1
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Petri N, Nordbrink R, Tsikolia N, Kremnyov S. Abnormal left-right organizer and laterality defects in Xenopus embryos after formin inhibitor SMIFH2 treatment. PLoS One 2022; 17:e0275164. [PMCID: PMC9639825 DOI: 10.1371/journal.pone.0275164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 09/12/2022] [Indexed: 11/09/2022] Open
Abstract
Left-right symmetry breaking in most studied vertebrates makes use of so-called leftward flow, a mechanism which was studied in detail especially in mouse and Xenopus laevis embryos and is based on rotation of monocilia on specialized epithelial surface designated as left-right organizer or laterality coordinator. However, it has been argued that prior to emergence of leftward flow an additional mechanism operates during early cleavage stages in Xenopus embryo which is based on cytoskeletal processes. Evidence in favour of this early mechanism was supported by left-right abnormalities after chemical inhibition of cytoskeletal protein formin. Here we analyzed temporal dimension of this effect in detail and found that reported abnormalities arise only after treatment at gastrula-neurula stages, i.e. just prior to and during the operation of left-right organizer. Moreover, molecular and morphological analysis of the left-right organizer reveals its abnormal development. Our results strongly indicate that left-right abnormalities reported after formin inhibition cannot serve as support of models based on early symmetry breaking event in Xenopus embryo.
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Affiliation(s)
- Natalia Petri
- Department of Embryology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Rhea Nordbrink
- Anatomy and Embryology, University Medicine Göttingen, Göttingen, Germany
| | - Nikoloz Tsikolia
- Anatomy and Embryology, University Medicine Göttingen, Göttingen, Germany
- * E-mail: (NT); (SK)
| | - Stanislav Kremnyov
- Department of Embryology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
- Laboratory of Morphogenesis Evolution, Koltzov Institute of Developmental Biology RAS, Moscow, Russia
- * E-mail: (NT); (SK)
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2
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Boer LL, Schepens-Franke AN, Oostra RJ. Two is a Crowd: Two is a Crowd: On the Enigmatic Etiopathogenesis of Conjoined Twinning. Clin Anat 2019; 32:722-741. [PMID: 31001856 PMCID: PMC6849862 DOI: 10.1002/ca.23387] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 04/16/2019] [Indexed: 12/31/2022]
Abstract
In this article, we provide a comprehensive overview of multiple facets in the puzzling genesis of symmetrical conjoined twins. The etiopathogenesis of conjoined twins remains matter for ongoing debate and is currently cited-in virtually every paper on conjoined twins-as partial fission or secondary fusion. Both theories could potentially be extrapolated from embryological adjustments exclusively seen in conjoined twins. Adoption of these, seemingly factual, theoretical proposals has (unconsciously) resulted in crystallized patterns of verbal and graphic representations concerning the enigmatic genesis of conjoined twins. Critical evaluation on their plausibility and solidity remains however largely absent. As it appears, both the fission and fusion theories cannot be applied to the full range of conjunction possibilities and thus remain matter for persistent inconclusiveness. We propose that initial duplication of axially located morphogenetic potent primordia could be the initiating factor in the genesis of ventrally, laterally, and caudally conjoined twins. The mutual position of two primordia results in neo-axial orientation and/or interaction aplasia. Both these embryological adjustments result in conjunction patterns that may seemingly appear as being caused by fission or fusion. However, as we will substantiate, neither fission nor fusion are the cause of most conjoined twinning types; rather what is interpreted as fission or fusion is actually the result of the twinning process itself. Furthermore, we will discuss the currently held views on the origin of conjoined twins and its commonly assumed etiological correlation with monozygotic twinning. Finally, considerations are presented which indicate that the dorsal conjunction group is etiologically and pathogenetically different from other symmetric conjoined twins. This leads us to propose that dorsally united twins could actually be caused by secondary fusion of two initially separate monozygotic twins. An additional reason for the ongoing etiopathogenetic debate on the genesis of conjoined twins is because different types of conjoined twins are classically placed in one overarching receptacle, which has hindered the quest for answers. Clin. Anat. 32:722-741, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Lucas L Boer
- Department of Anatomy and Museum for Anatomy and Pathology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Annelieke N Schepens-Franke
- Department of Anatomy and Museum for Anatomy and Pathology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Roelof Jan Oostra
