- Bedington Terrier
CT - Deletion
There is great news for all Bedlington breeders and owners in the fight to eliminate copper toxicosis from the breed. Thanks to the hard work of many investigators, a better picture of the causes of the disease is beginning to appear. In 1996 the Brewer lab at the University of Michigan discovered the linked marker (Co 4107) to the disease and the current marker typing system was developed. This marker system had two alleles, called 1 and 2. It was discovered that at least 95% of the disease alleles, called Ct, were associated with the 2 marker allele. Further, about 75% of 2 alleles were associated with a Ct allele. So the breeding strategy has been to breed out the 2 alleles, and try to breed 1,1 dogs. The recent discovery that a deletion in part of the Commd1 protein (Murr1) is one cause of the disease, has enabled the development of a test strategy to further eliminate the disease in 2,2 marker type dogs.
The situation is that all Ct (bad) alleles on 2 marker type chromosomes have the Commd1 deletion. However, there are occasional Ct alleles associated with a 1 marker type chromosome, and none of these have the deletion. A new test has been developed which detects the Commd1 deletion that is useful in 2,2 and 2,1 marker type dogs, but is not useful in 1,1 type dogs. By using a combination of the two tests, 2,2 marker type dogs can be clearly differentiated into Ct/Ct, Ct/n, and n/n dogs (n stands for the normal allele). (2,2) dogs that are n/n are fine to breed and are clear of Ct. 1,2 type dogs that are n/n are also fine to breed and have a 95% probability or better of not passing on a Ct allele along with the 1 allele.
Occasional dogs with a 1,1 marker type are now known to have copper toxicosis, both in the U.S. and Europe. The frequency of this is rather low, probably 5% or less, but the new Commd1 test is not helpful here because none of these Ct affected alleles on marker type 1 chromosomes carry the deletion.
To validate the correlation that has been shown in Canada and Europe between Ct and the Commd1 deletion, we tested 43 Bedlington Terriers of known Ct status from the families used in the validation of the VetGen marker system. We also tested 65 Bedlingtons of unknown Ct status.
The VetGen Solution
The results are as follows:
n = normal allele d = deleted allele
New dogs of unknown Ct status
48 of 65 2 marker alleles are associated with the deletion while 17 of 65 are associated with the normal allele
Old dogs of known Ct status
36 of 44 2 marker alleles are associated with the deletion while 8 of 44 are associated with the normal allel
* 2 of these 6 are affected
** All 15 of these are affected
Our earlier work identified 1,1 and 1,2 affected dogs in US, Canadian, and European pedigrees. We have now confirmed the findings of other labs that there are affected Bedlington Terriers that are 1,1 and n,n. Work is ongoing to find a test predictive of Ct on 1 marker chromosomes.