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An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9.

Goldstein O, Mezey JG, Boyko AR, Gao C, Wang W, Bustamante CD, Anguish LJ, Jordan JA, Pearce-Kelling SE, Aguirre GD, Acland GM - Mol. Vis. (2010)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, NY 14853-6401, USA.

ABSTRACT

Purpose: 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.

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Related in: MedlinePlus

Results of genome-wide association study in canine cone-rod dystrophy 3. The statistical signal (y-axis, negative Log10 [Fisher exact test 2-tailed probability]) for association between canine single-nucleotide polymorphism (SNP) genotype and canine cone-rod dystrophy 3 (crd3) phenotype, plotted against SNP chromosomal location (A), demonstrates a distinct peak on canine chromosome 16 (CFA16). Green dots are SNPs for which the association signal exceeded the Bonferroni threshold for genome-wide significance. Chromosome X is represented by the numbers 39 and 40. Homozygosity analysis of SNP genotypes (B), in the region of CFA16 yielding the peak association signal, reveals heterozygosity throughout the interval in 21 nonaffected control dogs, and demonstrates a 2.74 Mb homozygosity block in 20 crd3-affected dogs. Genotypes are color coded as follows: pink and green represent the major and minor genotypes observed in affecteds, respectively; yellow is heterozygous; and white is missing data. Black lines border the 2.74 Mb homozygosity block. Refseq genes screened as potential positional candidates for crd3 in the present study (arrowheads), and ADAM family genes identified within the crd3 minimal linkage disequilibrium interval (arrows) are indicated with annotation and order consistent with the CanFam2 canine genome assembly (C, not drawn to scale).
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f3: Results of genome-wide association study in canine cone-rod dystrophy 3. The statistical signal (y-axis, negative Log10 [Fisher exact test 2-tailed probability]) for association between canine single-nucleotide polymorphism (SNP) genotype and canine cone-rod dystrophy 3 (crd3) phenotype, plotted against SNP chromosomal location (A), demonstrates a distinct peak on canine chromosome 16 (CFA16). Green dots are SNPs for which the association signal exceeded the Bonferroni threshold for genome-wide significance. Chromosome X is represented by the numbers 39 and 40. Homozygosity analysis of SNP genotypes (B), in the region of CFA16 yielding the peak association signal, reveals heterozygosity throughout the interval in 21 nonaffected control dogs, and demonstrates a 2.74 Mb homozygosity block in 20 crd3-affected dogs. Genotypes are color coded as follows: pink and green represent the major and minor genotypes observed in affecteds, respectively; yellow is heterozygous; and white is missing data. Black lines border the 2.74 Mb homozygosity block. Refseq genes screened as potential positional candidates for crd3 in the present study (arrowheads), and ADAM family genes identified within the crd3 minimal linkage disequilibrium interval (arrows) are indicated with annotation and order consistent with the CanFam2 canine genome assembly (C, not drawn to scale).

Mentions: Fisher Exact analysis, comparing genotypes of cases to controls, identified an association signal on CFA16 (Figure 3) extending over 6 Mb and including 28 SNPs that exceeded the Bonferroni corrected significance threshold (-Log10(p) range=6.39–10.09, Table 5). The peak p-value (-Log10(p)=10.09) was shared by six SNPs comprising an interval of approximately 4.4 Mb (CFA16: 22,690,750–27,122,415). All affected dogs were homozygous at these SNP loci, suggesting a recessive mode of inheritance. With that in mind, all genotype calls on CFA16 were aligned to identify a homozygosity block, that is, where all genotype calls for all affected dogs were homozygous, between positions 27,854,074 and 30,597,700–a 2.74 Mb interval (Figure 3; Appendix 1). The block of homozygosity was not observed in controls except for one dog (dog number 17 in Appendix 1). This dog, when first examined at 10 years of age, had retinal lesions that were regarded as incompatible with a diagnosis of crd3, but in retrospect were likely to represent an unusually delayed and mild form of crd3 disease. Thus, this homozygosity block represents the region of absolute linkage disequilibrium (LD) of crd3 in the GIT population examined


An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9.

