Pangenome-based structural variant imputation enables large-scale genotype-phenotype studies in dairy cattle

Pangenomes of several species have been assembled recently, facilitating the detection and genotyping of structural variants. As part of the FarmGTEx Project, we previously constructed a Holstein pangenome (H20D) based on 40 phased haploid assemblies. Here, we use this breed specific pangenome to genotype 93,059 structural variants from whole-genome sequences of 1,571 cattle. We then develop a Holstein pangenome variation imputation reference panel we name HolPIP. Leveraging HolPIP, we impute 86.65% (68,354/78,886) of structural variants for 50,299 bulls with Beagle R² ≥ 0.8. Using these imputed structural variants and phenotypes for 43 complex traits, we conduct GWAS, identifying 1,225 structural variant-trait associations. We next use fine-mapping to prioritize 32 high-confidence candidate structural variants, including a 75-bp deletion in ANKRD11 linked to dairy form, rump width, and stature, as well as an insertion in DHX32 associated with RNA metabolism. Compared to SNPs across various functional annotations, structural variants show a stronger genome-wide enrichment across most complex traits in cattle, suggesting that structural variants may have an important contribution to the genetic basis of dairy traits.