Specificity of four monoclonal anti-NKx6-1 antibodies

db/db Mice Exhibit Features of Human Type 2 Diabetes That Are Not Present in Weight-Matched C57BL/6J Mice Fed a Western Diet

To understand features of human obesity and type 2 diabetes mellitus (T2D) that can be recapitulated in the mouse, we compared C57BL/6J mice fed a Western-style diet (WD) to weight-matched genetically obese leptin receptor-deficient mice (db/db). All mice were monitored for changes in body composition, glycemia, and total body mass. To objectively compare diet-induced and genetic models of obesity, tissue analyses were conducted using mice with similar body mass. We found that adipose tissue inflammation was present in both models of obesity. In addition, distinct alterations in metabolic flexibility were evident between WD-fed mice and db/db mice. Circulating insulin levels are elevated in each model of obesity, while glucagon was increased only in the db/db mice. Although both WD-fed and db/db mice exhibited adaptive increases in islet size, the db/db mice also displayed augmented islet expression of the dedifferentiation marker Aldh1a3 and reduced nuclear presence of the transcription factor Nkx6.1. Based on the collective results put forth herein, we conclude that db/db mice capture key features of human T2D that do not occur in WD-fed C57BL/6J mice of comparable body mass.

IL-1β reciprocally regulates chemokine and insulin secretion in pancreatic β-cells via NF-κB

Proinflammatory cytokines impact islet β-cell mass and function by altering the transcriptional activity within pancreatic β-cells, producing increases in intracellular nitric oxide abundance and the synthesis and secretion of immunomodulatory proteins such as chemokines. Herein, we report that IL-1β, a major mediator of inflammatory responses associated with diabetes development, coordinately and reciprocally regulates chemokine and insulin secretion. We discovered that NF-κB controls the increase in chemokine transcription and secretion as well as the decrease in both insulin secretion and proliferation in response to IL-1β. Nitric oxide production, which is markedly elevated in pancreatic β-cells exposed to IL-1β, is a negative regulator of both glucose-stimulated insulin secretion and glucose-induced increases in intracellular calcium levels. By contrast, the IL-1β-mediated production of the chemokines CCL2 and CCL20 was not influenced by either nitric oxide levels or glucose concentration. Instead, the synthesis and secretion of CCL2 and CCL20 in response to IL-1β were dependent on NF-κB transcriptional activity. We conclude that IL-1β-induced transcriptional reprogramming via NF-κB reciprocally regulates chemokine and insulin secretion while also negatively regulating β-cell proliferation. These findings are consistent with NF-κB as a major regulatory node controlling inflammation-associated alterations in islet β-cell function and mass.

Short-term effects of INGAP and Reg family peptides on the appearance of small β-cells clusters in non-diabetic mice

The Reg3 peptides INGAP-PP and human Reg3α/β (HIP) have been hypothesized to stimulate β-cell neogenesis in the pancreas. Administration of INGAP-PP has been shown to cause an increase in β-cell mass in multiple animal models, reverse streptozotocin (STZ) induced diabetes in mice and reduces HbA1c levels in type 2 diabetic humans. In this study, we have examined the ability of the INGAP-PP and HIP peptides to induce β-cell formation in vivo in normal mice through short-term administration of the peptides. We assessed the peptides ability to induce an increase in extra-islet insulin-positive cell clusters by looking at β-cell number by point counting morphometry on pancreata that had been randomized using the smooth fractionator principle in non-diabetic NMRI mice after short-term injections of the peptides (5 d). Five day continuous BrdU labeling was used to determine if the new β-cells were derived from replicating β-cells. Real time quantitative RT-PCR and immuno-histochemistry was used to analyze changes in pancreatic transcription factor expression. A 1.5- to 2-fold increase in the volume of small extra-islet insulin-positive clusters post 5 d treatment with INGAP-PP and HIP as compared with mice treated with a non-peptide control or scrambled peptide (p<0.05) (n = 7) was found. Five day continuous BrdU infusion during the 5 d period showed little or no incorporation in islets or small insulin clusters. Five days of treatment with INGAP-PP or HIP, showed a tendency toward increased levels of pancreatic progenitor markers such as Ngn3, Nkx6.1, Sox9 and Ins. These are the first studies to compare and indicate that the human Reg3 α/β (HIP) peptide has similar bioactivity in vivo as INGAP by causing formation of small β-cell clusters in extra-islet pancreatic tissue after only 5 d of treatment. Upregulation of pancreatic transcription factors may be part of the mechanism of action.

A BAC transgenic Hes1-EGFP reporter reveals novel expression domains in mouse embryos

Expression of the basic helix-loop-helix factor Hairy and Enhancer of Split-1 (Hes1) is required for normal development of a number of tissues during embryonic development. Depending on context, Hes1 may act as a Notch signalling effector which promotes the undifferentiated and proliferative state of progenitor cells, but increasing evidence also points to Notch independent regulation of Hes1 expression. Here we use high resolution confocal scanning of EGFP in a novel BAC transgenic mouse reporter line, Tg(Hes1-EGFP)(1Hri), to analyse Hes1 expression from embryonic day 7.0 (e7.0). Our data recapitulates some previous observations on Hes1 expression and suggests new, hitherto unrecognised expression domains including expression in the definitive endoderm at early somite stages before gut tube closure and thus preceding organogenesis. This mouse line will be a valuable tool for studies addressing the role of Hes1 in a number of different research areas including organ specification, development and regeneration.

An overview of the computational analyses and discovery of transcription factor binding sites

Here we provide a pragmatic, high-level overview of the computational approaches and tools for the discovery of transcription factor binding sites. Unraveling transcription regulatory networks and their malfunctions such as cancer became feasible due to recent stellar progress in experimental techniques and computational analyses. While predictions of isolated sites still pose notorious challenges, cis-regulatory modules (clusters) of binding sites can now be identified with high accuracy. Further support comes from conserved DNA segments, co-regulation, transposable elements, nucleosomes, and three-dimensional chromosomal structures. We introduce computational tools for the analysis and interpretation of chromatin immunoprecipitation, next-generation sequencing, SELEX, and protein-binding microarray results. Because immunoprecipitation produces overly large DNA segments and well over half of the sequencing reads from constitute background noise, methods are presented for background correction, sequence read mapping, peak calling, false discovery rate estimation, and co-localization analyses. To discover short binding site motifs from extensive immunoprecipitation segments, we recommend algorithms and software based on expectation maximization and Gibbs sampling. Data integration using several databases further improves performance. Binding sites can be visualized in genomic and chromatin context using genome browsers. Binding site information, integrated with co-expression in large compendia of gene expression experiments, allows us to reveal complex transcriptional regulatory networks.