For example, previous efforts to characterize the mechanism of action at the TCF7L2 locus have demonstrated that the fine-mapped T2D-risk allele at rs7903146 influences chromatin accessibility and enhancer activity in islets43, but evidence linking these events to TCF7L2 expression was not previously detected in genome-wide eQTL studies. This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.