1
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McMillen P, Levin M. Collective intelligence: A unifying concept for integrating biology across scales and substrates. Commun Biol 2024; 7:378. [PMID: 38548821 PMCID: PMC10978875 DOI: 10.1038/s42003-024-06037-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 03/11/2024] [Indexed: 04/01/2024] Open
Abstract
A defining feature of biology is the use of a multiscale architecture, ranging from molecular networks to cells, tissues, organs, whole bodies, and swarms. Crucially however, biology is not only nested structurally, but also functionally: each level is able to solve problems in distinct problem spaces, such as physiological, morphological, and behavioral state space. Percolating adaptive functionality from one level of competent subunits to a higher functional level of organization requires collective dynamics: multiple components must work together to achieve specific outcomes. Here we overview a number of biological examples at different scales which highlight the ability of cellular material to make decisions that implement cooperation toward specific homeodynamic endpoints, and implement collective intelligence by solving problems at the cell, tissue, and whole-organism levels. We explore the hypothesis that collective intelligence is not only the province of groups of animals, and that an important symmetry exists between the behavioral science of swarms and the competencies of cells and other biological systems at different scales. We then briefly outline the implications of this approach, and the possible impact of tools from the field of diverse intelligence for regenerative medicine and synthetic bioengineering.
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Affiliation(s)
- Patrick McMillen
- Department of Biology, Tufts University, Medford, MA, 02155, USA
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA
| | - Michael Levin
- Department of Biology, Tufts University, Medford, MA, 02155, USA.
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA.
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, 02115, USA.
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2
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Shylo NA, Smith SE, Price AJ, Guo F, McClain M, Trainor PA. Morphological changes and two Nodal paralogs drive left-right asymmetry in the squamate veiled chameleon ( C. calyptratus). Front Cell Dev Biol 2023; 11:1132166. [PMID: 37113765 PMCID: PMC10126504 DOI: 10.3389/fcell.2023.1132166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Accepted: 02/23/2023] [Indexed: 04/29/2023] Open
Abstract
The ancestral mode of left-right (L-R) patterning involves cilia in the L-R organizer. However, the mechanisms regulating L-R patterning in non-avian reptiles remains an enigma, since most squamate embryos are undergoing organogenesis at oviposition. In contrast, veiled chameleon (Chamaeleo calyptratus) embryos are pre-gastrula at oviposition, making them an excellent organism for studying L-R patterning evolution. Here we show that veiled chameleon embryos lack motile cilia at the time of L-R asymmetry establishment. Thus, the loss of motile cilia in the L-R organizers is a synapomorphy of all reptiles. Furthermore, in contrast to avians, geckos and turtles, which have one Nodal gene, veiled chameleon exhibits expression of two paralogs of Nodal in the left lateral plate mesoderm, albeit in non-identical patterns. Using live imaging, we observed asymmetric morphological changes that precede, and likely trigger, asymmetric expression of the Nodal cascade. Thus, veiled chameleons are a new and unique model for studying the evolution of L-R patterning.
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Affiliation(s)
- Natalia A. Shylo
- Stowers Institute for Medical Research, Kansas City, MO, United States
| | - Sarah E. Smith
- Stowers Institute for Medical Research, Kansas City, MO, United States
| | - Andrew J. Price
- Stowers Institute for Medical Research, Kansas City, MO, United States
| | - Fengli Guo
- Stowers Institute for Medical Research, Kansas City, MO, United States
| | - Melainia McClain
- Stowers Institute for Medical Research, Kansas City, MO, United States
| | - Paul A. Trainor
- Stowers Institute for Medical Research, Kansas City, MO, United States
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, MO, United States
- *Correspondence: Paul A. Trainor,
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3
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Truchado-García M, Perry KJ, Cavodeassi F, Kenny NJ, Henry JQ, Grande C. A Small Change With a Twist Ending: A Single Residue in EGF-CFC Drives Bilaterian Asymmetry. Mol Biol Evol 2022; 40:6947033. [PMID: 36537201 PMCID: PMC9907556 DOI: 10.1093/molbev/msac270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 11/28/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Asymmetries are essential for proper organization and function of organ systems. Genetic studies in bilaterians have shown signaling through the Nodal/Smad2 pathway plays a key, conserved role in the establishment of body asymmetries. Although the main molecular players in the network for the establishment of left-right asymmetry (LRA) have been deeply described in deuterostomes, little is known about the regulation of Nodal signaling in spiralians. Here, we identified orthologs of the egf-cfc gene, a master regulator of the Nodal pathway in vertebrates, in several invertebrate species, which includes the first evidence of its presence in non-deuterostomes. Our functional experiments indicate that despite being present, egf-cfc does not play a role in the establishment of LRA in gastropods. However, experiments in zebrafish suggest that a single amino acid mutation in the egf-cfc gene in at least the common ancestor of chordates was the necessary step to induce a gain of function in LRA regulation. This study shows that the egf-cfc gene likely appeared in the ancestors of deuterostomes and "protostomes", before being adopted as a mechanism to regulate the Nodal pathway and the establishment of LRA in some lineages of deuterostomes.