Goldstein O, Mezey JG, Boyko AR, Gao C, Wang W, Bustamante CD, Anguish LJ, Jordan JA, Pearce-Kelling SE, Aguirre GD, Acland GM - Mol. Vis. (2010)

Results of genome-wide association study in canine cone-rod dystrophy 3. The statistical signal (y-axis, negative Log10 [Fisher exact test 2-tailed probability]) for association between canine single-nucleotide polymorphism (SNP) genotype and canine cone-rod dystrophy 3 (crd3) phenotype, plotted against SNP chromosomal location (A), demonstrates a distinct peak on canine chromosome 16 (CFA16). Green dots are SNPs for which the association signal exceeded the Bonferroni threshold for genome-wide significance. Chromosome X is represented by the numbers 39 and 40. Homozygosity analysis of SNP genotypes (B), in the region of CFA16 yielding the peak association signal, reveals heterozygosity throughout the interval in 21 nonaffected control dogs, and demonstrates a 2.74 Mb homozygosity block in 20 crd3-affected dogs. Genotypes are color coded as follows: pink and green represent the major and minor genotypes observed in affecteds, respectively; yellow is heterozygous; and white is missing data. Black lines border the 2.74 Mb homozygosity block. Refseq genes screened as potential positional candidates for crd3 in the present study (arrowheads), and ADAM family genes identified within the crd3 minimal linkage disequilibrium interval (arrows) are indicated with annotation and order consistent with the CanFam2 canine genome assembly (C, not drawn to scale).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2925905&req=5

f3: Results of genome-wide association study in canine cone-rod dystrophy 3. The statistical signal (y-axis, negative Log10 [Fisher exact test 2-tailed probability]) for association between canine single-nucleotide polymorphism (SNP) genotype and canine cone-rod dystrophy 3 (crd3) phenotype, plotted against SNP chromosomal location (A), demonstrates a distinct peak on canine chromosome 16 (CFA16). Green dots are SNPs for which the association signal exceeded the Bonferroni threshold for genome-wide significance. Chromosome X is represented by the numbers 39 and 40. Homozygosity analysis of SNP genotypes (B), in the region of CFA16 yielding the peak association signal, reveals heterozygosity throughout the interval in 21 nonaffected control dogs, and demonstrates a 2.74 Mb homozygosity block in 20 crd3-affected dogs. Genotypes are color coded as follows: pink and green represent the major and minor genotypes observed in affecteds, respectively; yellow is heterozygous; and white is missing data. Black lines border the 2.74 Mb homozygosity block. Refseq genes screened as potential positional candidates for crd3 in the present study (arrowheads), and ADAM family genes identified within the crd3 minimal linkage disequilibrium interval (arrows) are indicated with annotation and order consistent with the CanFam2 canine genome assembly (C, not drawn to scale).
Mentions: Fisher Exact analysis, comparing genotypes of cases to controls, identified an association signal on CFA16 (Figure 3) extending over 6 Mb and including 28 SNPs that exceeded the Bonferroni corrected significance threshold (-Log10(p) range=6.39–10.09, Table 5). The peak p-value (-Log10(p)=10.09) was shared by six SNPs comprising an interval of approximately 4.4 Mb (CFA16: 22,690,750–27,122,415). All affected dogs were homozygous at these SNP loci, suggesting a recessive mode of inheritance. With that in mind, all genotype calls on CFA16 were aligned to identify a homozygosity block, that is, where all genotype calls for all affected dogs were homozygous, between positions 27,854,074 and 30,597,700–a 2.74 Mb interval (Figure 3; Appendix 1). The block of homozygosity was not observed in controls except for one dog (dog number 17 in Appendix 1). This dog, when first examined at 10 years of age, had retinal lesions that were regarded as incompatible with a diagnosis of crd3, but in retrospect were likely to represent an unusually delayed and mild form of crd3 disease. Thus, this homozygosity block represents the region of absolute linkage disequilibrium (LD) of crd3 in the GIT population examined

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Baker Institute for Animal Health, Cornell University College of Veterinary Medicine, Ithaca, NY 14853-6401, USA.

ABSTRACT

Purpose: 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.

Show MeSH
Related in: MedlinePlus