PreciousGem Miniature American Shepherds

Genetic Disease Testing for the Miniature American Shepherd:

Why is genetic disease testing important?

As a responsibility of breeding dogs, I strive to ensure healthy, quality Miniature American Shepherd (Mini Australian Shepherd) puppies. A very important role in improving the breed means testing for common genetic diseases. I need to be able to ensure that I am not allowing deleterious alleles to pass on. In purebred animals, we are essentially striving for homozygosity within the genes so that "like begat like". Often through homozygosity in purebred animals, we suddenly see some negative traits and we should not let them breed from that point on. Many dogs can still be "carriers" of the deleterious allele or disease. However, because they are only carriers, the trait or disease is not usually expressed BUT can still be passed down to offspring. If a carrier dog is bred with another carrier, they can produce puppies that are now expressing this unwanted trait or disease. It is my responsibility to make sure that I know the exact genetic make-up of the dogs I use in regards to these common diseases. My goal is to improve the breed and genetics is an important aspect.

Which testing laboratories are my favorites?

I often recommend Paw Print Genetics when considering laboratories to test breeding dogs through. They have amazing customer service and they use two different methods of testing to ensure accuracy. To my understanding, they are most accurate canine genetic lab because of this.
www.pawprintgenetics.com/products/breeds/189/

​Paw Print Genetics also has a sister company that you can test breeding dogs through as well as your own non-breeding pet. I would recommend Canine Health Check for a great comprehensive genetic disease and trait panel for a competitive price!
www.caninehealthcheck.com/

How is a gene passed from parent to offspring?

The following chart is a Punnet Square which demonstrates a what the probability is of how genetic traits are passed down from the parents to the offspring, particularly with a disease that is recessive. 

MDR1 (Multi-Drug Resistance Gene)

CEA (Collie Eye Anomaly)

Collie eye anomaly (CEA), also known as choroidal hypoplasia (CH), is an inherited disease affecting several dog breeds including the miniature American shepherd. The choroid is the layer of tissue in the eye responsible for supplying blood and nutrients to the Retina. In dogs affected with CEA, the choroid does not develop properly and is therefore thinner than normal. The severity of the condition can vary from dog to dog. In mild cases, affected dogs may only show signs of collie eye anomaly on eye exam between about 5 and 12 weeks of age, just prior to normal, age-related pigmentation of the retina which often masks the characteristic, disease-related changes. After this time period, mildly affected dogs may be impossible to distinguish from normal dogs on eye exam (a phenomenon often referred to as “going normal”) and may not display obvious vision deficits. In more severely affected dogs, clinical signs include malformations of the eye and/or optic nerve (colobomas), retinal detachment, intraocular bleeding, and subsequent blindness. Both mild and severe forms of CEA are associated with the same NHEJ1 gene Mutation. Therefore, predicting the potential severity of the disease in an affected puppy is difficult as mildly affected parents may produce offspring that are severely affected.
​ -Paw Print Genetics

PRA (Progressive Retinal Atrophy)

Progressive retinal Atrophy, progressive Rod-cone degeneration (PRA-prcd) is a late onset, inherited eye disease affecting many breeds of dog. PRA-prcd occurs as a result of degeneration of both rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. Evidence of retinal disease in affected dogs can first be seen on an Electroretinogram around 1.5 years of age for most breeds, but most affected dogs will not show signs of vision loss until 3 to 5 years of age or later. The rod type cells are affected first and affected dogs will initially have vision deficits in dim light (night blindness) and loss of peripheral vision. Over time affected dogs continue to lose night vision and begin to show visual deficits in bright light. Other signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the retina called the Tapetum that can be observed on a veterinary eye exam. Although there is individual and breed variation in the age of onset and the rate of disease progression, the disease eventually progresses to complete blindness in most dogs. Other inherited disorders of the eye can appear similar to PRA-prcd. Genetic testing may help clarify if a dog is affected with PRA-prcd or another inherited condition of the eye.
-Paw Print Genetics

HC (Hereditary Cataracts)

Hereditary cataracts (Australian shepherd type) is an inherited eye disease affecting dogs. Cataracts are opacities in the lens of the eye caused by structural changes in lens proteins. A normal lens allows light to pass through it to the Retina in the back of the eye. Light cannot pass through the parts of the lens affected by cataracts and vision becomes blurry. Dogs with Hereditary cataracts (Australian shepherd type) most commonly present between 2 to 7 years of age with small cataracts that are visible on a veterinary eye exam. Dogs that carry a single copy of the Mutation have an increased risk over the general (normal) population of developing cataracts. In dogs that inherit one copy of the mutation, cataracts develop slowly, sometimes leading to complete blindness. However, it has been speculated that dogs carrying two copies of the mutation are more likely to develop a more rapidly progressing and severe Cataract. Of note, not all forms of cataracts are inherited and environmental factors such as UV damage can also play a role in the severity of disease. This specific mutation in the HSF4 gene shows Incomplete Penetrance, meaning that not all dogs inheriting two copies of the mutation develop clinical disease. This suggests that other unknown genetic or environmental factors may play a role in modifying disease development and progression.
​ -Paw Print Genetics

DM (Degenerative Myelopathy)

Degenerative myelopathy is an inherited neurologic disorder caused by a Mutation of the SOD1 gene known to be carried by miniature American shepherds. This mutation is found in many breeds of dog, and the closely related breed, Australian shepherds, are known to develop degenerative myelopathy associated with this mutation. The variable presentation between breeds suggests that there are environmental or other genetic factors responsible for modifying disease expression. The average age of onset for dogs with degenerative myelopathy is approximately nine years of age. Affected dogs usually present in adulthood with gradual muscle Atrophy and loss of coordination typically beginning in the hind limbs due to degeneration of the nerves. The condition is not typically painful for the dog, but will progress until the dog is no longer able to walk. The gait of dogs affected with degenerative myelopathy can be difficult to distinguish from the gait of dogs with hip dysplasia, arthritis of other joints of the hind limbs, or intervertebral disc disease. Late in the progression of disease, dogs may lose fecal and urinary continence and the forelimbs may be affected. Affected dogs may fully lose the ability to walk 6 months to 2 years after the onset of symptoms. Affected small breed dogs, often progress more slowly than affected large breed dogs and owners may postpone euthanasia until the dog is paraplegic.
​-Paw Print Genetics

CD (Cone Degeneration)

Cone degeneration is an inherited eye disease affecting dogs. Affected dogs develop day blindness (blindness in bright light) and Photophobia (light sensitivity) between 8 to 12 weeks after birth due to degeneration of cells in the eye called cone photoreceptors which are responsible for vision in bright light. Affected dogs have normal vision in low light and structures of the inner eye appear normal on eye exam. Normal cone cell function can be seen on Electroretinogram (ERG) before six weeks of age, but becomes abnormal between 6 to 12 weeks of age and is completely absent in affected adult dogs signifying complete loss of Cone Cells. The cells responsible for vision in low light called Rod photoreceptors are not affected and thus, affected dogs will still be able to see normally in low light throughout life.
-Paw Print Genetics