1
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Xie G, Toledo MP, Hu X, Yong HJ, Sanchez PS, Liu C, Naji A, Irianto J, Wang YJ. NKX2-2 based nuclei sorting on frozen human archival pancreas enables the enrichment of islet endocrine populations for single-nucleus RNA sequencing. BMC Genomics 2024; 25:427. [PMID: 38689254 PMCID: PMC11059690 DOI: 10.1186/s12864-024-10335-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 04/22/2024] [Indexed: 05/02/2024] Open
Abstract
BACKGROUND Current approaches to profile the single-cell transcriptomics of human pancreatic endocrine cells almost exclusively rely on freshly isolated islets. However, human islets are limited in availability. Furthermore, the extensive processing steps during islet isolation and subsequent single cell dissolution might alter gene expressions. In this work, we report the development of a single-nucleus RNA sequencing (snRNA-seq) approach with targeted islet cell enrichment for endocrine-population focused transcriptomic profiling using frozen archival pancreatic tissues without islet isolation. RESULTS We cross-compared five nuclei isolation protocols and selected the citric acid method as the best strategy to isolate nuclei with high RNA integrity and low cytoplasmic contamination from frozen archival human pancreata. We innovated fluorescence-activated nuclei sorting based on the positive signal of NKX2-2 antibody to enrich nuclei of the endocrine population from the entire nuclei pool of the pancreas. Our sample preparation procedure generated high-quality single-nucleus gene-expression libraries while preserving the endocrine population diversity. In comparison with single-cell RNA sequencing (scRNA-seq) library generated with live cells from freshly isolated human islets, the snRNA-seq library displayed comparable endocrine cellular composition and cell type signature gene expression. However, between these two types of libraries, differential enrichments of transcripts belonging to different functional classes could be observed. CONCLUSIONS Our work fills a technological gap and helps to unleash frozen archival pancreatic tissues for molecular profiling targeting the endocrine population. This study opens doors to retrospective mappings of endocrine cell dynamics in pancreatic tissues of complex histopathology. We expect that our protocol is applicable to enrich nuclei for transcriptomics studies from various populations in different types of frozen archival tissues.
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Affiliation(s)
- Gengqiang Xie
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Maria Pilar Toledo
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Xue Hu
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Hyo Jeong Yong
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Pamela Sandoval Sanchez
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Chengyang Liu
- Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - Ali Naji
- Department of Surgery, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - Jerome Irianto
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA
| | - Yue J Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL, 32306, USA.
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2
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Abarinov V, Levine JA, Churchill AJ, Hopwood B, Deiter CS, Guney MA, Wells KL, Schrunk JM, Guo Y, Hammelman J, Gifford DK, Magnuson MA, Wichterle H, Sussel L. Major β cell-specific functions of NKX2.2 are mediated via the NK2-specific domain. Genes Dev 2023; 37:490-504. [PMID: 37364986 PMCID: PMC10393193 DOI: 10.1101/gad.350569.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 06/06/2023] [Indexed: 06/28/2023]
Abstract
The consolidation of unambiguous cell fate commitment relies on the ability of transcription factors (TFs) to exert tissue-specific regulation of complex genetic networks. However, the mechanisms by which TFs establish such precise control over gene expression have remained elusive-especially in instances in which a single TF operates in two or more discrete cellular systems. In this study, we demonstrate that β cell-specific functions of NKX2.2 are driven by the highly conserved NK2-specific domain (SD). Mutation of the endogenous NKX2.2 SD prevents the developmental progression of β cell precursors into mature, insulin-expressing β cells, resulting in overt neonatal diabetes. Within the adult β cell, the SD stimulates β cell performance through the activation and repression of a subset of NKX2.2-regulated transcripts critical for β cell function. These irregularities in β cell gene expression may be mediated via SD-contingent interactions with components of chromatin remodelers and the nuclear pore complex. However, in stark contrast to these pancreatic phenotypes, the SD is entirely dispensable for the development of NKX2.2-dependent cell types within the CNS. Together, these results reveal a previously undetermined mechanism through which NKX2.2 directs disparate transcriptional programs in the pancreas versus neuroepithelium.
