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Wen HJ, Gao S, Wang Y, Ray M, Magnuson MA, Wright CV, Di Magliano MP, Frankel TL, Crawford HC. Myeloid Cell-Derived HB-EGF Drives Tissue Recovery After Pancreatitis. Cell Mol Gastroenterol Hepatol 2019; 8:173-192. [PMID: 31125624 PMCID: PMC6661420 DOI: 10.1016/j.jcmgh.2019.05.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 05/09/2019] [Accepted: 05/14/2019] [Indexed: 12/23/2022]
Abstract
BACKGROUND & AIMS Pancreatitis is a major cause of morbidity and mortality and is a risk factor for pancreatic tumorigenesis. Upon tissue damage, an inflammatory response, made up largely of macrophages, provides multiple growth factors that promote repair. Here, we examine the molecular pathways initiated by macrophages to promote pancreas recovery from pancreatitis. METHODS To induce organ damage, mice were subjected to cerulein-induced experimental pancreatitis and analyzed at various times of recovery. CD11b-DTR mice were used to deplete myeloid cells. Hbegff/f;LysM-Cre mice were used to ablate myeloid cell-derived heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF). To ablate EGFR specifically during recovery, pancreatitis was induced in Egfrf/f;Ptf1aFlpO/+;FSF-Rosa26CAG-CreERT2 mice followed by tamoxifen treatment. RESULTS Macrophages infiltrating the pancreas in experimental pancreatitis make high levels of HB-EGF. Both depletion of myeloid cells and ablation of myeloid cell HB-EGF delayed recovery from experimental pancreatitis, resulting from a decrease in cell proliferation and an increase in apoptosis. Mechanistically, ablation of myeloid cell HB-EGF impaired epithelial cell DNA repair, ultimately leading to cell death. Soluble HB-EGF induced EGFR nuclear translocation and methylation of histone H4, facilitating resolution of DNA damage in pancreatic acinar cells in vitro. Consistent with its role as the primary receptor of HB-EGF, in vivo ablation of EGFR from pancreatic epithelium during recovery from pancreatitis resulted in accumulation of DNA damage. CONCLUSIONS By using novel conditional knockout mouse models, we determined that HB-EGF derived exclusively from myeloid cells induces epithelial cell proliferation and EGFR-dependent DNA repair, facilitating pancreas healing after injury.
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Affiliation(s)
- Hui-Ju Wen
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Shan Gao
- Department of Gastroenterology, The Second Xiangya Hospital, Central South University, China
| | - Yin Wang
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Michael Ray
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee
| | - Mark A. Magnuson
- Department of Molecular Physiology and Biophysics, Center for Stem Cell Biology, Vanderbilt University, Nashville, Tennessee
| | | | - Marina Pasca Di Magliano
- Department of Surgery, University of Michigan, Ann Arbor, Michigan,Rogel Comprehensive Cancer Center, University of Michigan, Ann Arbor, Michigan,Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, Michigan
| | | | - Howard C. Crawford
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan,Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan,Rogel Comprehensive Cancer Center, University of Michigan, Ann Arbor, Michigan,Correspondence Address correspondence to: Howard Crawford, PhD, University of Michigan, 4304 Rogel Cancer Center, 1500 East Medical Center Drive, SPC 5936, Ann Arbor, Michigan 48109-5936. fax: (734) 647–9654.
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Guo L, Inada A, Aguayo-Mazzucato C, Hollister-Lock J, Fujitani Y, Weir GC, Wright CV, Sharma A, Bonner-Weir S. PDX1 in ducts is not required for postnatal formation of β-cells but is necessary for their subsequent maturation. Diabetes 2013; 62:3459-68. [PMID: 23775765 PMCID: PMC3781453 DOI: 10.2337/db12-1833] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Pancreatic duodenal homeobox-1 (Pdx1), a transcription factor required for pancreatic development and maintenance of β-cell function, was assessed for a possible role in postnatal β-cell formation from progenitors in the pancreatic ducts by selectively deleting Pdx1 from the ducts. Carbonic anhydrase II (CAII)(Cre);Pdx1(Fl) mice were euglycemic for the first 2 postnatal weeks but showed moderate hyperglycemia from 3 to 7 weeks of age. By 10 weeks, they had near-normal morning fed glucose levels but showed severely impaired glucose tolerance and insulin secretion. Yet the loss of Pdx1 did not result in decreased islet and β-cell mass at 4 and 10 weeks of age. Within the same pancreas, there was a mixed population of islets, with PDX1 and MAFA protein expression normal in some cells and severely diminished in others. Even at 10 weeks, islets expressed immaturity markers. Thus, we conclude that Pdx1 is not necessary for the postnatal formation of β-cells but is essential for their full maturation to glucose-responsive β-cells.
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Affiliation(s)
- Lili Guo
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Akari Inada
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Diabetes and Genes, Advanced Medical Initiatives, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Cristina Aguayo-Mazzucato
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Jennifer Hollister-Lock
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Yoshio Fujitani
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Gordon C. Weir
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Christopher V.E. Wright
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Arun Sharma
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Susan Bonner-Weir
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Corresponding author: Susan Bonner-Weir,
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Fukuda A, Kawaguchi Y, Furuyama K, Kodama S, Horiguchi M, Kuhara T, Kawaguchi M, Terao M, Doi R, Wright CV, Hoshino M, Chiba T, Uemoto S. Reduction of Ptf1a gene dosage causes pancreatic hypoplasia and diabetes in mice. Diabetes 2008; 57:2421-31. [PMID: 18591390 PMCID: PMC2518493 DOI: 10.2337/db07-1558] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Accepted: 06/11/2008] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Most pancreatic endocrine cells derive from Ptf1a-expressing progenitor cells. In humans, nonsense mutations in Ptf1a have recently been identified as a cause of permanent neonatal diabetes associated with pancreatic agenesis. The death of Ptf1a-null mice soon after birth has not allowed further insight into the pathogenesis of the disease; it is therefore unclear how much pancreatic endocrine function is dependent on Ptf1a in mammals. This study aims to investigate gene-dosage effects of Ptf1a on pancreas development and function in mice. RESEARCH DESIGN AND METHODS Combining hypomorphic and null alleles of Ptf1a and Cre-mediated lineage tracing, we followed the cell fate of reduced Ptf1a-expressing progenitors and analyzed pancreas development and function in mice. RESULTS Reduced Ptf1a dosage resulted in pancreatic hypoplasia and glucose intolerance with insufficient insulin secretion in a dosage-dependent manner. In hypomorphic mutant mice, pancreatic bud size was small and substantial proportions of pancreatic progenitors were misspecified to the common bile duct and duodenal cells. Growth with branching morphogenesis and subsequent exocrine cytodifferentiation was reduced and delayed. Total beta-cell number was decreased, proportion of non-beta islet cells was increased, and alpha-cells were abnormally intermingled with beta-cells. Interestingly, Pdx1 expression was decreased in early pancreatic progenitors but elevated to normal level at the mid-to-late stages of pancreatogenesis. CONCLUSIONS-The dosage of Ptf1a is crucial for pancreas specification, growth, total beta-cell number, islet morphogenesis, and endocrine function. Some neonatal diabetes may be caused by mutation or single nucleotide polymorphisms in the Ptf1a gene that reduce gene expression levels.
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Affiliation(s)
- Akihisa Fukuda
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Gastroenterology & Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Diabetes Center, Department of Medicine, University of California, San Francisco, San Francisco, California
| | - Yoshiya Kawaguchi
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Kenichiro Furuyama
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Sota Kodama
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Masashi Horiguchi
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takeshi Kuhara
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Michiya Kawaguchi
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Mami Terao
- Department of Pathology and Tumor Biology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Ryuichiro Doi
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Christopher V.E. Wright
- Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Mikio Hoshino
- Department of Pathology and Tumor Biology, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Tsutomu Chiba
- Department of Gastroenterology & Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Shinji Uemoto
- Department of Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
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Fukuda A, Kawaguchi Y, Furuyama K, Kodama S, Horiguchi M, Kuhara T, Koizumi M, Boyer DF, Fujimoto K, Doi R, Kageyama R, Wright CV, Chiba T. Ectopic pancreas formation in Hes1 -knockout mice reveals plasticity of endodermal progenitors of the gut, bile duct, and pancreas. J Clin Invest 2006; 116:1484-93. [PMID: 16710472 PMCID: PMC1462947 DOI: 10.1172/jci27704] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Accepted: 03/22/2006] [Indexed: 01/26/2023] Open
Abstract
Ectopic pancreas is a developmental anomaly occasionally found in humans. Hes1, a main effector of Notch signaling, regulates the fate and differentiation of many cell types during development. To gain insights into the role of the Notch pathway in pancreatic fate determination, we combined the use of Hes1-knockout mice and lineage tracing employing the Cre/loxP system to specifically mark pancreatic precursor cells and their progeny in Ptf1a-cre and Rosa26 reporter mice. We show that inactivation of Hes1 induces misexpression of Ptf1a in discrete regions of the primitive stomach and duodenum and throughout the common bile duct. All ectopic Ptf1a-expressing cells were reprogrammed, or transcommitted, to multipotent pancreatic progenitor status and subsequently differentiated into mature pancreatic exocrine, endocrine, and duct cells. This process recapitulated normal pancreatogenesis in terms of morphological and genetic features. Furthermore, analysis of Hes1/Ptf1a double mutants revealed that ectopic Ptf1a-cre lineage-labeled cells adopted the fate of region-appropriate gut epithelium or endocrine cells similarly to Ptf1a-inactivated cells in the native pancreatic buds. Our data demonstrate that the Hes1-mediated Notch pathway is required for region-appropriate specification of pancreas in the developing foregut endoderm through regulation of Ptf1a expression, providing novel insight into the pathogenesis of ectopic pancreas development in a mouse model.
