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Edens BM, Bronner ME. Making developmental sense of the senses, their origin and function. Curr Top Dev Biol 2024; 159:132-167. [PMID: 38729675 DOI: 10.1016/bs.ctdb.2024.01.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
The primary senses-touch, taste, sight, smell, and hearing-connect animals with their environments and with one another. Aside from the eyes, the primary sense organs of vertebrates and the peripheral sensory pathways that relay their inputs arise from two transient stem cell populations: the neural crest and the cranial placodes. In this chapter we consider the senses from historical and cultural perspectives, and discuss the senses as biological faculties. We begin with the embryonic origin of the neural crest and cranial placodes from within the neural plate border of the ectodermal germ layer. Then, we describe the major chemical (i.e. olfactory and gustatory) and mechanical (i.e. vestibulo-auditory and somatosensory) senses, with an emphasis on the developmental interactions between neural crest and cranial placodes that shape their structures and functions.
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Affiliation(s)
- Brittany M Edens
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Marianne E Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States.
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2
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Johnson K, Freedman S, Braun R, LaBonne C. Quantitative analysis of transcriptome dynamics provides novel insights into developmental state transitions. BMC Genomics 2022; 23:723. [PMID: 36273135 PMCID: PMC9588240 DOI: 10.1186/s12864-022-08953-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 10/19/2022] [Indexed: 11/30/2022] Open
Abstract
Background During embryogenesis, the developmental potential of initially pluripotent cells becomes progressively restricted as they transit to lineage restricted states. The pluripotent cells of Xenopus blastula-stage embryos are an ideal system in which to study cell state transitions during developmental decision-making, as gene expression dynamics can be followed at high temporal resolution. Results Here we use transcriptomics to interrogate the process by which pluripotent cells transit to four different lineage-restricted states: neural progenitors, epidermis, endoderm and ventral mesoderm, providing quantitative insights into the dynamics of Waddington’s landscape. Our findings provide novel insights into why the neural progenitor state is the default lineage state for pluripotent cells and uncover novel components of lineage-specific gene regulation. These data reveal an unexpected overlap in the transcriptional responses to BMP4/7 and Activin signaling and provide mechanistic insight into how the timing of signaling inputs such as BMP are temporally controlled to ensure correct lineage decisions. Conclusions Together these analyses provide quantitative insights into the logic and dynamics of developmental decision making in early embryos. They also provide valuable lineage-specific time series data following the acquisition of specific lineage states during development. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08953-3.
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Affiliation(s)
- Kristin Johnson
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.,NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL, 60208, USA
| | - Simon Freedman
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL, 60208, USA.,Department of Engineering Sciences and Applied Math, Northwestern University, Evanston, IL, USA
| | - Rosemary Braun
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.,NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL, 60208, USA.,Department of Engineering Sciences and Applied Math, Northwestern University, Evanston, IL, USA.,Northwestern Institute On Complex Systems, Northwestern University, Evanston, IL, USA
| | - Carole LaBonne
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA. .,NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL, 60208, USA.
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3
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Keer S, Cousin H, Jourdeuil K, Neilson KM, Tavares ALP, Alfandari D, Moody SA. Mcrs1 is required for branchial arch and cranial cartilage development. Dev Biol 2022; 489:62-75. [PMID: 35697116 PMCID: PMC10426812 DOI: 10.1016/j.ydbio.2022.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 06/06/2022] [Accepted: 06/08/2022] [Indexed: 11/22/2022]
Abstract
Mcrs1 is a multifunctional protein that is critical for many cellular processes in a wide range of cell types. Previously, we showed that Mcrs1 binds to the Six1 transcription factor and reduces the ability of the Six1-Eya1 complex to upregulate transcription, and that Mcrs1 loss-of-function leads to the expansion of several neural plate genes, reduction of neural border and pre-placodal ectoderm (PPR) genes, and pleiotropic effects on various neural crest (NC) genes. Because the affected embryonic structures give rise to several of the cranial tissues affected in Branchio-otic/Branchio-oto-renal (BOR) syndrome, herein we tested whether these gene expression changes subsequently alter the development of the proximate precursors of BOR affected structures - the otic vesicles (OV) and branchial arches (BA). We found that Mcrs1 is required for the expression of several OV genes involved in inner ear formation, patterning and otic capsule cartilage formation. Mcrs1 knockdown also reduced the expression domains of many genes expressed in the larval BA, derived from either NC or PPR, except for emx2, which was expanded. Reduced Mcrs1 also diminished the length of the expression domain of tbx1 in BA1 and BA2 and interfered with cranial NC migration from the dorsal neural tube; this subsequently resulted in defects in the morphology of lower jaw cartilages derived from BA1 and BA2, including the infrarostral, Meckel's, and ceratohyal as well as the otic capsule. These results demonstrate that Mcrs1 plays an important role in processes that lead to the formation of craniofacial cartilages and its loss results in phenotypes consistent with reduced Six1 activity associated with BOR.
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Affiliation(s)
- Stephanie Keer
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC, 20037, USA
| | - Helene Cousin
- Department of Animal Science, University of Massachusetts Amherst, Integrated Science Building, 661 N. Pleasant Street, Amherst, MA, 01003, USA
| | - Karyn Jourdeuil
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC, 20037, USA
| | - Karen M Neilson
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC, 20037, USA
| | - Andre L P Tavares
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC, 20037, USA
| | - Dominique Alfandari
- Department of Animal Science, University of Massachusetts Amherst, Integrated Science Building, 661 N. Pleasant Street, Amherst, MA, 01003, USA
| | - Sally A Moody
- Department of Anatomy and Cell Biology, The George Washington University School of Medicine and Health Sciences, 2300 I (eye) Street, NW, Washington, DC, 20037, USA.
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4
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Plouhinec JL, Medina-Ruiz S, Borday C, Bernard E, Vert JP, Eisen MB, Harland RM, Monsoro-Burq AH. A molecular atlas of the developing ectoderm defines neural, neural crest, placode, and nonneural progenitor identity in vertebrates. PLoS Biol 2017; 15:e2004045. [PMID: 29049289 PMCID: PMC5663519 DOI: 10.1371/journal.pbio.2004045] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 10/31/2017] [Accepted: 09/29/2017] [Indexed: 12/18/2022] Open
Abstract
During vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. Here, we use Xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. In order to define the transcriptome of small groups of cells from a single germ layer and to retain spatial information, dorsal and ventral ectoderm was subdivided along the anterior-posterior and medial-lateral axes by microdissections. Principal component analysis on the transcriptomes of these ectoderm fragments primarily identifies embryonic axes and temporal dynamics. This provides a genetic code to define positional information of any ectoderm sample along the anterior-posterior and dorsal-ventral axes directly from its transcriptome. In parallel, we use nonnegative matrix factorization to predict enhanced gene expression maps onto early and mid-neurula embryos, and specific signatures for each ectoderm area. The clustering of spatial and temporal datasets allowed detection of multiple biologically relevant groups (e.g., Wnt signaling, neural crest development, sensory placode specification, ciliogenesis, germ layer specification). We provide an interactive network interface, EctoMap, for exploring synexpression relationships among genes expressed in the neurula, and suggest several strategies to use this comprehensive dataset to address questions in developmental biology as well as stem cell or cancer research. Vertebrate embryo germ layers become progressively regionalized by evolutionarily conserved molecular processes. Catching the early steps of this dynamic spatial cell diversification at the scale of the transcriptome was challenging, even with the advent of efficient RNA sequencing. We have microdissected complementary and defined areas of a single germ layer, the developing ectoderm, and explored how the transcriptome changes over time and space in the ectoderm during the differentiation of frog epidermis, neural plate, and neural crest. We have created EctoMap, a searchable interface using these regional transcriptomes, to predict the expression of the 31 thousand genes expressed in neurulae and their networks of co-expression, predictive of functional relationships. Through several examples, we illustrate how these data provide insights in development, cancer, evolution and stem cell biology.