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Affiliation(s)
| | - Kimberly J Perry
- Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801
| | - Florencia Cavodeassi
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain,Institute of Medical and Biomedical Education, St George's University of London, Cranmer Terrace, London SW17 0RE, United Kingdom
| | - Nathan J Kenny
- Natural History Museum, Cromwell Road, London, United Kingdom,Department of Biochemistry (Te Tari Matū Koiora), University of Otago, Dunedin, (Aotearoa) New Zealand
| | - Jonathan Q Henry
- Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801,The Marine Biological Laboratory, Woods Hole, MA 02543
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4
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Opazo JC, Kuraku S, Zavala K, Toloza-Villalobos J, Hoffmann FG. Evolution of nodal and nodal-related genes and the putative composition of the heterodimers that trigger the nodal pathway in vertebrates. Evol Dev 2019; 21:205-217. [PMID: 31210006 DOI: 10.1111/ede.12292] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/03/2019] [Accepted: 05/13/2019] [Indexed: 02/06/2023]
Abstract
Nodal is a signaling molecule that belongs to the transforming growth factor-β superfamily that plays key roles during the early stages of development of animals. In vertebrates Nodal forms an heterodimer with a GDF1/3 protein to activate the Nodal pathway. Vertebrates have a paralog of nodal in their genomes labeled Nodal-related, but the evolutionary history of these genes is a matter of debate, mainly because of the presence of a variable numbers of genes in the vertebrate genomes sequenced so far. Thus, the goal of this study was to investigate the evolutionary history of the Nodal and Nodal-related genes with an emphasis in tracking changes in the number of genes among vertebrates. Our results show the presence of two gene lineages (Nodal and Nodal-related) that can be traced back to the ancestor of jawed vertebrates. These lineages have undergone processes of differential retention and lineage-specific expansions. Our results imply that Nodal and Nodal-related duplicated at the latest in the ancestor of gnathostomes, and they still retain a significant level of functional redundancy. By comparing the evolution of the Nodal/Nodal-related with GDF1/3 gene family, it is possible to infer that there are several types of heterodimers that can trigger the Nodal pathway among vertebrates.
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Affiliation(s)
- Juan C Opazo
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Shigehiro Kuraku
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Japan
| | - Kattina Zavala
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Jessica Toloza-Villalobos
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Federico G Hoffmann
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Starkville, Mississippi.,Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Starkville, Mississippi
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5
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Li Y, Grover H, Dai E, Yang K, Chen Z. Probing the Roles of Physical Forces in Early Chick Embryonic Morphogenesis. J Vis Exp 2018. [PMID: 29939170 DOI: 10.3791/57150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Embryonic development is traditionally studied from the perspective of biomolecular genetics, but the fundamental importance of mechanics in morphogenesis is becoming increasingly recognized. In particular, the embryonic chick heart and brain tube, which undergo drastic morphological changes as they develop, are among the prime candidates to study the role of physical forces in morphogenesis. Progressive ventral bending and rightward torsion of the tubular embryonic chick brain happen at the earliest stage of organ-level left-right asymmetry in chick embryonic development. The vitelline membrane (VM) constrains the dorsal side of the embryo and has been implicated in providing the force necessary to induce torsion of the developing brain. Here we present a combination of new ex-ovo experiments and physical modeling to identify the mechanics of brain torsion. At Hamburger-Hamilton stage 11, embryos are harvested and cultured ex ovo (in media). The VM is subsequently removed using a pulled capillary tube. By controlling the level of the fluid and subjecting the embryo to a fluid-air interface, the fluid surface tension of the media can be used to replace the mechanical role of the VM. Microsurgery experiments were also performed to alter the position of the heart to find the resultant change in the chirality of brain torsion. Results from this protocol illustrate the fundamental roles of mechanics in driving morphogenesis.
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Affiliation(s)
- Yan Li
- Thayer School of Engineering, Dartmouth College
| | | | - Eric Dai
- Department of Bioengineering, University of Pennsylvania
| | - Kevin Yang
- Thayer School of Engineering, Dartmouth College
| | - Zi Chen
- Thayer School of Engineering, Dartmouth College;
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Baxter MFA, Latorre JD, Koltes DA, Dridi S, Greene ES, Bickler SW, Kim JH, Merino-Guzman R, Hernandez-Velasco X, Anthony NB, Bottje WG, Hargis BM, Tellez G. Assessment of a Nutritional Rehabilitation Model in Two Modern Broilers and Their Jungle Fowl Ancestor: A Model for Better Understanding Childhood Undernutrition. Front Nutr 2018; 5:18. [PMID: 29629373 PMCID: PMC5876931 DOI: 10.3389/fnut.2018.00018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 03/08/2018] [Indexed: 01/28/2023] Open
Abstract
This article is the first in a series of manuscripts to evaluate nutritional rehabilitation in chickens as a model to study interventions in children malnutrition (Part 1: Performance, Bone Mineralization, and Intestinal Morphometric Analysis). Inclusion of rye in poultry diets induces a nutritional deficit that leads to increased bacterial translocation, intestinal viscosity, and decreased bone mineralization. However, it is unclear the effect of diet on developmental stage or genetic strain. Therefore, the objective was to determine the effects of a rye diet during either the early or late phase of development on performance, bone mineralization, and intestinal morphology across three diverse genetic backgrounds. Modern 2015 (Cobb 500) broiler chicken, 1995 Cobb broiler chicken, and the Giant Jungle Fowl were randomly allocated into four different dietary treatments. Dietary treatments were (1) a control corn-based diet throughout the trial (corn-corn); (2) an early phase malnutrition diet where chicks received a rye-based diet for 10 days, and then switched to the control diet (rye-corn); (3) a malnutrition rye-diet that was fed throughout the trial (rye-rye); and (4) a late phase malnutrition diet where chicks received the control diet for 10 days, and then switched to the rye diet for the last phase (corn-rye). At 10 days of age, chicks were weighed and diets were switched in groups 2 and 4. At day 20 of age, all chickens were weighed and euthanized to collect bone and intestinal samples. Body weight, weight gain, and bone mineralization were different across diet, genetic line, age and all two- and three-way interactions (P < 0.05). Overall, Jungle Fowl were the most tolerant to a rye-based diet, and both the modern and 1995 broilers were significantly affected by the high rye-based diet. However, the 1995 broilers consuming the rye-based diet appeared to experience more permanent effects when compared with the modern broiler. The results of this study suggest that chickens have a great potential as a nutritional rehabilitation model in human trials. The 1995 broilers line was an intermediate genetic line between the fast growing modern line and the non-selected Jungle Fowl line, suggesting that it would be the most appropriate model to study for future studies.
