Bloom syndrome protein modulates protein-coding gene and miRNA expression as a function of G4 DNA content

Bloom syndrome is a rare autosomal recessive genetic instability and cancer predisposition syndrome caused by loss of function mutations in the BLM RECQ helicase gene. To ask if some of the distinctive pathological features of Bloom syndrome might reflect altered gene expression, we analyzed global mRNA and miRNA expression in fibroblasts from 16 patients and 15 matched normal controls, and in control primary diploid fibroblasts depleted of the BLM protein. We document significant differential expression of both protein-coding genes and miRNAs with well-characterized cancer associations in BLM-deficient cells. Differences in expression correlated significantly with G4 motifs, which are associated with potential to form G-quadruplex structures. These results indicate that BLM helicase may modulate gene expression by regulating the in vivo stability of G-quadruplex structures, and identify sets of genes and miRNAs whose expression, when altered, may drive the pathogenesis of Bloom syndrome and associated cancers. Global profiling of mRNA and miRNA expression was analyzed in primary fibroblasts from 16 patients and 15 matched normal controls, and in 9 primary diploid fibroblasts depleted of BLM protein by BLM-specific (3), control (3) and scrambled (3) shRNA.