The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Doris A. Stoffers - One of the best experts on this subject based on the ideXlab platform.
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PDX1 directs a core developmentally and evolutionarily conserved gene program in the pancreatic islet
bioRxiv, 2021Co-Authors: Xiaodun Yang, Doris A. Stoffers, Juxiang Yang, Jeffrey C. Raum, Junil Kim, Gabriella Rice, Kyoungjae Won, Diana E StanescuAbstract:Pancreatic and duodenal homeobox 1 (PDX1) is crucial for pancreas organogenesis, yet the dynamic changes in PDX1 targets in mouse or human pancreas development have not been examined. We integrated the PDX1 cistrome with cell lineage-specific gene expression in both mouse and human developing pancreas. We identified a core set of developmentally and evolutionarily conserved PDX1 bound genes that reveal the broad multifaceted role of PDX1 in pancreas development. Despite the well-known, dramatic changes in PDX1 function and expression, we showed that PDX1 binding is largely stable from embryonic pancreas to adult islet. This may point towards a dual role of PDX1, activating or repressing the expression of its targets at different ages, dependent on other functionally-congruent or directly-interacting partners. Our work also suggests that PDX1 functions not only in initiating pancreas differentiation, but also as a potential keepsake of the progenitor program in the adult beta cells.
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cell cycle regulation of the PDX1 transcription factor in developing pancreas and insulin producing β cells
Diabetes, 2021Co-Authors: Doris A. Stoffers, Scott A. Soleimanpour, Xiaogdong Zhu, Alexis U Oguh, Morgan A Gingerich, Maureen GannonAbstract:Current evidence indicates that proliferating β-cells express lower levels of some functional cell identity genes, suggesting that proliferating cells are not optimally functional. PDX1 is important for β-cell specification, function, and proliferation and is mutated in monogenic forms of diabetes. However, its regulation during the cell cycle is unknown. Here we examined PDX1 protein expression in immortalized β-cells, maternal mouse islets during pregnancy, and mouse embryonic pancreas. We demonstrate that PDX1 localization and protein levels are highly dynamic. In nonmitotic cells, PDX1 is not observed in constitutive heterochromatin, nucleoli, or most areas containing repressive epigenetic marks. At prophase, PDX1 is enriched around the chromosomes before Ki67 coating of the chromosome surface. PDX1 uniformly localizes in the cytoplasm at prometaphase and becomes enriched around the chromosomes again at the end of cell division, before nuclear envelope formation. Cells in S phase have lower PDX1 levels than cells at earlier cell cycle stages, and overexpression of PDX1 in INS-1 cells prevents progression toward G2, suggesting that cell cycle-dependent regulation of PDX1 is required for completion of mitosis. Together, we find that PDX1 localization and protein levels are tightly regulated throughout the cell cycle. This dynamic regulation has implications for the dichotomous role of PDX1 in β-cell function and proliferation.
