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G. M. Acland, O. Goldstein, A. V. Kukekova, G. D. Aguirre, S. E. Pearce-Kelling; Genetic and Phenotypic Heterogeneity in Canine Colobomatous Syndromes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4147.
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© ARVO (1962-2015); The Authors (2016-present)
Uveo-retinal colobomatous phenotypes segregate in several canine breeds. The locus, and a presumably causative genomic deletion, for one of these phenotypes (Collie Eye Anomaly [CEA]) has been identified on canine chromosome 37 (CFA37). In the present study, dogs with uveoretinal colobomas from several breeds were evaluated to determine whether the CFA37 locus and deletion is involved in all such phenotypes, or whether canine colobomas are genetically heterogeneous.
DNA was extracted from blood of dogs affected with uveoretinal colobomas. PCR primers were designed from genomic sequence flanking and within the CFA37 CEA deletion, to amplify products specific for the presence and absence of the CEA deletion.
Colobomatous phenotypes segregating in 2 canine breeds, Pyrenean Shepherds and Softcoated Wheaten Terriers, were consistently not associated with the CFA37 deletion reported in Collie Eye Anomaly. Some affected Pyrenean Shepherds exhibited the merle coat color phenotype, controlled by a mutation at the SILV locus on CFA10, which is known to cause both window defects in chorioretinal pigmentation and uveal colobomas, but others were nonmerle. Colobomas in Softcoated Wheaten Terriers were associated with additional ocular defects not seen in either CEA, Pyrenean Shepherds or merle dogs. In addition, several individual dogs from breeds in which CEA was known to segegate, had colobomas diagnosed that were not associated with the CFA37 deletion. In the latter group, several individual dogs also exhibited the merle phenotype, but others were nonmerle.
Uveo-retinal colobomatous syndromes in dogs are phenotypically and genetically heterogeneous. In Pyrenean Shepherds and Softcoated Wheaten Terriers colobomas appear to represent segregating mutations other than the previously recognized CEA and merle loci. Because these traits segregate in distinct closed populations (canine breeds), the opportunity arises to identify the causative loci, and unravel the pathways involved in uveoretinal differentiation and closure of the embryonic optic fissure.
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