1
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Gredler ML, Zallen JA. Multicellular rosettes link mesenchymal-epithelial transition to radial intercalation in the mouse axial mesoderm. Dev Cell 2023:S1534-5807(23)00134-X. [PMID: 37080203 DOI: 10.1016/j.devcel.2023.03.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 01/25/2023] [Accepted: 03/24/2023] [Indexed: 04/22/2023]
Abstract
Mesenchymal-epithelial transitions are fundamental drivers of development and disease, but how these behaviors generate epithelial structure is not well understood. Here, we show that mesenchymal-epithelial transitions promote epithelial organization in the mouse node and notochordal plate through the assembly and radial intercalation of three-dimensional rosettes. Axial mesoderm rosettes acquire junctional and apical polarity, develop a central lumen, and dynamically expand, coalesce, and radially intercalate into the surface epithelium, converting mesenchymal-epithelial transitions into higher-order tissue structure. In mouse Par3 mutants, axial mesoderm rosettes establish central tight junction polarity but fail to form an expanded apical domain and lumen. These defects are associated with altered rosette dynamics, delayed radial intercalation, and formation of a small, fragmented surface epithelial structure. These results demonstrate that three-dimensional rosette behaviors translate mesenchymal-epithelial transitions into collective radial intercalation and epithelial formation, providing a strategy for building epithelial sheets from individual self-organizing units in the mammalian embryo.
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Affiliation(s)
- Marissa L Gredler
- Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA
| | - Jennifer A Zallen
- Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, New York, NY, USA.
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2
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Lo JHH, Edwards M, Langerman J, Sridharan R, Plath K, Smale ST. Oct4:Sox2 binding is essential for establishing but not maintaining active and silent states of dynamically regulated genes in pluripotent cells. Genes Dev 2022; 36:1079-1095. [PMID: 36418052 PMCID: PMC9744233 DOI: 10.1101/gad.350113.122] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/14/2022] [Indexed: 11/24/2022]
Abstract
Much has been learned about the mechanisms of action of pluripotency factors Oct4 and Sox2. However, as with other regulators of cell identity, little is known about the impact of disrupting their binding motifs in a native environment or the characteristics of genes they regulate. By quantitatively examining dynamic ranges of gene expression instead of focusing on conventional measures of differential expression, we found that Oct4 and Sox2 enhancer binding is strongly enriched near genes subject to large dynamic ranges of expression among cell types, with binding sites near these genes usually within superenhancers. Mutagenesis of representative Oct4:Sox2 motifs near such active, dynamically regulated genes revealed critical roles in transcriptional activation during reprogramming, with more limited roles in transcriptional maintenance in the pluripotent state. Furthermore, representative motifs near silent genes were critical for establishing but not maintaining the fully silent state, while genes whose transcript levels varied by smaller magnitudes among cell types were unaffected by nearby Oct4:Sox2 motifs. These results suggest that Oct4 and Sox2 directly establish both active and silent transcriptional states in pluripotent cells at a large number of genes subject to dynamic regulation during mammalian development, but are less important than expected for maintaining transcriptional states.
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Affiliation(s)
- Jerry Hung-Hao Lo
- Molecular Biology Institute, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Broad Stem Cell Research Center, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Miguel Edwards
- Molecular Biology Institute, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Broad Stem Cell Research Center, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Justin Langerman
- Molecular Biology Institute, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Broad Stem Cell Research Center, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Rupa Sridharan
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53715, USA
| | - Kathrin Plath
- Molecular Biology Institute, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Broad Stem Cell Research Center, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Department of Biological Chemistry, University of California at Los Angeles, Los Angeles, California 90095, USA
| | - Stephen T Smale
- Molecular Biology Institute, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Broad Stem Cell Research Center, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
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3
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Joyner A, Lehmann R, Niswander L. In Memoriam: Kathryn V. Anderson (1952-2020). Dev Biol 2021; 472:125-126. [PMID: 33618188 DOI: 10.1016/j.ydbio.2021.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Alex Joyner
- Professor and Member, Developmental Biology Program, Sloan Kettering Institute, USA
| | - Ruth Lehmann
- Director, Whitehead Institute and Professor of Biology, Massachusetts Institute of Technology, USA
| | - Lee Niswander
- Professor and Chair, Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, USA
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4
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Yu T, Matsuda M. Epb41l5 interacts with Iqcb1 and regulates ciliary function in zebrafish embryos. J Cell Sci 2020; 133:jcs240648. [PMID: 32501287 PMCID: PMC7338265 DOI: 10.1242/jcs.240648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 05/13/2020] [Indexed: 11/20/2022] Open
Abstract
Erythrocyte protein band 4.1 like 5 (EPB41L5) is an adaptor protein beneath the plasma membrane that functions to control epithelial morphogenesis. Here we report a previously uncharacterized role of EPB41L5 in controlling ciliary function. We found that EPB41L5 forms a complex with IQCB1 (previously known as NPHP5), a ciliopathy protein. Overexpression of EPB41L5 reduced IQCB1 localization at the ciliary base in cultured mammalian epithelial cells. Conversely, epb41l5 knockdown increased IQCB1 localization at the ciliary base. epb41l5-deficient zebrafish embryos or embryos expressing C-terminally modified forms of Epb41l5 developed cilia with reduced motility and exhibited left-right patterning defects, an outcome of abnormal ciliary function. We observed genetic synergy between epb41l5 and iqcb1. Moreover, EPB41L5 decreased IQCB1 interaction with CEP290, another ciliopathy protein and a component of the ciliary base and centrosome. Together, these observations suggest that EPB41L5 regulates the composition of the ciliary base and centrosome through IQCB1 and CEP290.