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A PDX1-ATF transcriptional complex governs β cell survival during stress
Molecular Metabolism, 2018Co-Authors: Christine Juliana, Austin L. Good, Corey E. Cannon, Juxiang Yang, Matthew W. Haemmerle, Doris A. StoffersAbstract:Abstract Objective Loss of insulin secretion due to failure or death of the insulin secreting β cells is the central cause of diabetes. The cellular response to stress (endoplasmic reticulum (ER), oxidative, inflammatory) is essential to sustain normal β cell function and survival. Pancreatic and duodenal homeobox 1 (PDX1), Activating transcription factor 4 (ATF4), and Activating transcription factor 5 (ATF5) are transcription factors implicated in β cell survival and susceptibility to stress. Our goal was to determine if a PDX1-ATF transcriptional complex or complexes regulate β cell survival in response to stress and to identify direct transcriptional targets. Methods PDX1, Atf4 and Atf5 were silenced by viral delivery of gRNAs or shRNAs to Min6 insulinoma cells or primary murine islets. Gene expression was assessed by qPCR, RNAseq analysis, and Western blot analysis. Chromatin enrichment was measured in the Min6 β cell line and primary isolated mouse islets by ChIPseq and ChIP PCR. Immunoprecipitation was used to assess interactions among transcription factors in Min6 cells and isolated mouse islets. Activation of caspase 3 by immunoblotting or by irreversible binding to a fluorescent inhibitor was taken as an indication of commitment to an apoptotic fate. Results RNASeq identified a set of PDX1, ATF4 and ATF5 co-regulated genes enriched in stress and apoptosis functions. We further identified stress induced interactions among PDX1, ATF4, and ATF5. PDX1 chromatin occupancy peaks were identified over composite C/EBP-ATF (CARE) motifs of 26 genes; assessment of a subset of these genes revealed co-enrichment for ATF4 and ATF5. PDX1 occupancy over CARE motifs was conserved in the human orthologs of 9 of these genes. Of these, Glutamate Pyruvate Transaminase 2 (Gpt2), Cation transport regulator 1 (Chac1), and Solute Carrier Family 7 Member 1 (Slc7a1) induction by stress was conserved in human islets and abrogated by deficiency of PDX1, Atf4, and Atf5 in Min6 cells. Deficiency of Gpt2 reduced β cell susceptibility to stress induced apoptosis in both Min6 cells and primary islets. Conclusions Our results identify a novel PDX1 stress inducible complex (es) that regulates expression of stress and apoptosis genes to govern β cell survival.
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A PDX1-ATF transcriptional complex governs β cell survival during stress
Elsevier, 2018Co-Authors: Christine A. Juliana, Austin L. Good, Corey E. Cannon, Juxiang Yang, Matthew W. Haemmerle, Doris A. StoffersAbstract:Objective: Loss of insulin secretion due to failure or death of the insulin secreting β cells is the central cause of diabetes. The cellular response to stress (endoplasmic reticulum (ER), oxidative, inflammatory) is essential to sustain normal β cell function and survival. Pancreatic and duodenal homeobox 1 (PDX1), Activating transcription factor 4 (ATF4), and Activating transcription factor 5 (ATF5) are transcription factors implicated in β cell survival and susceptibility to stress. Our goal was to determine if a PDX1-ATF transcriptional complex or complexes regulate β cell survival in response to stress and to identify direct transcriptional targets. Methods: PDX1, Atf4 and Atf5 were silenced by viral delivery of gRNAs or shRNAs to Min6 insulinoma cells or primary murine islets. Gene expression was assessed by qPCR, RNAseq analysis, and Western blot analysis. Chromatin enrichment was measured in the Min6 β cell line and primary isolated mouse islets by ChIPseq and ChIP PCR. Immunoprecipitation was used to assess interactions among transcription factors in Min6 cells and isolated mouse islets. Activation of caspase 3 by immunoblotting or by irreversible binding to a fluorescent inhibitor was taken as an indication of