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Affiliation(s)
- Jean-Louis Plouhinec
- Université Paris Sud, Université Paris Saclay, CNRS UMR 3347, INSERM U1021, Orsay, France
- Institut Curie Research Division, PSL Research University, CNRS UMR 3347, INSERM U1021, Orsay, France
- MINES ParisTech, PSL Research University, CBIO - Centre for Computational Biology, Paris, France
| | - Sofía Medina-Ruiz
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development Biology, University of California, Berkeley, Berkeley, California, United States of America
| | - Caroline Borday
- Université Paris Sud, Université Paris Saclay, CNRS UMR 3347, INSERM U1021, Orsay, France
- Institut Curie Research Division, PSL Research University, CNRS UMR 3347, INSERM U1021, Orsay, France
| | - Elsa Bernard
- MINES ParisTech, PSL Research University, CBIO - Centre for Computational Biology, Paris, France
- Institut Curie, INSERM U900, Paris, France
- INSERM U900, Paris, France
| | - Jean-Philippe Vert
- MINES ParisTech, PSL Research University, CBIO - Centre for Computational Biology, Paris, France
- Institut Curie, INSERM U900, Paris, France
- INSERM U900, Paris, France
| | - Michael B. Eisen
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development Biology, University of California, Berkeley, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California, United States of America
| | - Richard M. Harland
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development Biology, University of California, Berkeley, Berkeley, California, United States of America
| | - Anne H. Monsoro-Burq
- Université Paris Sud, Université Paris Saclay, CNRS UMR 3347, INSERM U1021, Orsay, France
- Institut Curie Research Division, PSL Research University, CNRS UMR 3347, INSERM U1021, Orsay, France
- Institut Universitaire de France, Paris, France
- * E-mail:
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5
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Motahari Z, Martinez-De Luna RI, Viczian AS, Zuber ME. Tbx3 represses bmp4 expression and, with Pax6, is required and sufficient for retina formation. Development 2016; 143:3560-3572. [PMID: 27578778 DOI: 10.1242/dev.130955] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 08/05/2016] [Indexed: 12/30/2022]
Abstract
Vertebrate eye formation begins in the anterior neural plate in the eye field. Seven eye field transcription factors (EFTFs) are expressed in eye field cells and when expressed together are sufficient to generate retina from pluripotent cells. The EFTF Tbx3 can regulate the expression of some EFTFs; however, its role in retina formation is unknown. Here, we show that Tbx3 represses bmp4 transcription and is required in the eye field for both neural induction and normal eye formation in Xenopus laevis Although sufficient for neural induction, Tbx3-expressing pluripotent cells only form retina in the context of the eye field. Unlike Tbx3, the neural inducer Noggin can generate retina both within and outside the eye field. We found that the neural and retina-inducing activity of Noggin requires Tbx3. Noggin, but not Tbx3, induces Pax6 and coexpression of Tbx3 and Pax6 is sufficient to determine pluripotent cells to a retinal lineage. Our results suggest that Tbx3 represses bmp4 expression and maintains eye field neural progenitors in a multipotent state; then, in combination with Pax6, Tbx3 causes eye field cells to form retina.
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Affiliation(s)
- Zahra Motahari
- The Center for Vision Research, Department of Ophthalmology, Upstate Medical University, Syracuse, NY 13210, USA Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY 13210, USA
| | - Reyna I Martinez-De Luna
- The Center for Vision Research, Department of Ophthalmology, Upstate Medical University, Syracuse, NY 13210, USA
| | - Andrea S Viczian
- The Center for Vision Research, Department of Ophthalmology, Upstate Medical University, Syracuse, NY 13210, USA Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY 13210, USA Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY 13210, USA Department of Cell and Developmental Biology, Upstate Medical University, Syracuse, NY 13210, USA
| | - Michael E Zuber
- The Center for Vision Research, Department of Ophthalmology, Upstate Medical University, Syracuse, NY 13210, USA Department of Biochemistry and Molecular Biology, Upstate Medical University, Syracuse, NY 13210, USA Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY 13210, USA
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6
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Li WH, Zhou L, Li Z, Wang Y, Shi JT, Yang YJ, Gui JF. Zebrafish Lbh-like Is Required for Otx2-mediated Photoreceptor Differentiation. Int J Biol Sci 2015; 11:688-700. [PMID: 25999792 PMCID: PMC4440259 DOI: 10.7150/ijbs.11244] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 04/11/2015] [Indexed: 12/12/2022] Open
Abstract
The homeobox transcription factor orthodenticle homolog 2 (otx2) is supposed as an organizer that orchestrates a transcription factor network during photoreceptor development. However, its regulation in the process remains unclear. In this study, we have identified a zebrafish limb bud and heart-like gene (lbh-like), which is expressed initially at 30 hours post fertilization (hpf) in the developing brain and eyes. Lbh-like knockdown by morpholinos specifically inhibits expression of multiple photoreceptor-specific genes, such as opsins, gnat1, gnat2 and irbp. Interestingly, otx2 expression in the morphants is not significantly reduced until 32 hpf when lbh-like begins to express, but its expression level in 72 hpf morphants is higher than that in wild type embryos. Co-injection of otx2 and its downstream target neuroD mRNAs can rescue the faults in eyes of Lbh-like morphants. Combined with the results of promoter-reporter assay, we suggest that lbh-like is a new regulator of photoreceptor differentiation directly through affecting otx2 expression in zebrafish. Furthermore, knockdown of lbh-like increases the activity of Notch pathway and perturbs the balance among proliferation, differentiation and survival of photoreceptor precursors.
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Affiliation(s)
- Wen-Hua Li
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, ; 2. Graduate University of the Chinese Academy of Sciences, Wuhan 430072, China
| | - Li Zhou
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
| | - Zhi Li
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
| | - Yang Wang
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
| | - Jian-Tao Shi
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
| | - Yan-Jing Yang
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, ; 2. Graduate University of the Chinese Academy of Sciences, Wuhan 430072, China
| | - Jian-Fang Gui
- 1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
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7
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Hartenstein V, Reh TA. Homologies between vertebrate and invertebrate eyes. Results Probl Cell Differ 2015; 37:219-55. [PMID: 25707078 DOI: 10.1007/978-3-540-45398-7_14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Affiliation(s)
- Volker Hartenstein
- Department of Biology, University of California, Los Angeles, California, USA
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8
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Walton T, Preston E, Nair G, Zacharias AL, Raj A, Murray JI. The Bicoid class homeodomain factors ceh-36/OTX and unc-30/PITX cooperate in C. elegans embryonic progenitor cells to regulate robust development. PLoS Genet 2015; 11:e1005003. [PMID: 25738873 PMCID: PMC4349592 DOI: 10.1371/journal.pgen.1005003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 01/14/2015] [Indexed: 01/30/2023] Open
Abstract
While many transcriptional regulators of pluripotent and terminally differentiated states have been identified, regulation of intermediate progenitor states is less well understood. Previous high throughput cellular resolution expression studies identified dozens of transcription factors with lineage-specific expression patterns in C. elegans embryos that could regulate progenitor identity. In this study we identified a broad embryonic role for the C. elegans OTX transcription factor ceh-36, which was previously shown to be required for the terminal specification of four neurons. ceh-36 is expressed in progenitors of over 30% of embryonic cells, yet is not required for embryonic viability. Quantitative phenotyping by computational analysis of time-lapse movies of ceh-36 mutant embryos identified cell cycle or cell migration defects in over 100 of these cells, but most defects were low-penetrance, suggesting redundancy. Expression of ceh-36 partially overlaps with that of the PITX transcription factor unc-30. unc-30 single mutants are viable but loss of both ceh-36 and unc-30 causes 100% lethality, and double mutants have significantly higher frequencies of cellular developmental defects in the cells where their expression normally overlaps. These factors are also required for robust expression of the downstream developmental regulator mls-2/HMX. This work provides the first example of genetic redundancy between the related yet evolutionarily distant OTX and PITX families of bicoid class homeodomain factors and demonstrates the power of quantitative developmental phenotyping in C. elegans to identify developmental regulators acting in progenitor cells.
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Affiliation(s)
- Travis Walton
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Elicia Preston
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Gautham Nair
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amanda L. Zacharias
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Arjun Raj
- Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - John Isaac Murray
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Penn Genome Frontiers Institute, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Yan B, Neilson KM, Ranganathan R, Maynard T, Streit A, Moody SA. Microarray identification of novel genes downstream of Six1, a critical factor in cranial placode, somite, and kidney development. Dev Dyn 2014; 244:181-210. [PMID: 25403746 DOI: 10.1002/dvdy.24229] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 11/03/2014] [Accepted: 11/12/2014] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Six1 plays an important role in the development of several vertebrate organs, including cranial sensory placodes, somites, and kidney. Although Six1 mutations cause one form of branchio-otic syndrome (BOS), the responsible gene in many patients has not been identified; genes that act downstream of Six1 are potential BOS candidates. RESULTS We sought to identify novel genes expressed during placode, somite and kidney development by comparing gene expression between control and Six1-expressing ectodermal explants. The expression patterns of 19 of the significantly up-regulated and 11 of the significantly down-regulated genes were assayed from cleavage to larval stages. A total of 28/30 genes are expressed in the otocyst, a structure that is functionally disrupted in BOS, and 26/30 genes are expressed in the nephric mesoderm, a structure that is functionally disrupted in the related branchio-otic-renal (BOR) syndrome. We also identified the chick homologues of five genes and show that they have conserved expression patterns. CONCLUSIONS Of the 30 genes selected for expression analyses, all are expressed at many of the developmental times and appropriate tissues to be regulated by Six1. Many have the potential to play a role in the disruption of hearing and kidney function seen in BOS/BOR patients.
