scholarly journals The pancreatic islet β-cell-enriched transcription factor Pdx-1 regulates Slc30a8 gene transcription through an intronic enhancer

2010 ◽  
Vol 433 (1) ◽  
pp. 95-105 ◽  
Author(s):  
Lynley D. Pound ◽  
Yan Hang ◽  
Suparna A. Sarkar ◽  
Yingda Wang ◽  
Laurel A. Milam ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Pancreatic Islet ◽  
Fusion Gene ◽  
Association Studies ◽  
Genome Wide Association Studies ◽  
Β Cells ◽  
Β Cell ◽  
Specific Expression

The SLC30A8 gene encodes the zinc transporter ZnT-8, which provides zinc for insulin-hexamer formation. Genome-wide association studies have shown that a polymorphic variant in SLC30A8 is associated with altered susceptibility to Type 2 diabetes and we recently reported that glucose-stimulated insulin secretion is decreased in islets isolated from Slc30a8-knockout mice. The present study examines the molecular basis for the islet-specific expression of Slc30a8. VISTA analyses identified two conserved regions in Slc30a8 introns 2 and 3, designated enhancers A and B respectively. Transfection experiments demonstrated that enhancer B confers elevated fusion gene expression in both βTC-3 cells and αTC-6 cells. In contrast, enhancer A confers elevated fusion gene expression selectively in βTC-3 and not αTC-6 cells. These data suggest that enhancer A is an islet β-cell-specific enhancer and that the mechanisms controlling Slc30a8 expression in α- and β-cells are overlapping, but distinct. Gel retardation and ChIP (chromatin immunoprecipitation) assays revealed that the islet-enriched transcription factor Pdx-1 binds enhancer A in vitro and in situ respectively. Mutation of two Pdx-1-binding sites in enhancer A markedly reduces fusion gene expression suggesting that this factor contributes to Slc30a8 expression in β-cells, a conclusion consistent with developmental studies showing that restriction of Pdx-1 to pancreatic islet β-cells correlates with the induction of Slc30a8 gene expression and ZnT-8 protein expression in vivo.

scholarly journals Autocrine IGF2 programmes β-cell plasticity under conditions of increased metabolic demand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ionel Sandovici ◽  
Constanze M. Hammerle ◽  
Sam Virtue ◽  
Yurena Vivas-Garcia ◽  
Adriana Izquierdo-Lahuerta ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Glucose Homeostasis ◽  
Association Studies ◽  
Susceptibility Gene ◽  
Chow Diet ◽  
Genome Wide Association Studies ◽  
Cell Plasticity ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

AbstractWhen exposed to nutrient excess and insulin resistance, pancreatic β-cells undergo adaptive changes in order to maintain glucose homeostasis. The role that growth control genes, highly expressed in early pancreas development, might exert in programming β-cell plasticity in later life is a poorly studied area. The imprinted Igf2 (insulin-like growth factor 2) gene is highly transcribed during early life and has been identified in recent genome-wide association studies as a type 2 diabetes susceptibility gene in humans. Hence, here we investigate the long-term phenotypic metabolic consequences of conditional Igf2 deletion in pancreatic β-cells (Igf2βKO) in mice. We show that autocrine actions of IGF2 are not critical for β-cell development, or for the early post-natal wave of β-cell remodelling. Additionally, adult Igf2βKO mice maintain glucose homeostasis when fed a chow diet. However, pregnant Igf2βKO females become hyperglycemic and hyperinsulinemic, and their conceptuses exhibit hyperinsulinemia and placentomegalia. Insulin resistance induced by congenital leptin deficiency also renders Igf2βKO females more hyperglycaemic compared to leptin-deficient controls. Upon high-fat diet feeding, Igf2βKO females are less susceptible to develop insulin resistance. Based on these findings, we conclude that in female mice, autocrine actions of β-cell IGF2 during early development determine their adaptive capacity in adult life.

scholarly journals TCF19 Impacts a Network of Inflammatory and DNA Damage Response Genes in the Pancreatic β-Cell

Metabolites ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 513
Author(s):  
Grace H. Yang ◽  
Danielle A. Fontaine ◽  
Sukanya Lodh ◽  
Joseph T. Blumer ◽  
Avtar Roopra ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Damage ◽  
Dna Damage Response ◽  
Association Studies ◽  
Cell Cycle Gene ◽  
Genome Wide Association Studies ◽  
Β Cell ◽  
Nucleotide Incorporation ◽  
Damage Response ◽  
The Impact

