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Downs KM. The mouse allantois: new insights at the embryonic-extraembryonic interface. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210251. [PMID: 36252214 PMCID: PMC9574631 DOI: 10.1098/rstb.2021.0251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 01/20/2022] [Indexed: 12/23/2022] Open
Abstract
During the early development of Placentalia, a distinctive projection emerges at the posterior embryonic-extraembryonic interface of the conceptus; its fingerlike shape presages maturation into the placental umbilical cord, whose major role is to shuttle fetal blood to and from the chorion for exchange with the mother during pregnancy. Until recently, the biology of the cord's vital vascular anlage, called the body stalk/allantois in humans and simply the allantois in rodents, has been largely unknown. Here, new insights into the development of the mouse allantois are featured, from its origin and mechanism of arterial patterning through its union with the chorion. Key to generating the allantois and its critical functions are the primitive streak and visceral endoderm, which together are sufficient to create the entire fetal-placental connection. Their newly discovered roles at the embryonic-extraembryonic interface challenge conventional wisdom, including the physical limits of the primitive streak, its function as sole purveyor of mesoderm in the mouse, potency of visceral endoderm, and the putative role of the allantois in the germ line. With this working model of allantois development, understanding a plethora of hitherto poorly understood orphan diseases in humans is now within reach. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.
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Affiliation(s)
- Karen M. Downs
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison School of Medicine and Public Health, 1111 Highland Avenue, Madison, WI 53705, USA
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Matsumoto K, Kumar V, Varshney S, Nairn AV, Ito A, Pennarubia F, Moremen KW, Stanley P, Haltiwanger RS. Fringe GlcNAc-transferases differentially extend O-fucose on endogenous NOTCH1 in mouse activated T cells. J Biol Chem 2022; 298:102064. [PMID: 35623385 PMCID: PMC9234238 DOI: 10.1016/j.jbc.2022.102064] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 05/13/2022] [Accepted: 05/16/2022] [Indexed: 11/26/2022] Open
Abstract
NOTCH1 is a transmembrane receptor that initiates a cell-cell signaling pathway controlling various cell fate specifications in metazoans. The addition of O-fucose by protein O-fucosyltransferase 1 (POFUT1) to epidermal growth factor-like (EGF) repeats in the NOTCH1 extracellular domain is essential for NOTCH1 function, and modification of O-fucose with GlcNAc by the Fringe family of glycosyltransferases modulates Notch activity. Prior cell-based studies showed that POFUT1 modifies EGF repeats containing the appropriate consensus sequence at high stoichiometry, while Fringe GlcNAc-transferases (LFNG, MFNG, and RFNG) modify O-fucose on only a subset of NOTCH1 EGF repeats. Previous in vivo studies showed that each FNG affects naïve T cell development. To examine Fringe modifications of NOTCH1 at a physiological level, we used mass spectral glycoproteomic methods to analyze O-fucose glycans of endogenous NOTCH1 from activated T cells obtained from mice lacking all Fringe enzymes or expressing only a single FNG. While most O-fucose sites were modified at high stoichiometry, only EGF6, EGF16, EGF26, and EGF27 were extended in WT T cells. Additionally, cell-based assays of NOTCH1 lacking fucose at each of those O-fucose sites revealed small but significant effects of LFNG on Notch-Delta binding in the EGF16 and EGF27 mutants. Finally, in activated T cells expressing only LFNG, MFNG, or RFNG alone, the extension of O-fucose with GlcNAc in the same EGF repeats was diminished, consistent with cooperative interactions when all three Fringes were present. The combined data open the door for the analysis of O-glycans on endogenous NOTCH1 derived from different cell types.