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Affiliation(s)
- Tiffany Yu
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, NJ 07302, USA
| | - Miho Matsuda
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, NJ 07302, USA
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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5
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Horstick EJ, Bayleyen Y, Burgess HA. Molecular and cellular determinants of motor asymmetry in zebrafish. Nat Commun 2020; 11:1170. [PMID: 32127541 PMCID: PMC7054361 DOI: 10.1038/s41467-020-14965-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 02/04/2020] [Indexed: 02/05/2023] Open
Abstract
Asymmetries in motor behavior, such as human hand preference, are observed throughout bilateria. However, neural substrates and developmental signaling pathways that impose underlying functional lateralization on a broadly symmetric nervous system are unknown. Here we report that in the absence of over-riding visual information, zebrafish larvae show intrinsic lateralized motor behavior that is mediated by a cluster of 60 posterior tuberculum (PT) neurons in the forebrain. PT neurons impose motor bias via a projection through the habenular commissure. Acquisition of left/right identity is disrupted by heterozygous mutations in mosaic eyes and mindbomb, genes that regulate Notch signaling. These results define the neuronal substrate for motor asymmetry in a vertebrate and support the idea that haploinsufficiency for genes in a core developmental pathway destabilizes left/right identity. Many animals show individual left/right biases in motor behaviour, but underlying neural substrates have proven elusive. Here the authors describe neurons that maintain individual, context-dependent lateralisation of swimming behaviour in zebrafish.
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Affiliation(s)
- Eric J Horstick
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892, USA. .,Department of Biology, West Virginia University, Morgantown, WV, USA.
| | - Yared Bayleyen
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892, USA
| | - Harold A Burgess
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892, USA.
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6
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Nowotschin S, Hadjantonakis AK. Guts and gastrulation: Emergence and convergence of endoderm in the mouse embryo. Curr Top Dev Biol 2019; 136:429-454. [PMID: 31959298 DOI: 10.1016/bs.ctdb.2019.11.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Gastrulation is a central process in mammalian development in which a spatiotemporally coordinated series of events driven by cross-talk between adjacent embryonic and extra-embryonic tissues results in stereotypical morphogenetic cell behaviors, massive cell proliferation and the acquisition of distinct cell identities. Gastrulation provides the blueprint of the body plan of the embryo, as well as generating extra-embryonic cell types of the embryo to make a connection with its mother. Gastrulation involves the specification of mesoderm and definitive endoderm from pluripotent epiblast, concomitant with a highly ordered elongation of tissue along the anterior-posterior (AP) axis. Interestingly, cells with an endoderm identity arise twice during mouse development. Cells with a primitive endoderm identity are specified in the preimplantation blastocyst, and which at gastrulation intercalate with the emergent definitive endoderm to form a mosaic tissue, referred to as the gut endoderm. The gut endoderm gives rise to the gut tube, which will subsequently become patterned along its AP axis into domains possessing unique visceral organ identities, such as thyroid, lung, liver and pancreas. In this way, proper endoderm development is essential for vital organismal functions, including the absorption of nutrients, gas exchange, detoxification and glucose homeostasis.
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Affiliation(s)
- Sonja Nowotschin
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, United States.
| | - Anna-Katerina Hadjantonakis
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, United States.
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7
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Catana A, Apostu AP. The determination factors of left-right asymmetry disorders- a short review. ACTA ACUST UNITED AC 2017; 90:139-146. [PMID: 28559696 PMCID: PMC5433564 DOI: 10.15386/cjmed-701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/02/2016] [Accepted: 11/23/2016] [Indexed: 12/17/2022]
Abstract
Laterality defects in humans, situs inversus and heterotaxy, are rare disorders, with an incidence of 1:8000 to 1:10 000 in the general population, and a multifactorial etiology. It has been proved that 1.44/10 000 of all cardiac problems are associated with malformations of left-right asymmetry and heterotaxy accounts for 3% of all congenital heart defects. It is considered that defects of situs appear due to genetic and environmental factors. Also, there is evidence that the ciliopathies (defects of structure or function) are involved in development abnormalities. Over 100 genes have been reported to be involved in left-right patterning in model organisms, but only a few are likely to candidate for left-right asymmetry defects in humans. Left-right asymmetry disorders are genetically heterogeneous and have variable manifestations (from asymptomatic to serious clinical problems). The discovery of the right mechanism of left-right development will help explain the clinical complexity and may contribute to a therapy of these disorders.
