Department of Genetics, University of North Carolina, Chapel Hill, North Carolina, USA.
Diabetes. 2013 May;62(5):1756-62. doi: 10.2337/db12-0972. Epub 2013 Jan 17.
Translation of noncoding common variant association signals into meaningful molecular and biological mechanisms explaining disease susceptibility remains challenging. For the type 2 diabetes association signal in JAZF1 intron 1, we hypothesized that the underlying risk variants have cis-regulatory effects in islets or other type 2 diabetes-relevant cell types. We used maps of experimentally predicted open chromatin regions to prioritize variants for functional follow-up studies of transcriptional activity. Twelve regions containing type 2 diabetes-associated variants were tested for enhancer activity in 832/13 and MIN6 insulinoma cells. Three regions exhibited enhancer activity and only rs1635852 displayed allelic differences in enhancer activity; the type 2 diabetes risk allele T showed lower transcriptional activity than the nonrisk allele C. This risk allele showed increased binding to protein complexes, suggesting that it functions as part of a transcriptional repressor complex. We applied DNA affinity capture to identify factors in the complex and determined that the risk allele preferentially binds the pancreatic master regulator PDX1. These data suggest that the rs1635852 region in JAZF1 intron 1 is part of a cis-regulatory complex and that maps of open chromatin are useful to guide identification of variants with allelic differences in regulatory activity at type 2 diabetes loci.
将非编码常见变异关联信号转化为解释疾病易感性的有意义的分子和生物学机制仍然具有挑战性。对于 JAZF1 内含子 1 中的 2 型糖尿病关联信号，我们假设潜在的风险变异在胰岛或其他与 2 型糖尿病相关的细胞类型中具有顺式调控作用。我们使用实验预测的开放染色质区域图谱来优先选择功能后续研究转录活性的变体。在 832/13 和 MIN6 胰岛素瘤细胞中测试了包含 2 型糖尿病相关变体的 12 个区域的增强子活性。三个区域表现出增强子活性，只有 rs1635852 在增强子活性中显示出等位基因差异；2 型糖尿病风险等位基因 T 的转录活性低于非风险等位基因 C。该风险等位基因显示出与蛋白质复合物结合增加，表明它作为转录抑制复合物的一部分发挥作用。我们应用 DNA 亲和捕获来鉴定复合物中的因子，并确定风险等位基因优先结合胰腺主调控因子 PDX1。这些数据表明，JAZF1 内含子 1 中的 rs1635852 区域是顺式调控复合物的一部分，开放染色质图谱可用于指导鉴定在 2 型糖尿病基因座中具有等位基因差异调节活性的变体。