Transcription factor 19 (TCF19) is a gene associated with type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in genome-wide association studies. Prior studies have demonstrated that Tcf19 knockdown impairs β-cell proliferation and increases apoptosis. However, little is known about its role in diabetes pathogenesis or the effects of TCF19 gain-of-function. The aim of this study was to examine the impact of TCF19 overexpression in INS-1 β-cells and human islets on proliferation and gene expression. With TCF19 overexpression, there was an increase in nucleotide incorporation without any change in cell cycle gene expression, alluding to an alternate process of nucleotide incorporation. Analysis of RNA-seq of TCF19 overexpressing cells revealed increased expression of several DNA damage response (DDR) genes, as well as a tightly linked set of genes involved in viral responses, immune system processes, and inflammation. This connectivity between DNA damage and inflammatory gene expression has not been well studied in the β-cell and suggests a novel role for TCF19 in regulating these pathways. Future studies determining how TCF19 may modulate these pathways can provide potential targets for improving β-cell survival.

scholarly journals RFX6-mediated dysregulation defines human β cell dysfunction in early type 2 diabetes

2021 ◽  
Author(s):  
John T Walker ◽  
Diane C Saunders ◽  
Vivek Rai ◽  
Chunhua Dai ◽  
Peter Orchard ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Insulin Secretion ◽  
Association Studies ◽  
Critical Role ◽  
Regulatory Elements ◽  
Genome Wide Association Studies ◽  
Β Cells ◽  
Β Cell ◽  
Gene Regulatory

A hallmark of type 2 diabetes (T2D), a major cause of world-wide morbidity and mortality, is dysfunction of insulin-producing pancreatic islet β cells. T2D genome-wide association studies (GWAS) have identified hundreds of signals, mostly in the non-coding genome and overlapping β cell regulatory elements, but translating these into biological mechanisms has been challenging. To identify early disease-driving events, we performed single cell spatial proteomics, sorted cell transcriptomics, and assessed islet physiology on pancreatic tissue from short-duration T2D and control donors. Here, through integrative analyses of these diverse modalities, we show that multiple gene regulatory modules are associated with early-stage T2D β cell-intrinsic defects. One notable example is the transcription factor RFX6, which we show is a highly connected β cell hub gene that is reduced in T2D and governs a gene regulatory network associated with insulin secretion defects and T2D GWAS variants. We validated the critical role of RFX6 in β cells through direct perturbation in primary human islets followed by physiological and single nucleus multiome profiling, which showed reduced dynamic insulin secretion and large-scale changes in the β cell transcriptome and chromatin accessibility landscape. Understanding the molecular mechanisms of complex, systemic diseases necessitates integration of signals from multiple molecules, cells, organs, and individuals and thus we anticipate this approach will be a useful template to identify and validate key regulatory networks and master hub genes for other diseases or traits with GWAS data.

scholarly journals MafB Is Critical for Glucagon Production and Secretion in Mouse Pancreatic α Cells In Vivo

2018 ◽  
Vol 38 (8) ◽  
Author(s):  
Megumi C. Katoh ◽  
Yunshin Jung ◽  
Chioma M. Ugboma ◽  
Miki Shimbo ◽  
Akihiro Kuno ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Cell Population ◽  
Pancreatic Polypeptide ◽  
Transporter Gene ◽  
Β Cells ◽  
Β Cell ◽  
Cell Numbers ◽  
Gene Expression Analyses