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Affiliation(s)
- Mikayla F. A. Baxter
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Juan D. Latorre
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Dawn A. Koltes
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
- Department of Animal Science, Iowa State University, Ames, IA, United States
| | - Sami Dridi
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Elizabeth S. Greene
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Stephen W. Bickler
- Department of Pediatrics, University of California, San Diego, San Diego, CA, United States
| | - Jae H. Kim
- Division Neonatology, University of California, San Diego, San Diego, CA, United States
| | - Ruben Merino-Guzman
- College of Veterinary Medicine, National Autonomous University of Mexico, Ciudad de Mexico, Mexico
| | | | - Nicholas B. Anthony
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Walter G. Bottje
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Billy M. Hargis
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
| | - Guillermo Tellez
- Department of Poultry Science, University of Arkansas, Fayetteville, AR, United States
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7
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McDowell G, Rajadurai S, Levin M. From cytoskeletal dynamics to organ asymmetry: a nonlinear, regulative pathway underlies left-right patterning. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0409. [PMID: 27821521 DOI: 10.1098/rstb.2015.0409] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 12/25/2022] Open
Abstract
Consistent left-right (LR) asymmetry is a fundamental aspect of the bodyplan across phyla, and errors of laterality form an important class of human birth defects. Its molecular underpinning was first discovered as a sequential pathway of left- and right-sided gene expression that controlled positioning of the heart and visceral organs. Recent data have revised this picture in two important ways. First, the physical origin of chirality has been identified; cytoskeletal dynamics underlie the asymmetry of single-cell behaviour and patterning of the LR axis. Second, the pathway is not linear: early disruptions that alter the normal sidedness of upstream asymmetric genes do not necessarily induce defects in the laterality of the downstream genes or in organ situs Thus, the LR pathway is a unique example of two fascinating aspects of biology: the interplay of physics and genetics in establishing large-scale anatomy, and regulative (shape-homeostatic) pathways that correct molecular and anatomical errors over time. Here, we review aspects of asymmetry from its intracellular, cytoplasmic origins to the recently uncovered ability of the LR control circuitry to achieve correct gene expression and morphology despite reversals of key 'determinant' genes. We provide novel functional data, in Xenopus laevis, on conserved elements of the cytoskeleton that drive asymmetry, and comparatively analyse it together with previously published results in the field. Our new observations and meta-analysis demonstrate that despite aberrant expression of upstream regulatory genes, embryos can progressively normalize transcriptional cascades and anatomical outcomes. LR patterning can thus serve as a paradigm of how subcellular physics and gene expression cooperate to achieve developmental robustness of a body axis.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.
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Affiliation(s)
- Gary McDowell
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA.,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
| | - Suvithan Rajadurai
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA.,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
| | - Michael Levin
- Biology Department, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA .,Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155-4243, USA
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8
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Pai VP, Willocq V, Pitcairn EJ, Lemire JM, Paré JF, Shi NQ, McLaughlin KA, Levin M. HCN4 ion channel function is required for early events that regulate anatomical left-right patterning in a nodal and lefty asymmetric gene expression-independent manner. Biol Open 2017; 6:1445-1457. [PMID: 28818840 PMCID: PMC5665463 DOI: 10.1242/bio.025957] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 08/12/2017] [Indexed: 12/13/2022] Open
Abstract
Laterality is a basic characteristic of all life forms, from single cell organisms to complex plants and animals. For many metazoans, consistent left-right asymmetric patterning is essential for the correct anatomy of internal organs, such as the heart, gut, and brain; disruption of left-right asymmetry patterning leads to an important class of birth defects in human patients. Laterality functions across multiple scales, where early embryonic, subcellular and chiral cytoskeletal events are coupled with asymmetric amplification mechanisms and gene regulatory networks leading to asymmetric physical forces that ultimately result in distinct left and right anatomical organ patterning. Recent studies have suggested the existence of multiple parallel pathways regulating organ asymmetry. Here, we show that an isoform of the hyperpolarization-activated cyclic nucleotide-gated (HCN) family of ion channels (hyperpolarization-activated cyclic nucleotide-gated channel 4, HCN4) is important for correct left-right patterning. HCN4 channels are present very early in Xenopus embryos. Blocking HCN channels (Ih currents) with pharmacological inhibitors leads to errors in organ situs. This effect is only seen when HCN4 channels are blocked early (pre-stage 10) and not by a later block (post-stage 10). Injections of HCN4-DN (dominant-negative) mRNA induce left-right defects only when injected in both blastomeres no later than the 2-cell stage. Analysis of key asymmetric genes' expression showed that the sidedness of Nodal, Lefty, and Pitx2 expression is largely unchanged by HCN4 blockade, despite the randomization of subsequent organ situs, although the area of Pitx2 expression was significantly reduced. Together these data identify a novel, developmental role for HCN4 channels and reveal a new Nodal-Lefty-Pitx2 asymmetric gene expression-independent mechanism upstream of organ positioning during embryonic left-right patterning.