commitment to an apoptotic fate. Results: RNASeq identified a set of PDX1, ATF4 and ATF5 co-regulated genes enriched in stress and apoptosis functions. We further identified stress induced interactions among PDX1, ATF4, and ATF5. PDX1 chromatin occupancy peaks were identified over composite C/EBP-ATF (CARE) motifs of 26 genes; assessment of a subset of these genes revealed co-enrichment for ATF4 and ATF5. PDX1 occupancy over CARE motifs was conserved in the human orthologs of 9 of these genes. Of these, Glutamate Pyruvate Transaminase 2 (Gpt2), Cation transport regulator 1 (Chac1), and Solute Carrier Family 7 Member 1 (Slc7a1) induction by stress was conserved in human islets and abrogated by deficiency of PDX1, Atf4, and Atf5 in Min6 cells. Deficiency of Gpt2 reduced β cell susceptibility to stress induced apoptosis in both Min6 cells and primary islets. Conclusions: Our results identify a novel PDX1 stress inducible complex (es) that regulates expression of stress and apoptosis genes to govern β cell survival. Keywords: Transcriptional regulation, Stress, Apoptosis, β cell, Pancrea
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Diabetes susceptibility genes PDX1 and Clec16a function in a pathway regulating mitophagy in β-cells
Diabetes, 2015Co-Authors: Scott A. Soleimanpour, David N. Groff, Juxiang Yang, Alana M. Ferrari, Jeffrey C. Raum, Brett A. Kaufman, Doris A. StoffersAbstract:Mitophagy is a critical regulator of mitochondrial quality control and is necessary for elimination of dysfunctional mitochondria to maintain cellular respiration. Here, we report that the homeodomain transcription factor PDX1, a gene associated with both type 2 diabetes and monogenic diabetes of the young, regulates mitophagy in pancreatic β-cells. Loss of PDX1 leads to abnormal mitochondrial morphology and function as well as impaired mitochondrial turnover. High-throughput expression microarray and chromatin occupancy analyses reveal that PDX1 regulates the expression of Clec16a, a type 1 diabetes gene and itself a key mediator of mitophagy through regulation of the E3 ubiquitin ligase Nrdp1. Indeed, expression of Clec16a and Nrdp1 are both reduced in PDX1 haploinsufficient islets, and reduction of PDX1 impairs fusion of autophagosomes containing mitochondria to lysosomes during mitophagy. Importantly, restoration of Clec16a expression after PDX1 loss of function restores mitochondrial trafficking during mitophagy and improves mitochondrial respiration and glucose-stimulated insulin release. Thus, PDX1 orchestrates nuclear control of mitochondrial function in part by controlling mitophagy through Clec16a. The novel PDX1-Clec16a-Nrdp1 pathway we describe provides a genetic basis for the pathogenesis of mitochondrial dysfunction in multiple forms of diabetes that could be targeted for future therapies to improve β-cell function.
Roland Stein - One of the best experts on this subject based on the ideXlab platform.
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Impact of PDX1-associated chromatin modifiers on islet β-cells
Diabetes Obesity and Metabolism, 2016Co-Authors: Jason M. Spaeth, Emily M. Walker, Roland SteinAbstract:Diabetes mellitus arises from insufficient insulin secretion from pancreatic islet β-cells. In type 2 diabetes (T2D), β-cell dysfunction is associated with inactivation and/or loss of transcription factor (TF) activity, including PDX1. Notably, this particular TF is viewed as a master regulator of pancreas development and islet β-cell formation, identity and function. TFs, like PDX1, recruit coregulators to transduce activating and/or repressing signals to the general transcriptional machinery for controlling gene expression, including modifiers of DNA, histones and nucleosome architecture. These coregulators impart a secondary layer of control that can be exploited to modulate TF activity. In this review, we describe PDX1-recruited coregulators that impact chromatin structure, consequently influencing normal β-cell function and likely PDX1 activity in pathophysiological settings.
