We cannot be sure which of the nearby genes are causally involved in influencing BMI. As a source of additional clues to likely causal mechanisms, we exploited publicly available eQTL data for lymphocytes42 and brain27, and tested for association between the eight replicated variants and mRNA levels of the nearby genes (Supplementary Fig. 3 and Supplementary Table 9 online). Other than variants in the MTCH2 locus (associated with MTCH2 mRNA levels in brain and NDUFS3 levels in lymphocytes) and in the SH2B1 locus (associated with EIF3C levels in lymphocytes and brain and with TUFM levels in lymphocytes only), these studies did not yield indications of the likely causal gene(s). The SH2B1 result also illustrates some of the difficulties in interpreting associations with gene expression levels, as the presence of a missense SNP in SH2B1 and the strong prior candidacy of this gene would seem to implicate strongly alteration in SH2B1 function as the causal mechanism for influencing obesity. One possibility is that the SH2B1 variant has a causal role but happens to be in LD with a different variant that