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Affiliation(s)
- Vaibhav P Pai
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Valerie Willocq
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Emily J Pitcairn
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Joan M Lemire
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Jean-François Paré
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Nian-Qing Shi
- Department of Medicine at University of Wisconsin-Madison, Madison, WI 53792, USA
| | - Kelly A McLaughlin
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
| | - Michael Levin
- Allen Discovery Center at Tufts University, 200 Boston Ave, Suite 4600, Medford, MA 02155, USA
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9
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Palmquist K, Davidson B. Establishment of lateral organ asymmetries in the invertebrate chordate, Ciona intestinalis. EvoDevo 2017; 8:12. [PMID: 28770040 PMCID: PMC5526266 DOI: 10.1186/s13227-017-0075-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/17/2017] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The evolutionary emergence and diversification of the chordates appear to involve dramatic changes in organ morphogenesis along the left/right axis. However, the ancestral chordate mechanism for establishing lateral asymmetry remains ambiguous. Additionally, links between the initial establishment of lateral asymmetry and subsequent asymmetries in organ morphogenesis are poorly characterized. RESULTS To explore asymmetric organ morphogenesis during chordate evolution, we have begun to characterize left/right patterning of the heart and endodermal organs in an invertebrate chordate, Ciona intestinalis. Here, we show that Ciona has a laterally asymmetric, right-sided heart. Our data indicate that cardiac lateral asymmetry requires H+/K+ ion flux, but is independent of Nodal signaling. Our pharmacological inhibitor studies show that ion flux is required for polarization of epidermal cilia and neurula rotation and suggest that ion flux functions synergistically with chorion contact to drive cardiac laterality. Live imaging analysis revealed that larval heart progenitor cells undergo a lateral shift without displaying any migratory behaviors. Furthermore, we find that this passive shift corresponds with the emergence of lateral asymmetry in the endoderm, which is also ion flux dependent. CONCLUSIONS Our data suggest that ion flux promotes laterally asymmetric morphogenesis of the larval endoderm rudiment leading to a passive, Nodal-independent shift in the position of associated heart progenitor cells. These findings help to refine hypotheses regarding ancestral chordate left/right patterning mechanisms and how they have diverged within invertebrate and vertebrate chordate lineages.
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Affiliation(s)
- Karl Palmquist
- Department of Biology, Swarthmore College, 500 College Ave., Swarthmore, PA 19081 USA
| | - Brad Davidson
- Department of Biology, Swarthmore College, 500 College Ave., Swarthmore, PA 19081 USA
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10
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Lin CY, Tsai MY, Liu YH, Lu YF, Chen YC, Lai YR, Liao HC, Lien HW, Yang CH, Huang CJ, Hwang SPL. Klf8 regulates left-right asymmetric patterning through modulation of Kupffer's vesicle morphogenesis and spaw expression. J Biomed Sci 2017; 24:45. [PMID: 28716076 PMCID: PMC5513281 DOI: 10.1186/s12929-017-0351-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/07/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although vertebrates are bilaterally symmetric organisms, their internal organs are distributed asymmetrically along a left-right axis. Disruption of left-right axis asymmetric patterning often occurs in human genetic disorders. In zebrafish embryos, Kupffer's vesicle, like the mouse node, breaks symmetry by inducing asymmetric expression of the Nodal-related gene, spaw, in the left lateral plate mesoderm (LPM). Spaw then stimulates transcription of itself and downstream genes, including lft1, lft2, and pitx2, specifically in the left side of the diencephalon, heart and LPM. This developmental step is essential to establish subsequent asymmetric organ positioning. In this study, we evaluated the role of krüppel-like factor 8 (klf8) in regulating left-right asymmetric patterning in zebrafish embryos. METHODS Zebrafish klf8 expression was disrupted by both morpholino antisense oligomer-mediated knockdown and a CRISPR-Cas9 system. Whole-mount in situ hybridization was conducted to evaluate gene expression patterns of Nodal signalling components and the positions of heart and visceral organs. Dorsal forerunner cell number was evaluated in Tg(sox17:gfp) embryos and the length and number of cilia in Kupffer's vesicle were analyzed by immunocytochemistry using an acetylated tubulin antibody. RESULTS Heart jogging, looping and visceral organ positioning were all defective in zebrafish klf8 morphants. At the 18-22 s stages, klf8 morphants showed reduced expression of genes encoding Nodal signalling components (spaw, lft1, lft2, and pitx2) in the left LPM, diencephalon, and heart. Co-injection of klf8 mRNA with klf8 morpholino partially rescued spaw expression. Furthermore, klf8 but not klf8△zf overexpressing embryos showed dysregulated bilateral expression of Nodal signalling components at late somite stages. At the 10s stage, klf8 morphants exhibited reductions in length and number of cilia in Kupffer's vesicle, while at 75% epiboly, fewer dorsal forerunner cells were observed. Interestingly, klf8 mutant embryos, generated by a CRISPR-Cas9 system, showed bilateral spaw expression in the LPM at late somite stages. This observation may be partly attributed to compensatory upregulation of klf12b, because klf12b knockdown reduced the percentage of klf8 mutants exhibiting bilateral spaw expression. CONCLUSIONS Our results demonstrate that zebrafish Klf8 regulates left-right asymmetric patterning by modulating both Kupffer's vesicle morphogenesis and spaw expression in the left LPM.