- Department of Medical Biology, Section Clinical Anatomy & Embryology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Bérard A, Levin M, Sadler T, Healy D. Selective Serotonin Reuptake Inhibitor Use During Pregnancy and Major Malformations: The Importance of Serotonin for Embryonic Development and the Effect of Serotonin Inhibition on the Occurrence of Malformations. Bioelectricity 2019; 1:18-29. [PMID: 34471805 DOI: 10.1089/bioe.2018.0003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Bioelectric signaling is transduced by neurotransmitter pathways in many cell types. One of the key mediators of bioelectric control mechanisms is serotonin, and its transporter SERT, which is targeted by a broad class of blocker drugs (selective serotonin reuptake inhibitors [SSRIs]). Studies showing an increased risk of multiple malformations associated with gestational use of SSRI have been accumulating but debate remains on whether SSRI as a class has the potential to generate these malformations. This review highlights the importance of serotonin for embryonic development; the effect of serotonin inhibition during early pregnancy on the occurrence of multiple diverse malformations that have been shown to occur in human pregnancies; that the risks outweigh the benefits of SSRI use during gestation in populations of mild to moderately depressed pregnant women, which encompass the majority of pregnant depressed women; and that the malformations seen in human pregnancies constitute a pattern of malformations consistent with the known mechanisms of action of SSRIs. We present at least three mechanisms by which SSRI can affect development. These studies highlight the relevance of basic bioelectric and neurotransmitter mechanism for biomedicine.
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Affiliation(s)
- Anick Bérard
- Faculty of Pharmacy, University of Montreal; Research Center, CHU Sainte-Justine, Montreal, Quebec, Canada
| | - Michael Levin
- Allen Discovery Center at Tufts University, Department of Biology, Medford, Massachusetts
| | - Thomas Sadler
- Department of Pediatrics, School of Medicine, University of Utah, Salt Lake City, Utah
| | - David Healy
- Department of Psychiatry, Hergest Unit, Bangor, United Kingdom
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4
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Tisler M, Schweickert A, Blum M. Xenopus, an ideal model organism to study laterality in conjoined twins. Genesis 2017; 55. [PMID: 28132423 DOI: 10.1002/dvg.22993] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 11/02/2016] [Accepted: 11/04/2016] [Indexed: 11/11/2022]
Abstract
Conjoined twins occur at low frequency in all vertebrates including humans. Many twins fused at the chest or abdomen display a very peculiar laterality defect: while the left twin is normal with respect to asymmetric organ morphogenesis and placement (situs solitus), the organ situs is randomized in right twins. Although this phenomenon has fascinated already some of the founders of experimental embryology in the 19th and early 20th century, such as Dareste, Fol, Warynsky and Spemann, its embryological basis has remained enigmatic. Here we summarize historical experiments and interpretations as well as current models, argue that the frog Xenopus is the only vertebrate model organism to tackle the issue, and outline suitable experiments to address the question of twin laterality in the context of cilia-based symmetry breakage.
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Affiliation(s)
- Matthias Tisler
- University of Hohenheim, Institute of Zoology, Stuttgart, D-70593, Germany
| | | | - Martin Blum
- University of Hohenheim, Institute of Zoology, Stuttgart, D-70593, Germany
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5
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Tisler M, Thumberger T, Schneider I, Schweickert A, Blum M. Leftward Flow Determines Laterality in Conjoined Twins. Curr Biol 2017; 27:543-548. [PMID: 28190730 DOI: 10.1016/j.cub.2016.12.049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 12/21/2016] [Accepted: 12/22/2016] [Indexed: 02/02/2023]
Abstract
Conjoined twins fused at the thorax display an enigmatic left-right defect: although left twins are normal, laterality is disturbed in one-half of right twins [1-3]. Molecularly, this randomization corresponds to a lack of asymmetric Nodal cascade induction in right twins [4]. We studied leftward flow [5, 6] at the left-right organizer (LRO) [7, 8] in thoracopagus twins in Xenopus, which displayed a duplicated, fused, and ciliated LRO. Cilia were motile and produced a leftward flow from the right LRO margin of the right to the left margin of the left twin. Motility was required for correct laterality in left twins, as knockdown of dynein motor dnah9 prevented Nodal cascade induction. Nodal was rescued by parallel knockdown of the inhibitor dand5 [9, 10] on the left side of the left twin. Lack of Nodal induction in the right twin, despite the presence of flow, was due to insufficient suppression of dand5. Knockdown of dand5 at the center of the fused LRO resulted in asymmetric Nodal cascade induction in the right twin as well. Manipulation of leftward flow and dand5 in a targeted and sided manner induced the Nodal cascade in a predictable manner, in the left twin, the right one, both, or neither. Laterality in conjoined twins thus was determined by cilia-driven leftward fluid flow like in single embryos, which solves a century-old riddle, as the phenomenon was already studied by some of the founders of experimental embryology, including Dareste [11], Fol and Warynsky [12], and Spemann and Falkenberg [13] (reviewed in [14]).