ABSTRACT The MafB transcription factor is expressed in pancreatic α and β cells during development but becomes exclusive to α cells in adult rodents. Mafb -null ( Mafb −/− ) mice were reported to have reduced α- and β-cell numbers throughout embryonic development. To further analyze the postnatal function of MafB in the pancreas, we generated endocrine cell-specific ( Mafb Δ Endo ) and tamoxifen-dependent ( Mafb Δ TAM ) Mafb knockout mice. Mafb Δ Endo mice exhibited reduced populations of insulin-positive (insulin + ) and glucagon + cells at postnatal day 0, but the insulin + cell population recovered by 8 weeks of age. In contrast, the Arx + glucagon + cell fraction and glucagon expression remained decreased even in adulthood. Mafb Δ TAM mice, with Mafb deleted after pancreas maturation, also demonstrated diminished glucagon + cells and glucagon content without affecting β cells. A decreased Arx + glucagon + cell population in Mafb Δ Endo mice was compensated for by an increased Arx + pancreatic polypeptide + cell population. Furthermore, gene expression analyses from both Mafb Δ Endo and Mafb Δ TAM islets revealed that MafB is a key regulator of glucagon expression in α cells. Finally, both mutants failed to respond to arginine, likely due to impaired arginine transporter gene expression and glucagon production ability. Taken together, our findings reveal that MafB is critical for the functional maintenance of mouse α cells in vivo , including glucagon production and secretion, as well as in development.

scholarly journals The β-cell specific transcription factor Nkx6.1 inhibits glucagon gene transcription by interfering with Pax6

2007 ◽  
Vol 403 (3) ◽  
pp. 593-601 ◽  
Author(s):  
Benoit R. Gauthier ◽  
Yvan Gosmain ◽  
Aline Mamin ◽  
Jacques Philippe
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Gene Transcription ◽  
Promoter Activity ◽  
Islet Cells ◽  
Gene Activation ◽  
Physical Interaction ◽  
Specific Expression

The transcription factor Nkx6.1 is required for the establishment of functional insulin-producing β-cells in the endocrine pancreas. Overexpression of Nkx6.1 has been shown to inhibit glucagon gene expression while favouring insulin gene activation. Down-regulation resulted in the opposite effect, suggesting that absence of Nkx6.1 favours glucagon gene expression. To understand the mechanism by which Nkx6.1 suppresses glucagon gene expression, we studied its effect on the glucagon gene promoter activity in non-islet cells using transient transfections and gel-shift analyses. In glucagonoma cells transfected with an Nkx6.1-encoding vector, the glucagon promoter activity was reduced by 65%. In BHK21 cells, Nkx6.1 inhibited by 93% Pax6-mediated activation of the glucagon promoter, whereas Cdx2/3 and Maf stimulations were unaltered. Although Nkx6.1 could interact with both the G1 and G3 element, only the former displayed specificity for Nkx6.1. Mutagenesis of the three potential AT-rich motifs within the G1 revealed that only the Pax6-binding site preferentially interacted with Nkx6.1. Chromatin immunoprecipitation confirmed interaction of Nkx6.1 with the glucagon promoter and revealed a direct competition for binding between Pax6 and Nkx6.1. A weak physical interaction between Pax6 and Nkx6.1 was detected in vitro and in vivo suggesting that Nkx6.1 predominantly inhibits glucagon gene transcription through G1-binding competition. We suggest that cell-specific expression of the glucagon gene may only proceed when Nkx6.1, in combination with Pdx1 and Pax4, are silenced in early α-cell precursors.

scholarly journals ERASE: Extended Randomization for assessment of annotation enrichment in ASE datasets

2019 ◽  
Author(s):  
Karishma D’Sa ◽  
Regina H. Reynolds ◽  
Sebastian Guelfi ◽  
David Zhang ◽  
Sonia Garcia Ruiz ◽  
...  
Keyword(s):  
Gene Expression ◽  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Association Studies ◽  
Genetic Regulation ◽  
Regulation Of Gene Expression ◽  
Gwas Data ◽  
Genome Wide Association Studies ◽  
Specific Expression ◽  
Individual Snps

AbstractGenome-wide association studies (GWAS) have identified thousands of genetic variants associated with various human phenotypes and many of these loci are thought to act at a molecular level by regulating gene expression. Detection of allele specific expression (ASE), namely preferential usage of an allele at a transcribed locus, is an increasingly important means of studying the genetic regulation of gene expression. However, there are currently a paucity of tools available to link ASE sites with GWAS risk loci. Existing integration methods first use ASE sites to infer cis-acting expression quantitative trait loci (eQTL) and then apply eQTL-based approaches. ERASE is a method that assesses the enrichment of risk loci amongst ASE sites directly. Furthermore, ERASE enables additional biological insights to be made through the addition of other SNP level annotations. ERASE is based on a randomization approach and controls for read depth, a significant confounder in ASE analyses. In this paper, we demonstrate that ERASE can efficiently detect the enrichment of eQTLs and risk loci within ASE data and that it remains sensitive even when used with underpowered GWAS datasets. Finally, using ERASE in combination with GWAS data for Parkinson’s disease and data on the splicing potential of individual SNPs, we provide evidence to suggest that risk loci for Parkinson’s disease are enriched amongst ASEs likely to affect splicing. Thus, we show that ERASE is an important new tool for the integration of ASE and GWAS data, capable of providing novel insights into the pathophysiology of complex diseases.