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Affiliation(s)
- Che-Yi Lin
- Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan.,Present address: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Ming-Yuan Tsai
- Graduate Institute of Life Sciences, National Defence Medical Center, National Defence University, Neihu, Taipei, Taiwan.,Present address: Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Yu-Hsiu Liu
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Yu-Fen Lu
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan
| | - Yi-Chung Chen
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan
| | - Yun-Ren Lai
- Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan
| | - Hsin-Chi Liao
- Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan
| | - Huang-Wei Lien
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | | | - Chang-Jen Huang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Sheng-Ping L Hwang
- Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan. .,Department of Life Science, National Taiwan University, Taipei, Taiwan. .,Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan.
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11
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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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12
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Intarapat S, Stern CD. Sexually dimorphic and sex-independent left-right asymmetries in chicken embryonic gonads. PLoS One 2013; 8:e69893. [PMID: 23894556 PMCID: PMC3716703 DOI: 10.1371/journal.pone.0069893] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 06/12/2013] [Indexed: 11/20/2022] Open
Abstract
Female birds develop asymmetric gonads: a functional ovary develops on the left, whereas the right gonad regresses. In males, however, testes develop on both sides. We examined the distribution of germ cells using Vasa/Cvh as a marker. Expression is asymmetric in both sexes: at stage 35 the left gonad contains significantly more germ cells than the right. A similar expression pattern is seen for expression of ERNI (Ens1), a gene expressed in chick embryonic stem cells while they self-renew, but downregulated upon differentiation. Other pluripotency-associated markers (PouV/Oct3/4, Nanog and Sox2) also show asymmetric expression (more expressing cells on the left) in both sexes, but this asymmetry is at least partly due to expression in stromal cells of the developing gonad, and the pattern is different for all the genes. Therefore germ cell and pluripotency-associated genes show both sex-dependent and independent left-right asymmetry and a complex pattern of expression.
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Affiliation(s)
- Sittipon Intarapat
- Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand
- Department of Cell and Developmental Biology and UCL Centre for Stem Cells and Regenerative Medicine, University College London, London, United Kingdom
| | - Claudio D. Stern
- Department of Cell and Developmental Biology and UCL Centre for Stem Cells and Regenerative Medicine, University College London, London, United Kingdom
- * E-mail:
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13
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de Lussanet MH, Osse JW. An ancestral axial twist explains the contralateral forebrain and the optic chiasm in vertebrates. ANIM BIOL 2012. [DOI: 10.1163/157075611x617102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Among the best-known facts of the brain are the contralateral visual, auditory, sensational, and motor mappings in the forebrain. How and why did these evolve? The few theories to this question provide functional answers, such as better networks for visuomotor control. However, these theories contradict the data, as discussed here. Instead we propose that a 90-deg turn on the left side evolved in a common ancestor of all vertebrates. Compensatory migrations of the tissues during development restore body symmetry. Eyes, nostrils and forebrain compensate in the direction of the turn, whereas more caudal structures migrate in the opposite direction. As a result of these opposite migrations the forebrain becomes crossed and inverted with respect to the rest of the nervous system. We show that such compensatory migratory movements can indeed be observed in the zebrafish (Danio rerio) and the chick (Gallus gallus). With a model we show how the axial twist hypothesis predicts that an optic chiasm should develop on the ventral side of the brain, whereas the olfactory tract should be uncrossed. In addition, the hypothesis explains the decussation of the trochlear nerve, why olfaction is non-crossed, why the cerebellar hemispheres represent the ipsilateral bodyside, why in sharks the forebrain halves each represent the ipsilateral eye, why the heart and other inner organs are asymmetric in the body. Due to the poor fossil record, the possible evolutionary scenarios remain speculative. Molecular evidence does support the hypothesis. The findings may shed new insight on the problematic structure of the forebrain.
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Affiliation(s)
- Marc H.E. de Lussanet
- Institute of Psychology, Westf. Wilhelms-Universität, Fliednerstraße 21, 48149 Münster, Germany
| | - Jan W.M. Osse
- Bennekomseweg 83, 6704 AH Wageningen, The Netherlands
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14
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HES6-1 and HES6-2 function through different mechanisms during neuronal differentiation. PLoS One 2010; 5:e15459. [PMID: 21151987 PMCID: PMC2996300 DOI: 10.1371/journal.pone.0015459] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 10/01/2010] [Indexed: 01/19/2023] Open
Abstract
Background Notch signalling plays a central role in the mechanisms regulating neuronal differentiation in the vertebrate nervous system. The transcriptional repressors encoded by Hes genes are the main effectors of this pathway, acting in neural progenitors during the lateral inhibition process to repress proneural genes and inhibit differentiation. However, Hes6 genes seem to behave differently: they are expressed in differentiating neurons and facilitate the activity of proneural genes in promoting neurogenesis. Still, the molecular mechanisms underlying this unique function of Hes6 genes are not yet understood. Methodology/Principal Findings Here, we identify two subgroups of Hes6 genes that seem conserved in most vertebrate species and characterize a novel Hes6 gene in chicken: cHes6-1. The embryonic expression pattern of cHes6-1 suggests roles for this gene in the formation of the pancreas, nervous system and in the generation of body asymmetry. We show that cHes6-1 is negatively regulated by Notch signalling in the developing embryonic spinal cord and in pancreatic progenitors, but requires Notch for the observed asymmetric expression at the lateral mesoderm. Functional studies by ectopic expression in the chick embryonic neural tube revealed that cHES6-1 up-regulates the expression of cDelta1 and cHes5 genes, in contrast with overexpression of cHES6-2, which represses the same genes. We show that this activity of cHES6-2 is dependent on its capacity to bind DNA and repress transcription, while cHES6-1 seems to function by sequestering other HES proteins and inhibit their activity as transcriptional repressors. Conclusions/Significance Our results indicate that the two chick HES6 proteins act at different phases of neuronal differentiation, contributing to the progression of neurogenesis by different mechanisms: while cHES6-2 represses the transcription of Hes genes, cHES6-1 acts later, sequestering HES proteins. Together, the two cHES6 proteins progressively shut down the Notch-mediated progenitor program and ensure that neuronal differentiation can proceed.