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Affiliation(s)
- Matthias Tisler
- Institute of Zoology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany
| | - Thomas Thumberger
- Institute of Zoology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany
| | - Isabelle Schneider
- Institute of Zoology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany
| | - Axel Schweickert
- Institute of Zoology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany
| | - Martin Blum
- Institute of Zoology, University of Hohenheim, Garbenstrasse 30, 70593 Stuttgart, Germany.
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6
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Funk RHW. Endogenous electric fields as guiding cue for cell migration. Front Physiol 2015; 6:143. [PMID: 26029113 PMCID: PMC4429568 DOI: 10.3389/fphys.2015.00143] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 04/21/2015] [Indexed: 12/17/2022] Open
Abstract
This review covers two topics: (1) "membrane potential of low magnitude and related electric fields (bioelectricity)" and (2) "cell migration under the guiding cue of electric fields (EF)."Membrane potentials for this "bioelectricity" arise from the segregation of charges by special molecular machines (pumps, transporters, ion channels) situated within the plasma membrane of each cell type (including eukaryotic non-neural animal cells). The arising patterns of ion gradients direct many cell- and molecular biological processes such as embryogenesis, wound healing, regeneration. Furthermore, EF are important as guiding cues for cell migration and are often overriding chemical or topographic cues. In osteoblasts, for instance, the directional information of EF is captured by charged transporters on the cell membrane and transferred into signaling mechanisms that modulate the cytoskeleton and motor proteins. This results in a persistent directional migration along an EF guiding cue. As an outlook, we discuss questions concerning the fluctuation of EF and the frequencies and mapping of the "electric" interior of the cell. Another exciting topic for further research is the modeling of field concepts for such distant, non-chemical cellular interactions.
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7
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Blackiston DJ, Anderson GM, Rahman N, Bieck C, Levin M. A novel method for inducing nerve growth via modulation of host resting potential: gap junction-mediated and serotonergic signaling mechanisms. Neurotherapeutics 2015; 12:170-84. [PMID: 25449797 PMCID: PMC4322068 DOI: 10.1007/s13311-014-0317-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A major goal of regenerative medicine is to restore the function of damaged or missing organs through the implantation of bioengineered or donor-derived components. It is necessary to understand the signals and cues necessary for implanted structures to innervate the host, as organs devoid of neural connections provide little benefit to the patient. While developmental studies have identified neuronal pathfinding molecules required for proper patterning during embryogenesis, strategies to initiate innervation in structures transplanted at later times or alternate locations remain limited. Recent work has identified membrane resting potential of nerves as a key regulator of growth cone extension or arrest. Here, we identify a novel role of bioelectricity in the generation of axon guidance cues, showing that neurons read the electric topography of surrounding cells, and demonstrate these cues can be leveraged to initiate sensory organ transplant innervation. Grafts of fluorescently labeled embryological eye primordia were used to produce ectopic eyes in Xenopus laevis tadpoles. Depolarization of host tissues through anion channel activation or other means led to a striking hyperinnervation of the body by these ectopic eyes. A screen of possible transduction mechanisms identified serotonergic signaling to be essential for hyperinnervation to occur, and our molecular data suggest a possible model of bioelectrical control of the distribution of neurotransmitters that guides nerve growth. Together, these results identify the molecular components of bioelectrical signaling among cells that regulates axon guidance, and suggest novel biomedical and bioengineering strategies for triggering neuronal outgrowth using ion channel drugs already approved for human use.