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Affiliation(s)
- Kenjiroo Matsumoto
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Vivek Kumar
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York, USA
| | - Shweta Varshney
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York, USA
| | - Alison V Nairn
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Atsuko Ito
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Florian Pennarubia
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Pamela Stanley
- Department of Cell Biology, Albert Einstein College of Medicine, New York, New York, USA.
| | - Robert S Haltiwanger
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
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Varshney S, Wei HX, Batista F, Nauman M, Sundaram S, Siminovitch K, Tanwar A, Stanley P. A modifier in the 129S2/SvPasCrl genome is responsible for the viability of Notch1[12f/12f] mice. BMC DEVELOPMENTAL BIOLOGY 2019; 19:19. [PMID: 31590629 PMCID: PMC6781419 DOI: 10.1186/s12861-019-0199-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 09/06/2019] [Indexed: 12/27/2022]
Abstract
Background Mouse NOTCH1 carries a highly conserved O-fucose glycan at Thr466 in epidermal growth factor-like repeat 12 (EGF12) of the extracellular domain. O-Fucose at this site has been shown by X-ray crystallography to be recognized by both DLL4 and JAG1 Notch ligands. We previously showed that a Notch1 Thr466Ala mutant exhibits very little ligand-induced NOTCH1 signaling in a reporter assay, whereas a Thr466Ser mutation enables the transfer of O-fucose and reverts the NOTCH1 signaling defect. We subsequently generated a mutant mouse with the Thr466Ala mutation termed Notch1[12f](Notch1tm2Pst). Surprisingly, homozygous Notch1[12f/12f] mutants on a mixed background were viable and fertile. Results We now report that after backcrossing to C57BL/6 J mice for 11–15 generations, few homozygous Notch1[12f/12f] embryos were born. Timed mating showed that embryonic lethality occurred by embryonic day (E) ~E11.5, somewhat delayed compared to mice lacking Notch1 or Pofut1 (the O-fucosyltransferase that adds O-fucose to Notch receptors), which die at ~E9.5. The phenotype of C57BL/6 J Notch1[12f/12f] embryos was milder than mutants affected by loss of a canonical Notch pathway member, but disorganized vasculogenesis in the yolk sac, delayed somitogenesis and development were characteristic. In situ hybridization of Notch target genes Uncx4.1 and Dll3 or western blot analysis of NOTCH1 cleavage did not reveal significant differences at E9.5. However, qRT-PCR of head cDNA showed increased expression of Dll3, Uncx4.1 and Notch1 in E9.5 Notch1[12f/12f] embryos. Sequencing of cDNA from Notch1[12f/12f] embryo heads and Southern analysis showed that the Notch1[12f] locus was intact following backcrossing. We therefore looked for evidence of modifying gene(s) by crossing C57BL/6 J Notch1 [12f/+] mice to 129S2/SvPasCrl mice. Intercrosses of the F1 progeny gave viable F2 Notch1[12f/12f] mice. Conclusion We conclude that the 129S2/SvPasCrl genome contains a dominant modifying gene that rescues the functions of NOTCH1[12f] in signaling. Identification of the modifying gene has the potential to illuminate novel factor(s) that promote Notch signaling when an O-fucose glycan is absent from EGF12 of NOTCH1.
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Affiliation(s)
- Shweta Varshney
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA.,Present address: ETHOS Health Communications, Yardley, PA, 19067, USA
| | - Hua-Xing Wei
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA.,Present address: The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230001, People's Republic of China
| | - Frank Batista
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA
| | - Mohd Nauman
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA
| | - Subha Sundaram
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA
| | - Katherine Siminovitch
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, CA, M5G 1X5, Canada
| | - Ankit Tanwar
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA
| | - Pamela Stanley
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, 10461, USA.