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Affiliation(s)
- Vladimir Abarinov
- Department of Genetics and Development, Columbia University, New York, New York 10032, USA
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Joshua A Levine
- Department of Genetics and Development, Columbia University, New York, New York 10032, USA
| | - Angela J Churchill
- Department of Genetics and Development, Columbia University, New York, New York 10032, USA
| | - Bryce Hopwood
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Cailin S Deiter
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Michelle A Guney
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Kristen L Wells
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Jessica M Schrunk
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | - Yuchun Guo
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jennifer Hammelman
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - David K Gifford
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Mark A Magnuson
- Department of Molecular Physiology and Biophysics, Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Hynek Wichterle
- Department of Pathology and Cell Biology, Columbia University, New York, New York 10032, USA
- Department of Neurology, Columbia University, New York, New York 10032, USA
- Department of Neuroscience, Columbia University, New York, New York 10032, USA
| | - Lori Sussel
- Department of Genetics and Development, Columbia University, New York, New York 10032, USA;
- Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, USA
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3
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Transcriptional control of pancreatic β-cell identity and plasticity during the pathogenesis of type 2 diabetes. J Genet Genomics 2022; 49:316-328. [DOI: 10.1016/j.jgg.2022.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/23/2022] [Accepted: 03/06/2022] [Indexed: 11/21/2022]
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4
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Targeted Mutation of NGN3 Gene Disrupts Pancreatic Endocrine Cell Development in Pigs. Sci Rep 2018; 8:3582. [PMID: 29483633 PMCID: PMC5827570 DOI: 10.1038/s41598-018-22050-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 02/15/2018] [Indexed: 12/12/2022] Open
Abstract
The domestic pig is an attractive model for biomedical research because of similarities in anatomy and physiology to humans. However, key gaps remain in our understanding of the role of developmental genes in pig, limiting its full potential. In this publication, the role of NEUROGENIN 3 (NGN3), a transcription factor involved in endocrine pancreas development has been investigated by CRISPR/Cas9 gene ablation. Precomplexed Cas9 ribonucleoproteins targeting NGN3 were injected into in vivo derived porcine embryos, and transferred into surrogate females. On day 60 of pregnancy, nine fetuses were collected for genotypic and phenotypic analysis. One of the piglets was identified as an in-frame biallelic knockout (Δ2/Δ2), which showed a loss of putative NGN3-downstream target genes: NEUROD1 and PAX4, as well as insulin, glucagon, somatostatin and pancreatic polypeptide-Y. Fibroblasts from this fetus were used in somatic cell nuclear transfer to generate clonal animals to qualify the effect of mutation on embryonic lethality. Three live piglets were born, received colostrum and suckled normally, but experienced extreme weight loss over a 24 to 36-hour period requiring humane euthanasia. Expression of pancreatic endocrine hormones: insulin, glucagon, and somatostatin were lost. The data support a critical role of NGN3 in porcine endocrine pancreas development.
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5
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Churchill AJ, Gutiérrez GD, Singer RA, Lorberbaum DS, Fischer KA, Sussel L. Genetic evidence that Nkx2.2 acts primarily downstream of Neurog3 in pancreatic endocrine lineage development. eLife 2017; 6. [PMID: 28071588 PMCID: PMC5224921 DOI: 10.7554/elife.20010] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 12/21/2016] [Indexed: 02/06/2023] Open
Abstract
Many pancreatic transcription factors that are essential for islet cell differentiation have been well characterized; however, because they are often expressed in several different cell populations, their functional hierarchy remains unclear. To parse out the spatiotemporal regulation of islet cell differentiation, we used a Neurog3-Cre allele to ablate Nkx2.2, one of the earliest and most broadly expressed islet transcription factors, specifically in the Neurog3+ endocrine progenitor lineage (Nkx2.2△endo). Remarkably, many essential components of the β cell transcriptional network that were down-regulated in the Nkx2.2KO mice, were maintained in the Nkx2.2△endo mice - yet the Nkx2.2△endo mice displayed defective β cell differentiation and recapitulated the Nkx2.2KO phenotype. This suggests that Nkx2.2 is not only required in the early pancreatic progenitors, but has additional essential activities within the endocrine progenitor population. Consistently, we demonstrate Nkx2.2 functions as an integral component of a modular regulatory program to correctly specify pancreatic islet cell fates. DOI:http://dx.doi.org/10.7554/eLife.20010.001
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Affiliation(s)
- Angela J Churchill
- Naomi Berrie Diabetes Institute, Columbia University Medical School, New York, Columbia.,Department of Genetics and Development, Columbia University Medical School, New York, Columbia.,Genetics and Development Doctoral Program, Columbia University Medical School, New York, Columbia