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Affiliation(s)
- Douglas J. Blackiston
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155 USA
| | - George M. Anderson
- Yale Child Study Center and Department of Laboratory Medicine, Yale University School of Medicine, 230 S. Frontage Rd., New Haven, CT 06519 USA
| | - Nikita Rahman
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155 USA
| | - Clara Bieck
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155 USA
| | - Michael Levin
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155 USA
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8
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Blum M, Schweickert A, Vick P, Wright CVE, Danilchik MV. Symmetry breakage in the vertebrate embryo: when does it happen and how does it work? Dev Biol 2014; 393:109-23. [PMID: 24972089 PMCID: PMC4481729 DOI: 10.1016/j.ydbio.2014.06.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 06/08/2014] [Accepted: 06/17/2014] [Indexed: 10/25/2022]
Abstract
Asymmetric development of the vertebrate embryo has fascinated embryologists for over a century. Much has been learned since the asymmetric Nodal signaling cascade in the left lateral plate mesoderm was detected, and began to be unraveled over the past decade or two. When and how symmetry is initially broken, however, has remained a matter of debate. Two essentially mutually exclusive models prevail. Cilia-driven leftward flow of extracellular fluids occurs in mammalian, fish and amphibian embryos. A great deal of experimental evidence indicates that this flow is indeed required for symmetry breaking. An alternative model has argued, however, that flow simply acts as an amplification step for early asymmetric cues generated by ion flux during the first cleavage divisions. In this review we critically evaluate the experimental basis of both models. Although a number of open questions persist, the available evidence is best compatible with flow-based symmetry breakage as the archetypical mode of symmetry breakage.
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Affiliation(s)
- Martin Blum
- University of Hohenheim, Institute of Zoology (220), Garbenstrasse 30, D-70593 Stuttgart, Germany.
| | - Axel Schweickert
- University of Hohenheim, Institute of Zoology (220), Garbenstrasse 30, D-70593 Stuttgart, Germany
| | - Philipp Vick
- University of Hohenheim, Institute of Zoology (220), Garbenstrasse 30, D-70593 Stuttgart, Germany
| | - Christopher V E Wright
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232-0494, USA
| | - Michael V Danilchik
- Department of Integrative Biosciences, Oregon Health & Science University, Portland, OR 97239-3098, USA
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9
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Wertelecki W, Yevtushok L, Zymak-Zakutnia N, Wang B, Sosyniuk Z, Lapchenko S, Hobart HH. Blastopathies and microcephaly in a Chornobyl impacted region of Ukraine. Congenit Anom (Kyoto) 2014; 54:125-49. [PMID: 24666273 PMCID: PMC4233949 DOI: 10.1111/cga.12051] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 01/05/2014] [Indexed: 12/17/2022]
Abstract
This population-based descriptive epidemiology study demonstrates that rates of conjoined twins, teratomas, neural tube defects, microcephaly, and microphthalmia in the Rivne province of Ukraine are among the highest in Europe. The province is 200 km distant from the Chornobyl site and its northern half, a region known as Polissia, is significantly polluted by ionizing radiation. The rates of neural tube defects, microcephaly and microphthalmia in Polissia are statistically significantly higher than in the rest of the province. A survey of at-birth head size showed that values were statistically smaller in males and females born in one Polissia county than among neonates born in the capital city. These observations provide clues for confirmatory and cause-effect prospective investigations. The strength of this study stems from a reliance on international standards prevalent in Europe and a decade-long population-based surveillance of congenital malformations in two distinct large populations. The limitations of this study, as those of other descriptive epidemiology investigations, is that identified cause-effect associations require further assessment by specific prospective investigations designed to address specific teratogenic factors.
