The utility of low-density genotyping for imputation in the Thoroughbred horse

Corbin, Laura; Kranis, Andreas; Blott, Sarah; Swinburne, June; Vaudin, Mark; Bishop, Stephen; Woolliams, John

Abstract

Background
Despite the dramatic reduction in the cost of high-density genotyping that has occurred over the last decade, it remains one of the limiting factors for obtaining the large datasets required for genomic studies of disease in the horse. In this study, we investigated the potential for low-density genotyping and subsequent imputation to address this problem.

Results
Using the haplotype phasing and imputation program, BEAGLE, it is possible to impute genotypes from low- to high-density (50K) in the Thoroughbred horse with reasonable to high accuracy. Analysis of the sources of variation in imputation accuracy revealed dependence both on the minor allele frequency of the single nucleotide polymorphisms (SNPs) being imputed and on the underlying linkage disequilibrium structure. Whereas equidistant spacing of the SNPs on the low-density panel worked well, optimising SNP selection to increase their minor allele frequency was advantageous, even when the panel was subsequently used in a population of different geographical origin. Replacing base pair position with linkage disequilibrium map distance reduced the variation in imputation accuracy across SNPs. Whereas a 1K SNP panel was generally sufficient to ensure that more than 80% of genotypes were correctly imputed, other studies suggest that a 2K to 3K panel is more efficient to minimize the subsequent loss of accuracy in genomic prediction analyses. The relationship between accuracy and genotyping costs for the different low-density panels, suggests that a 2K SNP panel would represent good value for money.

Conclusions
Low-density genotyping with a 2K SNP panel followed by imputation provides a compromise between cost and accuracy that could promote more widespread genotyping, and hence the use of genomic information in horses. In addition to offering a low cost alternative to high-density genotyping, imputation provides a means to combine datasets from different genotyping platforms, which is becoming necessary since researchers are starting to use the recently developed equine 70K SNP chip. However, more work is needed to evaluate the impact of between-breed differences on imputation accuracy.

Citation

Corbin, L., Kranis, A., Blott, S., Swinburne, J., Vaudin, M., Bishop, S., & Woolliams, J. (2014). The utility of low-density genotyping for imputation in the Thoroughbred horse. Genetics Selection Evolution, 46, Article 9. https://doi.org/10.1186/1297-9686-46-9

• Journal Article Type: Article
• Acceptance Date: Dec 20, 2013
• Online Publication Date: Feb 4, 2014
• Publication Date: Jan 1, 2014
• Deposit Date: Oct 11, 2017
• Publicly Available Date: Jan 24, 2024
• Journal: Genetics Selection Evolution
• Print ISSN: 0999-193X
• Electronic ISSN: 1297-9686
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 46
• Article Number: 9
• DOI: https://doi.org/10.1186/1297-9686-46-9
• Public URL: https://nottingham-repository.worktribe.com/output/1099459
• Publisher URL: https://gsejournal.biomedcentral.com/articles/10.1186/1297-9686-46-9
• PMID: 24495673