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Affiliation(s)
- Akihisa Fukuda
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Yoshiya Kawaguchi
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Kenichiro Furuyama
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Sota Kodama
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Masashi Horiguchi
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Takeshi Kuhara
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Masayuki Koizumi
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Daniel F. Boyer
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Koji Fujimoto
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Ryuichiro Doi
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Ryoichiro Kageyama
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Christopher V.E. Wright
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Tsutomu Chiba
- Department of Surgery and Surgical Basic Science and
Department of Gastroenterology and Hepatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Japan Society for the Promotion of Science (JSPS), Tokyo, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Japan.
Vanderbilt Developmental Biology Program, Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Institute for Virus Research, Kyoto University, Kyoto, Japan
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Kushner JA, Ye J, Schubert M, Burks DJ, Dow MA, Flint CL, Dutta S, Wright CV, Montminy MR, White MF. Pdx1 restores β cell function in Irs2 knockout mice. J Clin Invest 2002. [DOI: 10.1172/jci0214439] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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Abstract
pdx1 (pancreatic and duodenal homeobox gene-1), which is expressed broadly in the embryonic pancreas and, later, in a more restricted manner in the mature beta cells in the islets of Langerhans, is essential both for organ formation and beta cell gene expression and function. We carried out a transgenic reporter gene analysis to identify region- and cell type-specific regulatory regions in pdx1. A 14.5-kb pdx1 genomic fragment corrected the glucose intolerance of pdx1(+/-) animals but, moreover, fully rescued the severe gut and pancreas defects in pdx1(-/-) embryos. Sequences sufficient to direct reporter expression to the entire endogenous pdx1 expression domain lie within 4.3 kb of 5' flanking DNA. In this region, we identified two distinct fragments that drive reporter gene expression to different sets of islet neuroendocrine cells. One shows pan-endocrine cell specificity, the other is selectively activated in insulin-producing beta cells. The endocrine-specific regulatory regions overlap a localized region of 5' flanking DNA that is remarkably conserved in sequence between vertebrate pdx1 genes, and which has been associated with beta cell-selective expression in cultured cell lines. This region contains potential binding sites for several transcription factors implicated in endodermal development and the pathogenesis of some forms of type-2 diabetes. These results are consistent with our previous proposal that conserved upstream pdx1 sequences exert control over pdx1 during embryonic organogenesis and islet endocrine cell differentiation. We propose that mutations affecting the expression and/or activity of transcription factors operating via these sequences may predispose towards diabetes, at least in part by direct effects on endocrine pdx1 expression.
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Affiliation(s)
- M Gannon
- Department of Cell Biology, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, Tennessee 37232, USA
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Abstract
The dorsal ectoderm of the vertebrate gastrula was proposed by Nieuwkoop to be specified towards an anterior neural fate by an activation signal, with its subsequent regionalization along the anteroposterior (AP) axis regulated by a graded transforming activity, leading to a properly patterned forebrain, midbrain, hindbrain and spinal cord. The activation phase involves inhibition of BMP signals by dorsal antagonists, but the later caudalization process is much more poorly characterized. Explant and overexpression studies in chick, Xenopus, mouse and zebrafish implicate lateral/paraxial mesoderm in supplying the transforming influence, which is largely speculated to be a Wnt family member.
We have analyzed the requirement for the specific ventrolaterally expressed Wnt8 ligand in the posteriorization of neural tissue in zebrafish wild-type and Nodal-deficient embryos (Antivin overexpressing or cyclops;squint double mutants), which show extensive AP brain patterning in the absence of dorsal mesoderm. In different genetic situations that vary the extent of mesodermal precursor formation, the presence of lateral wnt8-expressing cells correlates with the establishment of AP brain pattern. Cell tracing experiments show that the neuroectoderm of Nodal-deficient embryos undergoes a rapid anterior-to-posterior transformation in vivo during a short period at the end of the gastrula stage. Moreover, in both wild-type and Nodal-deficient embryos, inactivation of Wnt8 function by morpholino (MOwnt8) translational interference dose-dependently abrogates formation of spinal cord and posterior brain fates, without blocking ventrolateral mesoderm formation. MOwnt8 also suppresses the forebrain deficiency in bozozok mutants, in which inactivation of a homeobox gene causes ectopic wnt8 expression. In addition, the bozozok forebrain reduction is suppressed in bozozok;squint;cyclops triple mutants, and is associated with reduced wnt8 expression, as seen in cyclops;squint mutants. Hence, whereas boz and Nodal signaling largely cooperate in gastrula organizer formation, they have opposing roles in regulating wnt8 expression and forebrain specification. Our findings provide strong support for a model of neural transformation in which a planar gastrula-stage Wnt8 signal, promoted by Nodal signaling and dorsally limited by Bozozok, acts on anterior neuroectoderm from the lateral mesoderm to produce the AP regional patterning of the CNS.
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Affiliation(s)
- C E Erter
- Department of Cell Biology, Vanderbilt University School of Medicine, 1161 21st Avenue South, Nashville, TN 37232-2175, USA
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Abstract
A recent meeting at the Juan March Foundation in Madrid, Spain, covered current understanding of the pathways and mechanisms involved in generating left-right asymmetry.
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Affiliation(s)
- C V Wright
- Department of Cell Biology, Vanderbilt University Medical School, Nashville, Tennessee 37232, USA.
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Gonzalez EM, Fekany-Lee K, Carmany-Rampey A, Erter C, Topczewski J, Wright CV, Solnica-Krezel L. Head and trunk in zebrafish arise via coinhibition of BMP signaling by bozozok and chordino. Genes Dev 2000; 14:3087-92. [PMID: 11124801 PMCID: PMC317122 DOI: 10.1101/gad.852400] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2000] [Accepted: 10/31/2000] [Indexed: 11/25/2022]
Abstract
Spatial variations in the levels of bone morphogenetic protein (BMP) signaling are a critical determinant of dorsoanterior-ventroposterior pattern in vertebrate embryos. Whereas BMP overexpression abolishes both head and trunk development, known single and double loss-of-function mutations in BMP inhibitors have less dramatic effects. We report that combining mutations in the zebrafish genes bozozok and chordino causes a synergistic loss of head and trunk, whereas most cells express ventro-posterior markers and develop into a tail. Genetic inactivation of BMP signaling fully suppresses these defects. Thus, a remarkably simple genetic mechanism, involving a coinhibition of BMP function by the partially overlapping bozozok and chordino pathways is used to specify vertebrate head and trunk.
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Affiliation(s)
- E M Gonzalez
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
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Gannon M, Ray MK, Van Zee K, Rausa F, Costa RH, Wright CV. Persistent expression of HNF6 in islet endocrine cells causes disrupted islet architecture and loss of beta cell function. Development 2000; 127:2883-95. [PMID: 10851133 DOI: 10.1242/dev.127.13.2883] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We used transgenesis to explore the requirement for downregulation of hepatocyte nuclear factor 6 (HNF6) expression in the assembly, differentiation, and function of pancreatic islets. In vivo, HNF6 expression becomes downregulated in pancreatic endocrine cells at 18. 5 days post coitum (d.p.c.), when definitive islets first begin to organize. We used an islet-specific regulatory element (pdx1(PB)) from pancreatic/duodenal homeobox (pdx1) gene to maintain HNF6 expression in endocrine cells beyond 18.5 d.p.c. Transgenic animals were diabetic. HNF6-overexpressing islets were hyperplastic and remained very close to the pancreatic ducts. Strikingly, alpha, delta, and PP cells were increased in number and abnormally intermingled with islet beta cells. Although several mature beta cell markers were expressed in beta cells of transgenic islets, the glucose transporter GLUT2 was absent or severely reduced. As glucose uptake/metabolism is essential for insulin secretion, decreased GLUT2 may contribute to the etiology of diabetes in pdx1(PB)-HNF6 transgenics. Concordantly, blood insulin was not raised by glucose challenge, suggesting profound beta cell dysfunction. Thus, we have shown that HNF6 downregulation during islet ontogeny is critical to normal pancreas formation and function: continued expression impairs the clustering of endocrine cells and their separation from the ductal epithelium, disrupts the spatial organization of endocrine cell types within the islet, and severely compromises beta cell physiology, leading to overt diabetes.