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Affiliation(s)
- Wladimir Wertelecki
- Department of Medical Genetics, College of Medicine, University of South AlabamaMobile, Alabama, USA
- OMNI-Net for Children International Charitable FundRivne, Rivne Province, Ukraine
| | - Lyubov Yevtushok
- OMNI-Net for Children International Charitable FundRivne, Rivne Province, Ukraine
- Rivne Regional Medical Diagnostic CenterRivne, Rivne Province, Ukraine
| | - Natalia Zymak-Zakutnia
- OMNI-Net for Children International Charitable FundRivne, Rivne Province, Ukraine
- Khmelnytsky Perinatal CenterKhmelnytsky, Khmelnytsky Province, Ukraine
| | - Bin Wang
- Department of Mathematics and Statisitcs, University of South AlabamaMobile, Alabama, USA
| | - Zoriana Sosyniuk
- OMNI-Net for Children International Charitable FundRivne, Rivne Province, Ukraine
- Rivne Regional Medical Diagnostic CenterRivne, Rivne Province, Ukraine
| | - Serhiy Lapchenko
- OMNI-Net for Children International Charitable FundRivne, Rivne Province, Ukraine
| | - Holly H Hobart
- Cyto-Genetics Laboratory, Department of Pathology, University of Mississippi Medical CenterJackson, Mississippi, USA
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10
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Stephen LA, Johnson EJ, Davis GM, McTeir L, Pinkham J, Jaberi N, Davey MG. The chicken left right organizer has nonmotile cilia which are lost in a stage-dependent manner in the talpid(3) ciliopathy. Genesis 2014; 52:600-13. [PMID: 24700455 PMCID: PMC4314677 DOI: 10.1002/dvg.22775] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 03/23/2014] [Accepted: 03/29/2014] [Indexed: 01/31/2023]
Abstract
Motile cilia are an essential component of the mouse, zebrafish, and Xenopus laevis Left Right Organizers, generating nodal flow and allowing the reception and transduction of mechanosensory signals. Nonmotile primary cilia are also an important component of the Left Right Organizer's chemosensory mechanism. It has been proposed in the chicken that signaling in Hensen's node, the Left Right Organizer of the chicken, is independent of cilia, based on a lack of evidence of motile cilia or nodal flow. It is speculated that the talpid3 chicken mutant, which has normal left–right patterning despite lacking cilia at many stages of development, is proof of this hypothesis. Here, we examine the evidence for cilia in Hensen's node and find that although cilia are present; they are likely to be immotile and incapable of generating nodal flow. Furthermore, we find that early planar cell polarity patterning and ciliogenesis is normal in early talpid3 chicken embryos. We conclude that patterning and development of the early talpid3 chicken is normal, but not necessarily independent of cilia. Although it appears that Hensen's node does not require motile cilia or the generation of motile flow, there may remain a requirement for cilia in the transduction of SHH signaling.
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Affiliation(s)
- Louise A Stephen
- Division of Developmental Biology, The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, United Kingdom
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11
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Tingler M, Ott T, Tözser J, Kurz S, Getwan M, Tisler M, Schweickert A, Blum M. Symmetry breakage in the frog Xenopus
: Role of Rab11 and the ventral-right blastomere. Genesis 2014; 52:588-99. [DOI: 10.1002/dvg.22766] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/12/2014] [Accepted: 02/25/2014] [Indexed: 02/04/2023]
Affiliation(s)
- Melanie Tingler
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Tim Ott
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Janos Tözser
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Sabrina Kurz
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Maike Getwan
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Matthias Tisler
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Axel Schweickert
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
| | - Martin Blum
- Institute of Zoology, University of Hohenheim; Stuttgart D-70593 Germany
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12
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Su YH. Telling left from right: Left-right asymmetric controls in sea urchins. Genesis 2014; 52:269-78. [DOI: 10.1002/dvg.22739] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/20/2013] [Accepted: 12/31/2013] [Indexed: 12/30/2022]
Affiliation(s)
- Yi-Hsien Su
- Institute of Cellular and Organismic Biology; Academia Sinica; Nankang Taipei Taiwan
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13
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VANDENBERG LAURAN, BLACKISTON DOUGLASJ, REA ADAMC, DORE TIMOTHYM, LEVIN MICHAEL. Left-right patterning in Xenopus conjoined twin embryos requires serotonin signaling and gap junctions. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2014; 58:799-809. [PMID: 25896280 PMCID: PMC10471180 DOI: 10.1387/ijdb.140215ml] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
A number of processes operating during the first cell cleavages enable the left-right (LR) axis to be consistently oriented during Xenopus laevis development. Prior work showed that secondary organizers induced in frog embryos after cleavage stages (i.e. conjoined twins arising from ectopic induced primary axes) correctly pattern their own LR axis only when a primary (early) organizer is also present. This instructive effect confirms the unique LR patterning functions that occur during early embryogenesis, but leaves open the question: which mechanisms that operate during early stages are also involved in the orientation of later-induced organizers? We sought to distinguish the two phases of LR patterning in secondary organizers (LR patterning of the primary twin and the later transfer of this information to the secondary twin) by perturbing only the latter process. Here, we used reagents that do not affect primary LR patterning at the time secondary organizers form to inhibit each of 4 mechanisms in the induced twin. Using pharmacological, molecular-genetic, and photo-chemical tools, we show that serotonergic and gap-junctional signaling, but not proton or potassium flows, are required for the secondary organizer to appropriately pattern its LR axis in a multicellular context. We also show that consistently-asymmetric gene expression begins prior to ciliary flow. Together, our data highlight the importance of physiological signaling in the propagation of cleavage-derived LR orientation to multicellular cell fields.
