Genome-wide Significant Associations for Variants With Minor Allele Frequency of 5% or Less—An Overview: A HuGE Review

The authors survey uncommon variants (minor allele frequency, ≤5%) that have reached genome-wide significance (P ≤ 10⁻⁷) in genome-wide association study(ies) (GWAS). They examine the typical effect sizes of these associations; whether they have arisen in multiple GWAS on the same phenotype; and whether they pertain to genetic loci that have other variants discovered through GWAS, perceived biologic plausibility from the candidate gene era, or known mutations associated with related phenotypes. Forty-three associations with minor allele frequency of 5% or less and P ≤ 10⁻⁷ were studied, 12 of which involved nonsynonymous variants. Per-allele odds ratios ranged from 1.03 to 22.11. Thirty-two associations had P ≤ 10⁻⁸. Eight uncommon variants were identified in multiple GWAS. For 14 associations, also other common polymorphisms with genome-wide significance were identified in the same loci. Thirteen associations pertained to genetic loci considered to have biologic plausibility for association in the candidate gene era, and mutations with related phenotypic effects were identified for 11 associations. Twenty-five uncommon variants are common in at least 1 of the 4 different ancestry samples of the International HapMap Project. Although the number of uncommon variants with genome-wide significance is still limited, these data suggest a possible confluence of rare/uncommon and common genetic variation on the same genetic loci.