An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9.
OBJECTIVE
To identify the causative mutation in a canine cone-rod dystrophy (crd3) that segregates as an adult onset disorder in the Glen of Imaal Terrier breed of dog.


METHODS
Glen of Imaal Terriers were ascertained for crd3 phenotype by clinical ophthalmoscopic examination, and in selected cases by electroretinography. Blood samples from affected cases and non-affected controls were collected and used, after DNA extraction, to undertake a genome-wide association study using Affymetrix Version 2 Canine single nucleotide polymorphism chips and 250K Sty Assay protocol. Positional candidate gene analysis was undertaken for genes identified within the peak-association signal region. Retinal morphology of selected crd3-affected dogs was evaluated by light and electron microscopy.


RESULTS
A peak association signal exceeding genome-wide significance was identified on canine chromosome 16. Evaluation of genes in this region suggested A Disintegrin And Metalloprotease domain, family member 9 (ADAM9), identified concurrently elsewhere as the cause of human cone-rod dystrophy 9 (CORD9), as a strong positional candidate for canine crd3. Sequence analysis identified a large genomic deletion (over 20 kb) that removed exons 15 and 16 from the ADAM9 transcript, introduced a premature stop, and would remove critical domains from the encoded protein. Light and electron microscopy established that, as in ADAM9 knockout mice, the primary lesion in crd3 appears to be a failure of the apical microvilli of the retinal pigment epithelium to appropriately invest photoreceptor outer segments. By electroretinography, retinal function appears normal in very young crd3-affected dogs, but by 15 months of age, cone dysfunction is present. Subsequently, both rod and cone function degenerate.


CONCLUSIONS
Identification of this ADAM9 deletion in crd3-affected dogs establishes this canine disease as orthologous to CORD9 in humans, and offers opportunities for further characterization of the disease process, and potential for genetic therapeutic intervention.
Goldstein
Orly
O
Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, NY 14853-6401, USA.
Mezey
Jason G
JG
Boyko
Adam R
AR
Gao
Chuan
C
Wang
Wei
W
Bustamante
Carlos D
CD
Anguish
Lynne J
LJ
Jordan
Julie Ann
JA
Pearce-Kelling
Susan E
SE
Aguirre
Gustavo D
GD
Acland
Gregory M
GM
D051722:ADAM Proteins / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001947:Breeding; D019295:Computational Biology; D004252:DNA Mutational Analysis; D004283:Dog Diseases / Q000201:enzymology* / Q000235:genetics* / Q000503:physiopathology; D004285:Dogs; D004596:Electroretinography; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005820:Genetic Testing; D055106:Genome-Wide Association Study; D006720:Homozygote; D006801:Humans; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D012160:Retina / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D012174:Retinitis Pigmentosa / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology / Q000662:veterinary*
D051722:ADAM Proteins
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