Breeds Affected: Chinese Crested, Chihuahuas
Samples Accepted: Blood, Buccal Swabs
Disease Information: NCL7 is a lysosomal storage disease well known in humans, that has now been described and genetically characterized in one Chinese Crested dog. The affected dog was known for compulsive licking and had, between 12-18 months of age, developed blindness, anxiety, and disorientation. With progression of the disease, the dog began to eat non-food items (pica), and showed agitation, a lack of coordination, and increased sleeping. The disease is untreatable, and the dog was humanely euthanized.
Inheritance Information: NCL7 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 affected offspring.
N/ncl7 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/nlc7 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
ncl7/ncl7 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/nlc7 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/ncl7 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/ncl7 x N/ncl7) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (ncl7/ncl7) should not be used for breeding.
Test Information: This mutation test identifies a single base deletion in MFSD8 gene.
Ashwini, A., D’Angelo, A., Yamato, O., Giordano, C., Cagnotti, G., Harcourt-Brown, T., Mhlanga-Mutangadura, T., Guo, J., Johnson, G.S., Katz, M.L. :Neuronal ceroid lipofuscinosis associated with an MFSD8 mutation in Chihuahuas. Mol Genet Metab 118:326-32, 2016. Pubmed reference: 27211611. DOI: 10.1016/j.ymgme.2016.05.008.
Guo J, O’Brien DP, Mhlanga-Mutangadura T, Olby NJ, Taylor JF, Schnabel RD, Katz ML, Johnson GS.: A rare homozygous MFSD8 single-base-pair deletion and frameshift in the whole genome sequence of a Chinese Crested dog with neuronal ceroid lipofuscinosis. BMC Veterinary Research 2015, 10:960 doi:10.1186/s12917-014-0181-z.
Further information is available at the Online Mendelian Inheritance in Animals website.