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Affiliation(s)
- Andreea Catana
- Genetics Department, Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania
| | - Adina Patricia Apostu
- Genetics Department, Iuliu Hatieganu University of Medicine and Pharmacy, Cluj-Napoca, Romania
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8
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Dasgupta A, Amack JD. Cilia in vertebrate left-right patterning. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150410. [PMID: 27821522 PMCID: PMC5104509 DOI: 10.1098/rstb.2015.0410] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2016] [Indexed: 01/10/2023] Open
Abstract
Understanding how left-right (LR) asymmetry is generated in vertebrate embryos is an important problem in developmental biology. In humans, a failure to align the left and right sides of cardiovascular and/or gastrointestinal systems often results in birth defects. Evidence from patients and animal models has implicated cilia in the process of left-right patterning. Here, we review the proposed functions for cilia in establishing LR asymmetry, which include creating transient leftward fluid flows in an embryonic 'left-right organizer'. These flows direct asymmetric activation of a conserved Nodal (TGFβ) signalling pathway that guides asymmetric morphogenesis of developing organs. We discuss the leading hypotheses for how cilia-generated asymmetric fluid flows are translated into asymmetric molecular signals. We also discuss emerging mechanisms that control the subcellular positioning of cilia and the cellular architecture of the left-right organizer, both of which are critical for effective cilia function during left-right patterning. Finally, using mosaic cell-labelling and time-lapse imaging in the zebrafish embryo, we provide new evidence that precursor cells maintain their relative positions as they give rise to the ciliated left-right organizer. This suggests the possibility that these cells acquire left-right positional information prior to the appearance of cilia.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.
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Affiliation(s)
- Agnik Dasgupta
- Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
| | - Jeffrey D Amack
- Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA
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9
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Benz BA, Nandadasa S, Takeuchi M, Grady RC, Takeuchi H, LoPilato RK, Kakuda S, Somerville RPT, Apte SS, Haltiwanger RS, Holdener BC. Genetic and biochemical evidence that gastrulation defects in Pofut2 mutants result from defects in ADAMTS9 secretion. Dev Biol 2016; 416:111-122. [PMID: 27297885 DOI: 10.1016/j.ydbio.2016.05.038] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 05/31/2016] [Accepted: 05/31/2016] [Indexed: 02/07/2023]
Abstract
Protein O-fucosyltransferase 2 (POFUT2) adds O-linked fucose to Thrombospondin Type 1 Repeats (TSR) in 49 potential target proteins. Nearly half the POFUT2 targets belong to the A Disintegrin and Metalloprotease with ThromboSpondin type-1 motifs (ADAMTS) or ADAMTS-like family of proteins. Both the mouse Pofut2 RST434 gene trap allele and the Adamts9 knockout were reported to result in early embryonic lethality, suggesting that defects in Pofut2 mutant embryos could result from loss of O-fucosylation on ADAMTS9. To address this question, we compared the Pofut2 and Adamts9 knockout phenotypes and used Cre-mediated deletion of Pofut2 and Adamts9 to dissect the tissue-specific role of O-fucosylated ADAMTS9 during gastrulation. Disruption of Pofut2 using the knockout (LoxP) or gene trap (RST434) allele, as well as deletion of Adamts9, resulted in disorganized epithelia (epiblast, extraembryonic ectoderm, and visceral endoderm) and blocked mesoderm formation during gastrulation. The similarity between Pofut2 and Adamts9 mutants suggested that disruption of ADAMTS9 function could be responsible for the gastrulation defects observed in Pofut2 mutants. Consistent with this prediction, CRISPR/Cas9 knockout of POFUT2 in HEK293T cells blocked secretion of ADAMTS9. We determined that Adamts9 was dynamically expressed during mouse gastrulation by trophoblast giant cells, parietal endoderm, the most proximal visceral endoderm adjacent to the ectoplacental cone, extraembryonic mesoderm, and anterior primitive streak. Conditional deletion of either Pofut2 or Adamts9 in the epiblast rescues the gastrulation defects, and identified a new role for O-fucosylated ADAMTS9 during morphogenesis of the amnion and axial mesendoderm. Combined, these results suggested that loss of ADAMTS9 function in the extra embryonic tissue is responsible for gastrulation defects in the Pofut2 knockout. We hypothesize that loss of ADAMTS9 function in the most proximal visceral endoderm leads to slippage of the visceral endoderm and altered characteristics of the extraembryonic ectoderm. Consequently, loss of input from the extraembryonic ectoderm and/or compression of the epiblast by Reichert's membrane blocks gastrulation. In the future, the Pofut2 and Adamts9 knockouts will be valuable tools for understanding how local changes in the properties of the extracellular matrix influence the organization of tissues during mammalian development.
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Affiliation(s)
- Brian A Benz
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Sumeda Nandadasa
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States
| | - Megumi Takeuchi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| | - Richard C Grady
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Hideyuki Takeuchi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| | - Rachel K LoPilato
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| | - Shinako Kakuda
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Robert P T Somerville
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States
| | - Suneel S Apte
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States
| | - Robert S Haltiwanger
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States.
| | - Bernadette C Holdener
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States.