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Affiliation(s)
- M Gannon
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-2175, USA
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Osada SI, Saijoh Y, Frisch A, Yeo CY, Adachi H, Watanabe M, Whitman M, Hamada H, Wright CV. Activin/nodal responsiveness and asymmetric expression of a Xenopus nodal-related gene converge on a FAST-regulated module in intron 1. Development 2000; 127:2503-14. [PMID: 10804190 DOI: 10.1242/dev.127.11.2503] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vertebrate Nodal-related factors play central roles in mesendoderm induction and left-right axis specification, but the mechanisms regulating their expression are largely unknown. We identify an element in Xnr1 intron 1 that is activated by activin and Vg1, autoactivated by Xnrs, and suppressed by ventral inducers like BMP4. Intron 1 contains three FAST binding sites on which FAST/Smad transcriptional complexes can assemble; these sites are differentially involved in intron 1-mediated reporter gene expression. Interference with FAST function abolishes intron 1 activity, and transcriptional activation of Xnrs by activin in embryonic tissue explant assays, identifying FAST as an essential mediator of Xnr autoregulation and/or ‘signal relay’ from activin-like molecules. Furthermore, the mapping of endogenous activators of the Xnr1 intronic enhancer within Xenopus embryos agrees well with the pattern of Xnr1 transcription during embryogenesis. In transgenic mice, Xnr1 intron 1 mimics a similarly located enhancer in the mouse nodal gene, and directs FAST site-dependent expression in the primitive streak during gastrulation, and unilateral expression during early somitogenesis. The FAST cassette is similar in an ascidian nodal-related gene, suggesting an ancient origin for this regulatory module. Thus, an evolutionarily conserved intronic enhancer in Xnr1 is involved in both mesendoderm induction and asymmetric expression during left-right axis formation.
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Affiliation(s)
- S I Osada
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2175, USA
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Cheng AM, Thisse B, Thisse C, Wright CV. The lefty-related factor Xatv acts as a feedback inhibitor of nodal signaling in mesoderm induction and L-R axis development in xenopus. Development 2000; 127:1049-61. [PMID: 10662644 DOI: 10.1242/dev.127.5.1049] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
In mouse, lefty genes play critical roles in the left-right (L-R) axis determination pathway. Here, we characterize the Xenopus lefty-related factor antivin (Xatv). Xatv expression is first observed in the marginal zone early during gastrulation, later becoming restricted to axial tissues. During tailbud stages, axial expression resolves to the neural tube floorplate, hypochord, and (transiently) the notochord anlage, and is joined by dynamic expression in the left lateral plate mesoderm (LPM) and left dorsal endoderm. An emerging paradigm in embryonic patterning is that secreted antagonists regulate the activity of intercellular signaling factors, thereby modulating cell fate specification. Xatv expression is rapidly induced by dorsoanterior-type mesoderm inducers such as activin or Xnr2. Xatv is not an inducer itself, but antagonizes both Xnr2 and activin. Together with its expression pattern, this suggests that Xatv functions during gastrulation in a negative feedback loop with Xnrs to affect the amount and/or character of mesoderm induced. Our data also provide insights into the way that lefty/nodal signals interact in the initiation of differential L-R morphogenesis. Right-sided misexpression of Xnr1 (endogenously expressed in the left LPM) induces bilateral Xatv expression. Left-sided Xatv overexpression suppresses Xnr1/XPitx2 expression in the left LPM, and leads to severely disturbed visceral asymmetry, suggesting that active ‘left’ signals are critical for L-R axis determination in frog embryos. We propose that the induction of lefty/Xatv in the left LPM by nodal/Xnr1 provides an efficient self-regulating mechanism to downregulate nodal/Xnr1 expression and ensure a transient ‘left’ signal within the embryo.
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Affiliation(s)
- A M Cheng
- Dept. Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-2175, USA
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13
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Gerrish K, Gannon M, Shih D, Henderson E, Stoffel M, Wright CV, Stein R. Pancreatic beta cell-specific transcription of the pdx-1 gene. The role of conserved upstream control regions and their hepatic nuclear factor 3beta sites. J Biol Chem 2000; 275:3485-92. [PMID: 10652343 DOI: 10.1074/jbc.275.5.3485] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To identify potential transactivators of pdx-1, we sequenced approximately 4.5 kilobases of the 5' promoter region of the human and chicken homologs, assuming that sequences conserved with the mouse gene would contain critical cis-regulatory elements. The sequences associated with hypersensitive site 1 (HSS1) represented the principal area of homology within which three conserved subdomains were apparent: area I (-2694 to -2561 base pairs (bp)), area II (-2139 to -1958 bp), and area III (-1879 to -1799 bp). The identities between the mouse and chicken/human genes are very high, ranging from 78 to 89%, although only areas I and III are present within this region in chicken. Pancreatic beta cell-selective expression was shown to be controlled by mouse and human area I or area II, but not area III, from an analysis of pdx-1-driven reporter activity in transfected beta- and non-beta cells. Mutational and functional analyses of conserved hepatic nuclear factor 3 (HNF3)-like sites located within area I and area II demonstrated that activation by these regions was mediated by HNF3beta. To determine if a similar regulatory relationship might exist within the context of the endogenous gene, pdx-1 expression was measured in embryonic stem cells in which one or both alleles of HNF3beta were inactivated. pdx-1 mRNA levels induced upon differentiation to embryoid bodies were down-regulated in homozygous null HNF3beta cells. Together, these results suggest that the conserved sequences represented by areas I and II define the binding sites for factors such as HNF3beta, which control islet beta cell-selective expression of the pdx-1 gene.
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Affiliation(s)
- K Gerrish
- Department of Molecular Physiology, Vanderbilt Medical Center, Nashville, Tennessee 37232, USA
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14
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Affiliation(s)
- M Gannon
- Department of Cell Biology, Vanderbilt University Medical Center, Nashville, TN 37232-0615, USA
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15
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Affiliation(s)
- M Gannon
- Department of Cell Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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16
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17
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Abstract
Definition of cell fates along the dorso-ventral axis depends on an antagonistic relationship between ventralizing transforming growth factor-beta superfamily members, the bone morphogenetic proteins and factors secreted from the dorsal organizer, such as Noggin and Chordin. The extracellular binding of the last group to the bone morphogenetic proteins prevents them from activating their receptors, and the relative ventralizer:antagonist ratio is thought to specify different dorso-ventral cell fates. Here, by taking advantage of a non-genetic interference method using a specific competitive inhibitor, the Lefty-related gene product Antivin, we provide evidence that cell fate along the antero-posterior axis of the zebrafish embryo is controlled by the morphogenetic activity of another transforming growth factor-beta superfamily subgroup--the Activin and Nodal-related factors. Increasing antivin doses progressively deleted posterior fates within the ectoderm, eventually resulting in the removal of all fates except forebrain and eyes. In contrast, overexpression of activin or nodal-related factors converted ectoderm that was fated to be forebrain into more posterior ectodermal or mesendodermal fates. We propose that modulation of intercellular signalling by Antivin/Activin and Nodal-related factors provides a mechanism for the graded establishment of cell fates along the antero-posterior axis of the zebrafish embryo.
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Affiliation(s)
- B Thisse
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch, CU de Strasbourg, France
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18
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Song SY, Gannon M, Washington MK, Scoggins CR, Meszoely IM, Goldenring JR, Marino CR, Sandgren EP, Coffey RJ, Wright CV, Leach SD. Expansion of Pdx1-expressing pancreatic epithelium and islet neogenesis in transgenic mice overexpressing transforming growth factor alpha. Gastroenterology 1999; 117:1416-26. [PMID: 10579983 DOI: 10.1016/s0016-5085(99)70292-1] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS The progenitor cells responsible for transforming growth factor (TGF)-alpha-induced pancreatic ductal metaplasia and neoplasia remain uncharacterized. During pancreatic development, differentiated cell types arise from ductal progenitor cells expressing the Pdx1 homeodomain transcription factor. The aims of this study were, first, to evaluate the role of Pdx1-expressing stem cells in MT-TGFalpha transgenic mice, and second, to further characterize cell proliferation and differentiation in this model. METHODS To assess Pdx1 gene expression in normal and metaplastic epithelium, we performed in vivo reporter gene analysis using heterozygous Pdx1(lacZ/+) and bigenic Pdx1(lacZ/+)/MT-TGFalpha mice. RESULTS Pdx1(lacZ/+)/MT-TGFalpha bigenics showed up-regulated Pdx1 expression in premalignant metaplastic ductal epithelium. In addition to Pdx1 gene activation, TGF-alpha-induced metaplastic epithelium demonstrated a pluripotent differentiation capacity, as evidenced by focal expression of Pax6 and initiation of islet cell neogenesis. The majority of Pdx1-positive epithelial cells showed no expression of insulin, similar to the pattern observed during embryonic development. CONCLUSIONS Overexpression of TGF-alpha induces expansion of a Pdx1-expressing epithelium characterized by focal expression of Pax6 and initiation of islet neogenesis. These findings suggest that premalignant events induced by TGF-alpha in mouse pancreas may recapitulate a developmental program active during embryogenesis.
