Foxa2 regulates multiple pathways of insulin secretion
Kristen A. Lantz, … , Franz M. Matschinsky, Klaus H. Kaestner
Kristen A. Lantz, … , Franz M. Matschinsky, Klaus H. Kaestner
Published August 16, 2004
Citation Information: J Clin Invest. 2004;114(4):512-520. https://doi.org/10.1172/JCI21149.
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Article Metabolism

Foxa2 regulates multiple pathways of insulin secretion

Abstract

The regulation of insulin secretion by pancreatic β cells is perturbed in several diseases, including adult-onset (type 2) diabetes and persistent hyperinsulinemic hypoglycemia of infancy (PHHI). The first mouse model for PHHI has a conditional deletion of the gene encoding the winged-helix transcription factor Foxa2 (Forkhead box a2, formerly Hepatocyte nuclear factor 3β) in pancreatic β cells. Using isolated islets, we found that Foxa2 deficiency resulted in excessive insulin release in response to amino acids and complete loss of glucose-stimulated insulin secretion. Most PHHI cases are associated with mutations in SUR1 (Sulfonylurea receptor 1) or KIR6.2 (Inward rectifier K+ channel member 6.2), which encode the subunits of the ATP-sensitive K+ channel, and RNA in situ hybridization of mutant mouse islets revealed that expression of both genes is Foxa2 dependent. We utilized expression profiling to identify additional targets of Foxa2. Strikingly, one of these genes, Hadhsc, encodes short-chain L-3-hydroxyacyl-coenzyme A dehydrogenase, deficiency of which has been shown to cause PHHI in humans. Hadhsc is a direct target of Foxa2, as demonstrated by cotransfection as well as in vivo chromatin immunoprecipitation experiments using isolated islets. Thus, we have established Foxa2 as an essential activator of genes that function in multiple pathways governing insulin secretion.

Authors

Kristen A. Lantz, Marko Z. Vatamaniuk, John E. Brestelli, Joshua R. Friedman, Franz M. Matschinsky, Klaus H. Kaestner

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Figure 4

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Quality and purity assessment of islet RNA for gene expression analysis....
Quality and purity assessment of islet RNA for gene expression analysis. (A) RNA Nano 6000 Assay of P8 islet RNA pooled from 5 mutant Foxa2loxP/loxP;Ins.Cre mice using the Agilent 2100 Bioanalyzer. Islet RNA was quantified and evaluated for evidence of degradation using the ratio of 28S rRNA peaks to 18S rRNA peaks. In the representative sample shown, the 28S/18S ratio is approximately 2.5 with a concentration of 79 ng/μl and no evidence of degradation. (B) Real-time PCR analysis of total pancreas cDNA for endocrine and exocrine content using insulin (open circles) and amylase (filled squares) as markers and TBP, TATA-box binding protein (filled triangles), a “housekeeping” gene, as an internal control. (C) Representative real-time PCR analysis of cDNA from isolated islets. In relation to the total pancreas cDNA shown in B, the insulin/amylase ratio has been enriched for 12.24 cycles to achieve a purity of about 99%. dRn, raw fluorescence normalized for baseline and reference dye intensities by MX4000 software.