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Affiliation(s)
- Bo Yan
- Department of Anatomy and Regenerative Biology, The George Washington University, School of Medicine and Health Sciences, Washington, DC
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10
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FoxA4 favours notochord formation by inhibiting contiguous mesodermal fates and restricts anterior neural development in Xenopus embryos. PLoS One 2014; 9:e110559. [PMID: 25343614 PMCID: PMC4208771 DOI: 10.1371/journal.pone.0110559] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 09/24/2014] [Indexed: 11/19/2022] Open
Abstract
In vertebrates, the embryonic dorsal midline is a crucial signalling centre that patterns the surrounding tissues during development. Members of the FoxA subfamily of transcription factors are expressed in the structures that compose this centre. Foxa2 is essential for dorsal midline development in mammals, since knock-out mouse embryos lack a definitive node, notochord and floor plate. The related gene foxA4 is only present in amphibians. Expression begins in the blastula -chordin and -noggin expressing centre (BCNE) and is later restricted to the dorsal midline derivatives of the Spemann's organiser. It was suggested that the early functions of mammalian foxa2 are carried out by foxA4 in frogs, but functional experiments were needed to test this hypothesis. Here, we show that some important dorsal midline functions of mammalian foxa2 are exerted by foxA4 in Xenopus. We provide new evidence that the latter prevents the respecification of dorsal midline precursors towards contiguous fates, inhibiting prechordal and paraxial mesoderm development in favour of the notochord. In addition, we show that foxA4 is required for the correct regionalisation and maintenance of the central nervous system. FoxA4 participates in constraining the prospective rostral forebrain territory during neural specification and is necessary for the correct segregation of the most anterior ectodermal derivatives, such as the cement gland and the pituitary anlagen. Moreover, the early expression of foxA4 in the BCNE (which contains precursors of the whole forebrain and most of the midbrain and hindbrain) is directly required to restrict anterior neural development.
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11
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Grant PA, Yan B, Johnson MA, Johnson DLE, Moody SA. Novel animal pole-enriched maternal mRNAs are preferentially expressed in neural ectoderm. Dev Dyn 2013; 243:478-96. [PMID: 24155242 DOI: 10.1002/dvdy.24082] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/27/2013] [Accepted: 09/04/2013] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND Many animals utilize maternal mRNAs to pre-pattern the embryo before the onset of zygotic transcription. In Xenopus laevis, vegetal factors specify the germ line, endoderm, and dorsal axis, but there are few studies demonstrating roles for animal-enriched maternal mRNAs. Therefore, we carried out a microarray analysis to identify novel maternal transcripts enriched in 8-cell-stage animal blastomeres. RESULTS We identified 39 mRNAs isolated from 8-cell animal blastomeres that are >4-fold enriched compared to vegetal pole mRNAs. We characterized 14 of these that are of unknown function. We validated the microarray results for 8/14 genes by qRT-PCR and for 14/14 genes by in situ hybridization assays. Because no developmental functions are reported yet, we provide the expression patterns for each of the 14 genes. Each is expressed in the animal hemisphere of unfertilized eggs, 8-cell animal blastomeres, and diffusely in blastula animal cap ectoderm, gastrula ectoderm and neural ectoderm, neural crest (and derivatives) and cranial placodes (and derivatives). They have varying later expression in some mesodermal and endodermal tissues in tail bud through larval stages. CONCLUSIONS Novel animal-enriched maternal mRNAs are preferentially expressed in ectodermal derivatives, particularly neural ectoderm. However, they are later expressed in derivatives of other germ layers.
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Affiliation(s)
- Paaqua A Grant
- Department of Biological Sciences, The George Washington University, Columbian College of Arts and Sciences, Washington, DC
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12
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Mancini P, Castelli M, Vignali R. Identification and evolution of molecular domains involved in differentiating the cement gland-promoting activity of Otx proteins in Xenopus laevis. Mech Dev 2013; 130:628-39. [DOI: 10.1016/j.mod.2013.09.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 09/09/2013] [Accepted: 09/11/2013] [Indexed: 10/26/2022]
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13
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Veilleux HD, Van Herwerden L, Cole NJ, Don EK, De Santis C, Dixson DL, Wenger AS, Munday PL. Otx2 expression and implications for olfactory imprinting in the anemonefish, Amphiprion percula. Biol Open 2013; 2:907-15. [PMID: 24143277 PMCID: PMC3773337 DOI: 10.1242/bio.20135496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 06/13/2013] [Indexed: 11/20/2022] Open
Abstract
The otx2 gene encodes a transcription factor (OTX2) essential in the formation of the brain and sensory systems. Specifically, OTX2-positive cells are associated with axons in the olfactory system of mice and otx2 is upregulated in odour-exposed zebrafish, indicating a possible role in olfactory imprinting. In this study, otx2 was used as a candidate gene to investigate the molecular mechanisms of olfactory imprinting to settlement cues in the coral reef anemonefish, Amphiprion percula. The A. percula otx2 (Ap-otx2) gene was elucidated, validated, and its expression tested in settlement-stage A. percula by exposing them to behaviourally relevant olfactory settlement cues in the first 24 hours post-hatching, or daily throughout the larval phase. In-situ hybridisation revealed expression of Ap-otx2 throughout the olfactory epithelium with increased transcript staining in odour-exposed settlement-stage larval fish compared to no-odour controls, in all scenarios. This suggests that Ap-otx2 may be involved in olfactory imprinting to behaviourally relevant settlement odours in A. percula.
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Affiliation(s)
- Heather D Veilleux
- School of Marine and Tropical Biology, James Cook University , Townsville QLD 4811 , Australia ; Centre for Tropical Fisheries and Aquaculture, James Cook University , Townsville QLD 4811 , Australia
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Abstract
Lens regeneration among vertebrates is basically restricted to some amphibians. The most notable cases are the ones that occur in premetamorphic frogs and in adult newts. Frogs and newts regenerate their lens in very different ways. In frogs the lens is regenerated by transdifferentiation of the cornea and is limited only to a time before metamorphosis. On the other hand, regeneration in newts is mediated by transdifferentiation of the pigment epithelial cells of the dorsal iris and is possible in adult animals as well. Thus, the study of both systems could provide important information about the process. Molecular tools have been developed in frogs and recently also in newts. Thus, the process has been studied at the molecular and cellular levels. A synthesis describing both systems was long due. In this review we describe the process in both Xenopus and the newt. The known molecular mechanisms are described and compared.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801, USA.
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Posnien N, Koniszewski N, Bucher G. Insect Tc-six4 marks a unit with similarity to vertebrate placodes. Dev Biol 2010; 350:208-16. [PMID: 21034730 DOI: 10.1016/j.ydbio.2010.10.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 10/18/2010] [Accepted: 10/19/2010] [Indexed: 11/20/2022]
Abstract
Cranial placodes are specialized ectodermal regions in the developing vertebrate head that give rise to both neural and non-neural cell types of the neuroendocrine system and the sense organs of the visual, olfactory and acoustic systems. The cranial placodes develop from a panplacodal region which is specifically marked by genes of the eyes absent/eya and two "six homeobox" family members (sine oculis/six1 and six4). It had been believed that cranial placodes are evolutionary novelties of vertebrates. However, data from non-vertebrate chordates suggest that placode-like structures evolved in the chordate ancestor already. Here, we identify a morphological structure in the embryonic head of the beetle Tribolium castaneum with placode-like features. It is marked by the orthologs of the panplacodal markers Tc-six4, Tc-eya and Tc-sine oculis/six1 (Tc-six1) and expresses several genes known to be involved in adenohypophyseal placode development in vertebrates. Moreover, it contributes to both epidermal and neural tissues. We identify Tc-six4 as a specific marker for this structure that we term the insect head placode. Finally, we reveal the regulatory gene network of the panplacodal genes Tc-six4, Tc-eya and Tc-six1 and identify them as head epidermis patterning genes. Our finding of a placode-like structure in an insect suggests that a placode precursor was already present in the last common ancestor of bilaterian animals.
