the integrated haplotype score (iHS) [21,22], the rMHH [23], and the composite of multiple signals (CMS) [24]. In this last study, the strongest signal of selection was found for variant rs9622363 (NCBI36.3 position 34,986,501, Genome-wide CMS 14.987, p=1.3×10−5, untyped in our study) and according to Hapmap this variant in African Yoruba is in strong linkage disequilibrium with rs7364143 (D′=0.7, r2=0.18), rs2239785 (D′=1.0, r2=0.8), rs136187 (D′=0.7, r2=0.14), and rs1699672 (D′=0.6, r2=0.07), four out of seven of the variants in Table 2. It is therefore possible that the disease causing variant rose to higher frequency in Africans due to a selective sweep which took place near or at the MYH9 locus in the African population, and which was recent enough to leave extensive patterns of linkage disequilibrium. The Illumina chips that we used for genotyping, despite being the densest commercially available at the time of this study, do not have sufficient numbers of SNPs that are highly polymorphic in the African population to allow us to be more precise at the present time. This is likely due to an ascertainment bias in the way SNPs have been discovered with, until recently, a reliance on non-African samples.
