Musculoskeletal Research Group, Institute of Cellular Medicine, Newcastle University, 4th Floor Catherine Cookson Building, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Hum Mol Genet. 2011 Sep 1;20(17):3450-60. doi: 10.1093/hmg/ddr253. Epub 2011 Jun 3.
GDF5 is involved in synovial joint development, maintenance and repair, and the rs143383 C/T single nucleotide polymorphism (SNP) located in the 5'UTR of GDF5 is associated, at the genome-wide significance level, with osteoarthritis susceptibility, and with other musculoskeletal phenotypes including height, congenital hip dysplasia and Achilles tendinopathy. There is a significant reduction in the expression of the disease-associated T allele relative to the C allele in synovial joint tissues, an effect influenced by a second SNP (rs143384, C/T) also within the 5'UTR. The differential allelic expression (DAE) imbalance of the C and T alleles of rs143383 varies intra- and inter-individually, suggesting that DAE may be modulated epigenetically. The C alleles of both SNPs form CpG dinucleotides that are potentially amenable to regulation by methylation. Here, we have examined whether DNA methylation regulates GDF5 expression and the allelic imbalance caused by rs143383. We observed methylation of the GDF5 promoter and 5'UTR in cell lines and joint tissues, with demethylation correlating with increased GDF5 expression. The CpG sites created by the C alleles at rs143383 and rs143384 were variably methylated, and treatment of a heterozygous cell line with a demethylating agent further increased the allelic expression imbalance between the C and T alleles. This demonstrates that the genetic effect of the rs143383 SNP on GDF5 expression is modulated epigenetically by DNA methylation. The variability in DAE of rs143383 is therefore partly accounted for by differences in DNA methylation that could influence the penetrance of this allele in susceptibility to common musculoskeletal diseases.
GDF5 参与滑膜关节的发育、维持和修复，位于 GDF5 5'UTR 中的 rs143383 C/T 单核苷酸多态性 (SNP) 与骨关节炎易感性以及其他肌肉骨骼表型相关，这些表型包括身高、先天性髋关节发育不良和跟腱病。在滑膜关节组织中，与疾病相关的 T 等位基因相对于 C 等位基因的表达显著降低，这种效应受第二个位于 5'UTR 内的 SNP(rs143384，C/T)影响。rs143383 的 C 和 T 等位基因的差异等位基因表达 (DAE) 不平衡在个体内和个体间存在差异，表明 DAE 可能受到表观遗传调控。这两个 SNP 的 C 等位基因形成 CpG 二核苷酸，可能受甲基化调节。在这里，我们研究了 DNA 甲基化是否调节 GDF5 表达以及 rs143383 引起的等位基因失衡。我们观察到细胞系和关节组织中 GDF5 启动子和 5'UTR 的甲基化，去甲基化与 GDF5 表达增加相关。rs143383 和 rs143384 的 C 等位基因产生的 CpG 位点存在可变甲基化，用去甲基化剂处理杂合细胞系进一步增加了 C 和 T 等位基因之间的等位基因表达失衡。这表明 rs143383 SNP 对 GDF5 表达的遗传效应受 DNA 甲基化的表观遗传调控。因此，rs143383 的 DAE 变异性部分归因于 DNA 甲基化的差异，这些差异可能影响该等位基因在常见肌肉骨骼疾病易感性中的表现度。