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Affiliation(s)
- Nico Posnien
- Center of Molecular Brain Physiology, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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16
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Abstract
Vertebrate eyes begin as a small patch of cells at the most anterior end of the early brain called the eye field. If these cells are removed from an amphibian embryo, the eyes do not form. If the eye field is transplanted to another location on the embryo or cultured in a dish, it forms eyes. These simple cut and paste experiments were performed at the beginning of the last century and helped to define the embryonic origin of the vertebrate eye. The genes necessary for eye field specification and eventual eye formation, by contrast, have only recently been identified. These genes and the molecular mechanisms regulating the initial formation of the Xenopus laevis eye field are the subjects of this review.
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Affiliation(s)
- Michael E Zuber
- Center for Vision Research, SUNY Eye Institute, Departments of Ophthalmology and Biochemistry & Molecular Biology, Upstate Medical University, Syracuse, New York, USA
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17
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Suda Y, Kurokawa D, Takeuchi M, Kajikawa E, Kuratani S, Amemiya C, Aizawa S. Evolution of Otx paralogue usages in early patterning of the vertebrate head. Dev Biol 2008; 325:282-95. [PMID: 18848537 DOI: 10.1016/j.ydbio.2008.09.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 09/10/2008] [Accepted: 09/12/2008] [Indexed: 11/17/2022]
Abstract
To assess evolutional changes in the expression pattern of Otx paralogues, expression analyses were undertaken in fugu, bichir, skate and lamprey. Together with those in model vertebrates, the comparison suggested that a gnathostome ancestor would have utilized all of Otx1, Otx2 and Otx5 paralogues in organizer and anterior mesendoderm for head development. In this animal, Otx1 and Otx2 would have also functioned in specification of the anterior neuroectoderm at presomite stage and subsequent development of forebrain/midbrain at somite stage, while Otx5 expression would have already been specialized in epiphysis and eyes. Otx1 and Otx2 functions in anterior neuroectoderm and brain of the gnathostome ancestor would have been differentially maintained by Otx1 in a basal actinopterygian and by Otx2 in a basal sarcopterygian. Otx5 expression in head organizer and anterior mesendoderm seems to have been lost in the teleost lineage after divergence of bichir, and also from the amniotes after divergence of amphibians as independent events. Otx1 expression was lost from the organizer in the tetrapod lineage. In contrast, in a teleost ancestor prior to whole genome duplication, Otx1 and Otx2 would have both been expressed in the dorsal margin of blastoderm, embryonic shield, anterior mesendoderm, anterior neuroectoderm and forebrain/midbrain, at respective stages of head development. Subsequent whole genome duplication and the following genome changes would have caused different Otx paralogue usages in each teleost lineage. Lampreys also have three Otx paralogues; their sequences are highly diverged from gnathostome cognates, but their expression pattern is well related to those of skate Otx cognates.
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Affiliation(s)
- Yoko Suda
- Laboratory for Vertebrate Body Plan, Center for Developmental Biology, RIKEN Kobe, Chuo-ku, Kobe 650-0047, Japan
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18
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Kataoka K, Tazaki A, Kitayama A, Ueno N, Watanabe K, Mochii M. Identification of asymmetrically localized transcripts along the animal-vegetal axis of the Xenopus egg. Dev Growth Differ 2008; 47:511-21. [PMID: 16287483 DOI: 10.1111/j.1440-169x.2005.00826.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In many organisms, proper embryo development depends on the asymmetrical distribution of mRNA in the cytoplasm of the egg. Here we report comprehensive screening of RNA localized in the animal or vegetal hemisphere of the Xenopus egg. Macroarrays including over 40,000 independent embryonic cDNA clones, representing at least 17,000 unigenes, were differentially hybridized with labeled probes synthesized from the mRNA of animal or vegetal blastomeres. After two rounds of screening, we identified 33 clones of transcripts that may be preferentially distributed in the vegetal region of the early stage embryo, but transcripts localized in the animal region were not found. To assess the array results, we performed northern blot and quantitative real-time reverse transcription-polymerase chain reaction analysis. As a result, 21 transcripts of the 33 were confirmed to be localized in the vegetal region of the early stage embryo. Whole-mount in situ hybridization analysis revealed that 11 transcripts, including 7 previously reported genes, were localized in the vegetal hemisphere of the egg. These 11 transcripts were categorized into three groups according to their expression patterns in the egg. The first group, which contained four transcripts, showed uniform expression in the vegetal hemisphere, similar to VegT. The second group, which contained three transcripts, showed gradual expression from the vegetal pole to the equator, similar to Vg1. The last group, which contained three transcripts, was expressed at the germ plasm, similar to Xdazl. One transcript, Xwnt11, showed both the second and the third expression patterns.
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Affiliation(s)
- Kensuke Kataoka
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Akou 678-1297, Japan.
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19
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Coolen M, Sauka-Spengler T, Nicolle D, Le-Mentec C, Lallemand Y, Silva CD, Plouhinec JL, Robert B, Wincker P, Shi DL, Mazan S. Evolution of axis specification mechanisms in jawed vertebrates: insights from a chondrichthyan. PLoS One 2007; 2:e374. [PMID: 17440610 PMCID: PMC1847705 DOI: 10.1371/journal.pone.0000374] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Accepted: 03/22/2007] [Indexed: 12/31/2022] Open
Abstract
The genetic mechanisms that control the establishment of early polarities and their link with embryonic axis specification and patterning seem to substantially diverge across vertebrates. In amphibians and teleosts, the establishment of an early dorso-ventral polarity determines both the site of axis formation and its rostro-caudal orientation. In contrast, amniotes retain a considerable plasticity for their site of axis formation until blastula stages and rely on signals secreted by extraembryonic tissues, which have no clear equivalents in the former, for the establishment of their rostro-caudal pattern. The rationale for these differences remains unknown. Through detailed expression analyses of key development genes in a chondrichthyan, the dogfish Scyliorhinus canicula, we have reconstructed the ancestral pattern of axis specification in jawed vertebrates. We show that the dogfish displays compelling similarities with amniotes at blastula and early gastrula stages, including the presence of clear homologs of the hypoblast and extraembryonic ectoderm. In the ancestral state, these territories are specified at opposite poles of an early axis of bilateral symmetry, homologous to the dorso-ventral axis of amphibians or teleosts, and aligned with the later forming embryonic axis, from head to tail. Comparisons with amniotes suggest that a dorsal expansion of extraembryonic ectoderm, resulting in an apparently radial symmetry at late blastula stages, has taken place in their lineage. The synthesis of these results with those of functional analyses in model organisms supports an evolutionary link between the dorso-ventral polarity of amphibians and teleosts and the embryonic-extraembryonic organisation of amniotes. It leads to a general model of axis specification in gnathostomes, which provides a comparative framework for a reassessment of conservations both among vertebrates and with more distant metazoans.
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Affiliation(s)
- Marion Coolen
- Equipe Développement et Evolution des Vertébrés, UMR 6218, Université d'Orléans, Orleans, France
| | - Tatjana Sauka-Spengler
- Equipe Développement et Evolution des Vertébrés, UPRES-A 8080, Université Paris-Sud, Orsay, France
| | - Delphine Nicolle
- Equipe Développement et Evolution des Vertébrés, UMR 6218, Université d'Orléans, Orleans, France
| | - Chantal Le-Mentec
- Equipe Développement et Evolution des Vertébrés, UPRES-A 8080, Université Paris-Sud, Orsay, France
| | - Yvan Lallemand
- Unité de Génétique Moléculaire de la Morphogenèse, URA Centre National de la Recherche Scientifique (CNRS) 2578, Institut Pasteur, Paris, France
| | - Corinne Da Silva
- Genoscope and UMR Centre National de la Recherche Scientifique (CNRS) 8030, Evry, France
| | - Jean-Louis Plouhinec
- Equipe Développement et Evolution des Vertébrés, UMR 6218, Université d'Orléans, Orleans, France
| | - Benoît Robert
- Unité de Génétique Moléculaire de la Morphogenèse, URA Centre National de la Recherche Scientifique (CNRS) 2578, Institut Pasteur, Paris, France
| | - Patrick Wincker
- Genoscope and UMR Centre National de la Recherche Scientifique (CNRS) 8030, Evry, France
| | - De-Li Shi
- UMR7622, Université Pierre et Marie Curie, Paris, France
| | - Sylvie Mazan
- Equipe Développement et Evolution des Vertébrés, UMR 6218, Université d'Orléans, Orleans, France
- * To whom correspondence should be addressed. E-mail:
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20
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Steinmetz PRH, Zelada-Gonzáles F, Burgtorf C, Wittbrodt J, Arendt D. Polychaete trunk neuroectoderm converges and extends by mediolateral cell intercalation. Proc Natl Acad Sci U S A 2007; 104:2727-32. [PMID: 17301244 PMCID: PMC1815249 DOI: 10.1073/pnas.0606589104] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
During frog and fish development, convergent extension movements transform the spherical gastrula into an elongated neurula. Such transformation of a ball- into a worm-shaped embryo is an ancestral and fundamental feature of bilaterian development, yet this is modified or absent in the protostome model organisms Caenorhabditis or Drosophila. In the polychaete annelid Platynereis dumerilii, early embryonic and larval stages resemble a sphere that subsequently elongates into worm shape. Cellular and molecular mechanisms of polychaete body elongation are yet unknown. Our in vivo time-lapse analysis of Platynereis axis elongation reveals that the polychaete neuroectoderm converges and extends by mediolateral cell intercalation. This occurs on both sides of the neural midline, the line of fusion of the slit-like blastopore. Convergent extension moves apart mouth and anus that are both derived from the blastopore. Tissue elongation is actin-dependent but microtubule-independent. Dependence on JNK activity and spatially restricted expression of strabismus indicates involvement of the noncanonical Wnt pathway. We detect a morphogenetic boundary between the converging and extending trunk neuroectoderm and the anterior otx-expressing head neuroectoderm that does not elongate. Our comparative analysis uncovers striking similarities but also differences between convergent extension in the polychaete and in the frog (the classical vertebrate model for convergent extension). Based on these findings, we propose that convergent extension movements of the trunk neuroectoderm represent an ancestral feature of bilaterian development that triggered the separation of mouth and anus along the elongating trunk.