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transcriptional activity of the islet β cell factor PDX1 is augmented by lysine methylation catalyzed by the methyltransferase set7 9
Publisher, 2015Co-Authors: Aarthi V. Maganti, Bernhard Maier, Sarah A. Tersey, Megan L. Sampley, Amber L. Mosley, Sabire Özcan, Boobalan Pachaiyappan, Patrick M. Woster, Chad S. Hunter, Roland SteinAbstract:Background: PDX1 interacts with the methyltransferase Set7/9 to transactivate β cell genes. Results: Methylation of PDX1 residue Lys-131 by Set7/9 augments PDX1 activity. Conclusion: The ability of PDX1 to regulate genes in β cells is partially dependent upon its methylation by Set7/9. Significance: This study reveals a previously unappreciated role for Lys methylation in the maintenance of PDX1 activity and β cell function. The transcription factor PDX1 is crucial to islet β cell function and regulates target genes in part through interaction with coregulatory factors. Set7/9 is a Lys methyltransferase that interacts with PDX1. Here we tested the hypothesis that Lys methylation of PDX1 by Set7/9 augments PDX1 transcriptional activity. Using mass spectrometry and mutational analysis of purified proteins, we found that Set7/9 methylates the N-terminal residues Lys-123 and Lys-131 of PDX1. Methylation of these residues occurred only in the context of intact, full-length PDX1, suggesting a specific requirement of secondary and/or tertiary structural elements for catalysis by Set7/9. Immunoprecipitation assays and mass spectrometric analysis using β cells verified Lys methylation of endogenous PDX1. Cell-based luciferase reporter assays using wild-type and mutant transgenes revealed a requirement of PDX1 residue Lys-131, but not Lys-123, for transcriptional augmentation by Set7/9. Lys-131 was not required for high-affinity interactions with DNA in vitro, suggesting that its methylation likely enhances post-DNA binding events. To define the role of Set7/9 in β cell function, we generated mutant mice in which the gene encoding Set7/9 was conditionally deleted in β cells (SetΔβ). SetΔβ mice exhibited glucose intolerance similar to PDX1-deficient mice, and their isolated islets showed impaired glucose-stimulated insulin secretion with reductions in expression of PDX1 target genes. Our results suggest a previously unappreciated role for Set7/9-mediated methylation in the maintenance of PDX1 activity and β cell function.
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dynamic recruitment of functionally distinct swi snf chromatin remodeling complexes modulates PDX1 activity in islet β cells
Cell Reports, 2015Co-Authors: Brian Mckenna, Min Guo, Albert B Reynolds, Manami Hara, Roland SteinAbstract:PDX1 is a transcription factor of fundamental importance to pancreas formation and adult islet β cell function. However, little is known about the positive- and negative-acting coregulators recruited to mediate transcriptional control. Here, we isolated numerous PDX1-interacting factors possessing a wide range of cellular functions linked with this protein, including, but not limited to, coregulators associated with transcriptional activation and repression, DNA damage response, and DNA replication. Because chromatin remodeling activities are essential to developmental lineage decisions and adult cell function, our analysis focused on investigating the influence of the Swi/Snf chromatin remodeler on PDX1 action. The two mutually exclusive and indispensable Swi/Snf core ATPase subunits, Brg1 and Brm, distinctly affected target gene expression in β cells. Furthermore, physiological and pathophysiological conditions dynamically regulated PDX1 binding to these Swi/Snf complexes in vivo. We discuss how context-dependent recruitment of coregulatory complexes by PDX1 could impact pancreas cell development and adult islet β cell activity.
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Transcriptional Activity of the Islet β Cell Factor PDX1 Is Augmented by Lysine Methylation Catalyzed by the Methyltransferase Set7/9
Journal of Biological Chemistry, 2015Co-Authors: Aarthi V. Maganti, Bernhard Maier, Sarah A. Tersey, Megan L. Sampley, Amber L. Mosley, Sabire Özcan, Boobalan Pachaiyappan, Patrick M. Woster, Chad S. Hunter, Roland SteinAbstract:Abstract The transcription factor PDX1 is crucial to islet β cell function, and regulates target genes in part through interaction with co-regulatory factors. Set7/9 is a Lys methyltransferase that interacts with PDX1. Here, we tested the hypothesis that Lys methylation of PDX1 by Set7/9 augments PDX1 transcriptional activity. Using mass spectrometry and mutational analysis of purified proteins, we found that Set7/9 methylates N-terminal residues K123 and K131 of PDX1. Methylation of these residues occurred only in the context of intact, full-length PDX1, suggesting a specific requirement of secondary and/or tertiary structural elements for catalysis by Set7/9. Immunoprecipitation assays and mass spectrometric analysis using β cells verified Lys methylation of endogenous PDX1. Cell-based luciferase reporter assays using wild-type and mutant transgenes revealed a requirement of PDX1 residue K131, but not K123, for transcriptional augmentation by Set7/9. K131 was not required for high affinity interactions with DNA in vitro, suggesting that its methylation likely enhances post-DNA binding events. To define the role of Set7/9 in β cell function, we generated mutant mice in which the gene encoding Set7/9 was conditionally deleted in β cells (SetΔβ). SetΔβ mice exhibited glucose intolerance similar to PDX1-deficient mice, and their isolated islets showed impaired glucose-stimulated insulin secretion with reductions in expression of PDX1 target genes. Our results suggest a previously unappreciated role for Set7/9-mediated methylation in the maintenance of PDX1 activity and β cell function.
