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

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.

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(-578)-G(-151)-G(+94)] MolHap2 [G(-578)-A(-151)-T(+94)] and MolHap3 [A(-578)-G(-151)-G(+94)]. 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.

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.