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Affiliation(s)
- Patrick R. H. Steinmetz
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69012 Heidelberg, Germany
| | - Fabiola Zelada-Gonzáles
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69012 Heidelberg, Germany
| | - Carola Burgtorf
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69012 Heidelberg, Germany
| | - Joachim Wittbrodt
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69012 Heidelberg, Germany
| | - Detlev Arendt
- European Molecular Biology Laboratory, Developmental Biology Unit, Meyerhofstrasse 1, 69012 Heidelberg, Germany
- To whom correspondence should be addressed. E-mail:
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21
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Elkins MB, Henry JJ. Isolation and characterization of a novel gene, xMADML, involved in Xenopus laevis eye development. Dev Dyn 2006; 235:1845-57. [PMID: 16607642 DOI: 10.1002/dvdy.20824] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
We have identified Xenopus MADM-like (xMADML), a Xenopus laevis gene related to the murine MADM and the human NRBP genes. xMADML is expressed throughout early development and is expressed most strongly in the developing lens and more weakly in the retina and other anterior tissues. We demonstrate that disruption of xMADML translation by means of morpholino injection results in impaired retina and lens development. Reciprocal transplantation of the presumptive lens ectoderm between morpholino-injected embryos and those injected solely with a dextran lineage tracer demonstrates that xMADML is necessary in both the lens and the retina for correct development of these eye tissues. Analysis of gene expression after knockdown of xMADML revealed significant alterations in the expression of some genes, including Pax6, xSix3, Sox2, and Sox3, suggesting that xMADML plays a role in regulating gene expression during development of the eye. This investigation is the first in vivo study examining the developmental role of this novel gene and reveals an important role of xMADML in eye tissue development and differentiation.
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Affiliation(s)
- Matthew B Elkins
- Department of Cell and Developmental Biology and College of Medicine, University of Illinois, Urbana, Illinois, USA
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22
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Kawakami S, Kashiwagi K, Furuno N, Yamashita M, Kashiwagi A. Effects of hypergravity environments on amphibian development, gene expression and apoptosis. Comp Biochem Physiol A Mol Integr Physiol 2006; 145:65-72. [PMID: 16807024 DOI: 10.1016/j.cbpa.2006.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 05/02/2006] [Accepted: 05/03/2006] [Indexed: 12/11/2022]
Abstract
This study investigates how rearing under conditions of hypergravity affects amphibian development, Xotx2 and Xag1 gene expression and apoptosis. Uncleaved Xenopus laevis eggs 20 min after insemination, 2 cell stage embryos, and gastrula stage embryos were raised at 2G and 5G, while controls were raised in normal gravity. Apoptosis in brain and eye inner structures of hatching embryos was scored using the TUNEL staining method, and gene expression in tail-bud embryos was analyzed by whole-mount in situ hybridization. Results showed that: (1) 5G retarded the development of eggs and embryos and induced microcephaly and microphthalmia. (2) 5G suppressed the expression of the two genes, Xotx2 (involved in fore- and midbrain and eye development) and Xag1 (regulating cement gland formation). (3) Eggs and 2 cell stage embryos raised at 5G showed a greater extent of brain and eye apoptosis compared with controls, while those raised at 2G showed no significant difference. These findings suggest that high gravity suppresses certain gene functions and induces abnormal apoptosis in brain and eyes, resulting in developmental retardation and various morphological abnormalities.
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Affiliation(s)
- Satomi Kawakami
- Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, Higashihiroshima 739-8526, Japan
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23
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Schlosser G. Induction and specification of cranial placodes. Dev Biol 2006; 294:303-51. [PMID: 16677629 DOI: 10.1016/j.ydbio.2006.03.009] [Citation(s) in RCA: 280] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 12/22/2005] [Accepted: 12/23/2005] [Indexed: 12/17/2022]
Abstract
Cranial placodes are specialized regions of the ectoderm, which give rise to various sensory ganglia and contribute to the pituitary gland and sensory organs of the vertebrate head. They include the adenohypophyseal, olfactory, lens, trigeminal, and profundal placodes, a series of epibranchial placodes, an otic placode, and a series of lateral line placodes. After a long period of neglect, recent years have seen a resurgence of interest in placode induction and specification. There is increasing evidence that all placodes despite their different developmental fates originate from a common panplacodal primordium around the neural plate. This common primordium is defined by the expression of transcription factors of the Six1/2, Six4/5, and Eya families, which later continue to be expressed in all placodes and appear to promote generic placodal properties such as proliferation, the capacity for morphogenetic movements, and neuronal differentiation. A large number of other transcription factors are expressed in subdomains of the panplacodal primordium and appear to contribute to the specification of particular subsets of placodes. This review first provides a brief overview of different cranial placodes and then synthesizes evidence for the common origin of all placodes from a panplacodal primordium. The role of various transcription factors for the development of the different placodes is addressed next, and it is discussed how individual placodes may be specified and compartmentalized within the panplacodal primordium. Finally, tissues and signals involved in placode induction are summarized with a special focus on induction of the panplacodal primordium itself (generic placode induction) and its relation to neural induction and neural crest induction. Integrating current data, new models of generic placode induction and of combinatorial placode specification are presented.
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Affiliation(s)
- Gerhard Schlosser
- Brain Research Institute, AG Roth, University of Bremen, FB2, 28334 Bremen, Germany.
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24
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Chou SJ, Hermesz E, Hatta T, Feltner D, El-Hodiri HM, Jamrich M, Mahon K. Conserved regulatory elements establish the dynamic expression of Rpx/HesxI in early vertebrate development. Dev Biol 2006; 292:533-45. [PMID: 16527264 DOI: 10.1016/j.ydbio.2005.12.053] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Revised: 12/06/2005] [Accepted: 12/23/2005] [Indexed: 10/24/2022]
Abstract
TheRpx/Hesx1 homeobox gene is expressed during gastrulation in the anterior visceral and definitive endoderm and the cephalic neural plate. At later stages of development, its expression is restricted to Rathke's pouch, the primordium of the pituitary gland. This expression pattern suggests the presence of at least two distinct regulatory regions that control early and late Rpx transcription. Using transgenic mice, we have demonstrated that regulatory sequences in the 5' upstream region of Rpx are important for early expression in the anterior endoderm and neural plate and regulatory elements in the 3' region are required for late expression in Rathke's pouch. We have found that the genetically required LIM homeodomain-containing proteins Lim1/Lhx1 and Lhx3 are directly involved in the regulation of Rpx transcription. They bind two LIM protein-binding sites in the 5' upstream region of Rpx, which are required for Rpx promoter activity in both mice and Xenopus. Furthermore, we have found that a conserved enhancer in the 3' regulatory sequences of Rpx is not only required, but is also sufficient for the expression of Rpx transgenes in the developing Rathke's pouch.