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10
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Balmer S, Nowotschin S, Hadjantonakis AK. Notochord morphogenesis in mice: Current understanding & open questions. Dev Dyn 2016; 245:547-57. [PMID: 26845388 DOI: 10.1002/dvdy.24392] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 01/26/2016] [Accepted: 01/26/2016] [Indexed: 12/25/2022] Open
Abstract
The notochord is a structure common to all chordates, and the feature that the phylum Chordata has been named after. It is a rod-like mesodermal structure that runs the anterior-posterior length of the embryo, adjacent to the ventral neural tube. The notochord plays a critical role in embryonic tissue patterning, for example the dorsal-ventral patterning of the neural tube. The cells that will come to form the notochord are specified at gastrulation. Axial mesodermal cells arising at the anterior primitive streak migrate anteriorly as the precursors of the notochord and populate the notochordal plate. Yet, even though a lot of interest has centered on investigating the functional and structural roles of the notochord, we still have a very rudimentary understanding of notochord morphogenesis. The events driving the formation of the notochord are rapid, taking place over the period of approximately a day in mice. In this commentary, we provide an overview of our current understanding of mouse notochord morphogenesis, from the initial specification of axial mesendodermal cells at the primitive streak, the emergence of these cells at the midline on the surface of the embryo, to their submergence and organization of the stereotypically positioned notochord. We will also discuss some key open questions. Developmental Dynamics 245:547-557, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Sophie Balmer
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Sonja Nowotschin
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Anna-Katerina Hadjantonakis
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York
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11
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Costello I, Nowotschin S, Sun X, Mould AW, Hadjantonakis AK, Bikoff EK, Robertson EJ. Lhx1 functions together with Otx2, Foxa2, and Ldb1 to govern anterior mesendoderm, node, and midline development. Genes Dev 2016; 29:2108-22. [PMID: 26494787 PMCID: PMC4617976 DOI: 10.1101/gad.268979.115] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Costello et al. demonstrate that Smad4/Eomes-dependent Lhx1 expression in the epiblast marks the entire definitive endoderm lineage, the anterior mesendoderm, and midline progenitors. In proteomic experiments, they characterize a complex comprised of Lhx1, Otx2, and Foxa2 as well as the chromatin-looping protein Ldb1. Gene regulatory networks controlling functional activities of spatially and temporally distinct endodermal cell populations in the early mouse embryo remain ill defined. The T-box transcription factor Eomes, acting downstream from Nodal/Smad signals, directly activates the LIM domain homeobox transcription factor Lhx1 in the visceral endoderm. Here we demonstrate Smad4/Eomes-dependent Lhx1 expression in the epiblast marks the entire definitive endoderm lineage, the anterior mesendoderm, and midline progenitors. Conditional inactivation of Lhx1 disrupts anterior definitive endoderm development and impedes node and midline morphogenesis in part due to severe disturbances in visceral endoderm displacement. Transcriptional profiling and ChIP-seq (chromatin immunoprecipitation [ChIP] followed by high-throughput sequencing) experiments identified Lhx1 target genes, including numerous anterior definitive endoderm markers and components of the Wnt signaling pathway. Interestingly, Lhx1-binding sites were enriched at enhancers, including the Nodal-proximal epiblast enhancer element and enhancer regions controlling Otx2 and Foxa2 expression. Moreover, in proteomic experiments, we characterized a complex comprised of Lhx1, Otx2, and Foxa2 as well as the chromatin-looping protein Ldb1. These partnerships cooperatively regulate development of the anterior mesendoderm, node, and midline cell populations responsible for establishment of the left–right body axis and head formation.
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Affiliation(s)
- Ita Costello
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Sonja Nowotschin
- Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA
| | - Xin Sun
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Arne W Mould
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | | | - Elizabeth K Bikoff
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Elizabeth J Robertson
- The Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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12
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Grego-Bessa J, Bloomekatz J, Castel P, Omelchenko T, Baselga J, Anderson KV. The tumor suppressor PTEN and the PDK1 kinase regulate formation of the columnar neural epithelium. eLife 2016; 5:e12034. [PMID: 26809587 PMCID: PMC4739759 DOI: 10.7554/elife.12034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/02/2015] [Indexed: 01/16/2023] Open
Abstract
Epithelial morphogenesis and stability are essential for normal development and organ homeostasis. The mouse neural plate is a cuboidal epithelium that remodels into a columnar pseudostratified epithelium over the course of 24 hr. Here we show that the transition to a columnar epithelium fails in mutant embryos that lack the tumor suppressor PTEN, although proliferation, patterning and apical-basal polarity markers are normal in the mutants. The Pten phenotype is mimicked by constitutive activation of PI3 kinase and is rescued by the removal of PDK1 (PDPK1), but does not depend on the downstream kinases AKT and mTORC1. High resolution imaging shows that PTEN is required for stabilization of planar cell packing in the neural plate and for the formation of stable apical-basal microtubule arrays. The data suggest that appropriate levels of membrane-associated PDPK1 are required for stabilization of apical junctions, which promotes cell elongation, during epithelial morphogenesis.
