Recently, the 1000 Genomes project (http://www.1000genomes.org/) released sequence and variation data from the DNS samples used in Hapmap data. These data, accessible through the Integretive Genomics Viewer (http://www.broadinstitute.org/igv/), show the existence of many variants at the APOL1-MYH9 locus that are observed at high frequency in Africans but are rare or non-existent in Europeans and Asians and have not been analyzed in Hapmap. Recent studies [25,26] based on variants genotyped in Hapmap failed at defining a clear candidate for causal association. If it is in fact true that one single variant can explain the association between this locus and FSGS, then it is likely that it is one of the variants which are highly polymorphic exclusively among Africans, but rare or non-existent in non-Africans, which would explain the lack of replication of association of this locus in other large studies in different populations [27]. The small level of associations observed in Europeans by others [14] could also be explained by low levels of African ancestry in the cases considered or even by the fact that Southern European populations have a 1–3% level of African ancestry due to migrations which took place 50–70 generations ago (private communication with Nick Patterson).