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Affiliation(s)
- S Y Song
- Department of Surgery, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center and Nashville VAMC, Nashville, TN 37232-2736, USA
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19
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Abstract
Previously, we showed that Xenopus nodal-related factors (Xnrs) can act as mesoderm inducers, and that activin induces Xnr transcription, suggesting that Xnrs relay or maintain induction processes initiated by activin-like molecules. We used a dominant negative cleavage mutant Xnr2 (cmXnr2) to carry out loss-of-function experiments to explore the requirement for Xnr signaling in early amphibian embryogenesis, and the relationship between activin and Xnrs. cmXnr2 blocked mesoderm induction caused by Xnr, but not activin, RNA. In contrast, cmXnr2 did suppress mesoderm and endoderm induction by activin protein, while Xnr transcript induction was unaffected by cmXnr2, consistent with an interference with the function of Xnr peptides that were induced by activin protein treatment. The severe hyperdorsalization and gastrulation defects caused by Xnr2 in whole embryos were rescued by cmXnr2, establishing a specific antagonistic relationship between the normal and cleavage mutant proteins. Expression of cmXnr2 resulted in delayed dorsal lip formation and a range of anterior truncations that were associated with delayed and suppressed expression of markers for dorsoanterior endoderm, in which the recently recognized head organizer activity resides. Reciprocally, Xnr2 induced dorsoanterior endodermal markers, such as cerberus, Xhex-1 and Frzb, in animal cap ectoderm. The migratory behavior of head mesendoderm explanted from cmXnr2 RNA-injected embryos was drastically reduced. These results indicate that Xnrs play crucial roles in initiating gastrulation, probably by acting downstream of an activin-like signaling pathway that leads to dorsal mesendodermal specification, including setting up the head organizer.
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Affiliation(s)
- S I Osada
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN37232-2175, USA
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Mankoo BS, Collins NS, Ashby P, Grigorieva E, Pevny LH, Candia A, Wright CV, Rigby PW, Pachnis V. Mox2 is a component of the genetic hierarchy controlling limb muscle development. Nature 1999; 400:69-73. [PMID: 10403250 DOI: 10.1038/21892] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The skeletal muscles of the limbs develop from myogenic progenitors that originate in the paraxial mesoderm and migrate into the limb-bud mesenchyme. Among the genes known to be important for muscle development in mammalian embryos are those encoding the basic helix-loop-helix (bHLH) myogenic regulatory factors (MRFs; MyoD, Myf5, myogenin and MRF4) and Pax3, a paired-type homeobox gene that is critical for the development of limb musculature. Mox1 and Mox2 are closely related homeobox genes that are expressed in overlapping patterns in the paraxial mesoderm and its derivatives. Here we show that mice homozygous for a null mutation of Mox2 have a developmental defect of the limb musculature, characterized by an overall reduction in muscle mass and elimination of specific muscles. Mox2 is not needed for the migration of myogenic precursors into the limb bud, but it is essential for normal appendicular muscle formation and for the normal regulation of myogenic genes, as demonstrated by the downregulation of Pax3 and Myf5 but not MyoD in Mox2-deficient limb buds. Our findings show that the MOX2 homeoprotein is an important regulator of vertebrate limb myogenesis.
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Affiliation(s)
- B S Mankoo
- Division of Developmental Neurobiology, MRC National Institute for Medical Research, London, UK
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21
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Lawson KA, Dunn NR, Roelen BA, Zeinstra LM, Davis AM, Wright CV, Korving JP, Hogan BL. Bmp4 is required for the generation of primordial germ cells in the mouse embryo. Genes Dev 1999; 13:424-36. [PMID: 10049358 PMCID: PMC316469 DOI: 10.1101/gad.13.4.424] [Citation(s) in RCA: 919] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In many organisms the allocation of primordial germ cells (PGCs) is determined by the inheritance of maternal factors deposited in the egg. However, in mammals, inductive cell interactions are required around gastrulation to establish the germ line. Here, we show that Bmp4 homozygous null embryos contain no PGCs. They also lack an allantois, an extraembryonic mesodermal tissue derived, like the PGCs, from precursors in the proximal epiblast. Heterozygotes have fewer PGCs than normal, due to a reduction in the size of the founding population and not to an effect on its subsequent expansion. Analysis of beta-galactosidase activity in Bmp4(lacZneo) embryos reveals that prior to gastrulation, Bmp4 is expressed in the extraembryonic ectoderm. Later, Bmp4 is expressed in the extraembryonic mesoderm, but not in PGCs. Chimera analysis indicates that it is the Bmp4 expression in the extraembryonic ectoderm that regulates the formation of allantois and primordial germ cell precursors, and the size of the founding population of PGCs. The initiation of the germ line in the mouse therefore depends on a secreted signal from the previously segregated, extraembryonic, trophectoderm lineage.
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Affiliation(s)
- K A Lawson
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, 3584 CT Utrecht, The Netherlands.
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22
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Erter CE, Solnica-Krezel L, Wright CV. Zebrafish nodal-related 2 encodes an early mesendodermal inducer signaling from the extraembryonic yolk syncytial layer. Dev Biol 1998; 204:361-72. [PMID: 9882476 DOI: 10.1006/dbio.1998.9097] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nodal-related factors have been implicated in mesodermal and neural patterning, and left-right asymmetry, in mouse, frog, and chicken embryos. We describe the isolation and characterization of zebrafish nodal-related 2 (znr2). znr2 is expressed at low levels maternally, and zygotic transcripts localize to dorsal blastomeres at MBT. Slightly later, znr2 is also expressed dorsally in the extraembryonic yolk syncytial layer (YSL). During early gastrulation, znr2 expression expands to include deep and superficial cells in the entire marginal zone and YSL. During shield stages, expression is primarily localized to superficial noninvoluting cells of the organizer called dorsal forerunners. Znr2 misexpression in whole fish embryos expands or duplicates dorsoanterior and axial cell fates. Furthermore, Znr2 overexpression exclusively in the YSL, a region implicated in endogenous mesodermal induction, causes broadened or duplicated gsc expression in the overlying blastoderm. Functional comparison of Znr2 and another recently identified zebrafish nodal-related factor, Znr1/Cyclops, reveals distinct inductive properties of each ligand. Znr2 efficiently induces organizer-type dorsoanterior mesodermal and endodermal markers, but only weakly, if at all, neural markers. In contrast, while Znr1/Cyclops reproducibly induces mesodermal and neural markers, it is an inefficient inducer of organizer-type mesoderm. Our results suggest that znr2 encodes a robust mesendodermal inducer that signals nonautonomously during the earliest stages of embryonic patterning, and that part of this activity arises from within the YSL.
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Affiliation(s)
- C E Erter
- Department of Molecular Biology, Vanderbilt University, 1161 21st Avenue South, Nashville, Tennessee, 37232-2175, USA
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23
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Sampath K, Rubinstein AL, Cheng AM, Liang JO, Fekany K, Solnica-Krezel L, Korzh V, Halpern ME, Wright CV. Induction of the zebrafish ventral brain and floorplate requires cyclops/nodal signalling. Nature 1998; 395:185-9. [PMID: 9744278 DOI: 10.1038/26020] [Citation(s) in RCA: 400] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Zebrafish cyclops (cyc) mutations cause deficiencies in the dorsal mesendoderm and ventral neural tube, leading to neural defects and cyclopia. Here we report that cyc encodes a transforming growth factor-beta (TGF-beta)-related intercellular signalling molecule that is similar to mouse nodal. cyc is expressed in dorsal mesendoderm at gastrulation and in the prechordal plate until early somitogenesis. Expression reappears transiently in the left lateral-plate mesoderm, and in an unprecedented asymmetric pattern in the left forebrain. Injection of cyc RNA non-autonomously restores sonic hedgehog-expressing cells of the ventral brain and floorplate that are absent in cyc mutants, whereas inducing activities are abolished by cyc, a mutation of a conserved cysteine in the mature ligand. Our results indicate that cyc provides an essential non-cell-autonomous signal at gastrulation, leading to induction of the floorplate and ventral brain.
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Affiliation(s)
- K Sampath
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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24
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Swift GH, Liu Y, Rose SD, Bischof LJ, Steelman S, Buchberg AM, Wright CV, MacDonald RJ. An endocrine-exocrine switch in the activity of the pancreatic homeodomain protein PDX1 through formation of a trimeric complex with PBX1b and MRG1 (MEIS2). Mol Cell Biol 1998; 18:5109-20. [PMID: 9710595 PMCID: PMC109096 DOI: 10.1128/mcb.18.9.5109] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/1998] [Accepted: 06/01/1998] [Indexed: 11/20/2022] Open
Abstract
HOX proteins and some orphan homeodomain proteins form complexes with either PBX or MEIS subclasses of homeodomain proteins. This interaction can increase the binding specificity and transcriptional effectiveness of the HOX partner. Here we show that specific members of both PBX and MEIS subclasses form a multimeric complex with the pancreatic homeodomain protein PDX1 and switch the nature of its transcriptional activity. The two activities of PDX1 are exhibited through the 10-bp B element of the transcriptional enhancer of the pancreatic elastase I gene (ELA1). In pancreatic acinar cells the activity of the B element requires other elements of the ELA1 enhancer; in beta-cells the B element can activate a promoter in the absence of other enhancer elements. In acinar cell lines the activity is mediated by a complex comprising PDX1, PBX1b, and MRG1 (MEIS2). In contrast, beta-cell lines are devoid of PBX1b and MRG1, so that a trimeric complex does not form, and the beta-cell-type activity is mediated by PDX1 without PBX1b and MRG1. The presence of specific nuclear isoforms of PBX and MEIS is precisely regulated in a cell-type-specific manner. The beta-cell-type activity can be detected in acinar cells if the B element is altered to retain binding of PDX1 but prevent binding of the PDX1-PBX1b-MRG1 complex. These observations suggest that association with PBX and MEIS partners controls the nature of the transcriptional activity of the organ-specific PDX1 transcription factor in exocrine versus endocrine cells.
