Test specialties: Important information on specific tests

Many DNA-tests are offered in routine settings. Incidentally, a specific comment applies to a test. For tests in production, this is present in the field ´Test specific information´  in various webshops. However, for quick reference below an overview of these important comments is provided.

Furthermore, the overview below includes comments on tests which were removed from the portfolio.

Finally, the overview contains a list of test for which reference samples are needed for validation purposes.

DOGS

Hip Laxity 1 and 2  H919 en H421Test available in webshop.

Laxity of the hip joint is a frequent disorder in dogs. The disease is of multifactorial origin, which means that the symptoms are a combination of genetic factors as well as the environment.

Hip Laxity has two main characteristics:

• Laxity: This can be defined by ‘an abnormal freedom of movement of the bone in the hip joint’. As a result, the hip is less stable compared to healthy dogs.

• Ossification and bone formation. In younger dogs, the normal process of bone formation can be slowed down.

Both Laxity and Ossifcation disorders lead to the development of artrosis when dogs mature. Dogs which are affected most can already express symptoms after a few months. Other affected dogs develop artrosis at later ages.

This marker is part of a panel of genetic factors influencing hip laxity.

The disease is of multifactorial origin, which means that the symptoms are a combination of genetic factors as well as the environment. The marker is part of a panel of genetic factors influencing hip laxity. Examples of environmental factors are feeding patterns and exercise.

For each genetic factor of a multifactorial disease, the results can be reported as ‘Normal’, ‘Carrier’ or ‘Affected’.

Animals with the favourable variant are indicated as 'Normal'. Animals carrying one copy of the undesirable genetic variant are indicated as 'Carrier', whereas animals carrying two copies of the undesirable genetic variant are indicated as 'Affected'.

Each individual test is part of a multifactorial disease. An animal may be normal for Hiplaxity 1 and affected for Hiplaxity 2 at the same time. This information may be applied when breeding.

Regarding the actual development of hiplaxity in dogs, these markers should be interpreted as risk assessment. Dogs ‘Normal’ for Hip Laxity 1 and 2 have a lower risk compared to dogs being ‘Affected’ for Hip Laxity 1 and 2.

Leukoencephalomyelopathy (Previously: H.417). This test is no longer available in our webshop.

The scientific basis for this test is invalid based on laboratory results. According to literature, the mutation described results in a lethal disease in which affected dogs develop tremors at 2 –9 weeks of age followed by progressive neurological worsening nerve dysfunction. In our laboratory, we have seen many dogs with the affected genotype which were completely healthy.

The test was described by F-Y Li et al, in ‘Canine spongiform Leukoencephalomyelopathy is associated with a missense mutation in cytochrome b’. Neurobiology of Disease 21 (2006) 35 – 42.

Skull diversity (Previously: H.376). This test is no longer available in our webshop.

This test is not active, as the genetic variant described in the scientific literature is not relevant for breeding.

The test was described by Jeffrey J. Schoenebeck et al, in ‘Variation of BMP3 Contributes to Dog Breed Skull Diversity’. Scientific journal Plos Genetics, August 2012, Volume 8,  Issue 8, e1002849.

CATS

Hypertrophic Cardio Myopathy 2 (HCM2, K.764). Test available in webshop.

Hypertrophic Cardiomyopathy (HCM) is known in virtually all animal species, including humans. HCM is the most common cause for heart failure in young adults, both humans and animal species. The heart failure is caused by a thickening of the heart muscle, which ultimately results in a loss of function of the heart. In several cat population the clinical risks have been associated with genetic mutations.

It should be noted that in humans with the same disease, there are many different genetic mutations which can cause this disease. Presumably, the situation is similar in cats. In the statistics currently available, approximately half of the Maine Coon cats, which have been diagnosed with HCM by echocardiography or necropsy have the HCM mutation. Obviously, the remaining half have HCM from other causes, probably other mutations. This means that the absence of a mutation in a cat does not mean that it will never develop HCM. Additional mutations will be identified that may be tested for as well. Cats that are positive for the test will not necessarily develop significant heart disease and die from the disease. Some cats will develop a very mild form of the disease and will live quite comfortably, and some might even never develop any signs of the disease. It is not known at this time what makes one cat with the mutation develop HCM early, while another cat develops a much milder and later form, or no signs at all of any heart disease.

In humans, at least 10 mutations have been described, all resulting in HCM. In cats the first mutations have been found, but certainly more mutations in many breeds will be found in future research.

Several tests are available in different breeds. For the different mutations, clinical studies linking a mutation to HCM are not always available. It is up to the owner to decide which test to perform.

Based on a recent inventory at other laboratories, we have learned that the test for HCM2 is not offered internationally. Consequently, we have contacted researchers in the USA. Based on our current information, we have decided to remove the HCM2 test from the Combination Package for Hereditary Diseases. For the moment, the HCM2 test remains available as a separate test.

HORSES

For our test portfolio in horses, no comments are available.