Interindividual transcriptional regulation of the human biglycan gene involves three common molecular haplotypes

Abstract

OBJECTIVE: The extracellular matrix proteoglycan biglycan (BGN) is involved in cardiovascular disease pathophysiology, as it mediates the subendothelial retention of atherogenic apolipoprotein B-containing lipoproteins, affects adaptive remodeling after myocardial infarction, and exerts proinflammatory effects in macrophages. In a cardiovascular disease-related setting of vascular endothelial cells and human monocytes, we examined the molecular mechanisms of common molecular haplotypes affecting human BGN transcriptional regulation. APPROACH AND RESULTS: After the molecular characterization of the BGN promoter, we determined the prevalence of BGN promoter variants (1199 base pair portion) in 87 individuals of European ancestry, and identified 3 molecular haplotypes by subcloning and sequencing of subjects' single DNA strands: MolHap1 [G-G-G] MolHap2 [G-A-T] and MolHap3 [A-G-G]. By 5′ rapid amplification of cDNA-ends, we detected 1 additional upstream transcription start site at position -46 in EA.hy926 endothelial cells. Reporter gene assays located the BGN core promoter to the region spanning positions -39 and +162. Strongest promoter activity was mapped to the region between -1231 and -935. The introduction of MolHap2 and MolHap3 into the active BGN promoter led to a significant loss of transcriptional activity (all probability values <0.05), compared with MolHap1. By use of electrophoretic mobility shift assays, chromatin immunoprecipitation assays, and cotransfection of transcription factors, we identified specificity protein 1, v-ets erythroblastosis virus E26 oncogene homolog (ETS) family members, and an activator protein-1 complex to interact differentially with the BGN promoter in the context of each individual MolHap. CONCLUSIONS: Our results indicate that molecular haplotypes within the BGN promoter may contribute to the molecular basis of interindividually different transcriptional BGN regulation, possibly modulating the predisposition to cardiovascular disease-related phenotypes. © 2013 American Heart Association, Inc.