scholarly journals Characterization of the human SLC30A8 promoter and intronic enhancer

2011 ◽  
Vol 47 (3) ◽  
pp. 251-259 ◽  
Author(s):  
Lynley D Pound ◽  
Suparna A Sarkar ◽  
Stéphane Cauchi ◽  
Yingda Wang ◽  
James K Oeser ◽  
...  
Keyword(s):  
Fusion Gene ◽  
Association Studies ◽  
Causal Variant ◽  
Proximal Promoter ◽  
Luciferase Expression ◽  
Genome Wide Association Studies ◽  
Promoter Regions ◽  
Specific Expression ◽  
Enhancer Activity ◽  
Intron 2

Genome-wide association studies have shown that a polymorphic variant inSLC30A8, which encodes zinc transporter-8, is associated with altered susceptibility to type 2 diabetes (T2D). This association is consistent with the observation that glucose-stimulated insulin secretion is decreased in islets isolated fromSlc30a8knockout mice. In this study, immunohistochemical staining was first used to show thatSLC30A8is expressed specifically in pancreatic islets. Fusion gene studies were then used to examine the molecular basis for the islet-specific expression ofSLC30A8. The analysis ofSLC30A8-luciferase expression in βTC-3 cells revealed that the proximal promoter region, located between −6154 and −1, relative to the translation start site, was only active in stable but not transient transfections. VISTA analyses identified three regions in theSLC30A8promoter and a region inSLC30A8intron 2 that are conserved in the mouseSlc30a8gene. Additional fusion gene experiments demonstrated that none of theseSlc30a8promoter regions exhibited enhancer activity when ligated to a heterologous promoter whereas the conserved region inSLC30A8intron 2 conferred elevated reporter gene expression selectively in βTC-3 but not in αTC-6 cells. Finally, the functional effects of a single nucleotide polymorphism (SNP), rs62510556, in this conserved intron 2 enhancer were investigated. Gel retardation studies showed that rs62510556 affects the binding of an unknown transcription factor and fusion gene analyses showed that it modulates enhancer activity. However, genetic analyses suggest that this SNP is not a causal variant that contributes to the association betweenSLC30A8and T2D, at least in Europeans.

Naringin (4′,5,7-Trihydroxyflavanone 7-Rhamnoglucoside) Attenuates β-Cell Dysfunction in Diabetic Rats through Upregulation of PDX-1

2018 ◽  
Vol 206 (3) ◽  
pp. 133-143 ◽  
Author(s):  
Manickam Subramanian ◽  
Balaji Thotakura ◽  
Swathi Priyadarshini Chandra Sekaran ◽  
Ashok kumar Jyothi ◽  
Indumathi Sundaramurthi
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Insulin Secretion ◽  
Protein Expression ◽  
Serum Insulin ◽  
Diabetic Rats ◽  
Insulin Gene ◽  
Β Cells ◽  
Β Cell ◽  
Insulin Gene Expression

Background: Pancreatic duodenal homeobox-1 (PDX-1) is a key transcription factor which regulates Insulin gene expression and insulin secretion in adult β-cells and helps to maintain β-cells mass. Naringin, a flavanone, owing to its anti­oxidant property, is reported to have antidiabetic effects. Objectives: The present study tries to evaluate the role of naringin on the β-cell-specific transcription factor PDX-1 in diabetic rats. Methods: Diabetes was induced in male rats using streptozotocin and treated with naringin (100 mg/kg) orally for 4 and 8 weeks. Serum insulin level, Pdx-1 and Insulin gene expression, and PDX-1 protein expression were assessed in the rat pancreas. Histopathological and ultrastructural changes in the islet and β-cells were observed. Results: Naringin prevented leukocytic infiltration in the pancreas of diabetic rats and recouped the β-cells with adequate secretory granules. Naringin-treated diabetic rats showed significantly increased mRNA expression of Pdx-1 and Insulin genes, increased expression of transcription factor PDX-1, and higher serum insulin levels than the diabetic control animals. These changes were more pronounced in the 8-week naringin-treated diabetic animals. Conclusions: Naringin was found to be an effective antidiabetic agent which increased Insulin gene expression and insulin secretion by upregulating the PDX-1 gene and protein expression.