| | - Giselle Dominguez Gutiérrez
- Naomi Berrie Diabetes Institute, Columbia University Medical School, New York, Columbia.,Department of Genetics and Development, Columbia University Medical School, New York, Columbia.,Nutritional and Metabolic Biology Doctoral Program, Columbia University Medical School, New York, Columbia
| | - Ruth A Singer
- Naomi Berrie Diabetes Institute, Columbia University Medical School, New York, Columbia.,Department of Genetics and Development, Columbia University Medical School, New York, Columbia.,The Integrated Graduate Program in Cellular, Molecular and Biomedical Studies, Columbia University Medical School, New York, Columbia
| | | | - Kevin A Fischer
- Barbara Davis Center, University of Colorado, Denver, United States
| | - Lori Sussel
- Naomi Berrie Diabetes Institute, Columbia University Medical School, New York, Columbia.,Department of Genetics and Development, Columbia University Medical School, New York, Columbia.,Genetics and Development Doctoral Program, Columbia University Medical School, New York, Columbia.,Nutritional and Metabolic Biology Doctoral Program, Columbia University Medical School, New York, Columbia.,The Integrated Graduate Program in Cellular, Molecular and Biomedical Studies, Columbia University Medical School, New York, Columbia.,Barbara Davis Center, University of Colorado, Denver, United States
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6
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Gutiérrez GD, Bender AS, Cirulli V, Mastracci TL, Kelly SM, Tsirigos A, Kaestner KH, Sussel L. Pancreatic β cell identity requires continual repression of non-β cell programs. J Clin Invest 2016; 127:244-259. [PMID: 27941248 DOI: 10.1172/jci88017] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 10/13/2016] [Indexed: 12/12/2022] Open
Abstract
Loss of β cell identity, the presence of polyhormonal cells, and reprogramming are emerging as important features of β cell dysfunction in patients with type 1 and type 2 diabetes. In this study, we have demonstrated that the transcription factor NKX2.2 is essential for the active maintenance of adult β cell identity as well as function. Deletion of Nkx2.2 in β cells caused rapid onset of a diabetic phenotype in mice that was attributed to loss of insulin and downregulation of many β cell functional genes. Concomitantly, NKX2.2-deficient murine β cells acquired non-β cell endocrine features, resulting in populations of completely reprogrammed cells and bihormonal cells that displayed hybrid endocrine cell morphological characteristics. Molecular analysis in mouse and human islets revealed that NKX2.2 is a conserved master regulatory protein that controls the acquisition and maintenance of a functional, monohormonal β cell identity by directly activating critical β cell genes and actively repressing genes that specify the alternative islet endocrine cell lineages. This study demonstrates the highly volatile nature of the β cell, indicating that acquiring and sustaining β cell identity and function requires not only active maintaining of the expression of genes involved in β cell function, but also continual repression of closely related endocrine gene programs.
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7
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Gross S, Garofalo DC, Balderes DA, Mastracci TL, Dias JM, Perlmann T, Ericson J, Sussel L. The novel enterochromaffin marker Lmx1a regulates serotonin biosynthesis in enteroendocrine cell lineages downstream of Nkx2.2. Development 2016; 143:2616-28. [PMID: 27287799 DOI: 10.1242/dev.130682] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 05/26/2016] [Indexed: 12/17/2022]
Abstract
Intestinal hormone-producing cells represent the largest endocrine system in the body, but remarkably little is known about enteroendocrine cell type specification in the embryo and adult. We analyzed stage- and cell type-specific deletions of Nkx2.2 and its functional domains in order to characterize its role in the development and maintenance of enteroendocrine cell lineages in the mouse duodenum and colon. Although Nkx2.2 regulates enteroendocrine cell specification in the duodenum at all stages examined, it controls the differentiation of progressively fewer enteroendocrine cell populations when deleted from Ngn3(+) progenitor cells or in the adult duodenum. During embryonic development Nkx2.2 regulates all enteroendocrine cell types, except gastrin and preproglucagon. In developing Ngn3(+) enteroendocrine progenitor cells, Nkx2.2 is not required for the specification of neuropeptide Y and vasoactive intestinal polypeptide, indicating that a subset of these cell populations derive from an Nkx2.2-independent lineage. In adult duodenum, Nkx2.2 becomes dispensable for cholecystokinin and secretin production. In all stages and Nkx2.2 mutant conditions, serotonin-producing enterochromaffin cells were the most severely reduced enteroendocrine lineage in the duodenum and colon. We determined that the transcription factor Lmx1a is expressed in enterochromaffin cells and functions downstream of Nkx2.2. Lmx1a-deficient mice have reduced expression of Tph1, the rate-limiting enzyme for serotonin biosynthesis. These data clarify the function of Nkx2.2 in the specification and homeostatic maintenance of enteroendocrine populations, and identify Lmx1a as a novel enterochromaffin cell marker that is also essential for the production of the serotonin biosynthetic enzyme Tph1.