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Sawaguchi S, Varshney S, Ogawa M, Sakaidani Y, Yagi H, Takeshita K, Murohara T, Kato K, Sundaram S, Stanley P, Okajima T. O-GlcNAc on NOTCH1 EGF repeats regulates ligand-induced Notch signaling and vascular development in mammals. eLife 2017; 6:e24419. [PMID: 28395734 PMCID: PMC5388531 DOI: 10.7554/elife.24419] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/10/2017] [Indexed: 12/16/2022] Open
Abstract
The glycosyltransferase EOGT transfers O-GlcNAc to a consensus site in epidermal growth factor-like (EGF) repeats of a limited number of secreted and membrane proteins, including Notch receptors. In EOGT-deficient cells, the binding of DLL1 and DLL4, but not JAG1, canonical Notch ligands was reduced, and ligand-induced Notch signaling was impaired. Mutagenesis of O-GlcNAc sites on NOTCH1 also resulted in decreased binding of DLL4. EOGT functions were investigated in retinal angiogenesis that depends on Notch signaling. Global or endothelial cell-specific deletion of Eogt resulted in defective retinal angiogenesis, with a mild phenotype similar to that caused by reduced Notch signaling in retina. Combined deficiency of different Notch1 mutant alleles exacerbated the abnormalities in Eogt-/- retina, and Notch target gene expression was decreased in Eogt-/-endothelial cells. Thus, O-GlcNAc on EGF repeats of Notch receptors mediates ligand-induced Notch signaling required in endothelial cells for optimal vascular development.
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Affiliation(s)
- Shogo Sawaguchi
- Department of Molecular Biochemistry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shweta Varshney
- Department of Cell Biology, Albert Einstein College of Medicine, New York, United States
| | - Mitsutaka Ogawa
- Department of Molecular Biochemistry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yuta Sakaidani
- Department of Molecular Biochemistry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hirokazu Yagi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Kyosuke Takeshita
- Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Toyoaki Murohara
- Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Koichi Kato
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
- Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan
| | - Subha Sundaram
- Department of Cell Biology, Albert Einstein College of Medicine, New York, United States
| | - Pamela Stanley
- Department of Cell Biology, Albert Einstein College of Medicine, New York, United States
| | - Tetsuya Okajima
- Department of Molecular Biochemistry, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Stanley P. What Have We Learned from Glycosyltransferase Knockouts in Mice? J Mol Biol 2016; 428:3166-3182. [PMID: 27040397 DOI: 10.1016/j.jmb.2016.03.025] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 11/16/2022]
Abstract
There are five major classes of glycan including N- and O-glycans, glycosaminoglycans, glycosphingolipids, and glycophosphatidylinositol anchors, all expressed at the molecular frontier of each mammalian cell. Numerous biological consequences of altering the expression of mammalian glycans are understood at a mechanistic level, but many more remain to be characterized. Mouse mutants with deleted, defective, or misexpressed genes that encode activities necessary for glycosylation have led the way to identifying key functions of glycans in biology. However, with the advent of exome sequencing, humans with mutations in genes involved in glycosylation are also revealing specific requirements for glycans in mammalian development. The aim of this review is to summarize glycosylation genes that are necessary for mouse embryonic development, pathway-specific glycosylation genes whose deletion leads to postnatal morbidity, and glycosylation genes for which effects are mild, but perturbation of the organism may reveal functional consequences. General strategies for generating and interpreting the phenotype of mice with glycosylation defects are discussed in relation to human congenital disorders of glycosylation (CDG).
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Affiliation(s)
- Pamela Stanley
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY 10461, USA.
