Coronary Heart Disease-Associated Variation in <i>TCF21</i> Disrupts a miR-224 Binding Site and miRNA-Mediated Regulation

<div><p>Genome-wide association studies (GWAS) have identified chromosomal loci that affect risk of coronary heart disease (CHD) independent of classical risk factors. One such association signal has been identified at 6q23.2 in both Caucasians and East Asians. The lead CHD-associated polymorphism in this region, rs12190287, resides in the 3′ untranslated region (3′-UTR) of <i>TCF21</i>, a basic-helix-loop-helix transcription factor, and is predicted to alter the seed binding sequence for miR-224. Allelic imbalance studies in circulating leukocytes and human coronary artery smooth muscle cells (HCASMC) showed significant imbalance of the <i>TCF21</i> transcript that correlated with genotype at rs12190287, consistent with this variant contributing to allele-specific expression differences. 3′ UTR reporter gene transfection studies in HCASMC showed that the disease-associated C allele has reduced expression compared to the protective G allele. Kinetic analyses <i>in vitro</i> revealed faster RNA-RNA complex formation and greater binding of miR-224 with the <i>TCF21</i> C allelic transcript. In addition, <i>in vitro</i> probing with Pb²⁺ and RNase T1 revealed structural differences between the <i>TCF21</i> variants in proximity of the rs12190287 variant, which are predicted to provide greater access to the C allele for miR-224 binding. miR-224 and <i>TCF21</i> expression levels were anti-correlated in HCASMC, and miR-224 modulates the transcriptional response of <i>TCF21</i> to transforming growth factor-β (TGF-β) and platelet derived growth factor (PDGF) signaling in an allele-specific manner. Lastly, miR-224 and TCF21 were localized in human coronary artery lesions and anti-correlated during atherosclerosis. Together, these data suggest that miR-224 interaction with the <i>TCF21</i> transcript contributes to allelic imbalance of this gene, thus partly explaining the genetic risk for coronary heart disease associated at 6q23.2. These studies implicating rs12190287 in the miRNA-dependent regulation of <i>TCF21</i>, in conjunction with previous studies showing that this variant modulates transcriptional regulation through activator protein 1 (AP-1), suggests a unique bimodal level of complexity previously unreported for disease-associated variants.</p>