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characterization of an apparently novel β cell line enriched 80 88 kda transcriptional activator of the mafa and PDX1 genes
Journal of Biological Chemistry, 2013Co-Authors: Chad S. Hunter, Roland SteinAbstract:MafA and PDX1 represent critical transcriptional regulators required for the maintenance of pancreatic islet β-cell function. The in vivo β-cell-enriched expression pattern of these genes is principally directed by islet transcription factors binding within conserved Region 3 (base pairs (bp) −8118/−7750) of MafA and Area II (bp −2153/−1923) of the PDX1 gene. Comprehensive mutational analysis of conserved MafA Region 3 revealed two new β-cell line-specific cis-activation elements, termed Site 4 (bp −7997 to −7988) and Site 12 (bp −7835 to −7826). Gel mobility and antibody super-shift analysis identified PDX1 as the Site 4 binding factor, while an 80–88 kilodalton (kDa) β-cell line-enriched protein complex bound Site 12 and similar aligned nucleotides within PDX1 Area II. The 80–88 kDa activator was also found in adult mouse islet extract. Strikingly, the molecular weight, DNA binding, and antibody recognition properties of this activator were unique when compared with all other key islet transcription factors tested, including Prox1 (83 kDa), Hnf1α (67 kDa), FoxA2 (48 kDa), MafA (46 kDa), Isl1 (44 kDa), PDX1 (42 kDa), and Nkx2.2 (30 kDa). Collectively, these data define an apparently novel MafA Region 3 and PDX1 Area II activator contributing to expression in β-cells.
Kenneth S Polonsky - One of the best experts on this subject based on the ideXlab platform.
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pancreatic β cell death due to pdx 1 deficiency requires multi bh domain protein bax but not bak
Journal of Biological Chemistry, 2016Co-Authors: Kenneth S PolonskyAbstract:Diabetes develops in PDX1-haploinsufficient mice due to an increase in β-cell death leading to reduced β-cell mass and decreased insulin secretion. Knockdown of PDX1 gene expression in mouse MIN6 insulinoma cells induced apoptotic cell death with an increase in Bax activation and knockdown of Bax reduced apoptotic β-cell death. In PDX1 haploinsufficient mice, Bax ablation in β-cells increased β-cell mass, decreased the number of TUNEL positive cells and improved glucose tolerance after glucose challenge. These changes were not observed with Bak ablation in PDX1-haploinsufficient mice. These results suggest that Bax mediates β-cell apoptosis in PDX1-deficient diabetes.
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Role of BH3-only molecules Bim and Puma in β-cell death in PDX1 deficiency.
Diabetes, 2014Co-Authors: Decheng Ren, Juan Sun, Changzheng Wang, Liqun Mao, Emily H. Cheng, Graeme I. Bell, Kenneth S PolonskyAbstract:Mutations in pancreatic duodenal homeobox-1 (PDX1) are associated with diabetes in humans. PDX1-haploinsufficient mice develop diabetes due to an increase in β-cell death leading to reduced β-cell mass. For definition of the molecular link between PDX1 deficiency and β-cell death, PDX1-haploinsufficient mice in which the genes for the BH3-only molecules Bim and Puma had been ablated were studied on a high-fat diet. Compared with PDX1+/− mice, animals haploinsufficient for both PDX1 and Bim or Puma genes showed improved glucose tolerance, enhanced β-cell mass, and reduction in the number of TUNEL-positive cells in islets. These results suggest that Bim and Puma ablation improves β-cell survival in PDX1+/− mice. For exploration of the mechanisms responsible for these findings, PDX1 gene expression was knocked down in mouse MIN6 insulinoma cells resulting in apoptotic cell death that was found to be associated with increased expression of BH3-only molecules Bim and Puma. If the upregulation of Bim and Puma that occurs during PDX1 suppression was prevented, apoptotic β-cell death was reduced in vitro. These results suggest that Bim and Puma play an important role in β-cell apoptosis in PDX1-deficient diabetes.
