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.

Project Start
Project End
Budget Start
Budget End
Support Year
5
Fiscal Year
2011
Total Cost
$263,573
Indirect Cost
City
State
Country
Zip Code
Xu, Zhixiong; Lefevre, Gaelle M; Gavrilova, Oksana et al. (2014) Mapping of long-range INS promoter interactions reveals a role for calcium-activated chloride channel ANO1 in insulin secretion. Proc Natl Acad Sci U S A 111:16760-5
Xu, Zhixiong; Felsenfeld, Gary (2012) Order from chaos in the nucleus. Mol Cell 48:327-8
Xu, Z; Lefevre, G M; Felsenfeld, G (2012) Chromatin structure, epigenetic mechanisms and long-range interactions in the human insulin locus. Diabetes Obes Metab 14 Suppl 3:1-11
Xu, Zhixiong; Wei, Gang; Chepelev, Iouri et al. (2011) Mapping of INS promoter interactions reveals its role in long-range regulation of SYT8 transcription. Nat Struct Mol Biol 18:372-8
Mutskov, Vesco; Felsenfeld, Gary (2009) The human insulin gene is part of a large open chromatin domain specific for human islets. Proc Natl Acad Sci U S A 106:17419-24