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MESH Headings
- Animals
- Base Sequence
- Binding Sites
- Cells, Cultured
- Electrophoretic Mobility Shift Assay
- Embryo, Mammalian/cytology
- Embryo, Nonmammalian
- Endoderm/cytology
- Gastrula
- Gene Expression Regulation, Developmental
- Genes, Homeobox
- Genes, Reporter
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Hypothalamus/embryology
- Hypothalamus/metabolism
- Lac Operon
- Luciferases/metabolism
- Mice
- Mice, Transgenic
- Models, Biological
- Point Mutation
- Promoter Regions, Genetic
- Protein Binding
- Regulatory Sequences, Nucleic Acid/genetics
- Transgenes
- Vertebrates/embryology
- Xenopus
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Affiliation(s)
- Shen-Ju Chou
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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25
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Lunardi A, Cremisi F, Dente L. Dystroglycan is required for proper retinal layering. Dev Biol 2006; 290:411-20. [PMID: 16406325 DOI: 10.1016/j.ydbio.2005.11.044] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2005] [Revised: 09/05/2005] [Accepted: 11/30/2005] [Indexed: 10/25/2022]
Abstract
Dystroglycan (DG) is a transmembrane receptor linking the extracellular matrix to the internal cytoskeleton. Its structural function has been mainly characterized in muscle fibers, but DG plays signaling and developmental roles also in different tissues and cell types. We have investigated the effects of dystroglycan depletion during eye development of Xenopus laevis. We have injected a specific morpholino (Mo) antisense oligonucleotide in the animal pole of one dorsal blastomere of embryos at four cells stage. Mo-mediated loss of DG function caused disruption of the basal lamina layers, increased apoptosis and reduction of the expression domains of specific retinal markers, at early stages. Later in development, morphants displayed unilateral ocular malformations, such as microphtalmia and retinal delayering with photoreceptors and ganglion cells scattered throughout the retina or aggregated in rosette-like structures. These results recall the phenotypes observed in specific human diseases and suggest that DG presence is crucial at early stages for the organization of retinal architecture.
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Affiliation(s)
- Andrea Lunardi
- Dipartimento di Fisiologia e Biochimica, Laboratori di Biologia Cellulare e dello Sviluppo, Università di Pisa, via G. Carducci 13, Ghezzano, Pisa 56010, Italy
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26
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Brunet I, Weinl C, Piper M, Trembleau A, Volovitch M, Harris W, Prochiantz A, Holt C. The transcription factor Engrailed-2 guides retinal axons. Nature 2005; 438:94-8. [PMID: 16267555 PMCID: PMC3785142 DOI: 10.1038/nature04110] [Citation(s) in RCA: 216] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Accepted: 08/04/2005] [Indexed: 11/08/2022]
Abstract
Engrailed-2 (En-2), a homeodomain transcription factor, is expressed in a caudal-to-rostral gradient in the developing midbrain, where it has an instructive role in patterning the optic tectum--the target of topographic retinal input. In addition to its well-known role in regulating gene expression through its DNA-binding domain, En-2 may also have a role in cell-cell communication, as suggested by the presence of other domains involved in nuclear export, secretion and internalization. Consistent with this possibility, here we report that an external gradient of En-2 protein strongly repels growth cones of Xenopus axons originating from the temporal retina and, conversely, attracts nasal axons. Fluorescently tagged En-2 accumulates inside growth cones within minutes of exposure, and a mutant form of the protein that cannot enter cells fails to elicit axon turning. Once internalized, En-2 stimulates the rapid phosphorylation of proteins involved in translation initiation and triggers the local synthesis of new proteins. Furthermore, the turning responses of both nasal and temporal growth cones in the presence of En-2 are blocked by inhibitors of protein synthesis. The differential guidance of nasal and temporal axons reported here suggests that En-2 may participate directly in topographic map formation in the vertebrate visual system.
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Affiliation(s)
- Isabelle Brunet
- CNRS UMR 8542, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France
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27
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Schlosser G. Evolutionary origins of vertebrate placodes: insights from developmental studies and from comparisons with other deuterostomes. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2005; 304:347-99. [PMID: 16003766 DOI: 10.1002/jez.b.21055] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ectodermal placodes comprise the adenohypophyseal, olfactory, lens, profundal, trigeminal, otic, lateral line, and epibranchial placodes. The first part of this review presents a brief overview of placode development. Placodes give rise to a variety of cell types and contribute to many sensory organs and ganglia of the vertebrate head. While different placodes differ with respect to location and derivative cell types, all appear to originate from a common panplacodal primordium, induced at the anterior neural plate border by a combination of mesodermal and neural signals and defined by the expression of Six1, Six4, and Eya genes. Evidence from mouse and zebrafish mutants suggests that these genes promote generic placodal properties such as cell proliferation, cell shape changes, and specification of neurons. The common developmental origin of placodes suggests that all placodes may have evolved in several steps from a common precursor. The second part of this review summarizes our current knowledge of placode evolution. Although placodes (like neural crest cells) have been proposed to be evolutionary novelties of vertebrates, recent studies in ascidians and amphioxus have proposed that some placodes originated earlier in the chordate lineage. However, while the origin of several cellular and molecular components of placodes (e.g., regionalized expression domains of transcription factors and some neuronal or neurosecretory cell types) clearly predates the origin of vertebrates, there is presently little evidence that these components are integrated into placodes in protochordates. A scenario is presented according to which all placodes evolved from an adenohypophyseal-olfactory protoplacode, which may have originated in the vertebrate ancestor from the anlage of a rostral neurosecretory organ (surviving as Hatschek's pit in present-day amphioxus).
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28
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Acampora D, Annino A, Tuorto F, Puelles E, Lucchesi W, Papalia A, Simeone A. Otx genes in the evolution of the vertebrate brain. Brain Res Bull 2005; 66:410-20. [PMID: 16144623 DOI: 10.1016/j.brainresbull.2005.02.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Indexed: 12/01/2022]
Abstract
Only until a decade ago, animal phylogeny was traditionally based on the assumption that evolution of bilaterians went from simple to complex through gradual steps in which the extant species would represent grades of intermediate complexity that reflect the organizational levels of their ancestors. The advent of more sophisticated molecular biology techniques combined to an increasing variety of functional experiments has provided new tools, which lead us to consider evolutionary studies under a brand new light. An ancestral versus derived low-complexity of a given organism has now to be carefully re-assessed and also the molecular data so far accumulated needs to be re-evaluated. Conserved gene families expressed in the nervous system of all the species have been extensively used to reconstruct evolutionary steps, which may lead to identify the morphological as well as molecular features of the last common ancestor of bilaterians (Urbilateria). The Otx gene family is among these and will be here reviewed.
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Affiliation(s)
- Dario Acampora
- MRC Centre for Developmental Neurobiology, New Hunt's House, 4th Floor, King's College London, UK
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Seufert DW, Prescott NL, El-Hodiri HM. Xenopus aristaless-related homeobox (xARX) gene product functions as both a transcriptional activator and repressor in forebrain development. Dev Dyn 2005; 232:313-24. [PMID: 15614781 DOI: 10.1002/dvdy.20234] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Mutations in the aristaless-related homeobox (ARX) gene have been found in patients with a variety of X-linked mental retardation syndromes with forebrain abnormalities, including lissencephaly. Arx is expressed in the developing mouse, Xenopus, and zebrafish forebrain. We have used whole-mount in situ hybridization, overexpression, and loss-of-function studies to investigate the involvement of xArx in Xenopus brain development. We verified that xArx is expressed in the prospective diencephalon, as the forebrain is patterned and specified during neural plate stages. Expression spreads into the ventral and medial telencephalon as development proceeds through neural tube and tadpole stages. Overexpression of xArx resulted in morphological abnormalities in forebrain development, including loss of rostral midline structures, syn- or anophthalmia, dorsal displacement of the nasal organ, and ventral neural tube hyperplasia. Additionally, there is a delay in expression of many molecular markers of brain and retinal development. However, expression of some markers, dlx5 and wnt8b, was enhanced in xArx-injected embryos. Loss-of-function experiments indicated that xArx was necessary for normal forebrain development. Expansion of wnt8b expression depended on xArx function as a transcriptional repressor, whereas ectopic expression of dlx5, accompanied by development of ectopic otic structures, depended on function of Arx as a transcriptional activator. These results suggest that Arx acts as a bifunctional transcriptional regulator in brain development.
