RAPGEF6 variant constitutes a major risk factor for laryngeal paralysis in dogs

RASOULIHA, SHEIDA HADJI; KLESTY, CARINA; LEEB, TOSSO; BARRIENTOS, LAURA; ANDEREGG, LINDA; RÖSCH, SARAH; JAGANNATHAN, VIDHYA

BERNE

Conferencia; 10th International Conference on Canine and Feline Genetics and Genomics; 2019

UNIBE

Introduction:Laryngealparalysis (LP) is the inability to abduct the arytenoid cartilagesduring inspiration, resulting in a partial airway obstruction andconsequent respiratory distress. Acquired LP may result from traumato the recurrent laryngeal nerve. Hereditary early onset forms of LPhave been reported in several dog breeds including Miniature BullTerriers.Objective:Identificationof the underlying genetic cause for LP in Miniature Bull Terriers.Materials& Methods: GenomicDNAwas isolated from EDTA blood samples from 287 Miniature Bull Terriersand 89 Bull Terriers. Seventy-eightdogs were genotyped on the illumina canine_HD chip. GWAS was donewith a final set of 23cases and 62 controls, using R Studio with the GenABEL package.Phasing and haplotype analysis on chromosome 11 was done using thefastPHASE program. The genome of an LP affected Miniature BullTerrier was sequenced with 13.2x coverage using an illumina HiSeq3000instrument. Variants were called and Sanger sequencing was used toconfirm and genotypecandidate variants. RT-PCR was performed with RNA isolated from bloodsamples.Results:UsingGWAS and haplotype analyses, we mapped a major genetic risk factorfor LP in Miniature Bull Terriers to a ~1.3 Mb interval on chromosome11. Whole genome sequencing of an affected Miniature Bull Terrier andcomparison to 596 control genomes revealed a single privateprotein-changing variant in the critical interval, a 36 bp insertioninto exon 15 of the RAPGEF6gene (c.1793_1794ins36). The imperfect genotype-phenotype correlationsuggested an autosomal recessive mode of inheritance with incompletepenetrance. Homozygosity for the insertion was associated with a23-fold increased risk for LP. The insertion allele was only found inMiniature Bull Terriers and Bull Terriers. It was absent from anadditionally genotyped cohort of 551 dogs from 41 other dog breeds.The insertion sequence contains a splice acceptor motif leading toaberrant splicing of transcripts originating from the mutant allele(r.1732_1780del). This leads to a frameshift and a premature stopcodon, p.(Ile587ProfsTer5), removing 64% of the open reading frame.Conclusions:Weidentified the RAPGEF6:c.1793_1794ins36variantleading to a splicedefect in the RAPGEF6gene as candidate causative variant for LP in Miniature Bull Terriersand Bull Terriers. The variant does not show a completely perfectgenotype-phenotype association, indicating heterogeneity and/or thepresence of additional modifier genes and/or environmental riskfactors. The physiological function of RAPGEF6has not been conclusively established. Our data suggest that it maybe involved in peripheral nerve function. The results also enablegenetic testing to reduce the prevalence of LP in the dog population.p { margin-bottom: 0cm; direction: ltr; line-height: 100%; text-align: left; orphans: 2; widows: 2 }p.western { font-family: "Arial", serif; font-size: 14pt; so-language: en-GB; font-weight: bold }p.cjk { font-family: "Times New Roman"; font-size: 14pt; so-language: de-DE; font-weight: bold }p.ctl { font-family: "Times New Roman"; font-size: 12pt; font-weight: bold }