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Ogawa M, Sawaguchi S, Furukawa K, Okajima T. N-acetylglucosamine modification in the lumen of the endoplasmic reticulum. Biochim Biophys Acta Gen Subj 2015; 1850:1319-24. [PMID: 25791024 DOI: 10.1016/j.bbagen.2015.03.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/07/2015] [Accepted: 03/11/2015] [Indexed: 12/25/2022]
Abstract
BACKGROUND O-linked β-N-acetylglucosamine (O-GlcNAc) modification of epidermal growth factor (EGF) domains catalyzed by EGF domain O-GlcNAc transferase (EOGT) is the first example of GlcNAc modification in the lumen of the endoplasmic reticulum (ER). SCOPE OF REVIEW This review summarizes current knowledge on the EOGT-catalyzed O-GlcNAc modification of EGF domains obtained through biochemical characterization, genetic analysis in Drosophila, and identification of human EOGT mutation. Additionally, this review discusses GTDC2-another ER protein homologous to EOGT that catalyzes the GlcNAc modification of O-mannosylated α-dystroglycan-and other components of the biosynthetic pathway involved in GlcNAc modification in the ER lumen. MAJOR CONCLUSIONS GlcNAc modification in the ER lumen has been identified as a novel type of protein modification that regulates specific protein function. Moreover, abnormal GlcNAc modification in the ER lumen is responsible for Adams-Oliver syndrome and Walker-Warburg syndrome. GENERAL SIGNIFICANCE Elucidation of the biological function of GlcNAc modification in the ER lumen will provide new insights into the unique roles of O-glycans, whose importance has been demonstrated in multifunctional glycoproteins such as Notch receptors and α-dystroglyan.
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Affiliation(s)
- Mitsutaka Ogawa
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan; Department of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan
| | - Shogo Sawaguchi
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan
| | - Koichi Furukawa
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan
| | - Tetsuya Okajima
- Department of Biochemistry II, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan.
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van den Akker NMS, Caolo V, Molin DGM. Cellular decisions in cardiac outflow tract and coronary development: an act by VEGF and NOTCH. Differentiation 2012; 84:62-78. [PMID: 22683047 DOI: 10.1016/j.diff.2012.04.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 03/28/2012] [Accepted: 04/10/2012] [Indexed: 01/09/2023]
Abstract
Congenital cardiac abnormalities are, due to their relatively high frequency and severe impact on quality of life, an important focus in cardiovascular research. Recently, various human studies have revealed a high coincidence of VEGF and NOTCH polymorphisms with cardiovascular outflow tract anomalies, such as bicuspid aortic valves and Tetralogy of Fallot, next to predisposition for cardiovascular pathologies, including atherosclerosis and aortic valve calcification. This genetic association between VEGF/NOTCH mutations and congenital cardiovascular defects in humans has been supported by substantial proof from animal models, revealing interaction of both pathways in cellular processes that are crucial for cardiac development. This review focuses on the role of VEGF and NOTCH signaling and their interplay in cardiogenesis with special interest to coronary and outflow tract development. An overview of the association between congenital malformations and VEGF/NOTCH polymorphisms in humans will be discussed along with their potential mechanisms and processes as revealed by transgenic mouse models. The molecular and cellular interaction of VEGF and subsequent Notch-signaling in these processes will be highlighted.
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Affiliation(s)
- Nynke M S van den Akker
- Department of Physiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands.
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Kwon C, Cheng P, King IN, Andersen P, Shenje L, Nigam V, Srivastava D. Notch post-translationally regulates β-catenin protein in stem and progenitor cells. Nat Cell Biol 2011; 13:1244-51. [PMID: 21841793 PMCID: PMC3187850 DOI: 10.1038/ncb2313] [Citation(s) in RCA: 210] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 07/05/2011] [Indexed: 02/07/2023]
Abstract
Cellular decisions of self-renewal or differentiation arise from integration and reciprocal titration of numerous regulatory networks. Notch and Wnt/β-catenin signalling often intersect in stem and progenitor cells and regulate each other transcriptionally. The biological outcome of signalling through each pathway often depends on the context and timing as cells progress through stages of differentiation. Here, we show that membrane-bound Notch physically associates with unphosphorylated (active) β-catenin in stem and colon cancer cells and negatively regulates post-translational accumulation of active β-catenin protein. Notch-dependent regulation of β-catenin protein did not require ligand-dependent membrane cleavage of Notch or the glycogen synthase kinase-3β-dependent activity of the β-catenin destruction complex. It did, however, require the endocytic adaptor protein Numb and lysosomal activity. This study reveals a previously unrecognized function of Notch in negatively titrating active β-catenin protein levels in stem and progenitor cells.