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loss of nix in PDX1 deficient mice prevents apoptotic and necrotic β cell death and diabetes
Journal of Clinical Investigation, 2010Co-Authors: Kei Fujimoto, Gerald W Dorn, Eric L Ford, Burton M Wice, Hung Tran, Seth D. Crosby, Kenneth S PolonskyAbstract:Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, PDX1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between PDX1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete PDX1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition–dependent necrotic pathways. Preventing Nix upregulation during PDX1 suppression abrogated apoptotic and necrotic β cell death in vitro. In PDX1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in PDX1-deficient diabetes.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of β-cells, leading to decreased β-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 β-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Δψm. Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Δψm and rescued cell viability. Reduced β-cell mass, markers of β-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored β-cell mass and decreased TUNEL and complement complex labeling without affecting β-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of β-cell death caused by PDX1 insufficiency.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of beta-cells, leading to decreased beta-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 beta-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Deltapsi(m). Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Deltapsi(m) and rescued cell viability. Reduced beta-cell mass, markers of beta-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored beta-cell mass and decreased TUNEL and complement complex labeling without affecting beta-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of beta-cell death caused by PDX1 insufficiency.
Kei Fujimoto - One of the best experts on this subject based on the ideXlab platform.
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loss of nix in PDX1 deficient mice prevents apoptotic and necrotic β cell death and diabetes
Journal of Clinical Investigation, 2010Co-Authors: Kei Fujimoto, Gerald W Dorn, Eric L Ford, Burton M Wice, Hung Tran, Seth D. Crosby, Kenneth S PolonskyAbstract:Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, PDX1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between PDX1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete PDX1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition–dependent necrotic pathways. Preventing Nix upregulation during PDX1 suppression abrogated apoptotic and necrotic β cell death in vitro. In PDX1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in PDX1-deficient diabetes.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of β-cells, leading to decreased β-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 β-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Δψm. Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Δψm and rescued cell viability. Reduced β-cell mass, markers of β-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored β-cell mass and decreased TUNEL and complement complex labeling without affecting β-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of β-cell death caused by PDX1 insufficiency.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of beta-cells, leading to decreased beta-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 beta-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Deltapsi(m). Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Deltapsi(m) and rescued cell viability. Reduced beta-cell mass, markers of beta-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored beta-cell mass and decreased TUNEL and complement complex labeling without affecting beta-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of beta-cell death caused by PDX1 insufficiency.
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autophagy regulates pancreatic beta cell death in response to PDX1 deficiency and nutrient deprivation
Journal of Biological Chemistry, 2009Co-Authors: Kei Fujimoto, Eric L Ford, Burton M Wice, Hung Tran, James D Johnson, Piia T Hanson, Robert E Schmidt, Karen G Green, Kenneth S PolonskyAbstract:There are three types of cell death; apoptosis, necrosis, and autophagy. The possibility that activation of the macroautophagy (autophagy) pathway may increase beta cell death is addressed in this study. Increased autophagy was present in pancreatic islets from PDX1(+/-) mice with reduced insulin secretion and beta cell mass. PDX1 expression was reduced in mouse insulinoma 6 (MIN6) cells by delivering small hairpin RNAs using a lentiviral vector. The MIN6 cells died after 7 days of PDX1 deficiency, and autophagy was evident prior to the onset of cell death. Inhibition of autophagy prolonged cell survival and delayed cell death. Nutrient deprivation increased autophagy in MIN6 cells and mouse and human islets after starvation. Autophagy inhibition partly prevented amino acid starvation-induced MIN6 cell death. The in vivo effects of reduced autophagy were studied by crossing PDX1(+/-) mice to Becn1(+/-) mice. After 1 week on a high fat diet, 4-week-old PDX1(+/-) Becn1(+/-) mice showed normal glucose tolerance, preserved beta cell function, and increased beta cell mass compared with PDX1(+/-) mice. This protective effect of reduced autophagy had worn off after 7 weeks on a high fat diet. Increased autophagy contributes to pancreatic beta cell death in PDX1 deficiency and following nutrient deprivation. The role of autophagy should be considered in studies of pancreatic beta cell death and diabetes and as a target for novel therapeutic intervention.
