American Diabetes Association
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An Enhancer Within Abcb11 Regulates G6pc2 in C57BL/6 Mouse Pancreatic Islets

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posted on 2023-08-08, 20:52 authored by Mark P. Keller, Emily M. Hawes, Kathryn L. Schueler, Donnie S. Stapleton, Kelly A. Mitok, Shane P. Simonett, James K. Oeser, Leesa L. Sampson, Alan D. Attie, Mark A. Magnuson, Richard M. O’Brien

G6PC2 is predominantly expressed in pancreatic islet beta cells where it encodes a glucose-6-phosphatase catalytic subunit that modulates the sensitivity of insulin secretion to glucose by opposing the action of glucokinase, thereby regulating fasting blood glucose (FBG). Prior studies have shown that the G6pc2 promoter alone is unable to confer sustained islet-specific gene expression in mice, suggesting the existence of distal enhancers that regulate G6pc2 expression. Using information from both mice and humans, and knowledge that single nucleotide polymorphisms (SNPs) both within and near G6PC2 are associated with variations in FBG in humans, we identified several putative enhancers 3' of G6pc2. One region, herein referred to as enhancer I, resides in the 25th intron of Abcb11 and binds multiple islet-enriched transcription factors. CRISPR-mediated deletion of enhancer I in C57BL/6 mice had selective effects on the expression of genes near the G6pc2 locus: in isolated islets G6pc2 and Spc25 expression were reduced ~50%, and Gm13613 expression was abolished, whereas Cers6 and Nostrin expression were unaffected. This partial reduction in G6pc2 expression enhanced islet insulin secretion at basal glucose concentrations but did not affect FBG or glucose tolerance in vivo, consistent with the absence of a phenotype in G6pc2 heterozygous C57BL/6 mice.


Generation of G6pc2EnhI/EnhI mice by the Vanderbilt Genome Editing Resource (RRID: SCR_018826) was supported by the Vanderbilt Cancer Center Support Grant (CA68485), the Vanderbilt Diabetes Research and Training Center (DK020593), and the Vanderbilt Center for Stem Cell Biology. This work was supported by the following grants: DK132259 (R.M.O’B); DK101573, DK102948, and DK125961 (A.D.A.); the University of Wisconsin–Madison, Department of Biochemistry and Office of the Vice Chancellor for Research and Graduate Education with funding from the Wisconsin Alumni Research Foundation (M.P.K.). E.M.H. was supported by the Vanderbilt Molecular Endocrinology Training Program grant 5T32 DK07563 and the American Heart Association Pre-doctoral Fellowship 23PRE1017904.


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