heterogeneity in the effect sizes across the six cohorts (Pheterogeneity = 0.007). Additionally, the T-allele was associated with increased BMI in our study as opposed to the C-allele reported in the European populations,14 though allele frequencies are similar between the two populations (Supplementary Table 4). Both sample heterogeneity and the difference in effect allele could contribute to the lack of association for this SNP in our study. Recently Kang et al.28 reported a GWAS and follow-up analysis of anthropometric traits in African-derived populations. No SNPs reached a genome-wide significance level for association with BMI. However, rs6567160 in MC4R showed evidence of replication in their GWA panel (P = 0.0035). Rs6567160 is in high LD with rs633265 and rs1942880 (r2 = 0.93, D’ ≈ 0.98). In Europeans, the extent of LD block containing associated SNPs in the MC4R gene region is greater (18 kb), compared with that observed in African Americans (13 kb). Therefore, the causal variant(s) may be in high LD in European-derived, but not in African-derived populations, due to differences in LD structure. This feature of African-derived genomes may facilitate identification of the true risk variant. We have recently used such an approach to strongly implicate a single SNP