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Affiliation(s)
- Joaquim Grego-Bessa
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Joshua Bloomekatz
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Pau Castel
- Human Oncology and Pathogenesis Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Tatiana Omelchenko
- Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
| | - José Baselga
- Human Oncology and Pathogenesis Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
- Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Kathryn V Anderson
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, United States
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13
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Grego-Bessa J, Hildebrand J, Anderson KV. Morphogenesis of the mouse neural plate depends on distinct roles of cofilin 1 in apical and basal epithelial domains. Development 2015; 142:1305-14. [PMID: 25742799 DOI: 10.1242/dev.115493] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The genetic control of mammalian epithelial polarity and dynamics can be studied in vivo at cellular resolution during morphogenesis of the mouse neural tube. The mouse neural plate is a simple epithelium that is transformed into a columnar pseudostratified tube over the course of ∼ 24 h. Apical F-actin is known to be important for neural tube closure, but the precise roles of actin dynamics in the neural epithelium are not known. To determine how the organization of the neural epithelium and neural tube closure are affected when actin dynamics are blocked, we examined the cellular basis of the neural tube closure defect in mouse mutants that lack the actin-severing protein cofilin 1 (CFL1). Although apical localization of the adherens junctions, the Par complex, the Crumbs complex and SHROOM3 is normal in the mutants, CFL1 has at least two distinct functions in the apical and basal domains of the neural plate. Apically, in the absence of CFL1 myosin light chain does not become phosphorylated, indicating that CFL1 is required for the activation of apical actomyosin required for neural tube closure. On the basal side of the neural plate, loss of CFL1 has the opposite effect on myosin: excess F-actin and myosin accumulate and the ectopic myosin light chain is phosphorylated. The basal accumulation of F-actin is associated with the assembly of ectopic basal tight junctions and focal disruptions of the basement membrane, which eventually lead to a breakdown of epithelial organization.
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Affiliation(s)
- Joaquim Grego-Bessa
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Jeffrey Hildebrand
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Kathryn V Anderson
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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14
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Abstract
Humans and other vertebrates exhibit left-right (LR) asymmetric arrangement of the internal organs, and failure to establish normal LR asymmetry leads to internal laterality disorders, including situs inversus and heterotaxy. Situs inversus is complete mirror-imaged arrangement of the internal organs along LR axis, whereas heterotaxy is abnormal arrangement of the internal thoraco-abdominal organs across LR axis of the body, most of which are associated with complex cardiovascular malformations. Both disorders are genetically heterogeneous with reduced penetrance, presumably because of monogenic, polygenic or multifactorial causes. Research in genetics of LR asymmetry disorders has been extremely prolific over the past 17 years, and a series of loci and disease genes involved in situs inversus and heterotaxy have been described. The review highlights the classification, chromosomal abnormalities, pathogenic genes and the possible mechanism of human LR asymmetry disorders.
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15
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Pulina M, Liang D, Astrof S. Shape and position of the node and notochord along the bilateral plane of symmetry are regulated by cell-extracellular matrix interactions. Biol Open 2014; 3:583-90. [PMID: 24928429 PMCID: PMC4154294 DOI: 10.1242/bio.20148243] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The node and notochord (and their equivalents in other species) are essential signaling centers, positioned along the plane of bilateral symmetry in developing vertebrate embryos. However, genes and mechanisms regulating morphogenesis of these structures and their placement along the embryonic midline are not well understood. In this work, we provide the first evidence that the position of the node and the notochord along the bilateral plane of symmetry are under genetic control and are regulated by integrin α5β1 and fibronectin in mice. We found that the shape of the node is often inverted in integrin α5-null and fibronectin-null mutants, and that the positioning of node and the notochord is often skewed away from the perceived plane of embryonic bilateral of symmetry. Our studies also show that the shape and position of the notochord are dependent on the shape and embryonic placement of the node. Our studies suggest that fibronectin regulates the shape of the node by affecting apico-basal polarity of the nodal cells. Taken together, our data indicate that cell–extracellular matrix interactions mediated by integrin α5β1 and fibronectin regulate the geometry of the node as well as the placement of the node and notochord along the plane of bilateral symmetry in the mammalian embryo.
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Affiliation(s)
- Maria Pulina
- Present address: Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065, USA
| | - Dong Liang
- Department of Medicine, Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA Present address: Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065, USA
| | - Sophie Astrof
- Department of Medicine, Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA Present address: Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10065, USA.
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16
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Abstract
Many internal organs develop distinct left and right sides that are essential for their functions. In several vertebrate embryos, motile cilia generate an asymmetric fluid flow that plays an important role in establishing left-right (LR) signaling cascades. These ‘LR cilia’ are found in the ventral node and posterior notochordal plate in mammals, the gastrocoel roof plate in amphibians and Kupffer’s vesicle in teleost fish. I consider these transient ciliated structures as the ‘organ of asymmetry’ that directs LR patterning of the developing embryo. Variations in size and morphology of the organ of asymmetry in different vertebrate species have raised questions regarding the fundamental features that are required for LR determination. Here, I review current models for how LR asymmetry is established in vertebrates, discuss the cellular architecture of the ciliated organ of asymmetry and then propose key features of this organ that are critical for orienting the LR body axis.
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Affiliation(s)
- Jeffrey D Amack
- Department of Cell and Developmental Biology; State University of New York; Upstate Medical University; Syracuse, NY USA
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17
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Abstract
The transforming growth factor-β (TGF-β) system signals via protein kinase receptors and SMAD mediators to regulate a large number of biological processes. Alterations of the TGF-β signalling pathway are implicated in human cancer. Prior to tumour initiation and early during progression, TGF-β acts as a tumour suppressor; however, at later stages, it is often a tumour promoter. Knowledge about the mechanisms involved in TGF-β signal transduction has allowed a better understanding of cancer progression, invasion, metastasis and epithelial-to-mesenchymal transition. Furthermore, several molecular targets with great potential in therapeutic interventions have been identified. This review discusses the TGF-β signalling pathway, its involvement in cancer and current therapeutic approaches.