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Affiliation(s)
- LAURA N. VANDENBERG
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
- Department of Public Health, Division of Environmental Health Sciences, University of Massachusetts – Amherst, Amherst, MA, USA
| | - DOUGLAS J. BLACKISTON
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
| | - ADAM C. REA
- Department of Chemistry, University of Georgia, Athens, GA, USA and
| | - TIMOTHY M. DORE
- Department of Chemistry, University of Georgia, Athens, GA, USA and
- New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - MICHAEL LEVIN
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
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14
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Vandenberg LN, Lemire JM, Levin M. It's never too early to get it Right: A conserved role for the cytoskeleton in left-right asymmetry. Commun Integr Biol 2013; 6:e27155. [PMID: 24505508 PMCID: PMC3912007 DOI: 10.4161/cib.27155] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 01/08/2023] Open
Abstract
For centuries, scientists and physicians have been captivated by the consistent left-right (LR) asymmetry of the heart, viscera, and brain. A recent study implicated tubulin proteins in establishing laterality in several experimental models, including asymmetric chemosensory receptor expression in C. elegans neurons, polarization of HL-60 human neutrophil-like cells in culture, and asymmetric organ placement in Xenopus. The same mutations that randomized asymmetry in these diverse systems also affect chirality in Arabidopsis, revealing a remarkable conservation of symmetry-breaking mechanisms among kingdoms. In Xenopus, tubulin mutants only affected LR patterning very early, suggesting that this axis is established shortly after fertilization. This addendum summarizes and extends the knowledge of the cytoskeleton's role in the patterning of the LR axis. Results from many species suggest a conserved role for the cytoskeleton as the initiator of asymmetry, and indicate that symmetry is first broken during early embryogenesis by an intracellular process.
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Affiliation(s)
- Laura N Vandenberg
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA ; Current affiliation: Department of Public Health; Division of Environmental Health Sciences; University of Massachusetts, Amherst; Amherst, MA USA
| | - Joan M Lemire
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA
| | - Michael Levin
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA
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Vandenberg LN, Levin M. A unified model for left-right asymmetry? Comparison and synthesis of molecular models of embryonic laterality. Dev Biol 2013; 379:1-15. [PMID: 23583583 PMCID: PMC3698617 DOI: 10.1016/j.ydbio.2013.03.021] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 03/15/2013] [Accepted: 03/22/2013] [Indexed: 12/31/2022]
Abstract
Understanding how and when the left-right (LR) axis is first established is a fundamental question in developmental biology. A popular model is that the LR axis is established relatively late in embryogenesis, due to the movement of motile cilia and the resultant directed fluid flow during late gastrulation/early neurulation. Yet, a large body of evidence suggests that biophysical, molecular, and bioelectrical asymmetries exist much earlier in development, some as early as the first cell cleavage after fertilization. Alternative models of LR asymmetry have been proposed that accommodate these data, postulating that asymmetry is established due to a chiral cytoskeleton and/or the asymmetric segregation of chromatids. There are some similarities, and many differences, in how these various models postulate the origin and timing of symmetry breaking and amplification, and these events' linkage to the well-conserved subsequent asymmetric transcriptional cascades. This review examines experimental data that lend strong support to an early origin of LR asymmetry, yet are also consistent with later roles for cilia in the amplification of LR pathways. In this way, we propose that the various models of asymmetry can be unified: early events are needed to initiate LR asymmetry, and later events could be utilized by some species to maintain LR-biases. We also present an alternative hypothesis, which proposes that individual embryos stochastically choose one of several possible pathways with which to establish their LR axis. These two hypotheses are both tractable in appropriate model species; testing them to resolve open questions in the field of LR patterning will reveal interesting new biology of wide relevance to developmental, cell, and evolutionary biology.