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Affiliation(s)
- G H Swift
- Department of Molecular Biology and Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
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25
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Jetton TL, Moates JM, Lindner J, Wright CV, Magnuson MA. Targeted oncogenesis of hormone-negative pancreatic islet progenitor cells. Proc Natl Acad Sci U S A 1998; 95:8654-9. [PMID: 9671733 PMCID: PMC21131 DOI: 10.1073/pnas.95.15.8654] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/1998] [Indexed: 02/08/2023] Open
Abstract
Transgenic mice containing an upstream glucokinase (betaGK) promoter- simian virus 40 T antigen (Tag) fusion gene develop neuroendocrine tumors primarily in the pancreas, gut, and pituitary. Pancreatic tumors from a line with delayed tumorigenesis were of two different types: insulinomas and noninsulinomas. The noninsulinomas are often periductal in location, express none of the four major islet peptide hormones, Glut-2, Pdx1, tyrosine hydroxylase, Pax4, Pax6, or Nkx6.1, but do express glucokinase, Sur1, Isl1, Hnf3beta, Hnf6, Beta2/NeuroD, and Nkx2.2. Cells from two different noninsulinoma tumors, when adapted to culture, began to express either insulin, glucagon, or somatostatin. Given the partial gene expression repertoire of the noninsulinoma tumors, their apparent periductal origin, and the ability of these cells to partially cytodifferentiate in culture, we suggest that these tumors are derived from islet progenitor cells. Thus, betaGK-Tag transgenic mice provide a new model system for studying the events that occur during both islet cell neogenesis and normal embryonic development.
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Affiliation(s)
- T L Jetton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA
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26
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Wright CV. Lateral asymmetry in multicellular organisms. Semin Cell Dev Biol 1998; 9:31-3. [PMID: 9572111 DOI: 10.1006/scdb.1997.0198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- C V Wright
- Department of Cell Biology, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA
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27
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Abstract
Bone Morphogenetic Proteins (BMPs) are potent regulators of embryonic cell fate that are presumed to initiate signal transduction in recipient cells through multimeric, transmembrane, serine/threonine kinase complexes made up of type I and type II receptors. BMPRII was identified previously in mammals as the only type II receptor that binds BMPs, but not activin or TGFbeta, in vitro. We report the cloning and functional analysis in vivo of its Xenopus homolog, XBMPRII. XBMPRII is expressed maternally and zygotically in an initially unrestricted manner. Strikingly, XBMPRII transcripts then become restricted to the mesodermal precursors during gastrulation. Expression is lower in the dorsal organizer region, potentially providing a mechanism to suppress the actions of BMP4 on dorsally fated tissues. Similar to the results seen for a truncated type I BMP receptor (tBR), a dominant-negative form of XBMPRII (tBRII) can dorsalize ventral mesoderm, induce extensive secondary body axes, block mesoderm induction by BMP4 and directly neuralize ectoderm, strongly suggesting that XBMPRII mediates BMP signals in vivo. However, although both tBRII and tBR can induce partial secondary axes, marker analysis shows that tBRII-induced axes are more anteriorly extended. Additionally, coinjection of tBRII and tBR synergistically increases the incidence of secondary axis formation. A truncated activin type II receptor (deltaXAR1) is known to block both activin and BMP signaling in vivo. Here we show that such crossreactivity does not occur for tBRII, in that it does not affect activin signaling. Furthermore, our studies indicate that the full-length activin type II receptor (XAR1) overcomes a block in BMP4 signaling imposed by tBRII, implicating XAR1 as a common component of BMP and activin signaling pathways in vivo. These data implicate XBMPRII as a type II receptor with high selectivity for BMP signaling, and therefore as a critical mediator of the effects of BMPs as mesodermal patterning agents and suppressors of neural fate during embryogenesis.
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Affiliation(s)
- A Frisch
- Department of Cell Biology, Vanderbilt University Medical School, Nashville, TN 37232-2175, USA
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28
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Wu KL, Gannon M, Peshavaria M, Offield MF, Henderson E, Ray M, Marks A, Gamer LW, Wright CV, Stein R. Hepatocyte nuclear factor 3beta is involved in pancreatic beta-cell-specific transcription of the pdx-1 gene. Mol Cell Biol 1997; 17:6002-13. [PMID: 9315659 PMCID: PMC232449 DOI: 10.1128/mcb.17.10.6002] [Citation(s) in RCA: 214] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The mammalian homeobox gene pdx-1 is expressed in pluripotent precursor cells in the dorsal and ventral pancreatic bud and duodenal endoderm, which will produce the pancreas and the rostral duodenum. In the adult, pdr-1 is expressed principally within insulin-secreting pancreatic islet beta cells and cells of the duodenal epithelium. Our objective in this study was to localize sequences within the mouse pdx-1 gene mediating selective expression within the islet. Studies of transgenic mice in which a genomic fragment of the mouse pdx-1 gene from kb -4.5 to +8.2 was used to drive a beta-galactosidase reporter showed that the control sequences sufficient for appropriate developmental and adult specific expression were contained within this region. Three nuclease-hypersensitive sites, located between bp -2560 and -1880 (site 1), bp -1330 and -800 (site 2), and bp -260 and +180 (site 3), were identified within the 5'-flanking region of the endogenous pdx-1 gene. Pancreatic beta-cell-specific expression was shown to be controlled by sequences within site 1 from an analysis of the expression pattern of various pdr-1-herpes simplex virus thymidine kinase promoter expression constructs in transfected beta-cell and non-beta-cell lines. Furthermore, we also established that this region was important in vivo by demonstrating that expression from a site 1-driven beta-galactosidase reporter construct was directed to islet beta-cells in transgenic mice. The activity of the site 1-driven constructs was reduced substantially in beta-cell lines by mutating a hepatocyte nuclear factor 3 (HNF3)-like site located between nucleotides -2007 and -1996. Gel shift analysis indicated that HNF3beta present in islet beta cells binds to this element. Immunohistochemical studies revealed that HNF3beta was present within the nuclei of almost all islet beta cells and subsets of pancreatic acinar cells. Together, these results suggest that HNF3beta, a key regulator of endodermal cell lineage development, plays an essential role in the cell-type-specific transcription of the pdx-1 gene in the pancreas.
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Affiliation(s)
- K L Wu
- Department of Molecular Physiology and Biophysics, Vanderbilt Medical Center, Nashville, Tennessee 37232, USA
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29
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Abstract
An association has been noted previously in chick, mouse and frog embryos between asymmetric nodal-related gene expression and embryonic situs, implying an evolutionarily conserved role in left-right specification. Of the four Xenopus nodal-related genes expressed during gastrulation, only Xnr-1 is re-expressed unilaterally in the left lateral plate mesoderm at neurula/tailbud stages. Here, we show that the asymmetric expression of Xnr-1 can be made bilaterally symmetric by right-sided microinjection of RNA encoding active Xenopus hedgehog proteins. Moreover, we provide the first evidence that Xnr-1 expression per se is a causal factor in left-right axis determination. When plasmids expressing Xnr-1 were delivered unilaterally to the right side of Xenopus embryos, a reversed laterality of both the heart and gut (homotaxic reversal) was induced in 40% of surviving embryos, while an additional 10–20% showed reversal of the heart or gut alone (heterotaxia). This effect on laterality was specific to Xnr-1, since neither Xnr-2 nor Xnr-3 plasmids had this activity. In addition, we find that Xnr-1 and Xnr-2, which have both been defined as mesoderm inducers from overexpression studies, show quantitative differences in their ability to induce dorsal mesoderm. Together, these findings suggest that the various Xnrs perform substantially different functions during Xenopus embryogenesis. Moreover, they strongly support the hypothesis that left lateral plate expression of nodal-related genes is a causative factor in the determination of asymmetry in vertebrate embryos.
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Affiliation(s)
- K Sampath
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-2175, USA
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30
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Peshavaria M, Henderson E, Sharma A, Wright CV, Stein R. Functional characterization of the transactivation properties of the PDX-1 homeodomain protein. Mol Cell Biol 1997; 17:3987-96. [PMID: 9199333 PMCID: PMC232251 DOI: 10.1128/mcb.17.7.3987] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Pancreas formation is prevented in mice carrying a null mutation in the PDX-1 homeoprotein, demonstrating a key role for this factor in development. PDX-1 can also bind to and activate transcription from cis-acting regulatory sequences in the insulin and somatostatin genes, which are expressed in pancreatic islet beta and delta cells, respectively. In this study, we compared the functional properties of PDX-1 with those of the closely related Xenopus homeoprotein XIHbox8. Analysis of chimeras between PDX-1, XIHbox8, and the DNA-binding domain of the Saccharomyces cerevisiae transcription factor GAL4 revealed that their transactivation domain was contained within the N-terminal region (amino acids 1 to 79). Detailed mutagenesis of this region indicated that transactivation is mediated by three highly conserved sequences, spanning amino acids 13 to 22 (subdomain A), 32 to 38 (subdomain B), and 60 to 73 (subdomain C). These sequences were also required by PDX-1 to synergistically activate insulin enhancer-mediated transcription with another key insulin gene activator, the E2A-encoded basic helix-loop-helix E2-5 and E47 proteins. These results indicated that N-terminal sequences conserved between the mammalian PDX-1 and Xenopus XIHbox8 proteins are important in transcriptional activation. Stable expression of the PDX-1 deltaABC mutant in the insulin- and PDX-1-expressing betaTC3 cell line resulted in a threefold reduction in the rate of endogenous insulin gene transcription. Strikingly, the level of the endogenous PDX-1 protein was reduced to very low levels in these cells. These results suggest that PDX-1 is not absolutely essential for insulin gene expression in betaTC3 cells. We discuss the possible significance of these findings for insulin gene transcription in islet beta cells.