Gerald W Dorn - One of the best experts on this subject based on the ideXlab platform.
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loss of nix in PDX1 deficient mice prevents apoptotic and necrotic β cell death and diabetes
Journal of Clinical Investigation, 2010Co-Authors: Kei Fujimoto, Gerald W Dorn, Eric L Ford, Burton M Wice, Hung Tran, Seth D. Crosby, Kenneth S PolonskyAbstract:Mutations in pancreatic duodenal homeobox (PDX1) are linked to human type 2 diabetes and maturity-onset diabetes of the young type 4. Consistent with this, PDX1-haploinsufficient mice develop diabetes. Both apoptosis and necrosis of β cells are mechanistically implicated in diabetes in these mice, but a molecular link between PDX1 and these 2 forms of cell death has not been defined. In this study, we introduced an shRNA into mouse insulinoma MIN6 cells to deplete PDX1 and found that expression of proapoptotic genes, including NIP3-like protein X (Nix), was increased. Forced Nix expression in MIN6 and pancreatic islet β cells induced programmed cell death by simultaneously activating apoptotic and mitochondrial permeability transition–dependent necrotic pathways. Preventing Nix upregulation during PDX1 suppression abrogated apoptotic and necrotic β cell death in vitro. In PDX1-haploinsufficient mice, Nix ablation normalized pancreatic islet architecture, β cell mass, and insulin secretion and eliminated reactive hyperglycemia after glucose challenge. These results establish Nix as a critical mediator of β cell apoptosis and programmed necrosis in PDX1-deficient diabetes.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of β-cells, leading to decreased β-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 β-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Δψm. Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Δψm and rescued cell viability. Reduced β-cell mass, markers of β-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored β-cell mass and decreased TUNEL and complement complex labeling without affecting β-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of β-cell death caused by PDX1 insufficiency.
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targeting cyclophilin d and the mitochondrial permeability transition enhances β cell survival and prevents diabetes in PDX1 deficiency
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Kei Fujimoto, Kenneth S Polonsky, Yun Chen, Gerald W DornAbstract:Mutations of the pancreatic duodenal homeobox gene-1, PDX1, cause heritable diabetes in humans and mice. A central abnormality with PDX1 deficiency is increased death of beta-cells, leading to decreased beta-cell mass. We show that lentiviral suppression of PDX1 increases death of mouse insulinoma MIN6 beta-cells associated with dissipation of the mitochondrial inner membrane electrochemical gradient, Deltapsi(m). Preventing mitochondrial permeability transition pore opening with the cyclophilin D inhibitor cyclosporin A restored Deltapsi(m) and rescued cell viability. Reduced beta-cell mass, markers of beta-cell apoptosis, necrosis, and decreased proliferation are present in PDX1 haploinsufficient mice. Genetic ablation of the Ppif gene, encoding cyclophilin D, restored beta-cell mass and decreased TUNEL and complement complex labeling without affecting beta-cell proliferation. In adult mice maintained on a high-fat diet, Ppif ablation normalized fasting glucose and glucose and insulin responses to acute glucose challenge. Thus, cyclophilin D and the mitochondrial permeability transition are critical regulators of beta-cell death caused by PDX1 insufficiency.