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Affiliation(s)
- Stefanie Gross
- Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
| | - Diana C Garofalo
- Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
| | - Dina A Balderes
- Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
| | - Teresa L Mastracci
- Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
| | - José M Dias
- Department of Cell and Molecular Biology, Karolinska Institute, von Eulers v. 3, 171 77, Stockholm, Sweden
| | - Thomas Perlmann
- Department of Cell and Molecular Biology, Karolinska Institute, von Eulers v. 3, 171 77, Stockholm, Sweden Ludwig Institute for Cancer Research, Stockholm Branch, Nobels v. 3, 171 77, Stockholm, Sweden
| | - Johan Ericson
- Department of Cell and Molecular Biology, Karolinska Institute, von Eulers v. 3, 171 77, Stockholm, Sweden
| | - Lori Sussel
- Department of Genetics and Development, Columbia University Medical Center, New York, NY, USA
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8
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Gross S, Balderes D, Liu J, Asfaha S, Gu G, Wang TC, Sussel L. Nkx2.2 is expressed in a subset of enteroendocrine cells with expanded lineage potential. Am J Physiol Gastrointest Liver Physiol 2015; 309:G975-87. [PMID: 26492922 PMCID: PMC4683302 DOI: 10.1152/ajpgi.00244.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/19/2015] [Indexed: 01/31/2023]
Abstract
There are two major stem cell populations in the intestinal crypt region that express either Bmi1 or Lgr5; however, it has been shown that other populations in the crypt can regain stemness. In this study, we demonstrate that the transcription factor NK2 homeobox 2 (Nkx2.2) is expressed in enteroendocrine cells located in the villus and crypt of the intestinal epithelium and is coexpressed with the stem cell markers Bmi1 and Lgr5 in a subset of crypt cells. To determine whether Nkx2.2-expressing enteroendocrine cells display cellular plasticity and stem cell potential, we performed genetic lineage tracing of the Nkx2.2-expressing population using Nkx2.2(Cre/+);R26RTomato mice. These studies demonstrated that Nkx2.2+ cells are able to give rise to all intestinal epithelial cell types in basal conditions. The proliferative capacity of Nkx2.2-expressing cells was also demonstrated in vitro using crypt organoid cultures. Injuring the intestine with irradiation, systemic inflammation, and colitis did not enhance the lineage potential of Nkx2.2-expressing cells. These findings demonstrate that a rare mature enteroendocrine cell subpopulation that is demarcated by Nkx2.2 expression display stem cell properties during normal intestinal epithelial homeostasis, but is not easily activated upon injury.
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Affiliation(s)
- Stefanie Gross
- Department of Genetics and Development, Columbia University Medical Center, New York, New York
| | - Dina Balderes
- Department of Genetics and Development, Columbia University Medical Center, New York, New York
| | - Jing Liu
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Samuel Asfaha
- Department of Digestive and Liver Diseases, Columbia University Medical Center, New York, New York; and
| | - Guoqiang Gu
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Timothy C Wang
- Department of Digestive and Liver Diseases, Columbia University Medical Center, New York, New York; and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, New York
| | - Lori Sussel
- Department of Genetics and Development, Columbia University Medical Center, New York, New York;
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9
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Abstract
PURPOSE OF REVIEW This review will discuss recent advances in understanding mouse and human pancreatic islet cell development, novel concepts related to β cell dysfunction and improved approaches for replenishing β cells to treat diabetes. RECENT FINDINGS Considerable knowledge about pancreatic islet development and function has been gained using model systems with subsequent validation in human tissues. Recently, several rodent studies have revealed that differentiated adult islet cells retain remarkable plasticity and can be converted to other islet cell types by perturbing their transcription factor profiles. Furthermore, significant advances have been made in the generation of β-like cells from stem cell populations. Therefore, the generation of functionally mature β cells by the in-situ conversion of non-β cell populations or by the directed differentiation of human pluripotent stem cells could represent novel mechanisms for replenishing β cells in diabetic patients. SUMMARY The overall conservation between mouse and human pancreatic development, islet physiology and etiology of diabetes encourages the translation of novel β cell replacement therapies to humans. Further deciphering the molecular mechanisms that direct islet cell regeneration, plasticity and function could improve and expand the β cell replacement strategies for treating diabetes.