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Affiliation(s)
- M Peshavaria
- Department of Molecular Physiology and Biophysics, Vanderbilt Medical Center, Nashville, Tennessee 37232, USA
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31
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Abstract
The ability of the adult pancreas to generate new insulin (beta) cells has been controversial because of difficulties in unequivocally identifying the precursor population. We recently determined that beta cells were generated during development from precursors that expressed the homeodomain-containing transcription factor pancreas duodenum homeobox gene-1 (PDX-1). To investigate whether PDX-1+ stem cells are present in adult pancreas, we examined two animal models of diabetes. One model was produced by injecting adult mice with streptozotocin (SZ), a toxin that produces hyperglycemia due to rapid and massive beta cell death. After SZ-mediated elimination of existing IN+/PDX-1+ cells, a population of somatostatin (SOM)+/PDX-1+ cells, a cell type thought to represent an embryonic islet precursor cell, appeared in islets. The appearance of SOM+/PDX-1+ cells was followed in time by the differentiation to SOM+/IN+/PDX-1+ cells. SOM+/PDX-1+ cells also appeared in islets of nonobese diabetic mice, a strain of mice in which beta cell destruction is immune-mediated. Our findings establish the existence of PDX-1+ beta cell precursors in the adult pancreas and indicate that their differentiation is induced by islet injury.
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Affiliation(s)
- A Fernandes
- Department of Anatomy and Cell Biology, SUNY Health Science Center at Brooklyn, New York 11203, USA
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32
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Candia AF, Wright CV. Differential localization of Mox-1 and Mox-2 proteins indicates distinct roles during development. Int J Dev Biol 1996; 40:1179-84. [PMID: 9032023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Transcript localizations for Mox genes have implicated this homeobox gene subfamily in the early steps of mesoderm formation. We have extended these studies by determining the protein expression profile of Mox-1 and Mox-2 during mouse development. The time of onset of Mox protein expression has been accurately obtained to provide clues as to their roles during gastrulation. Expression of Mox-1 protein is first detected in the newly formed mesoderm of primitive streak stage mouse embryos (7.5 days post-coitum, d.p.c.). In contrast, Mox-2 protein is first detected at 9.0 d.p.c. in thr already formed somites. Additionally, immunostaining reveals new and distinct areas of Mox expression in the branchial arches and limbs that were not reported in our previous mRNA localization analysis. Mouse Mox-2 antibodies cross-react specifically in similar embryonic tissues in chick indicating the conservation of function of Mox genes in vertebrates. These expression data suggest that the Mox genes function transiently in the formation of mesodermal and mesenchymal derivatives, after their initial specification, but before their overt differentiation. Furthermore, while there appears to be some overlap in protein expression between Mox-1 and Mox-2 during somitogenesis, unique areas of expression indicate several distinct roles for the Mox genes during development.
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Affiliation(s)
- A F Candia
- Department of Cell Biology, Vanderbilt University, Nashville, TN 37332-2175, USA
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33
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Lowe LA, Supp DM, Sampath K, Yokoyama T, Wright CV, Potter SS, Overbeek P, Kuehn MR. Conserved left-right asymmetry of nodal expression and alterations in murine situs inversus. Nature 1996; 381:158-61. [PMID: 8610013 DOI: 10.1038/381158a0] [Citation(s) in RCA: 366] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vertebrates have characteristic and conserved left-right (L-R) visceral asymmetries, for example the left-sided heart. In humans, alterations of L-R development can have serious clinical implications, including cardiac defects. Although little is known about how the embryonic L-R axis is established, a recent study in the chick embryo revealed L-R asymmetric expression of several previously cloned genes, including Cnr-1 (for chicken nodal-related-1), and indicated how this L-R molecular asymmetry might be important for subsequent visceral morphogenesis. Here we show that nodal is asymmetrically expressed in mice at similar stages, as is Xnr-1 (for Xenopus nodal related-1) in frogs. We also examine nodal expression in two mouse mutations that perturb L-R development, namely situs inversus viscerum (iv), in which assignment of L-R asymmetry is apparently random and individuals develop either normally or are mirror-image-reversed (situs inversus), and inversion of embryonic turning (inv), in which all individuals develop with situs inversus. In both, nodal expression is strikingly affected, being reversed or converted to symmetry. These results further support a key role for nodal and nodal-related genes in interpreting and relaying L-R patterning information in vertebrates. To our knowledge, our results provide the first direct evidence that iv and inv normally function well before the appearance of morphological L-R asymmetry.
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Affiliation(s)
- L A Lowe
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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34
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Jones CM, Dale L, Hogan BL, Wright CV, Smith JC. Bone morphogenetic protein-4 (BMP-4) acts during gastrula stages to cause ventralization of Xenopus embryos. Development 1996; 122:1545-54. [PMID: 8625841 DOI: 10.1242/dev.122.5.1545] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Injection of RNA encoding BMP-4 into the early Xenopus embryo suppresses formation of dorsal and anterior cell types. To understand this phenomenon, it is necessary to know the stage at which BMP-4 acts. In this paper, we present three lines of evidence showing that BMP-4 misexpression has no effect on the initial steps of mesoderm induction, either dorsal or ventral, but instead causes ventralization during gastrulation. Firstly, activation of organizer-specific genes such as goosecoid, Xnot, pintallavis and noggin occurs normally in embryos injected with BMP-4 RNA, but transcript levels are then rapidly down-regulated as gastrulation proceeds. Similarly, BMP-4 does not affect the initial activation of goosecoid by activin in animal caps, but expression then declines precipitously. Secondly, embryos made ventral by injection with BMP-4 RNA cannot be rescued by grafts of Spemann's organizer at gastrula stages. Such embryos therefore differ from those made ventral by UV-irradiation, where the defect occurs early and rescue can be effected by the organizer. Finally, the dorsalizing effects of the organizer, and of the candidate dorsalizing signal noggin, both of which exert their effects during gastrulation, can be counteracted by BMP-4. Together, these experiments demonstrate that BMP-4 can act during gastrulation both to promote ventral mesoderm differentiation and to attenuate dorsalizing signals derived from the organizer.
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Affiliation(s)
- C M Jones
- Division of Developmental Biology, National Institute for Medical Research, London, UK
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35
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Offield MF, Jetton TL, Labosky PA, Ray M, Stein RW, Magnuson MA, Hogan BL, Wright CV. PDX-1 is required for pancreatic outgrowth and differentiation of the rostral duodenum. Development 1996; 122:983-95. [PMID: 8631275 DOI: 10.1242/dev.122.3.983] [Citation(s) in RCA: 1042] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has been proposed that the Xenopus homeobox gene, XlHbox8, is involved in endodermal differentiation during pancreatic and duodenal development (Wright, C.V.E., Schnegelsberg, P. and De Robertis, E.M. (1988). Development 105, 787–794). To test this hypothesis directly, gene targeting was used to make two different null mutations in the mouse XlHbox8 homolog, pdx-1. In the first, the second pdx-1 exon, including the homeobox, was replaced by a neomycin resistance cassette. In the second, a lacZ reporter was fused in-frame with the N terminus of PDX-1, replacing most of the homeodomain. Neonatal pdx-1 −/− mice are apancreatic, in confirmation of previous reports (Jonsson, J., Carlsson, L., Edlund, T. and Edlund, H. (1994). Nature 371, 606–609). However, the pancreatic buds do form in homozygous mutants, and the dorsal bud undergoes limited proliferation and outgrowth to form a small, irregularly branched, ductular tree. This outgrowth does not contain insulin or amylase-positive cells, but glucagon-expressing cells are found. The rostral duodenum shows a local absence of the normal columnar epithelial lining, villi, and Brunner's glands, which are replaced by a GLUT2-positive cuboidal epithelium resembling the bile duct lining. Just distal of the abnormal epithelium, the numbers of enteroendocrine cells in the villi are greatly reduced. The PDX-1/beta-galactosidase fusion allele is expressed in pancreatic and duodenal cells in the absence of functional PDX-1, with expression continuing into perinatal stages with similar boundaries and expression levels. These results offer additional insight into the role of pdx-1 in the determination and differentiation of the posterior foregut, particularly regarding the proliferation and differentiation of the pancreatic progenitors.
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Affiliation(s)
- M F Offield
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-2175, USA
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36
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Abstract
Mouse embryos homozygous for a null mutation in nodal arrest development at early gastrulation and contain little or no embryonic mesoderm. Here, two Xenopus nodal-related genes (Xnr-1 and Xnr-2) are identified and shown to be expressed transiently during embryogenesis, first within the vegetal region of late blastulae and later in the marginal zone during gastrulation, with enrichment in the dorsal lip. Xnrs and mouse nodal function as dose-dependent dorsoanterior and ventral mesoderm inducers in whole embryos and explanted animal caps. Using a plasmid vector to produce Xnr proteins during gastrulation, we show that, in contrast to activin and other TGF beta-like molecules, Xnr-1 and Xnr-2 can dorsalize ventral marginal zone explants and induce muscle differentiation. Xnr signalling also rescues a complete embryonic axis in UV-ventralized embryos. The patterns of Xnr expression, the activities of the proteins and the phenotype of mouse nodal mutants, all argue strongly that a signaling pathway involving nodal, or nodal-related peptides, is an essential conserved element in mesoderm differentiation associated with vertebrate gastrulation and axial patterning.
