SNP genotyping by SNP array Genome variation profiling by SNP array
Summary
Canine gastric dilatation-volvulus (GDV) is a common life-threatening condition occurring primarily in large and giant breeds with a 3.9% to 36.7% lifetime risk. GDV is a complex disease with risk factors including age, diet, behavior, family history, and genetics. The genetic correlates of GDV have not previously been systematically explored. We undertook multiplatform genome-wide association analysis (GWAS) of 253 dogs including 106 healthy dogs and 147 dogs with at least one GDV episode. The study included ten dog breeds enriched for Borzoi, German Shepherd (GSD), Great Dane, and Standard Poodle. SNP array genotyping was performed on constitutional DNA from all 241 samples to identify GDV-associated SNPs and CNVs. To increase the coverage of our study we performed imputation analysis of the SNP data as well as additional whole genome sequencing (WGS) on a subset of 33 dogs (15 healthy dogs and 18 GDV patients from the three most represented breeds). Twenty-one patients were genotyped by both SNP and WGS platforms. The GWAS was conducted across breeds as well as on specific breeds using a mixed linear model adjusting for relatedness, population structure and sex. After genome-wide Bonferroni correction, we identified a significant protective GDV-associated SNP, rs851737064, occurring in an intergenic region, across all breeds. The signal was most significant in Collies, German Shorthaired Pointers, and Great Danes. Subsequent focused analysis across these three breeds identified 12 additional independent, protective and deleterious SNPs with significant GDV association. Additional GWAS conducted on Borzoi, GSD and Great Dane yielded significant genome-wide GDV associations in 11 independent SNPs, while that in Borzoi alone identified 2 independent GDV-associated SNPs. We then used WGS data to validate the imputation analysis. Notable significant SNPs included genes involved in gastric tone and motility including VHL, NALCN, and PRKCZ. From the WGS data we also detected two independent GDV-associated SNPs in Borzoi, GSD and Great Dane breeds on an intergenic region on chromosome 7 not covered by previous analyses. These data provide important new information regarding canine GDV risk factors and facilitate generation of hypotheses regarding the genetic and molecular underpinnings this syndrome.
Overall design
We analyzed a total of 147 GDV cases and 106 healthy controls using the CanineHD Whole-Genome Genotyping BeadChip. After quality controls, the final dataset was composed by 125 GDV cases and 90 HC. Data were imputed with Beagle using a reference panel of 365 dogs from different breeds characterized with Whole Genome Sequencing (Hayward et al., 2019; Plos Genetics 15:e1008003; BioProject: PRJNA517114). GWAS was conducted on the imputed data using a mixed linear model accounting for population stratification, relatedness and sex. P-values were adjusted for multiple testing with the Bonferroni method, accounting for the number of independent SNPs with a Linkage Disequilibrium estimate.
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