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Affiliation(s)
- Anthony I Romer
- Department of Genetics and Development, Columbia University, New York, New York, USA
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10
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Balderes DA, Magnuson MA, Sussel L. Nkx2.2:Cre knock-in mouse line: a novel tool for pancreas- and CNS-specific gene deletion. Genesis 2013; 51:844-51. [PMID: 23996959 DOI: 10.1002/dvg.22715] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 08/22/2013] [Accepted: 08/23/2013] [Indexed: 11/07/2022]
Abstract
Nkx2.2 is a homeodomain-containing transcriptional regulator necessary for the appropriate differentiation of ventral neuronal populations in the spinal cord and hindbrain, and endocrine cell populations in the pancreas and intestine. In each tissue, Nkx2.2 inactivation leads to reciprocal cell fate alterations. To confirm the cell fate changes are due to respecification of Nkx2.2-expressing progenitors and to provide a novel tool for lineage tracing in the pancreas and CNS, we generated an Nkx2.2:Cre mouse line by knocking in a Cre-EGFP cassette into the Nkx2.2 genomic locus and inactivating endogenous Nkx2.2. The R26R-CAG-LSL-tdTomato reporter was used to monitor the specificity and efficiency of Nkx2.2:Cre activity; the tomato reporter faithfully recapitulated endogenous Nkx2.2 expression and could be detected as early as embryonic day (e) 9.25 in the developing CNS and was initiated shortly thereafter at e9.5 in the pancreas. Lineage analyses in the CNS confirmed the cell populations thought to be derived from Nkx2.2-expressing progenitor domains. Furthermore, lineage studies verified Nkx2.2 expression in the earliest pancreatic progenitors that give rise to all cell types of the pancreas; however they also revealed more robust Cre activity in the dorsal versus ventral pancreas. Thus, the Nkx2.2:Cre line provides a novel tool for gene manipulations in the CNS and pancreas.
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Affiliation(s)
- Dina A Balderes
- Department of Genetics and Development, Columbia University, New York, New York, 10032
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11
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Generation of mice encoding a conditional allele of Nkx2.2. Transgenic Res 2013; 22:965-72. [PMID: 23494546 DOI: 10.1007/s11248-013-9700-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 02/28/2013] [Indexed: 10/27/2022]
Abstract
Nkx2.2 is a homeobox transcription factor that is expressed in the pancreas, intestine and central nervous system (CNS) during embryogenesis and in the adult. In mice, global deletion of Nkx2.2 results in cell mis-specification in each of the tissues where it is expressed, and the null mice die as neonates with severe hyperglycemia. Although a whole body knockout demonstrates the importance of Nkx2.2 in cell specification and postnatal viability, it precludes assessment of the cell-autonomous and postnatal functions of Nkx2.2. In this study we report the generation and functional characterization of mice encoding a conditional allele of Nkx2.2. We demonstrate the functional integrity of the conditional Nkx2.2 allele and report successful in vivo deletion using a pancreas-specific Cre recombinase. The pancreas-specific deletion of Nkx2.2 results in similar defects found in the Nkx2.2 null pancreas and the mice die shortly after birth, demonstrating that the neonatal lethality associated with the null allele is caused by pancreatic islet dysfunction. The generation of a conditional Nkx2.2 allele provides an important tool for identifying the cell-autonomous and postnatal activities of Nkx2.2 in establishing and maintaining cell type identities and functions in the pancreas, intestine and CNS.