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15
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Tsui MM, York JD. Roles of inositol phosphates and inositol pyrophosphates in development, cell signaling and nuclear processes. ACTA ACUST UNITED AC 2009; 50:324-37. [PMID: 20006638 DOI: 10.1016/j.advenzreg.2009.12.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Marco M Tsui
- Department of Pharmacology and Cancer Biology, Howard Hughes Medical Institute, Duke University Medical Center, Box 3813, Durham, NC 27710, USA
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16
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Ibañes M, Izpisúa Belmonte JC. Left–right axis determination. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2009; 1:210-219. [DOI: 10.1002/wsbm.31] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Marta Ibañes
- Department of Estructura i Constituents de la Matèria, University of Barcelona, Barcelona, Spain
| | - Juan Carlos Izpisúa Belmonte
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
- Centre of Regenerative Medicine in Barcelona, Barcelona, Spain
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17
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Raya Á, Izpisúa Belmonte JC. Insights into the establishment of left–right asymmetries in vertebrates. ACTA ACUST UNITED AC 2008; 84:81-94. [DOI: 10.1002/bdrc.20122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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18
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Tavares AT, Andrade S, Silva AC, Belo JA. Cerberus is a feedback inhibitor of Nodal asymmetric signaling in the chick embryo. Development 2008; 134:2051-60. [PMID: 17507406 DOI: 10.1242/dev.000901] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The TGF-beta-related molecule Nodal plays an essential and conserved role in left-right patterning of the vertebrate embryo. Previous reports have shown that the zebrafish and mouse Cerberus-related proteins Charon and Cerberus-like-2 (Cerl-2), respectively, act in the node region to prevent the Nodal signal from crossing to the right side, whereas chick Cerberus (cCer) has an unclear function in the left-side mesoderm. In this study, we investigate the transcriptional regulation and function of cCer in left-right development. By analyzing the enhancer activity of cCer 5' genomic sequences in electroporated chick embryos, we identified a cCer left-side enhancer that contains two FoxH1 and one SMAD binding site. We show that these Nodal-responsive elements are necessary and sufficient for the activation of transcription in the left-side mesoderm. In transgenic mouse embryos, cCer regulatory sequences behave as in chick embryos, suggesting that the cis-regulatory sequences of Cerberus-related genes have diverged during vertebrate evolution. Moreover, our findings from cCer overexpression and knockdown experiments indicate that cCer is a negative-feedback regulator of Nodal asymmetric signaling. We propose that cCer and mouse Cerl-2 have evolved distinct regulatory mechanisms but retained a conserved function in left-right development, which is to restrict Nodal activity to the left side of the embryo.
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19
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Shimada K, Valdez MB, Mizutani M, Namikawa T. Potential application of sperm bearing female-specific chromosome in chickens. Cytogenet Genome Res 2007; 117:240-7. [PMID: 17675865 DOI: 10.1159/000103185] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 09/10/2006] [Indexed: 11/19/2022] Open
Abstract
This paper reviews studies on sex reversal experiments in chickens, production of sperm bearing a female-specific chromosome, its application for poultry resources and finally a mechanism of sex differentiation of gonads in the chicken.
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Affiliation(s)
- K Shimada
- Division of Applied Genetics and Physiology, Graduate School of Bioagricultural Science, Nagoya University Chikusa, Nagoya, Japan.
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20
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Morales AV, Acloque H, Ocaña OH, de Frutos CA, Gold V, Nieto MA. Snail genes at the crossroads of symmetric and asymmetric processes in the developing mesoderm. EMBO Rep 2007; 8:104-9. [PMID: 17124510 PMCID: PMC1796742 DOI: 10.1038/sj.embor.7400867] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Revised: 10/02/2006] [Accepted: 10/10/2006] [Indexed: 01/03/2023] Open
Abstract
Retinoic acid (RA) signalling ensures that vertebrate mesoderm segmentation is bilaterally synchronized, and corrects transient interferences from asymmetric left-right (L-R) signals involved in organ lateralization. Snail genes participate in both these processes and, although they are expressed symmetrically in the presomitic mesoderm (PSM), Snail1 transcripts are asymmetrically distributed in the L-R lateral mesoderm. We show that the alteration of the symmetric Snail expression in the PSM induces asynchronous somite formation. Furthermore, in the absence of RA signalling, normal asymmetric Snail1 expression in the lateral mesoderm is extended to the PSM, desynchronizing somitogenesis. Thus, Snail1 is the first cue corrected by RA in the PSM to ensure synchronized bilateral segmentation.
