A Functional Variant rs6435156C > T in BMPR2 is Associated With Increased Risk of Chronic Obstructive Pulmonary Disease (COPD) in Southern Chinese Population

• The rs6435156 TT was associated with greater risk of COPD in smokers than in non-smokers.
• Cigarette smokers with rs6435156 TT were more susceptible to COPD than those with CC genotype.
• The T genotype of rs6435156 inhibited BMPR2 expression in PBMCs and lung epithelial cells.
• The rs6435156 T is the functional binding site for miR-20a.COPD is characterized by abnormal inflammation and structural remodeling in the airway. Bone morphogenetic protein receptor type 2 (BMPR2) mediated signaling has been demonstrated to regulate pro-inflammatory responses in vasculature, and decreased expression of BMPR2 was found in COPD lungs; however the relationship of BMPR2 to COPD is unknown. We found that rs6435156 TT was the functional binding site for miR-20a in 3′UTR of BMPR2 and significantly increased risk of COPD in southern Chinese population; rs6435156C > T could modulate the susceptibility to COPD by interacting with cigarette smoking, which down-regulated BMPR2 expression dependent in hsa-miR-20a.

BackgroundsBone morphogenetic protein receptor type 2 (BMPR2) signaling is anti-inflammatory. Decreased BMPR2 expression was seen in lung tissue from chronic obstructive pulmonary disease (COPD) patients.MethodsThe selected single nucleotide polymorphisms (SNPs) in BMPR2 were genotyped with polymerase chain reaction (PCR) ligase detection reaction. The effects of SNPs on gene expression were analyzed with luciferase assays. The mRNA and protein expression levels of BMPR2 in peripheral blood mononuclear cells (PBMCs) from COPD patients were determined by quantitative PCR and western blotting, respectively.FindingsTwo SNPs, rs6435156C > T and rs1048829G > T in the 3′-untranslated region (3′UTR) of BMPR2 were selected and genotyped in COPD case and healthy control subjects from southern Chinese population. Both of them were found associated with significantly increased COPD risk (adjusted odds ratio [OR] = 1.58 with 95% confidence interval [CI] = 1.14–2.15, P = 0.0056 for rs6435156C > T; adjusted OR = 1.47 and 95% CI = 1.10–1.97, P = 0.0092 for rs1048829G > T). Older age, cigarette smoking, family history of cancer and COPD were all factors that interacted with rs6435156C > T and rs1048829G > T causing increased COPD risk. Cigarette smokers with rs6435156 (CT + TT) or rs1048829 (GT + TT) were more susceptible to COPD than that with the rs6435156CC or rs1048829GG genotypes. In A549 human alveolar epithelial cells, luciferase reporter assays revealed that introduction of 3′UTR of BMPR2 plasmids carrying rs6435156T allele but not rs1048829T led to lower luciferase activity than the wild-type C or G alleles. Comparing to rs6435156CC, treatment with hsa-miR-20a mimics deceased whereas hsa-miR-20a inhibitor restored the luciferase reporter activity in cells transfected with constructs carrying rs6435156TT. BMPR2 mRNA and protein expressions were significantly lower in PBMCs from COPD smokers than that in non-smokers. COPD patients carrying rs6435156T allele had less BMPR2 expression in PBMCs.InterpretationThis study demonstrated that both rs6435156C > T and rs1048829G > T variants in BMPR2 contributed to increased susceptibility to COPD. The T variants of rs6435156 increased COPD risk likely by binding with hsa-miR-20a, thus leading to downregulated BMPR2 expression in lung epithelial and immune cells.