scholarly journals SSBP3 Interacts With Islet-1 and Ldb1 to Impact Pancreatic β-Cell Target Genes

2015 ◽  
Vol 29 (12) ◽  
pp. 1774-1786 ◽  
Author(s):  
Jamie R. Galloway ◽  
Maigen Bethea ◽  
Yanping Liu ◽  
Rachel Underwood ◽  
James A. Mobley ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Target Genes ◽  
Binding Protein ◽  
Β Cells ◽  
Β Cell ◽  
Complex Activity ◽  
Pancreatic Islet Cell ◽  
Cell Target ◽  
Islet 1

Abstract Islet-1 (Isl1) is a Lin11, Isl1, Mec3 (LIM)-homeodomain transcription factor important for pancreatic islet cell development, maturation, and function, which largely requires interaction with the LIM domain-binding protein 1 (Ldb1) coregulator. In other tissues, Ldb1 and Isl1 interact with additional factors to mediate target gene transcription, yet few protein partners are known in β-cells. Therefore, we hypothesize that Ldb1 and Isl1 participate in larger regulatory complexes to impact β-cell gene expression. To test this, we used cross-linked immunoprecipitation and mass spectrometry to identify interacting proteins from mouse β-cells. Proteomic datasets revealed numerous interacting candidates, including a member of the single-stranded DNA-binding protein (SSBP) coregulator family, SSBP3. SSBPs potentiate LIM transcription factor complex activity and stability in other tissues. However, nothing was known of SSBP3 interaction, expression, or activity in β-cells. Our analyses confirmed that SSBP3 interacts with Ldb1 and Isl1 in β-cell lines and in mouse and human islets and demonstrated SSBP3 coexpression with Ldb1 and Isl1 pancreas tissue. Furthermore, β-cell line SSBP3 knockdown imparted mRNA deficiencies similar to those observed upon Ldb1 reduction in vitro or in vivo. This appears to be (at least) due to SSBP3 occupancy of known Ldb1-Isl1 target promoters, including MafA and Glp1r. This study collectively demonstrates that SSBP3 is a critical component of Ldb1-Isl1 regulatory complexes, required for expression of critical β-cell target genes.

scholarly journals Elucidating the crosstalk between inflammation and DNA damage pathways in the pancreatic beta-cell through the diabetes susceptibility gene, TCF19

2021 ◽  
Author(s):  
Grace H Yang ◽  
Danielle A Fontaine ◽  
Sukanya Lodh ◽  
Joseph T Blumer ◽  
Avtar S Roopra ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Damage ◽  
Association Studies ◽  
Pancreatic Beta Cell ◽  
Susceptibility Gene ◽  
Cell Cycle Gene ◽  
Genome Wide Association Studies ◽  
Β Cell ◽  
Nucleotide Incorporation ◽  
The Impact

TCF19 is a gene that is associated with both type 1 diabetes (T1DM) and type 2 diabetes (T2DM) in genome-wide association studies. Prior studies have demonstrated that TCF19 knockdown impairs β-cell proliferation and increases apoptosis. However, little is known about its role in diabetes pathogenesis or the effects of TCF19 gain-of-function. The aim of this study was to examine the impact of TCF19 overexpression in INS-1 β-cells on proliferation and gene expression. With TCF19 overexpression, there was an increase in nucleotide incorporation without any change in cell cycle gene expression, alluding to an alternate process of nucleotide incorporation. Analysis of RNAseq of TCF19 overexpressing cells revealed increased expression of several DNA damage response (DDR) genes, as well as a tightly linked set of genes involved in cell stress, immune system processes, and inflammation. This connectivity between DNA damage and inflammatory gene expression has not been well studied in the β-cell, and suggests a novel role for TCF19 in regulating these pathways. Future studies determining how TCF19 may modulate these pathways may provide potential targets for β-cell survival.

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