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Affiliation(s)
- Aixa V Morales
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
| | - Hervé Acloque
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
- Instituto de Neurociencias de Alicante, CSIC-UMH, Apartado 18, Sant Joan d'Alacant, 03550, Spain
| | - Oscar H Ocaña
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
- Instituto de Neurociencias de Alicante, CSIC-UMH, Apartado 18, Sant Joan d'Alacant, 03550, Spain
| | - Cristina A de Frutos
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
- Instituto de Neurociencias de Alicante, CSIC-UMH, Apartado 18, Sant Joan d'Alacant, 03550, Spain
| | - Veronica Gold
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
- Instituto de Neurociencias de Alicante, CSIC-UMH, Apartado 18, Sant Joan d'Alacant, 03550, Spain
| | - M Angela Nieto
- Instituto Cajal, CSIC, Doctor Arce 37, 28002 Madrid, Spain
- Instituto de Neurociencias de Alicante, CSIC-UMH, Apartado 18, Sant Joan d'Alacant, 03550, Spain
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21
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Gourronc F, Ahmad N, Nedza N, Eggleston T, Rebagliati M. Nodal activity around Kupffer's vesicle depends on the T-box transcription factors notail and spadetail and on notch signaling. Dev Dyn 2007; 236:2131-46. [PMID: 17654709 DOI: 10.1002/dvdy.21249] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The node, or its zebrafish equivalent, Kupffers Vesicle (KV), is thought to generate laterality cues through cilia-dependent signaling. An interaction between Nodal ligands and Nodal antagonists around the node/KV is also required. Here we investigate whether loss of Brachyury/Notail or Tbx16/Spadetail disrupts the balance of Nodal ligands (Southpaw) and antagonists (Charon) around Kupffers Vesicle. Reduction of Spadetail or Notail disrupts expression of southpaw in the perinodal domains flanking Kupffers Vesicle. Similar to what was published for Notail, we find Spadetail is also required for expression of charon. We present evidence for the model that Notail has a direct role in regulating the charon promoter. In particular, a flanking genomic region with putative Notail binding sites can drive KV expression of a reporter in a Notail-dependent fashion. This region also contains motifs for CSL/RBP-J/Su(H). Consistent with this, we find charon expression is strongly Notch-dependent whereas perinodal southpaw expression is not.
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Affiliation(s)
- Francoise Gourronc
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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22
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Gerhart J, Elder J, Neely C, Schure J, Kvist T, Knudsen K, George-Weinstein M. MyoD-positive epiblast cells regulate skeletal muscle differentiation in the embryo. J Cell Biol 2006; 175:283-92. [PMID: 17060497 PMCID: PMC2064569 DOI: 10.1083/jcb.200605037] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Accepted: 09/15/2006] [Indexed: 11/22/2022] Open
Abstract
MyoD mRNA is expressed in a subpopulation of cells within the embryonic epiblast. Most of these cells are incorporated into somites and synthesize Noggin. Ablation of MyoD-positive cells in the epiblast subsequently results in the herniation of organs through the ventral body wall, a decrease in the expression of Noggin, MyoD, Myf5, and myosin in the somites and limbs, and an increase in Pax-3-positive myogenic precursors. The addition of Noggin lateral to the somites compensates for the loss of MyoD-positive epiblast cells. Skeletal muscle stem cells that arise in the epiblast are utilized in the somites to promote muscle differentiation by serving as a source of Noggin.
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Affiliation(s)
- Jacquelyn Gerhart
- Center for Chronic Disorders of Aging, Philadelphia College of Osteopathic Medicine, Philadelphia, PA 19131, USA
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23
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Esser AT, Smith KC, Weaver JC, Levin M. Mathematical model of morphogen electrophoresis through gap junctions. Dev Dyn 2006; 235:2144-59. [PMID: 16786594 DOI: 10.1002/dvdy.20870] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Gap junctional communication is important for embryonic morphogenesis. However, the factors regulating the spatial properties of small molecule signal flows through gap junctions remain poorly understood. Recent data on gap junctions, ion transporters, and serotonin during left-right patterning suggest a specific model: the net unidirectional transfer of small molecules through long-range gap junctional paths driven by an electrophoretic mechanism. However, this concept has only been discussed qualitatively, and it is not known whether such a mechanism can actually establish a gradient within physiological constraints. We review the existing functional data and develop a mathematical model of the flow of serotonin through the early Xenopus embryo under an electrophoretic force generated by ion pumps. Through computer simulation of this process using realistic parameters, we explored quantitatively the dynamics of morphogen movement through gap junctions, confirming the plausibility of the proposed electrophoretic mechanism, which generates a considerable gradient in the available time frame. The model made several testable predictions and revealed properties of robustness, cellular gradients of serotonin, and the dependence of the gradient on several developmental constants. This work quantitatively supports the plausibility of electrophoretic control of morphogen movement through gap junctions during early left-right patterning. This conceptual framework for modeling gap junctional signaling -- an epigenetic patterning mechanism of wide relevance in biological regulation -- suggests numerous experimental approaches in other patterning systems.
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Affiliation(s)
- Axel T Esser
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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24
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Raya A, Izpisúa Belmonte JC. Left-right asymmetry in the vertebrate embryo: from early information to higher-level integration. Nat Rev Genet 2006; 7:283-93. [PMID: 16543932 DOI: 10.1038/nrg1830] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although vertebrates seem to be essentially bilaterally symmetrical on the exterior, there are numerous interior left-right asymmetries in the disposition and placement of internal organs. These asymmetries are established during embryogenesis by complex epigenetic and genetic cascades. Recent studies in a range of model organisms have made important progress in understanding how this laterality information is generated and conveyed to large regions of the embryo. Both commonalities and divergences are emerging in the mechanisms that different vertebrates use in left-right axis specification. Recent evidence also provides intriguing links between the establishment of left-right asymmetries and the symmetrical elongation of the anterior-posterior axis.