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18
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Mahaffey JP, Grego-Bessa J, Liem KF, Anderson KV. Cofilin and Vangl2 cooperate in the initiation of planar cell polarity in the mouse embryo. Development 2013; 140:1262-71. [PMID: 23406901 DOI: 10.1242/dev.085316] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The planar cell polarity (PCP; non-canonical Wnt) pathway is required to orient the cells within the plane of an epithelium. Here, we show that cofilin 1 (Cfl1), an actin-severing protein, and Vangl2, a core PCP protein, cooperate to control PCP in the early mouse embryo. Two aspects of planar polarity can be analyzed quantitatively at cellular resolution in the mouse embryo: convergent extension of the axial midline; and posterior positioning of cilia on cells of the node. Analysis of the spatial distribution of brachyury(+) midline cells shows that the Cfl1 mutant midline is normal, whereas Vangl2 mutants have a slightly wider midline. By contrast, midline convergent extension fails completely in Vangl2 Cfl1 double mutants. Planar polarity is required for the posterior positioning of cilia on cells in the mouse node, which is essential for the initiation of left-right asymmetry. Node cilia are correctly positioned in Cfl1 and Vangl2 single mutants, but cilia remain in the center of the cell in Vangl2 Cfl1 double mutants, leading to randomization of left-right asymmetry. In both the midline and node, the defect in planar polarity in the double mutants arises because PCP protein complexes fail to traffic to the apical cell membrane, although other aspects of apical-basal polarity are unaffected. Genetic and pharmacological experiments demonstrate that F-actin remodeling is essential for the initiation, but not maintenance, of PCP. We propose that Vangl2 and cofilin cooperate to target Rab11(+) vesicles containing PCP proteins to the apical membrane during the initiation of planar cell polarity.
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Affiliation(s)
- James P Mahaffey
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10065, USA
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19
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Sutherland MJ, Wang S, Quinn ME, Haaning A, Ware SM. Zic3 is required in the migrating primitive streak for node morphogenesis and left-right patterning. Hum Mol Genet 2013; 22:1913-23. [PMID: 23303524 DOI: 10.1093/hmg/ddt001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In humans, loss-of-function mutations in ZIC3 cause isolated cardiovascular malformations and X-linked heterotaxy, a disorder with abnormal left-right asymmetry of organs. Zic3 null mice recapitulate the human heterotaxy phenotype but also have early gastrulation defects, axial patterning defects and neural tube defects complicating an assessment of the role of Zic3 in cardiac development. Zic3 is expressed ubiquitously during critical stages of left-right patterning but its later expression in the developing heart remains controversial and the molecular mechanism(s) by which it causes heterotaxy are unknown. To define the temporal and spatial requirements, for Zic3 in left-right patterning, we generated conditional Zic3 mice and Zic3-LacZ-BAC reporter mice. The latter provide compelling evidence that Zic3 is expressed in the mouse node and absent in the heart. Conditional deletion using T-Cre identifies a requirement for Zic3 in the primitive streak and migrating mesoderm for proper left-right patterning and cardiac development. In contrast, Zic3 is not required in heart progenitors or the cardiac compartment. In addition, the data demonstrate abnormal node morphogenesis in Zic3 null mice and identify similar node dysplasia when Zic3 was specifically deleted from the migrating mesoderm and primitive streak. These results define the temporal and spatial requirements for Zic3 in node morphogenesis, left-right patterning and cardiac development and suggest the possibility that a requirement for Zic3 in node ultrastructure underlies its role in heterotaxy and laterality disorders.
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Affiliation(s)
- Mardi J Sutherland
- Division of Molecular Cardiovascular Biology, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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20
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Abstract
Epithelial-mesenchymal transition (EMT) is a crucial, evolutionarily conserved process that occurs during development and is essential for shaping embryos. Also implicated in cancer, this morphological transition is executed through multiple mechanisms in different contexts, and studies suggest that the molecular programs governing EMT, albeit still enigmatic, are embedded within developmental programs that regulate specification and differentiation. As we review here, knowledge garnered from studies of EMT during gastrulation, neural crest delamination and heart formation have furthered our understanding of tumor progression and metastasis.
