ICCFGG 2022
#46 Identification of a frameshift variant in GUCY2D in German Spitz dogs with progressive retinal atrophy Paige Winkler1 , Bortolini M2, Moreno J2, Sato M3, Guareschi B2, Montiani-Ferreira F2, Petersen-Jones SM1 winkle38@msu.edu 1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA 2Department of Veterinary Medicine, Federal University of Paraná, Curitiba-PR, Brazil, 3Department of Ophthalmology, Federal University of Paraná, Alto da Glória, Curitiba, PR, BR Purpose Identify the variant associated with early-onset progressive retinal atrophy (PRA) in German Spitz dogs. Methods A family group of German Spitz dogs with early-onset PRA was characterized using full ophthalmic examination, electroretinogram and optical coherence tomography. Twelve candidate genes were screened for association with four affected German Spitz dogs. Marker variability was assessed using six unaffected dogs on the unexcluded genes. DNA samples from two affected siblings, one unaffected half sibling and one obligate carrier parent were sent for whole genome sequencing (WGS). Sequences were processed and filtered for variants unique to the affected dogs. Sanger se- quencing was used to confirm segregation of the variant with additional samples from the pedigree PRA-affected German Spitz dogs had undetectable rod and decreased cone responses at three months of age. Cone responses were unmeasurable by nine months of age. However, retinal thinning was not apparent until three years of age. Autosomal recessive inheritance was indicated by the pedigree. Nine of twelve candidate genes were excluded for association with the disease by microsatellite markers. Using WGS, a 1 bp insertion (c.1598_1599insT, p.Ser534GlufsTer20) was detected in one of the unexcluded candidate genes (GUCY2D) which segregated with the early-onset PRA phenotype within the pedigree. Discussion The combination approach of 1) well-phenotyped dogs; 2) initial candidate gene screening using microsatellites and 3) WGS variant filtering from a close family group, allowed for the quick identification of a frameshift variant within an unexcluded candidate gene. (N=12). Results
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