A trait-associated locus from GWAS typically implicates a large genomic region with many variants of similar significance. This set may contain a few causal variants, while the association of other variants is driven by their LD with the causal one(s). Fine-mapping refines GWAS loci to a smaller set of likely causal variants to facilitate interpretation and follow-up studies (Schaid et al., 2018). Fine-mapping studies in samples of European ancestry have made important advances, with some loci resolved even to single-variant resolution (Huang et al., 2017; Mahajan et al., 2018). Because fine-mapping assumes the causal variant(s) have been observed, non-European populations face a unique challenge due to the lack of representation of many variants as a result of incomplete sampling from these populations, suboptimal chip design, and limited imputation performance.