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12
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Regulation of Neurod1 contributes to the lineage potential of Neurogenin3+ endocrine precursor cells in the pancreas. PLoS Genet 2013; 9:e1003278. [PMID: 23408910 PMCID: PMC3567185 DOI: 10.1371/journal.pgen.1003278] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 12/12/2012] [Indexed: 12/12/2022] Open
Abstract
During pancreatic development, transcription factor cascades gradually commit precursor populations to the different endocrine cell fate pathways. Although mutational analyses have defined the functions of many individual pancreatic transcription factors, the integrative transcription factor networks required to regulate lineage specification, as well as their sites of action, are poorly understood. In this study, we investigated where and how the transcription factors Nkx2.2 and Neurod1 genetically interact to differentially regulate endocrine cell specification. In an Nkx2.2 null background, we conditionally deleted Neurod1 in the Pdx1+ pancreatic progenitor cells, the Neurog3+ endocrine progenitor cells, or the glucagon+ alpha cells. These studies determined that, in the absence of Nkx2.2 activity, removal of Neurod1 from the Pdx1+ or Neurog3+ progenitor populations is sufficient to reestablish the specification of the PP and epsilon cell lineages. Alternatively, in the absence of Nkx2.2, removal of Neurod1 from the Pdx1+ pancreatic progenitor population, but not the Neurog3+ endocrine progenitor cells, restores alpha cell specification. Subsequent in vitro reporter assays demonstrated that Nkx2.2 represses Neurod1 in alpha cells. Based on these findings, we conclude that, although Nkx2.2 and Neurod1 are both necessary to promote beta cell differentiation, Nkx2.2 must repress Neurod1 in a Pdx1+ pancreatic progenitor population to appropriately commit a subset of Neurog3+ endocrine progenitor cells to the alpha cell lineage. These results are consistent with the proposed idea that Neurog3+ endocrine progenitor cells represent a heterogeneous population of unipotent cells, each restricted to a particular endocrine lineage. Diabetes mellitus is a family of metabolic diseases that can result from either destruction or dysfunction of the insulin-producing beta cells of the pancreas. Recent studies have provided hope that generating insulin-producing cells from alternative cell sources may be a possible treatment for diabetes; this includes the observation that pancreatic glucagon-expressing alpha cells can be converted into beta cells under certain physiological or genetic conditions. Our study focuses on two essential beta cell regulatory factors, Nkx2.2 and Neurod1, and demonstrates how their genetic interactions can promote the development of other hormone-expressing cell types, including alpha cells. We determined that, while Nkx2.2 is required to activate Neurod1 to promote beta cell formation, Nkx2.2 must prevent expression of Neurod1 to allow alpha cell formation. Furthermore, the inactivation of Neurod1 must occur in the earliest pancreatic progenitors, at a stage in the differentiation process earlier than previously believed. These studies contribute to our understanding of the overlapping gene regulatory networks that specify islet cell types and identify the importance of timing and cellular context for these regulatory interactions. Furthermore, our data have broad implications regarding the manipulation of alpha cells or human pluripotent stem cells to generate insulin-producing beta cells for therapeutic purposes.
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13
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Ghrelin expression in the mouse pancreas defines a unique multipotent progenitor population. PLoS One 2012; 7:e52026. [PMID: 23251675 PMCID: PMC3520898 DOI: 10.1371/journal.pone.0052026] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 11/13/2012] [Indexed: 01/01/2023] Open
Abstract
Pancreatic islet cells provide the major source of counteractive endocrine hormones required for maintaining glucose homeostasis; severe health problems result when these cell types are insufficiently active or reduced in number. Therefore, the process of islet endocrine cell lineage allocation is critical to ensure there is a correct balance of islet cell types. There are four endocrine cell types within the adult islet, including the glucagon-producing alpha cells, insulin-producing beta cells, somatostatin-producing delta cells and pancreatic polypeptide-producing PP cells. A fifth islet cell type, the ghrelin-producing epsilon cells, is primarily found during gestational development. Although hormone expression is generally assumed to mark the final entry to a determined cell state, we demonstrate in this study that ghrelin-expressing epsilon cells within the mouse pancreas do not represent a terminally differentiated endocrine population. Ghrelin cells give rise to significant numbers of alpha and PP cells and rare beta cells in the adult islet. Furthermore, pancreatic ghrelin-producing cells are maintained in pancreata lacking the essential endocrine lineage regulator Neurogenin3, and retain the ability to contribute to cells within the pancreatic ductal and exocrine lineages. These results demonstrate that the islet ghrelin-expressing epsilon cells represent a multi-potent progenitor cell population that delineates a major subgrouping of the islet endocrine cell populations. These studies also provide evidence that many of hormone-producing cells within the adult islet represent heterogeneous populations based on their ontogeny, which could have broader implications on the regulation of islet cell ratios and their ability to effectively respond to fluctuations in the metabolic environment during development.
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