A Common Functional Regulatory Variant at a Type 2 Diabetes Locus Upregulates ARAP1 Expression in the Pancreatic Beta Cell
A Common Functional Regulatory Variant at a Type 2 Diabetes Locus Upregulates ARAP1 Expression in the Pancreatic Beta Cell
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DOI：
10.1016/j.ajhg.2013.12.011
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发表时间：
2014-02-06
影响因子：
9.8
通讯作者：
Mohlke, Karen L.
中科院分区：
文献类型：
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作者：
Kulzer, Jennifer R.;Stitzel, Michael L.;Mohlke, Karen L.
全基因组关联研究（GWAS）已经确定了70多个与2型糖尿病（T2 D）相关的基因座，但对于大多数人来说，潜在的致病变异，相关基因和功能机制仍然未知。在11q13.4上的T2 D和空腹胰岛素原相关位点，我们已经确定了一个功能性调控DNA变体，一个候选靶基因和一个合理的潜在分子机制。对来自男性代谢综合征研究的8，635名个体进行的精细定位、条件分析和外显子组阵列基因分型证实了空腹胰岛素原和非编码变体之间的单一主要关联信号（p = 7.4 x 10（-5））。对rs 11603334杂合子人类胰岛样本中等位基因特异性mRNA水平的测量显示，T2 D风险和胰岛素原降低等位基因（C）与ARAP 1表达增加相关（p < 0.02）。我们通过在啮齿动物胰腺β细胞系中进行报告基因测定，评估了四种候选功能性SNP对转录活性的等位基因效应。rs 11603334的C等位基因位于ARAPI启动子附近，其转录活性比T等位基因高2倍（p < 0.0001）;其他三个候选SNP没有显示等位基因差异。电泳迁移率变动分析表明胰腺β细胞转录调节因子PAX 6和PAX 4与rs 11603334 C等位基因的结合减少。总的来说，这些数据表明rs 11603334的T2 D风险等位基因可以消除含有PAX 6和PAX 4的复合物的结合，从而导致人类胰岛中启动子活性和ARAP 1表达增加。这项工作表明，增加ARAP 1表达可能有助于T2 D易感性在这个GWAS基因座。
Genome-wide association studies (GWASs) have identified more than 70 loci associated with type 2 diabetes (T2D), but for most, the underlying causal variants, associated genes, and functional mechanisms remain unknown. At a T2D- and fasting-proinsulin-associated locus on 11q13.4, we have identified a functional regulatory DNA variant, a candidate target gene, and a plausible underlying molecular mechanism. Fine mapping, conditional analyses, and exome array genotyping in 8,635 individuals from the Metabolic Syndrome in Men study confirmed a single major association signal between fasting proinsulin and noncoding variants (p = 7.4 x 10(-5)). Measurement of allele-specific mRNA levels in human pancreatic islet samples heterozygous for rs11603334 showed that the T2D-risk and proinsulin-decreasing allele (C) is associated with increased ARAP1 expression (p < 0.02). We evaluated four candidate functional SNPs for allelic effects on transcriptional activity by performing reporter assays in rodent pancreatic beta cell lines. The C allele of rs11603334, located near one of the ARAPI promoters, exhibited 2-fold higher transcriptional activity than did the T allele (p < 0.0001); three other candidate SNPs showed no allelic differences. Electrophoretic mobility shift assays demonstrated decreased binding of pancreatic beta cell transcriptional regulators PAX6 and PAX4 to the rs11603334 C allele. Collectively, these data suggest that the T2D-risk allele of rs11603334 could abrogate binding of a complex containing PAX6 and PAX4 and thus lead to increased promoter activity and ARAP1 expression in human pancreatic islets. This work suggests that increased ARAP1 expression might contribute to T2D susceptibility at this GWAS locus.