Although we were able to replicate moderate association with BMI at four loci in our study, some of the discrepant findings between our study and those performed in European populations could be due to several factors. (1) The study power of our samples may be limited. There are a substantial number of associated SNPs that showed large differences in allele frequencies between the ancestral HapMap European (CEU) and African (YRI) populations (Supplementary Table 4). Some of the SNPs, such as those in PRL, PTER, PCSK1 and MC4R are, or nearly are monomorphic in the YRI population, which will have little, if any, power to be detected. (2) Allelic heterogeneity and different LD patterns such that there may be different causal variants or that different set of SNPs tagging the same causal variant(s) in Europeans versus African Americans. (3) Locus heterogeneity in which there may be novel loci affecting adiposity in African Americans. (4) Complex and/or differential gene-gene and gene-environment interaction that modify the genetic risk of individual locus.