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Affiliation(s)
- Jormay Lim
- Institute of Molecular Cell Biology, ASTAR, 61 Biopolis Drive, Singapore
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21
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Ten Broek CMA, Bakker AJ, Varela-Lasheras I, Bugiani M, Van Dongen S, Galis F. Evo-Devo of the Human Vertebral Column: On Homeotic Transformations, Pathologies and Prenatal Selection. Evol Biol 2012; 39:456-471. [PMID: 23226903 PMCID: PMC3514701 DOI: 10.1007/s11692-012-9196-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022]
Abstract
Homeotic transformations of vertebrae are particularly common in humans and tend to come associated with malformations in a wide variety of organ systems. In a dataset of 1,389 deceased human foetuses and infants a majority had cervical ribs and approximately half of these individuals also had missing twelfth ribs or lumbar ribs. In ~10 % of all cases there was an additional shift of the lumbo-sacral boundary and, hence, homeotic transformations resulted in shifts of at least three vertebral boundaries. We found a strong coupling between the abnormality of the vertebral patterns and the amount and strength of associated malformations, i.e., the longer the disturbance of the vertebral patterning has lasted, the more associated malformations have developed and the more organ systems are affected. The germ layer of origin of the malformations was not significantly associated with the frequency of vertebral patterns. In contrast, we find significant associations with the different developmental mechanisms that are involved in the causation of the malformations, that is, segmentation, neural crest development, left-right patterning, etc. Our results, thus, suggest that locally perceived developmental signals are more important for the developmental outcome than the origin of the cells. The low robustness of vertebral A-P patterning apparent from the large number of homeotic transformations is probably caused by the strong interactivity of developmental processes and the low redundancy of involved morphogens during early organogenesis. Additionally, the early irreversibility of the specification of the A-P identity of vertebrae probably adds to the vulnerability of the process by limiting the possibility for recovery from developmental disturbances. The low developmental robustness of vertebral A-P patterning contrasts with a high robustness of the A-P patterning of the vertebral regions. Not only the order is invariable, also the variation in the number of vertebrae per region is small. This robustness is in agreement with the evolutionary stability of vertebral regions in tetrapods. Finally, we propose a new hypothesis regarding the constancy of the presacral number of vertebrae in mammals.
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Affiliation(s)
- Clara M A Ten Broek
- Group of Evolutionary Ecology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium ; Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
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22
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Alten L, Schuster-Gossler K, Beckers A, Groos S, Ulmer B, Hegermann J, Ochs M, Gossler A. Differential regulation of node formation, nodal ciliogenesis and cilia positioning by Noto and Foxj1. Development 2012; 139:1276-84. [DOI: 10.1242/dev.072728] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The mouse transcription factor Noto is expressed in the node and controls node morphogenesis, formation of nodal cilia and left-right asymmetry. Noto acts upstream of Foxj1, which regulates ciliogenesis in other mouse tissues. However, the significance of Foxj1 for the formation of cilia in the mouse node is unclear; in non-amniote species Foxj1 is required for ciliogenesis in the structures equivalent to the node. Here, we analyzed nodes, nodal cilia and nodal flow in mouse embryos in which we replaced the Noto-coding sequence with that of Foxj1, or in embryos that were deficient for Foxj1. We show that Foxj1 expressed from the Noto locus is functional and restores the formation of structurally normal motile cilia in the absence of Noto. However, Foxj1 is not sufficient for the correct positioning of cilia on the cell surface within the plane of the nodal epithelium, and cannot restore normal node morphology. We also show that Foxj1 is essential for ciliogenesis upstream of Rfx3 in the node. Thus, the function of Foxj1 in vertebrate organs of asymmetry is conserved, and Noto regulates node morphogenesis and the posterior localization of cilia on node cells independently of Foxj1.
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Affiliation(s)
- Leonie Alten
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Karin Schuster-Gossler
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Anja Beckers
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Stephanie Groos
- Department of Cell Biology, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Bärbel Ulmer
- University of Hohenheim, Institute of Zoology (220), Garbenstrasse 30, D-70593 Stuttgart, Germany
| | - Jan Hegermann
- Institute of Functional and Applied Anatomy, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Matthias Ochs
- Institute of Functional and Applied Anatomy, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
| | - Achim Gossler
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
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23
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Vandenberg LN, Levin M. Polarity proteins are required for left-right axis orientation and twin-twin instruction. Genesis 2012; 50:219-34. [PMID: 22086838 PMCID: PMC3294047 DOI: 10.1002/dvg.20825] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/08/2011] [Accepted: 11/09/2011] [Indexed: 01/31/2023]
Abstract
Two main classes of models address the earliest steps of left-right patterning: those postulating that asymmetry is initiated via cilia-driven fluid flow in a multicellular tissue at gastrulation, and those postulating that asymmetry is amplified from intrinsic chirality of individual cells at very early embryonic stages. A recent study revealed that cultured human cells have consistent left-right (LR) biases that are dependent on apical-basal polarity machinery. The ability of single cells to set up asymmetry suggests that cellular chirality could be converted to embryonic laterality by cilia-independent polarity mechanisms in cell fields. To examine the link between cellular polarity and LR patterning in a vertebrate model organism, we probed the roles of apical-basal and planar polarity proteins in the orientation of the LR axis in Xenopus. Molecular loss-of-function targeting these polarity pathways specifically randomizes organ situs independently of contribution to the ciliated organ. Alterations in cell polarity also disrupt tight junction integrity, localization of the LR signaling molecule serotonin, the normally left-sided expression of Xnr-1, and the LR instruction occurring between native and ectopic organizers. We propose that well-conserved polarity complexes are required for LR asymmetry and that cell polarity signals establish the flow of laterality information across the early blastoderm independently of later ciliary functions. genesis 50:219-234, 2012. © 2011 Wiley Periodicals, Inc.
