Glioma is the most common malignant primary brain tumor and is associated with poor prognosis. Genetic factors contributing to glioma risk have recently been investigated through genome-wide association studies (GWAS), implicating seven independent glioma risk loci in six chromosomal regions. Here, we performed an in-depth functional analysis of the risk locus proximal to the PHLDB1 gene on 11q23.3. We retrieved all SNPs in linkage disequilibrium (r 2 - 0.2) with the glioma-associated SNP (rs498872) and performed a comprehensive bioinformatics and experimental functional analysis for the region. After testing candidate SNPs for allele-specific activity in a luciferase-based enhancer scanning assay, we established a subset of 10 functional SNPs in the promoters of PHLDB1 and DDX6, and in a putative enhancer element. Chromatin conformation capture (3C) identified a physical interaction between the enhancer element containing a functional SNP (rs73001406) and the promoter of the DDX6 gene. Knockdown experiments in cell culture and 3D assays to evaluate the role of PHLDB1 and DDX6 suggest that both genes may contribute to the phenotype. These studies reveal the functional landscape of the 11q23.3 glioma susceptibility locus and identify a network of functional SNPs in regulatory elements and two target genes as a possible mechanism driving glioma risk association.
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