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Affiliation(s)
- Daniel W Seufert
- Center for Molecular and Human Genetics, Columbus Children's Research Institute, 700 Children's Drive, Columbus, OH 43205, USA
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Carron C, Bourdelas A, Li HY, Boucaut JC, Shi DL. Antagonistic interaction between IGF and Wnt/JNK signaling in convergent extension in Xenopus embryo. Mech Dev 2005; 122:1234-47. [PMID: 16169711 DOI: 10.1016/j.mod.2005.06.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Revised: 06/17/2005] [Accepted: 06/17/2005] [Indexed: 10/25/2022]
Abstract
The homeobox gene Otx2 is expressed during gastrulation in the anterior domain of the vertebrate embryo and is involved in neural and head induction during Xenopus early development. It also prevents convergent extension movements in trunk and posterior mesoderm. Insulin-like growth factors (IGFs) were shown to have similar function. However, whether they interact and the mechanism by which they affect convergent extension remain unclear. We show that IGF pathway specifically induces the expression of Otx2 in the early gastrula and blocks convergent extension of neuroectoderm and mesoderm through the transcriptional activation of Otx2 gene. Otx2 represses the expression of Xbra and Xwnt-11, and the effects of IGF on gastrulation movements can be partially rescued by antisense Otx2 morpholino oligonucleotide. These indicate that IGF pathway interacts with Otx2 to restrict Xbra and Xwnt-11 expression in the trunk and posterior regions. Consistent with this, we show that inhibition of IGF signaling or Otx2 function induces Xbra and Xwnt11 expression and convergent extension in ectodermal cells. Furthermore, the blockade of convergent extension by IGF-I and Otx2 can be rescued by coexpression of Xwnt-11 or a constitutively active Jun N-terminal kinase (JNK). Because Xbra and Xwnt-11 are required for convergent extension movements and Xwnt-11 activates the non-canonical Wnt-11/JNK pathway, our results reveal a mutually exclusive function between IGF and Wnt-11/JNK pathways in regulating cell behaviours during vertebrate head and trunk development.
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Affiliation(s)
- Clémence Carron
- Groupe de Biologie Expérimentale, Laboratoire de Biologie du Développement, CNRS UMR 7622, Université Paris 6, 9 quai Saint-Bernard, 75005 Paris, France
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Plouhinec JL, Leconte L, Sauka-Spengler T, Bovolenta P, Mazan S, Saule S. Comparative analysis of gnathostome Otx gene expression patterns in the developing eye: implications for the functional evolution of the multigene family. Dev Biol 2005; 278:560-75. [PMID: 15680370 DOI: 10.1016/j.ydbio.2004.11.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Revised: 11/12/2004] [Accepted: 11/12/2004] [Indexed: 10/26/2022]
Abstract
We have performed a detailed analysis of the expression pattern of the three gnathostome Otx classes in order to gain new insights into their functional evolution. Expression patterns were examined in the developing eye of a chondrichthyan, the dogfish, and an amniote, the chick, and compared with the capacity of paralogous proteins to induce a pigmented phenotype in cultured retina cells in cooperation with the bHLH-leucine zipper protein Mitf. This analysis indicates that each Otx class is characterized by highly specific and conserved expression features in the presumptive RPE, where Otx1 and Otx2, but not Otx5, are transcribed at optic vesicle stages, in the differentiating neural retina, where Otx2 and Otx5 show a conserved dynamic expression pattern, and in the forming ciliary process, a major site of Otx1 expression. Furthermore, the paralogous proteins of the dogfish and the mouse do not display any significant difference in their capacity to induce a pigmented phenotype, suggesting a functional equivalency in the specification and differentiation of the RPE. These data indicate that specific functions selectively involving each Otx orthology class were fixed prior to the gnathostome radiation and highlight the prominent role of regulatory changes in the functional diversification of the multigene family.
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Affiliation(s)
- J L Plouhinec
- Equipe Développement et Evolution des Vertébrés, UPRES-A 8080, Université Paris-Sud, Bat. 441 91405 Orsay Cedex, France
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Shin Y, Kitayama A, Koide T, Peiffer DA, Mochii M, Liao A, Ueno N, Cho KWY. Identification of neural genes usingXenopus DNA microarrays. Dev Dyn 2005; 232:432-44. [PMID: 15614765 DOI: 10.1002/dvdy.20229] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To isolate novel genes regulating neural induction, we used a DNA microarray approach. As neural induction is thought to occur by means of the inhibition of bone morphogenetic protein (BMP) signaling, BMP signaling was inhibited in ectodermal cells by overexpression of a dominant-negative receptor. RNAs were isolated from control animal cap explants and from dominant-negative BMP receptor expressing animal caps and subjected to a microarray experiment using newly generated high-density Xenopus DNA microarray chips representing over 17,000 unigenes. We have identified 77 genes that are induced in animal caps after inhibition of BMP signaling, and all of these genes were subjected to whole-mount in situ hybridization analysis. Thirty-two genes showed specific expression in neural tissues. Of the 32, 14 genes have never been linked to neural induction. Two genes that are highly induced by BMP inhibition are inhibitors of Wnt signaling, suggesting that a key step in neural induction is to produce Wnt antagonists to promote anterior neural plate development. Our current analysis also proves that a microarray approach is useful in identifying novel candidate factors involved in neural induction and patterning.
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Affiliation(s)
- Yongchol Shin
- Department of Developmental and Cell Biology, University of California, Irvine, California, USA
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33
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Kurokawa D, Takasaki N, Kiyonari H, Nakayama R, Kimura-Yoshida C, Matsuo I, Aizawa S. Regulation ofOtx2expression and its functions in mouse epiblast and anterior neuroectoderm. Development 2004; 131:3307-17. [PMID: 15201223 DOI: 10.1242/dev.01219] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have identified cis-regulatory sequences acting on Otx2expression in epiblast (EP) and anterior neuroectoderm (AN) at about 90 kb 5′ upstream. The activity of the EP enhancer is found in the inner cell mass at E3.5 and the entire epiblast at E5.5. The AN enhancer activity is detected initially at E7.0 and ceases by E8.5; it is found later in the dorsomedial aspect of the telencephalon at E10.5. The EP enhancer includes multiple required domains over 2.3 kb, and the AN enhancer is an essential component of the EP enhancer. Mutants lacking the AN enhancer have demonstrated that these cis-sequences indeed regulate Otx2 expression in EP and AN. At the same time, our analysis indicates that another EP and AN enhancer must exist outside of the –170 kb to +120 kb range. In Otx2ΔAN/– mutants, in which one Otx2allele lacks the AN enhancer and the other allele is null, anteroposterior axis forms normally and anterior neuroectoderm is normally induced. Subsequently, however, forebrain and midbrain are lost, indicating that Otx2 expression under the AN enhancer functions to maintain anterior neuroectoderm once induced. Furthermore, Otx2 under the AN enhancer cooperates with Emx2 in diencephalon development. The AN enhancer region is conserved among mouse, human and Xenopus; moreover, the counterpart region in Xenopus exhibited an enhancer activity in mouse anterior neuroectoderm.
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Affiliation(s)
- Daisuke Kurokawa
- Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB RIKEN Kobe, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0046, Japan
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34
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Schlosser G, Ahrens K. Molecular anatomy of placode development in Xenopus laevis. Dev Biol 2004; 271:439-66. [PMID: 15223346 DOI: 10.1016/j.ydbio.2004.04.013] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Revised: 04/15/2004] [Accepted: 04/16/2004] [Indexed: 11/18/2022]
Abstract
We analyzed the spatiotemporal pattern of expression of 15 transcription factors (Six1, Six4, Eya1, Sox3, Sox2, Pax6, Pax3, Pax2, Pax8, Dlx3, Msx1, FoxI1c, Tbx2, Tbx3, Xiro1) during placode development in Xenopus laevis from neural plate to late tail bud stages. Out of all genes investigated, only the expression of Eya1, Six1, and Six4 is maintained in all types of placode (except the lens) throughout embryonic development, suggesting that they may promote generic placodal properties and that their crescent-shaped expression domain surrounding the neural plate defines a panplacodal primordium from which all types of placode originate. Double-labeling procedures were employed to reveal the precise position of this panplacodal primordium relative to neural plate, neural crest, and other placodal markers. Already at neural plate stages, the panplacodal primordium is subdivided into several subregions defined by particular combinations of transcription factors allowing us to identify the approximate regions of origin of various types of placode. Whereas some types of placode were already prefigured by molecularly distinct areas at neural plate stages, the epibranchial, otic, and lateral line placodes arise from a common posterior placodal area (characterized by Pax8 and Pax2 expression) and acquire differential molecular signatures only after neural tube closure. Our findings argue for a multistep mechanism of placode induction, support a combinatorial model of placode specification, and suggest that different placodes evolved from a common placodal primordium by successive recruitment of new inducers and target genes.
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Affiliation(s)
- Gerhard Schlosser
- Brain Research Institute, University of Bremen, 28334 Bremen, Germany.