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Affiliation(s)
- Laura N. Vandenberg
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155
| | - Michael Levin
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155
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24
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Kevelam SHG, van Harssel JJT, van der Zwaag B, Smeets HJM, Paulussen ADC, Lichtenbelt KD. A patient with a mild holoprosencephaly spectrum phenotype and heterotaxy and a 1.3 Mb deletion encompassing GLI2. Am J Med Genet A 2011; 158A:166-73. [PMID: 22106008 DOI: 10.1002/ajmg.a.34350] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 09/04/2011] [Indexed: 11/12/2022]
Abstract
Loss-of-function mutations of GLI2 are associated with features at the mild end of the holoprosencephaly spectrum, including abnormal pituitary gland formation and/or function, and craniofacial abnormalities. In addition patients may have branchial arch anomalies and polydactyly. Large, microscopically visible, interstitial deletions spanning 2q14.2 have been reported in patients with multiple congenital anomalies and intellectual disability. We report here on a patient with a mild holoprosencephaly spectrum phenotype (bilateral cleft lip and palate and abnormal pituitary gland formation with panhypopituitarism) and normal psychomotor development, who was found to carry a 1.3 Mb submicroscopic heterozygous deletion in 2q14.2, encompassing the GLI2 gene. We review the genotype and phenotype of previously published probands with GLI2 aberrations. Our findings confirm the association of haploinsufficiency of GLI2 and mild HPE spectrum features. Consistent with prior reports, we observed incomplete penetrance of the deletion in the family, illustrating the multifactorial etiology of holoprosencephaly spectrum features. In addition to the holoprosencephaly spectrum features, the proband had heterotaxy of the abdominal organs. Mutations in the known heterotaxy genes (NODAL, ZIC3 and CFC1) were excluded. The deletion contains five genes, in addition to GLI2, including the EPB4.1l5 gene. Based on findings in Epb4.1l5 mutant mice we hypothesize that Epb4.1l5 is a candidate gene for the heterotaxy observed in the proband.
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Affiliation(s)
- Sietske H G Kevelam
- Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands.
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25
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Migeotte I, Grego-Bessa J, Anderson KV. Rac1 mediates morphogenetic responses to intercellular signals in the gastrulating mouse embryo. Development 2011; 138:3011-20. [PMID: 21693517 DOI: 10.1242/dev.059766] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The establishment of the mammalian body plan depends on signal-regulated cell migration and adhesion, processes that are controlled by the Rho family of GTPases. Here we use a conditional allele of Rac1, the only Rac gene expressed early in development, to define its roles in the gastrulating mouse embryo. Embryos that lack Rac1 in the epiblast (Rac1Δepi) initiate development normally: the signaling pathways required for gastrulation are active, definitive endoderm and all classes of mesoderm are specified, and the neural plate is formed. After the initiation of gastrulation, Rac1Δepi embryos have an enlarged primitive streak, make only a small amount of paraxial mesoderm, and the lateral anlage of the heart do not fuse at the midline. Because these phenotypes are also seen in Nap1 mutants, we conclude that Rac1 acts upstream of the Nap1/WAVE complex to promote migration of the nascent mesoderm. In addition to migration phenotypes, Rac1Δepi cells fail to adhere to matrix, which leads to extensive cell death. Cell death is largely rescued in Rac1Δepi mutants that are heterozygous for a null mutation in Pten, providing evidence that Rac1 is required to link signals from the basement membrane to activation of the PI3K-Akt pathway in vivo. Surprisingly, the frequency of apoptosis is greater in the anterior half of the embryo, suggesting that cell survival can be promoted either by matrix adhesion or by signals from the posterior primitive streak. Rac1 also has essential roles in morphogenesis of the posterior notochordal plate (the node) and the midline.
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Affiliation(s)
- Isabelle Migeotte
- Developmental Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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26
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Pulina MV, Hou SY, Mittal A, Julich D, Whittaker CA, Holley SA, Hynes RO, Astrof S. Essential roles of fibronectin in the development of the left-right embryonic body plan. Dev Biol 2011; 354:208-20. [PMID: 21466802 DOI: 10.1016/j.ydbio.2011.03.026] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 03/14/2011] [Accepted: 03/28/2011] [Indexed: 10/18/2022]
Abstract
Studies in Xenopus laevis suggested that cell-extracellular matrix (ECM) interactions regulate the development of the left-right axis of asymmetry; however, the identities of ECM components and their receptors important for this process have remained unknown. We discovered that FN is required for the establishment of the asymmetric gene expression pattern in early mouse embryos by regulating morphogenesis of the node, while cellular fates of the nodal cells, canonical Wnt and Shh signaling within the node were not perturbed by the absence of FN. FN is also required for the expression of Lefty 1/2 and activation of SMADs 2 and 3 at the floor plate, while cell fate specification of the notochord and the floor plate, as well as signaling within and between these two embryonic organizing centers remained intact in FN-null mutants. Furthermore, our experiments indicate that a major cell surface receptor for FN, integrin α5β1, is also required for the development of the left-right asymmetry, and that this requirement is evolutionarily conserved in fish and mice. Taken together, our studies demonstrate the requisite role for a structural ECM protein and its integrin receptor in the development of the left-right axis of asymmetry in vertebrates.
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Affiliation(s)
- Maria V Pulina
- Weill Cornell Medical College, Department of Medicine, Division of Cardiology, New York, NY, USA
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