DNA Test for Copper Toxicosis in Bedlington Terriers

04/07/2006

The Animal Health Test announces an updated DNA test for copper toxicosis in Bedlington Terriers. The research underlying this test was carried out jointly by a team led by Dr Mike Boursnell at the Animal Health Trust and at the University of Nottingham in the laboratory of Dr Paul Jones (Masterfoods Ltd.). This basic science was developed into a diagnostic test at the Animal Health Trust with funding from the American Kennel Club Canine Health Foundation Inc.

Copper toxicosis is an hereditary disease in which failure of the liver to expel dietary copper leads to a build-up of this toxic metal causing illness and death. It is inherited as an autosomal recessive trait. As such, two copies of the defective gene, one inherited from each parent, need to be present before an individual displays clinical signs. Dogs with one copy of the defective gene and one copy of the normal gene (carriers), will not show clinical signs, but will be able to transmit the defective gene to their offspring. A reservoir of symptom-less carriers exists in the population and when two carriers are bred, affected dogs may be thrown up in the litter. Unlike liver biopsy, DNA testing has the potential to pick out carriers as well as affected dogs so that all dogs bearing the defective gene can now be identified and the disease gene eventually eradicated from the population.

The previous DNA test detected changes in a DNA marker. Recent research has identified the mutation as a massive deletion of part of the DNA of a gene called COMMD1. Studies at the AHT and the University of Nottingham have now identified the limits of this deletion, enabling us to devise a new diagnostic test. This research has been published as: "Characterisation of the COMMD1 (MURR1) mutation causing copper toxicosis in Bedlington terriers" (2005). O. P. Forman, M.E.G. Boursnell, B. J. Dunmore, N. Stendall, B. van der Sluis, N. Fretwell, C. Jones, C. Wijmenga, J. Rothuizen, B. A. van Oost, N. G. Holmes, M. M. Binns and P. Jones. Animal Genetics Vol 36 pp497-501.

The results from the new test will be definitive for this mutation and will identify the dog as CLEAR of, a CARRIER of or AFFECTED by copper toxicosis caused by the deletion in the gene COMMD1.

An explanation of terms used will be provided as follows :

 CLEAR: The dog has 2 copies of the normal gene and will neither develop copper toxicosis caused by the known deletion in the COMMD1 gene, nor pass this mutation to its offspring.
 CARRIER: The dog has one copy of the normal gene and one copy of the mutated COMMD1 gene. It will not develop copper toxicosis caused by this mutation but if bred from will pass on the mutation to (on average) 50% of its offspring.
 AFFECTED: The dog has 2 copies of the mutant gene and has copper toxicosis.

 

This test is an extension of the previous test offered for this disease, which used the DNA marker C04107. The new test is not subject to the element of doubt, which existed in the old test. However, results from the old test are still valid.

While the test is definitive for this mutation, it is possible that there are other genetic causes of copper toxicosis in Bedlingtons, as yet unidentified, which will not be detected by this test.

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