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Affiliation(s)
- Chulan Kwon
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry & Biophysics, University of California, San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205 USA
| | - Paul Cheng
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry & Biophysics, University of California, San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Isabelle N. King
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry & Biophysics, University of California, San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Peter Andersen
- Division of Cardiology, Department of Medicine, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205 USA
| | - Lincoln Shenje
- Division of Cardiology, Department of Medicine, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205 USA
| | - Vishal Nigam
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry & Biophysics, University of California, San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Deepak Srivastava
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry & Biophysics, University of California, San Francisco, 1650 Owens Street, San Francisco, CA 94158, USA
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Protein O-fucosyltransferase 1 (Pofut1) regulates lymphoid and myeloid homeostasis through modulation of Notch receptor ligand interactions. Blood 2011; 117:5652-62. [PMID: 21464368 DOI: 10.1182/blood-2010-12-326074] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Notch signaling is essential for lymphocyte development and is also implicated in myelopoiesis. Notch receptors are modified by O-fucosylation catalyzed by protein O-fucosyltransferase 1 (Pofut1). Fringe enzymes add N-acetylglucosamine to O-fucose and modify Notch signaling by altering the sensitivity of Notch receptors to Notch ligands. To address physiologic functions in hematopoiesis of Notch modified by O-fucose glycans, we examined mice with inducible inactivation of Pofut1 using Mx-Cre. These mice exhibited a reduction in T lymphopoiesis and in the production of marginal-zone B cells, in addition to myeloid hyperplasia. Restoration of Notch1 signaling rescued T lymphopoiesis and the marrow myeloid hyperplasia. After marrow transfer, both cell-autonomous and environmental cues were found to contribute to lymphoid developmental defects and myeloid hyperplasia in Pofut1-deleted mice. Although Pofut1 deficiency slightly decreased cell surface expression of Notch1 and Notch2, it completely abrogated the binding of Notch receptors with Delta-like Notch ligands and suppressed downstream Notch target activation, indicating that O-fucose glycans are critical for efficient Notch-ligand binding that transduce Notch signals. The combined data support a key role for the O-fucose glycans generated by Pofut1 in Notch regulation of hematopoietic homeostasis through modulation of Notch-ligand interactions.
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NOTCH1 missense alleles associated with left ventricular outflow tract defects exhibit impaired receptor processing and defective EMT. Biochim Biophys Acta Mol Basis Dis 2010; 1812:121-9. [PMID: 20951801 DOI: 10.1016/j.bbadis.2010.10.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 09/21/2010] [Accepted: 10/11/2010] [Indexed: 01/04/2023]
Abstract
Notch signaling is essential for proper cardiac development. We recently identified missense variants in the NOTCH1 receptor in patients with diverse left ventricular outflow tract (LVOT) malformations (NOTCH1(G661S) and NOTCH1(A683T)) that reduce ligand-induced Notch signaling. Here, we examine the molecular mechanisms that contribute to reduced signaling and perturbed development. We find that NOTCH1(A683T) exhibits reduced S1 cleavage due to impaired trafficking through the endoplasmic reticulum (ER). This observation is consistent with improper localization of the variant receptor to the ER and decreased presentation at the cell surface. In contrast, the nearby mutation NOTCH1(G661S) exhibits reduced cell-surface presentation in the absence of overt folding or trafficking defects. To examine the implications of these variants in disease pathogenesis, we investigated their effect on epithelial-to-mesenchymal transition (EMT), a critical process for development of the outflow tract. We find that these LVOT-associated NOTCH1 alleles can contribute to defective EMT in endothelial cell lines through impaired induction of Snail and Hes family members. These data represent the first description of a molecular mechanism underlying NOTCH1 mutations in individuals with LVOT malformations, and have important implications regarding the functional contribution of these alleles to a complex set of developmental defects.
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