Organization and regulation of the human insulin locus

我们正在进行的研究组蛋白修饰的胰岛素基因位点及其附近的人胰岛细胞，在试图确定可能影响胰岛素基因表达的长期调控的影响。 我们正在进行胰岛素启动子和其他基因组位点之间的细胞核内长距离物理接触的测量。 为了检测这种相互作用，我们在人类胰岛中进行了4C（一种扩展的染色质构象捕获）实验，以绘制Ins启动子和11号染色体上远端位点之间的细胞核内接触。 我们选择了一个单一的候选人，synaptotagmin 8（Syt 8）基因，它像胰岛素基因座，有一个附近的CTCF结合位点进行进一步的研究。 在本文中，我们表明，Ins-Syt 8的接触是存在的，它们被刺激的葡萄糖和抑制时，Ins启动子被阻断沉默Ins基因的活性。 增加的接触与增加的Syt 8表达相关。 CTCF的消耗导致接触的丧失和Syt 8（但不是Ins）表达的丧失。 此外，我们发现Syt 8的缺失导致胰岛分泌胰岛素减少。 这些结果揭示了一个物理网络的远程相互作用，导致耦合的监管控制。 这些类型的调节网络似乎很可能发生在整个基因组中。 本文所述的方法也可应用于其他基因座。

We are carrying out studies of the histone modifications over the insulin gene locus and its neighborhood in human islet cells, in an attempt to identify long range regulatory influences that may affect insulin gene expression. We are carrying out measurements of long range physical contacts within the nucleus between the insulin promoter and other genomic sites. To detect such interactions we carried out 4C (an extended chromatin conformation capture) experiments in human islets, to map contacts within the nucleus between the Ins promoter and distant sites on chromosome 11. We selected for further study a single candidate, the synaptotagmin 8 (Syt8) gene, which like the insulin locus, has a nearby CTCF binding site. We show in this paper that Ins-Syt8 contacts are present, that they are stimulated by addition of glucose and inhibited when the Ins promoter is blocked to silence Ins gene activity. Increased contact is correlated with increased Syt8 expression. Depletion of CTCF results in loss of contact and loss of Syt8 (but not Ins) expression. Furthermore, we show that depletion of Syt8 results in decreased secretion of insulin from the islets. These results reveal a physical network of long range interactions that leads to coupled regulatory control. It seems likely that these kinds of regulatory networks occur throughout the genome. The methods described in this paper can be applied to other loci.