Breeds Affected: Boston Terrier
Samples Accepted: Blood, Buccal Swabs
Disease Information: Limb-girdle muscular dystrophy is a disease in which a mutation in an important structural protein causes abnormal muscle development.
Affected dogs usually show symptoms by 2-4 months of age, including muscle wasting, a stiff and stilted gait, an enlarged tongue and drooling, difficulty swallowing, and frequent vomiting. Affected pups are usually euthanized by 8-10 months of age.
Inheritance Information: Limb-girdle muscular dystrophy (LGMD) is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
The possible genotypes are:
N/N The dog is normal, and cannot produce LGMD-affected offspring.
N/lgmd The dog is a carrier of LGMD, and can pass the allele on to approximately 50% of any offspring. If bred to another N/lgmd carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
lgmd/lgmd The dog is affected with LGMD. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/lgmd carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/lgmd x N/N) without any risk of producing affected offspring. The offspring should be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/lgmd x N/lgmd) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (lgmd/lgmd) should not be used for breeding.
Test Information: Two mutations have been found in SGCD, each of which causes LGMD in one family of Boston Terriers. The Family 1 mutation (Case 3 in the Cox et al. paper) is a small indel in exon 6: SGCD c.534_535delGA, and the Family 2 mutation (Case 1 in the Cox et al. paper) is a complicated mutation, comprised of a small change in SGCD gene (chr4:53262018-53262020, ATG > CC), followed by a deletion of 19,403 bp (chr4:53262030-53281432), which eliminates SGCD exons 7 and 8.
The mutations have not been found outside of these two families, therefore the test is not currently on the list of routine tests recommended for all Boston terriers; however, any Boston Terriers with muscle disease, or its relatives, should be tested to rule out LGMD.
Cox,M.L., Evans, J.M., Davis, A.G., Guo, L.T., Levy, J.R., Starr-Moss, A.N., Salmela, E., Hytönen, M.K., Lohi,H., Campbell, K.P., Clark, L.A., Shelton, G.D.: Exome sequencing reveals independent SGCD deletions causing limb girdle muscular dystrophy in Boston terriers. Skeletal Muscle 7:15, 2017. DOI: 10.1186/s13395-017-0131-0 http://rdcu.be/t74N.
Deitz, K., Morrison, J.A., Kline, K., Guo, L.T., Shelton, G.D: Sarcoglycan-deficient muscular dystrophy in a Boston Terrier. J Vet Intern Med 22:476-80, 2008. Pubmed reference: 18371037. DOI: 10.1111/j.1939-1676.2008.0080.x.
This mutation was discovered, and genetic tests developed by CAG and academic collaborators.