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Affiliation(s)
- C M Jones
- Department of Cell Biology, Vanderbilt University Medical School, Nashville, TN 37232-2175, USA
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37
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Olson LK, Sharma A, Peshavaria M, Wright CV, Towle HC, Rodertson RP, Stein R. Reduction of insulin gene transcription in HIT-T15 beta cells chronically exposed to a supraphysiologic glucose concentration is associated with loss of STF-1 transcription factor expression. Proc Natl Acad Sci U S A 1995; 92:9127-31. [PMID: 7568086 PMCID: PMC40937 DOI: 10.1073/pnas.92.20.9127] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Chronic exposure of HIT-T15 beta cells to elevated glucose concentrations leads to decreased insulin gene transcription. The reduction in expression is accompanied by diminished binding of a glucose-sensitive transcription factor (termed GSTF) that interacts with two (A+T)-rich elements within the 5' flanking control region of the insulin gene. In this study we examined whether GSTF corresponds to the recently cloned insulin gene transcription factor STF-1, a homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and pancreas. We found that an affinity-purified antibody recognizing STF-1 supershifted the GSTF activator complex formed from HIT-T15 extracts. In addition, we demonstrated a reduction in STF-1 mRNA and protein levels that closely correlated with the change in GSTF binding in HIT-T15 cells chronically cultured under supraphysiologic glucose concentrations. The reduction in STF-1 expression in these cells could be accounted for by a change in the rate of STF-1 gene transcription, suggesting a posttranscriptional control mechanism. In support of this hypothesis, no STF-1 mRNA accumulated in HIT-T15 cells passaged in 11.1 mM glucose. The only RNA species detected was a 6.4-kb STF-1 RNA species that hybridized with 5' and 3' STF-1-specific cDNA probes. We suggest that the 6.4-kb RNA represents an STF-1 mRNA precursor and that splicing of this RNA is defective in these cells. Overall, this study suggests that reduced expression of a key transcriptional regulatory factor, STF-1, contributes to the decrease in insulin gene transcription in HIT-T15 cells chronically cultured in supraphysiologic glucose concentration.
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Affiliation(s)
- L K Olson
- Department of Medicine, University of Minnesota, Minneapolis 55455, USA
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38
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Abstract
In neural plate stage Xenopus embryos, XlHbox 8 expression marks anterior endodermal cells fated to develop into pancreas/duodenum, and expression continues in adult pancreas in exocrine duct, acinar, and islet cells. Here, XlHbox 8 is used as a marker in experiments addressing the mechanisms of early endodermal patterning, particularly with respect to the role of specific polypeptide growth factors. When mesoderm-free vegetal explants (VEs) from early blastula stage embryos are cultured in isolation, XlHbox 8 expression develops autonomously in the dorsal region, strongly suggesting that endodermal region-specific determination occurs before MBT. Data from microinjection experiments using RNA encoding the activin and FGF dominant negative receptors and growth factor treatments of isolated VEs suggest that activin positively regulates XlHbox 8 expression, whereas bFGF is a potent negative regulator. Moreover, bFGF induces mesodermal marker expression in VEs. This suggests that the early endodermal determination state is plastic and that elevated levels of bFGF may convert vegetal (endodermal) cells into mesoderm. We propose a model for XlHbox 8 regulation in which an early signal from the Nieuwkoop center (whose eventual fate is endoderm) predisposes dorsovegetal cells for autonomous XlHbox 8 expression, in an area of high local activin (or activin-like) ligand concentration, and low relative concentrations of bFGF.
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Affiliation(s)
- L W Gamer
- Department of Cell Biology, Vanderbilt University Medical School, Nashville, Tennessee 37232-2175, USA
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39
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Abstract
Focal adhesion kinase (FAK) is a widely produced nonreceptor protein-tyrosine kinase thought to participate in signalling pathways activated in response to cell interaction with the extracellular matrix. Fibronectin-dependent cell adhesion mediated by integrin receptors plays a critical role in mesodermal cell migration during amphibian gastrulation in early development. As a first step toward understanding the role of FAK in Xenopus laevis (Xl) early development, we isolated cDNAs encoding Xl FAK and deduced the entire amino acid (aa) sequence. Xl FAK has 89-91% overall identity to the homologs previously described from mouse, human and chicken sources. Within the catalytic domain, the aa identity is about 97%. Northern blot analysis revealed that abundant maternal FAK transcript is present in Xl eggs, with levels decreasing slightly through cleavage and early blastula stages. At early gastrulation, the FAK mRNA level becomes modestly elevated, followed by a steady decline through late gastrulation. The mRNA level undergoes a further drop at the neurula stage, then begins a steady increase through the tailbud and tadpole stages. These data indicate that the steady-state level of FAK mRNA is regulated during Xl early development, and are consistent with a proposed role for FAK in the process of gastrulation.
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Affiliation(s)
- X Zhang
- Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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40
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Abstract
We have isolated a Xenopus homolog of the murine Mox-2 gene. As is the case for the mouse homolog, mesoderm specific expression of Xenopus Mox-2 (X. Mox-2) expression begins during gastrulation. Using whole mount in situ hybridization, we show that X. Mox-2 is expressed in undifferentiated dorsal, lateral and ventral mesoderm in the posterior of neurula/tailbud embryos, with expression more anteriorly detected in the dermatomes. In the tailbud tadpole, X. Mox-2 is expressed in tissues of the tailbud itself that represent a site of continued gastrulation-like processes resulting in mesoderm formation. X. Mox-2 is not expressed in the marginal zone of blastula, nor in the dorsal lip of gastrula, nor midline tissues (i.e. prospective notochord). Treatments that affect mesodermal patterning during embryonic development, including LiCl and ultraviolet light, and injection of mRNAs encoding BMP-4, or dominant negative activin and FGF receptors, produce changes in X. Mox-2 expression consistent with the types of tissues affected by these manipulations. X. Mox-2 expression is induced more in animal caps treated with FGF than those treated with activin. Together with the fact that X. Mox-2 activation in animal caps requires protein synthesis, our data suggest that X. Mox-2 is involved in initial mesodermal differentiation, downstream of molecules affecting mesoderm induction and determination such as Brachyury and goosecoid, and upstream of factors controlling terminal differentiation such as MyoD and myf5. X. Mox-2, therefore, is another useful marker for understanding the formation of mesoderm in amphibian development.
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Affiliation(s)
- A F Candia
- Department of Cell Biology, Vanderbilt University, Nashville, TN 37232-2175, USA
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41
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Stoffel M, Stein R, Wright CV, Espinosa R, Le Beau MM, Bell GI. Localization of human homeodomain transcription factor insulin promoter factor 1 (IPF1) to chromosome band 13q12.1. Genomics 1995; 28:125-6. [PMID: 7590740 DOI: 10.1006/geno.1995.1120] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- M Stoffel
- Howard Hughes Medical Institute, University of Chicago, Illinois 60637, USA
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42
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Garms J, Wright CV. Managing the passive-aggressive resident. Acad Med 1995; 70:255. [PMID: 7718054 DOI: 10.1097/00001888-199504000-00004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Abstract
The mouse T (Brachyury) gene is required for early mesodermal patterning. Mice homozygous for mutations in T die at midgestation and display defects in mesodermal tissues such as the notochord, the allantois and the somitic mesoderm. To examine the role of T in patterning of somitic and posterior mesoderm along the anterior-posterior axis, we have examined the expression of a panel of molecular markers normally localized to the sub-set of cell types affected in TWis mutant mice. Through the use of whole-mount antibody double labelling techniques, we have analysed the spatial relationships of distinct mesodermal populations relative to cells expressing the T protein. We have also examined the consequences of the TWis mutation on mesodermal populations recognised by these markers. We demonstrate that TWis homozygous mutants retain the ability to form notochordal precursor cells, as identified both by the T antibody and the expression of sonic hedgehog/vertebrate homolog of hedgehog 1 (Shh/vhh-1) and goosecoid, however, these cells fail to proliferate or differentiate. These early notochordal defects appear to result in aberrant somitic differentiation as revealed by the distribution of mox-1 protein and twist RNA expression. Moreover, twist expression in paraxial mesoderm appears to be dependent on normal T activity, while Shh/vhh-1, goosecoid, mox-1 and cdx-4 are not T dependent. We propose that T is required for the maintenance of notochordal tissue and subsequent signals required for somite differentiation.
