Abstract 18570: Intronic SCARB1 (Scavenger Receptor Class B Type I, SR-BI) rs10846744 Variant Mediates Functional Effect by Enhancer Activity
Objective: We previously reported the significant association of SCARB1 intronic rs10846744 in reducing odds ratio for incident coronary heart disease (CHD) in participants of the Multi-Ethnic Study of Atherosclerosis. Using in vitro and ex vivo approaches, we sought to define the underlining molecular mechanism for this clinical association.
Methods and results: Using publicly available genome databases, a bioinformatic screen revealed that rs10846744 resided in a region exhibiting DNase I hypersensitivity and H3K4me1 chromatin methylation markers. Gel shift assays revealed significantly lower binding of nuclear proteins to the probe expressing the risk C allele for CHD (p<0.001). Yeast-One Hybrid screening revealed NR2F2 as a candidate transcription factor (TF), while bioinformatic screens (HaploReg v2) predicted binding of multiple TFs such as AP2[[Unable to Display Character: 𝛄]], Max, ERα, FOXA1, GATA3 and p300 to this region. Using RNA Seq, we confirmed that lymphocytes isolated from hyperalphalipoproteinemic (HALP) carriers of the risk C allele had significantly higher NR2F2 expression (6.3-fold upregulated, p<0.001). Interestingly, under basal conditions rs10846744 did not significantly regulate SR-BI RNA and protein expression in these lymphocytes. Global metabolic profiling from plasma samples of HALP carriers of the risk C allele had significantly higher markers of oxidative stress (42% higher cysteinyl-glycine, oxidized, p=0.0136, q=0.2437) and lower levels of lysolipids (46% lower, p=0.0043, q=0.1605).
Conclusion: The intronic rs10846744 variant resides within a functionally active regulatory region of SCARB1, without directly regulating SR-BI expression itself. Our results confirm the importance of dissecting the pathway by which this region influences CHD.
- © 2013 by American Heart Association, Inc.