Research performed in Professor Hannes Lohi’s canine genetics research laboratory at the University of Helsinki and Folkhälsan Institute of Genetics, Helsinki, Finland has led to the discovery of a genetic mutation responsible for a congenital eye disease in Irish Soft-coated Wheaten Terriers (ISCWTs). The work was funded in part by Wisdom Health and Genoscoper Laboratories, providers of the MyDogDNA™ (Europe) / Optimal Selection™ (United States) test.

Clinical, genetic and biochemical studies revealed that the eye disease in ISCWTs is caused by a mutation in the RBP4 gene. RBP4 encodes a protein that delivers vitamin A from hepatic stores to other tissues. During gestation, maternal vitamin A is transported with the RBP4 carrier protein through the placenta to the developing puppy. Because of the mutation, dams cannot deliver, and puppies not receive vitamin A properly. As a result, puppies suffer from vitamin A deficiency, which is a well-known risk factor for developmental diseases. Vitamin A deficiency in this situation results from the gene defect and therefore cannot be cured by feeding vitamin A supplement, as the affected dogs lack the crucial RBP4 carrier protein to transfer dietary vitamin A from dam to developing puppies.

As part of the study almost 300 ISCWTs both from Finland and multiple other countries were screened, revealing a special mode of inheritance: autosomal recessive with penetrance determined by the maternal genotype. It was found that the disease manifests only if the dam has two defective gene copies, i.e. is homozygous for the mutation. Further, the genotype of the puppy defined the severity of the symptoms. Heterozygous puppies had increased risk of developing coloboma or choroidal hypoplasia whereas homozygous puppies had a very high risk of microphthalmia and blindness. The detailed results of the study are published in a peer-reviewed scientific article that can be found here.

The breed carrier frequency was 22% for the discovered mutation. This gene discovery has enabled the development of a genetic test for the disease to allow management of the condition in breeding programs by recognizing the carriers of one or two copies of the mutation.

For Irish Soft-coated Wheaten Terriers, the MyDogDNA™/Optimal Selection™ screening includes not only the novel eye disease test, but also testing for Protein Losing Nephropathy and Paroxysmal Dyskinesia. Additional test results for inherited traits (e.g., coat color, coat type and body size) and genetic diversity level are also included. Testing for degenerative myelopathy (DM) is additionally available in the United States (Optimal Selection™).

For test ordering, and to learn more about genetic testing for your dog and its breed, please visit: (Europe) or (United States)