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Affiliation(s)
- F L Conlon
- Department of Molecular Biology, Harvard University, Cambridge, MA 02138, USA
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44
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Abstract
One of the first intercellular signalling events in the vertebrate embryo leads to mesoderm formation and axis determination. In the mouse, a gene encoding a new member of the TGF-beta superfamily, nodal, is disrupted in a mutant deficient in mesoderm formation (Zhou et al., 1993, Nature 361, 543). nodal mRNA is found in prestreak mouse embryos, consistent with a role in the development of the dorsal axis. To examine the biological activities of nodal, we have studied the action of this factor in eliciting axis determination in the zebrafish, Danio rerio. Injection of nodal mRNA into zebrafish embryos caused the formation of ectopic axes that included notochord and somites. Axis duplication was preceded by the generation of an apparent ectopic shield (organizer equivalent) in nodal-injected embryos, as indicated by the appearance of a region over-expressing gsc and lim1; isolation and expression in the shield of the lim1 gene is reported here. These results suggest a role for a nodal-like factor in pattern formation in zebrafish.
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Affiliation(s)
- R Toyama
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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45
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Guz Y, Montminy MR, Stein R, Leonard J, Gamer LW, Wright CV, Teitelman G. Expression of murine STF-1, a putative insulin gene transcription factor, in beta cells of pancreas, duodenal epithelium and pancreatic exocrine and endocrine progenitors during ontogeny. Development 1995; 121:11-8. [PMID: 7867492 DOI: 10.1242/dev.121.1.11] [Citation(s) in RCA: 391] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The XlHbox 8 homeodomain protein of Xenopus and STF-1, its mammalian homolog, are selectively expressed by beta cells of adult mouse pancreatic islets, where they are likely to regulate insulin expression. We sought to determine whether the expression of the homeobox protein/s during mouse embryonic development was specific to beta cells or, alternatively, whether XlHbox 8/STF-1 protein/s were initially expressed by multipotential precursors and only later became restricted to the insulin-containing cells. With two antibodies, we studied the localization of STF-1 during murine pancreatic development. In embryos, as in adults, STF-1 was expressed by most beta cells, by subsets of the other islet cell types and by mucosal epithelial cells of the duodenum. In addition, most epithelial cells of the pancreatic duct and exocrine cells of the pancreas transiently contained STF-1. We conclude that in mouse, STF-1 not only labels a domain of intestinal epithelial cells but also provides a spatial and temporal marker of endodermal commitment to a pancreatic and subsequently, to an endocrine beta cell fate. We propose a model of pancreatic cell development that suggests that exocrine and endocrine (alpha, beta, delta and PP) cells arise from a common precursor pool of STF-1+ cells and that progression towards a defined monospecific non-beta cell type is correlated with loss of STF-1 expression.
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Affiliation(s)
- Y Guz
- Department of Anatomy and Cell Biology, SUNY Health Science Center at Brooklyn 11203
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46
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Pierceall WE, Reale MA, Candia AF, Wright CV, Cho KR, Fearon ER. Expression of a homologue of the deleted in colorectal cancer (DCC) gene in the nervous system of developing Xenopus embryos. Dev Biol 1994; 166:654-65. [PMID: 7813784 DOI: 10.1006/dbio.1994.1345] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The deleted in colorectal cancer (DCC) gene has been identified as a candidate tumor suppressor gene on the basis of frequent allelic loss and decreased or absent gene expression in several human cancer types, as well as somatic mutations in the gene in colorectal tumors. We have identified a Xenopus DCC homologue (XDCC alpha) predicted to encode a protein of 1427 amino acids and have characterized XDCC expression in developing embryos and adult tissues. The predicted amino acid sequences of XDCC alpha and human DCC are greater than 80% identical; each has four immunoglobulin-like domains, six fibronectin type III domains, and a cytoplasmic domain of about 325 amino acids. While RNase protection assays and immunoblotting studies failed to detect XDCC alpha expression in embryos prior to developmental stage 15, XDCC alpha expression was present in embryos from stages 19 to 46. Whole mount in situ hybridization studies localized XDCC alpha expression to developing forebrain, midbrain, and hindbrain regions. DCC expression was inhibited by treatments that altered the development of mature neural structures; specifically, uv-ventralized embryos and exogastrulae had reduced DCC expression. These results indicate that XDCC alpha is developmentally regulated and expressed as a consequence of neural induction. Moreover, unlike some well-characterized tumor suppressor genes, such as the p53 and retinoblastoma genes, that are not differentially expressed in developing Xenopus embryos, the DCC gene may have a specific role in the morphogenesis of the brain and perhaps other tissues and organs.
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Affiliation(s)
- W E Pierceall
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06536
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47
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48
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Peshavaria M, Gamer L, Henderson E, Teitelman G, Wright CV, Stein R. XIHbox 8, an endoderm-specific Xenopus homeodomain protein, is closely related to a mammalian insulin gene transcription factor. Mol Endocrinol 1994; 8:806-16. [PMID: 7935494 DOI: 10.1210/mend.8.6.7935494] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The cis-acting sequences that mediate insulin gene expression exclusively in pancreatic islet beta-cells are localized within the 5'-flanking region between nucleotides -340 and -91. We have identified an evolutionarily conserved, A+T-rich element at -201/-196 basepairs in the rat insulin II gene that is essential for efficient expression in beta-cells. Affinity-purified antibody to the XIHbox 8 protein super-shifted the major beta-cell-activator factor complex binding to the -201/-196 element. XIHbox 8 is a Xenopus endoderm-specific homeodomain protein whose expression is restricted to the nucleus of endodermal cells of the duodenum and developing pancreas. Antibody to XIHbox 8 specifically interacts with a 47-kilodalton protein present in this DNA complex. Immunohistochemical studies revealed XIHbox 8-like proteins within the nucleus of almost all mouse islet beta-cells and a subset of islet alpha- and beta-cells. These results are consistent with the proposal that an XIHbox 8-related homeoprotein of 47 kilodalton is required for expression of the mammalian insulin gene in beta-cells. Experiments conducted with antiserum raised to somatostatin transcription factor-1 (STF-1), a recently isolated mammalian XIHbox 8-related homeoprotein, indicate that the STF-1 protein is the mammalian homolog of Xenopus XIHbox 8.
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Affiliation(s)
- M Peshavaria
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232
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49
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Barnes JD, Crosby JL, Jones CM, Wright CV, Hogan BL. Embryonic expression of Lim-1, the mouse homolog of Xenopus Xlim-1, suggests a role in lateral mesoderm differentiation and neurogenesis. Dev Biol 1994; 161:168-78. [PMID: 7904966 DOI: 10.1006/dbio.1994.1018] [Citation(s) in RCA: 185] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
cDNAs encoded by the mouse homolog (Lim-1) of the Xenopus LIM-class homeobox gene Xlim-1 have been isolated from an 8.5-day mouse embryo cDNA library. Nucleotide and deduced amino acid sequences show a high degree of identity with Xlim-1 in the LIM and homeodomains, and 85% identity over the whole protein. An interspecific back-cross has been used to show close linkage of Lim-1 to the endogenous proviral marker Mpmv-4 on mouse chromosome 11. Whole mount in situ hybridization studies have been carried out on mouse embryos between 6.5 and 10.5 days. In mid- to late-streak stage embryos, Lim-1 is expressed in a restricted region of mesoderm in the primitive streak, with the highest level of signal at the anterior. At 7.5 days, transcripts can be seen in a horseshoe-shaped pattern in the periphery of the node, as well as along both sides of the immediately adjacent notochord. In addition, transcripts are present in presumptive lateral and intermediate mesoderm. Later, expression becomes progressively restricted to intermediate mesoderm, the nephrogenic cords, and eventually mesonephric ducts and tubules. By 10.5 days Lim-1 transcripts also appear in restricted regions of the central nervous system (CNS) that are associated with sensory function. The lateral diencephalon, hindbrain, and presumed commissural neurons in the dorsal spinal cord all show Lim-1 expression. In the adult, Lim-1 is expressed in the cerebellum/medulla and kidney, and at very low levels in the cerebrum. These data suggest that in the mouse embryo Lim-1 plays a role in early mesoderm formation and later specification of a differentiated phenotype in subsets of cells of the mesonephros and sensory neurons of the CNS.
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Affiliation(s)
- J D Barnes
- Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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Lawler S, Candia AF, Ebner R, Shum L, Lopez AR, Moses HL, Wright CV, Derynck R. The murine type II TGF-beta receptor has a coincident embryonic expression and binding preference for TGF-beta 1. Development 1994; 120:165-75. [PMID: 8119124 DOI: 10.1242/dev.120.1.165] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have isolated cDNAs of the murine type II TGF-beta receptor and have found a conserved cytoplasmic domain, but a less extensive homology in the extracellular receptor domain between the human and murine homologues. In situ hybridization analysis of the mouse fetus during mid gestation localized the expression of this receptor to various developing tissues, primarily in the mesenchyme and epidermis. This expression pattern correlates well with the expression of TGF-beta in general and especially TGF-beta 1, suggesting that TGF-beta 1 exerts its developmental role through this receptor in an autocrine or paracrine fashion. Type II receptor expression was not detected in the central nervous system and developing cartilage. These tissues lack TGF-beta 1 expression but express TGF-beta 2 and/or TGF-beta 3, suggesting that they may exert their activities through separate receptor isoforms. In addition, the efficient binding of TGF-beta 1, but not TGF-beta 2, to the cloned type II receptor strengthens the likelihood that additional type II receptor isoforms exist which display preferential binding to TGF-beta 2 and have their own defined role in development.
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Affiliation(s)
- S Lawler
- Department of Growth and Development, University of California, San Francisco 94143-0640
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