Can you know if your puppies are inclined to either of these?

A: Addison's disease and Cushing’s disease are two sides of the same coin.  Addison’s disease, also known as hypoadrenocorticism, is a disorder where the adrenal glands produce insufficient levels of the hormones aldosterone and cortisol.  These two hormones are crucial for regulating typical body functions like blood pressure, metabolism, and the stress response.  Addison’s disease can affect any breed of dog, with certain breeds being more predisposed, including Nova Scotia Duck Tolling Retriever, Great Dane, Standard Poodle, West Highland White Terrier, Bearded Collie, and Portuguese Water Dog.  To diagnose Addison’s disease, a veterinarian uses a blood test to check levels of cortisol and aldosterone.  Cushing's disease, also known as hyperadrenocorticism, is a condition where a dog's body produces too much cortisol.  There are breeds that are more prone to Cushing's disease and can include Poodles, Dachshunds, Yorkshire Terriers, and German Shepherds and the disease is diagnosed by a veterinarian in a similar manner to Addison’s disease. 

The research and understanding of the genetic causes for both these diseases in dogs is ongoing with only a single mutation identified to date that has been correlated with Addisson’s disease.  It is known as Juvenile Addison's Disease (JADD) and the mutation has been demonstrated to only affect Nova Scotia Duck Tolling Retrievers.  This particular form of the disease is inherited in a recessive manner meaning that affected puppies must inherit a copy of the mutation from both parents to be affected.  The JADD mutation in Tollers is not completely penetrant meaning that not all puppies with two copies of the mutation will go on to develop the disease.

There is a number of research projects currently underway to determine the specific mutations for Addison’s disease in a number of other breeds.  Hopefully with more research, additional testing will become available to avoid the genetic inheritance of this condition.  There is also research being devoted towards finding the mutations responsible for Cushing’s disease with no available genetic tests for the disease to date.  It is important to know that there can be other causes for both of these diseases that are not genetic and hence diagnosis by a veterinarian is the best tool available for identifying and regulating the disease.

Q: Please review the risk associated with IVDD/CDDY when a dog inherits 1 copy versus 2 copies. I realize there is less risk for passing the trait on to offspring but as a dominant trait wouldn't the dog still be at risk with 1 copy? Is there less risk of disease with only 1 copy?

A: Intervertebral Disc Degeneration (IVDD) is a genetic disease characterized by vertebral disc rupture within the spinal cord.  Due to this mutation, the discs develop abnormal degeneration of the nucleus pulposus, which is the center of the intervertebral disc that normally provides cushion and flexibility to the spine. This degeneration eventually leads to a mineralized or calcified disc which is what predisposes it to herniate and move the disc into the spinal canal.  The same mutation responsible for IVDD is also one of the mutations responsible for Chondrodystrophy (CDDY) which leads to the dog having shortened legs.

With respect to IVDD, the mutation is inherited in a strictly dominant manner which means that 1 copy of the mutation is sufficient to cause the disease.  This means that dogs that inherit either 1 or 2 copies of the mutation have a similar risk of disease.  Interestingly, when it comes to leg length, dogs with 2 copies of the mutation typically exhibit shorter legs on average than dogs that have 1 copy of the mutation.  It is important to note that while the presence of the mutation does increase the risk of IVDD, there are cases of dogs testing clear that still go on to develop the disease as well as dogs that inherit 1 or 2 copies of the mutation that never appear to develop the disease.

One last thing to be aware of is that when it comes to testing for the IVDD/CDDY mutation, make sure that the test being performed is a direct test for the causative mutation.  There are IVDD/CDDY tests available that are known as "indirect" or "linkage" tests because they are detecting a mutation in close proximity to the disease causing mutation and therefore will never be 100% accurate.