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Affiliation(s)
- Angel Raya
- Center of Regenerative Medicine in Barcelona and Instituci Catalana de Recerca i Estudis Avanats (ICREA), Doctor Aiguader 80, 08003 Barcelona, Spain
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25
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Simard A, Di Pietro E, Young CR, Plaza S, Ryan AK. Alterations in heart looping induced by overexpression of the tight junction protein Claudin-1 are dependent on its C-terminal cytoplasmic tail. Mech Dev 2006; 123:210-27. [PMID: 16500087 DOI: 10.1016/j.mod.2005.12.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 12/21/2005] [Accepted: 12/21/2005] [Indexed: 10/25/2022]
Abstract
In vertebrates, the positioning of the internal organs relative to the midline is asymmetric and evolutionarily conserved. A number of molecules have been shown to play critical roles in left-right patterning. Using representational difference analysis to identify genes that are differentially expressed on the left and right sides of the chick embryo, we cloned chick Claudin-1, an integral component of epithelial tight junctions. Here, we demonstrate that retroviral overexpression of Claudin-1, but not Claudin-3, on the right side of the chick embryo between HH stages 4 and 7 randomizes the direction of heart looping. This effect was not observed when Claudin-1 was overexpressed on the left side of the embryo. A small, but reproducible, induction of Nodal expression in the perinodal region on the right side of the embryo was noted in embryos that were injected with Claudin-1 retroviral particles on their right sides. However, no changes in Lefty,Pitx2 or cSnR expression were observed. In addition, Flectin expression remained higher in the left dorsal mesocardial folds of embryos with leftwardly looped hearts resulting from Claudin-1 overexpression on the right side of the embryo. We demonstrated that Claudin-1's C-terminal cytoplasmic tail is essential for this effect: mutation of a PKC phosphorylation site in the Claudin-1 C-terminal cytoplasmic domain at threonine-206 eliminates Claudin-1's ability to randomize the direction of heart looping. Taken together, our data provide evidence that appropriate expression of the tight junction protein Claudin-1 is required for normal heart looping and suggest that phosphorylation of its cytoplasmic tail is responsible for mediating this function.
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Affiliation(s)
- Annie Simard
- Departments of Pediatrics and Human Genetics, McGill University, Montréal, Que., Canada
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26
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Leonard CM, Eckert MA, Kuldau JM. Exploiting human anatomical variability as a link between genome and cognome. GENES, BRAIN, AND BEHAVIOR 2006; 5 Suppl 1:64-77. [PMID: 16417619 PMCID: PMC2739009 DOI: 10.1111/j.1601-183x.2006.00196.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although talents and disabilities appear to run in families, direct links between genes and cognitive ability are difficult to establish. Investigators are currently searching for intermediate phenotypes with plausible links to both genome and cognome (the cognitive phenotype). Cortical anatomy could provide one such intermediate phenotype. Variation in cortical size, asymmetry and sulcal pattern is influenced by genetic variation in neurotrophic factors and can predict variation in verbal and mathematical talent. Anecdotal evidence suggests that individuals with a rare morphological variant of Sylvian fissure sometimes have superior visualization ability combined with verbal deficits. Documentation of such 'cognitive cortical syndromes' might prove as genetically informative as the identification of dysmorphic syndromes associated with mental retardation. A necessary prerequisite for the establishment of such syndromes is a reliable technique for the identification of cortical patterns. Recent technical advances in software for automatically labeling and measuring cortical sulci now provide the possibility of establishing standard measures for their shape, size and location. Such measures are a prerequisite for genetic studies of cortical patterns that could illuminate the neurodevelopmental pathways by which genes affect cognitive ability.
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Affiliation(s)
- C M Leonard
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL 32611-2250, USA.
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27
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Granata A, Quaderi NA. Asymmetric expression of Gli transcription factors in Hensen's node. Gene Expr Patterns 2005; 5:529-31. [PMID: 15749082 DOI: 10.1016/j.modgep.2004.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 11/05/2004] [Accepted: 11/08/2004] [Indexed: 11/26/2022]
Abstract
Avian left-right (L/R) axis determination involves the establishment of asymmetric gene expression in Hensen's node, resulting in two discrete signalling pathways on the left and right sides of the embryo. The extracellular signalling molecule Sonic Hedgehog (SHH) is known to be an important left-side determinant. Transcription of Shh is initially bilateral in Hensen's node (stage 4), but is restricted to the left side by stage 5. The Gli genes (Gli1, Gli2 and Gli3) are the main transcriptional mediators of the Hedgehog pathway in vertebrates. GLI1 and GLI2 are primarily transcriptional activators of Hedgehog target genes, while GLI3 is primarily a transcriptional repressor of Hedgehog targets. In order to gain insight into the mechanisms of asymmetrical Hedgehog signal transduction in the node, we have analysed the expression patterns of the Gli genes in Hensen's node from stage 4 to stage 8. Here, we reveal that the Gli genes are asymmetrically expressed in Hensen's node: Gli1 and Gli2, are expressed on the left side, while Gli3 is expressed on the right side.
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Affiliation(s)
- Alessandra Granata
- MRC Centre for Developmental Neurobiology, King's College London, 4th Floor New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UK
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28
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Abstract
The chick embryo has a long and distinguished history as a major model system in developmental biology and has also contributed major concepts to immunology, genetics, virology, cancer, and cell biology. Now, it has become even more powerful thanks to several new technologies: in vivo electroporation (allowing gain- and loss-of-function in vivo in a time- and space-controlled way), embryonic stem (ES) cells, novel methods for transgenesis, and the completion of the first draft of the sequence of its genome along with many new resources to access this information. In combination with classical techniques such as grafting and lineage tracing, the chicken is now one of the most versatile experimental systems available.
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Affiliation(s)
- Claudio D Stern
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
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