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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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Vandenberg LN, Morrie RD, Seebohm G, Lemire JM, Levin M. Rab GTPases are required for early orientation of the left-right axis in Xenopus. Mech Dev 2013; 130:254-71. [PMID: 23354119 PMCID: PMC10676213 DOI: 10.1016/j.mod.2012.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 11/14/2012] [Accepted: 11/16/2012] [Indexed: 02/04/2023]
Abstract
The earliest steps of left-right (LR) patterning in Xenopus embryos are driven by biased intracellular transport that ensures a consistently asymmetric localization of maternal ion channels and pumps in the first 2-4 blastomeres. The subsequent differential net efflux of ions by these transporters generates a bioelectrical asymmetry; this LR voltage gradient redistributes small signaling molecules along the LR axis that later regulate transcription of the normally left-sided Nodal. This system thus amplifies single cell chirality into a true left-right asymmetry across multi-cellular fields. Studies using molecular-genetic gain- and loss-of-function reagents have characterized many of the steps involved in this early pathway in Xenopus. Yet one key question remains: how is the chiral cytoskeletal architecture interpreted to localize ion transporters to the left or right side? Because Rab GTPases regulate nearly all aspects of membrane trafficking, we hypothesized that one or more Rab proteins were responsible for the directed, asymmetric shuttling of maternal ion channel or pump proteins. After performing a screen using dominant negative and wildtype (overexpressing) mRNAs for four different Rabs, we found that alterations in Rab11 expression randomize both asymmetric gene expression and organ situs. We also demonstrated that the asymmetric localization of two ion transporter subunits requires Rab11 function, and that Rab11 is closely associated with at least one of these subunits. Yet, importantly, we found that endogenous Rab11 mRNA and protein are expressed symmetrically in the early embryo. We conclude that Rab11-mediated transport is responsible for the movement of cargo within early blastomeres, and that Rab11 expression is required throughout the early embryo for proper LR patterning.
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Affiliation(s)
- Laura N. Vandenberg
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University Medford, MA 02155, United States
| | - Ryan D. Morrie
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University Medford, MA 02155, United States
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, Myocellular Electophysiology Group, University Hospital Münster, D-48149 Münster, Germany
| | - Joan M. Lemire
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University Medford, MA 02155, United States
| | - Michael Levin
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University Medford, MA 02155, United States
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Vandenberg LN, Lemire JM, Levin M. Serotonin has early, cilia-independent roles in Xenopus left-right patterning. Dis Model Mech 2013; 6:261-8. [PMID: 22899856 PMCID: PMC3529356 DOI: 10.1242/dmm.010256] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 08/07/2012] [Indexed: 12/16/2022] Open
Abstract
Consistent left-right (LR) patterning of the heart and viscera is a crucial part of normal embryogenesis. Because errors of laterality form a common class of birth defects, it is important to understand the molecular mechanisms and stage at which LR asymmetry is initiated. Frog embryos are a system uniquely suited to analysis of the mechanisms involved in orientation of the LR axis because of the many genetic and pharmacological tools available for use and the fate-map and accessibility of early blastomeres. Two major models exist for the origin of LR asymmetry and both implicate pre-nervous serotonergic signaling. In the first, the charged serotonin molecule is instructive for LR patterning; it is redistributed asymmetrically along the LR axis and signals intracellularly on the right side at cleavage stages. A second model suggests that serotonin is a permissive factor required to specify the dorsal region of the embryo containing chiral cilia that generate asymmetric fluid flow during neurulation, a much later process. We performed theory-neutral experiments designed to distinguish between these models. The results uniformly support a role for serotonin in the cleavage-stage embryo, long before the appearance of cilia, in ventral right blastomeres that do not contribute to the ciliated organ.
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Affiliation(s)
- Laura N. Vandenberg
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155, USA
| | - Joan M. Lemire
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155, USA
| | - Michael Levin
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155, USA
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