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Zuber ME, Gestri G, Viczian AS, Barsacchi G, Harris WA. Specification of the vertebrate eye by a network of eye field transcription factors. Development 2003; 130:5155-67. [PMID: 12944429 DOI: 10.1242/dev.00723] [Citation(s) in RCA: 361] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Several eye-field transcription factors (EFTFs) are expressed in the anterior region of the vertebrate neural plate and are essential for eye formation. The Xenopus EFTFs ET, Rx1, Pax6, Six3, Lhx2, tll and Optx2 are expressed in a dynamic, overlapping pattern in the presumptive eye field. Expression of an EFTF cocktail with Otx2 is sufficient to induce ectopic eyes outside the nervous system at high frequency. Using both cocktail subsets and functional (inductive) analysis of individual EFTFs, we have revealed a genetic network regulating vertebrate eye field specification. Our results support a model of progressive tissue specification in which neural induction then Otx2-driven neural patterning primes the anterior neural plate for eye field formation. Next, the EFTFs form a self-regulating feedback network that specifies the vertebrate eye field. We find striking similarities and differences to the network of homologous Drosophila genes that specify the eye imaginal disc, a finding that is consistent with the idea of a partial evolutionary conservation of eye formation.
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Affiliation(s)
- Michael E Zuber
- Department of Anatomy, University of Cambridge, Cambridge CB2 3DY, UK
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36
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Abstract
We have identified two Xenopus mRNAs that encode proteins homologous to a component of the Wnt/beta-catenin transcriptional machinery known as Pygopus. The predicted proteins encoded by both mRNAs share the same structural properties with human Pygo-2, but with Xpygo-2alpha having an additional 21 N-terminal residues. Xpygo-2alpha messages accumulate in the prospective anterior neural plate after gastrulation and then are localized to the nervous system, rostral to and including the hindbrain. Xpygo-2beta mRNA is expressed in oocytes and early embryos but declines in level before and during gastrulation. In late neurula, Xpygo-2beta mRNA is restricted to the retinal field, including eye primordia and prospective forebrain. A C-terminal truncated mutant of Xpygo-2 containing the N-terminal Homology Domain (NHD) caused both axis duplication when injected at the 2-cell stage and inhibition of anterior neural development when injected in the prospective head, mimicking the previously described effects of Wnt-signaling activators. Inhibition of Xpygo-2alpha and Xpygo-2beta by injection of gene-specific antisense morpholino oligonucleotides into prospective anterior neurectoderm caused brain defects that were prevented by coinjection of Xpygo-2 mRNA. Both Xpygo-2alpha and Xpygo-2beta morpholinos reduced the eye and forebrain markers Xrx-1, Xpax-6, and XBF-1, while the Xpygo-2alpha morpholino also eliminated expression of the mid-hindbrain marker En-2. The differential expression and regulatory activities of Xpygo-2alpha/beta in rostral neural tissue indicate that they represent essential components of a novel mechanism for Wnt signaling in regionalization of the brain.
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Affiliation(s)
- Blue B Lake
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6 Newfoundland, Canada.
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37
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Viczian AS, Vignali R, Zuber ME, Barsacchi G, Harris WA. XOtx5b and XOtx2 regulate photoreceptor and bipolar fates in the Xenopus retina. Development 2003; 130:1281-94. [PMID: 12588845 DOI: 10.1242/dev.00343] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Photoreceptor and bipolar cells are molecularly related cell types in the vertebrate retina. XOtx5b is expressed in both photoreceptors and bipolars, while a closely related member of the same family of transcription factors, XOtx2, is expressed in bipolar cells only. Lipofection of retinal precursors with XOtx5b biases them toward photoreceptor fates whereas a similar experiment with XOtx2 promotes bipolar cell fates. Domain swap experiments show that the ability to specify different cell fates is largely contained in the divergent sequence C-terminal to the homeodomain, while the more homologous N-terminal and homeodomain regions of both genes, when fused to VP16 activators, promote only photoreceptor fates. XOtx5b is closely related to Crx and like Crx it drives expression from an opsin reporter in vivo. XOtx2 suppresses this XOtx5b-driven reporter activity providing a possible explanation for why bipolars do not express opsin. Similarly, co-lipofection of XOtx2 with XOtx5b overrides the latter's ability to promote photoreceptor fates and the combination drives bipolar fates. The results suggest that the shared and divergent parts of these homologous genes may be involved in specifying the shared and distinct characters of related cell types in the vertebrate retina.
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Affiliation(s)
- Andrea S Viczian
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge, UK
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Wu CF, Chan APY, Etkin LD. Difference in the maternal and zygotic contributions of tumorhead on embryogenesis. Dev Biol 2003; 255:290-302. [PMID: 12648491 DOI: 10.1016/s0012-1606(02)00074-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tumorhead (TH) is a maternally expressed gene in Xenopus laevis, that when overexpressed, increased proliferation of ectodermal derivatives and inhibited neural and epidermal differentiation. However, injection of anti-TH antibodies inhibited cleavage of all blastomeres, not only those contributing to the ectoderm. The injection of TH morpholino antisense oligonucleotide (TH-MO), which inhibits translation of TH mRNA, did not affect early cleavage but inhibited cell division in both the neural field and epidermis. This was accompanied by the inhibition of neural and epidermal markers. TH-MO did not affect the formation and differentiation of mesoderm and endoderm derivatives. Our overexpression and loss-of-function studies demonstrated that TH plays an important role in differentiation of the ectoderm by regulating cell proliferation. They also supported the conclusion that the maternal component of TH may affect the cell cycle in all cells, while the zygotic component has a germ layer-specific effect on the ectoderm.
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Affiliation(s)
- Chuan Fen Wu
- Department of Molecular Genetics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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Henry JJ. The cellular and molecular bases of vertebrate lens regeneration. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 228:195-265. [PMID: 14667045 DOI: 10.1016/s0074-7696(03)28005-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Lens regeneration takes place in some vertebrates through processes of cellular dedifferentiation and transdifferentiation, processes by which certain differentiated cell types can give rise to others. This review describes the principal forms of lens regeneration that occur in vivo as well as related in vitro systems of transdifferentiation. Classic experimental studies are reviewed that define the tissue interactions that trigger these events in vivo. Recent molecular analyses have begun to identify the genes associated with these processes. These latter studies generally reveal tremendous similarities between embryonic lens development and lens regeneration. Different models are proposed to describe basic molecular pathways that define the processes of lens regeneration and transdifferentiation. Finally, studies are discussed suggesting that fibroblast growth factors play key roles in supporting the process of lens regeneration. Retinoids, such as retinoic acid, may also play important roles in this process.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois 61801, USA
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Abstract
Inner ear induction, like induction of other tissues examined in recent years, is likely to be comprised of several stages. The process begins during gastrulation when the ectoderm is competent to respond to induction. It appears that a signal from the endomesoderm underlying the otic area during gastrulation initiates induction complemented by a signal from presumptive neural tissue. By the neural plate stage, a region of ectoderm outside the neural plate is "biased" toward ear formation; this process may be part of a more general "placodal" bias shared by several sensory tissues. Induction continues during neurulation when a signal from neural tissue (possibly augmented by mesoderm underlying the otic area) results in ectoderm committed to otic vesicle formation at the time of neural tube closure. Studies on several gene families implicate them in the ear determination process. Fibroblast Growth Factor (FGF) family members are clearly involved in induction: FGFs are appropriately expressed for such a role, and have been shown to be essential for inner ear development. FGFs also have inductive activity, although it is not clear if they are sufficient for ear induction. Activation of transcription factors in the otic ectoderm, for example, by Pax gene family members, provides evidence for important changes in the responding ectoderm beginning during gastrulation and continuing through specification at the end of neurulation, although few functional tests have defined the role of these genes in determination. The challenge remains to merge embryologic data with gene function studies to develop a clear model for the molecular basis of inner ear induction.
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Affiliation(s)
- Selina Noramly
- Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, Virginia 22904, USA
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Henry JJ, Carinato ME, Schaefer JJ, Wolfe AD, Walter BE, Perry KJ, Elbl TN. Characterizing gene expression during lens formation in Xenopus laevis: evaluating the model for embryonic lens induction. Dev Dyn 2002; 224:168-85. [PMID: 12112470 DOI: 10.1002/dvdy.10097] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Few directed searches have been undertaken to identify the genes involved in vertebrate lens formation. In the frog Xenopus, the larval cornea can undergo a process of transdifferentiation to form a new lens once the original lens is removed. Based on preliminary evidence, we have shown that this process shares many elements of a common molecular/genetic pathway to that involved in embryonic lens development. A subtracted cDNA library, enriched for genes expressed during cornea-lens transdifferentiation, was prepared. The similarities/identities of specific clones isolated from the subtracted cDNA library define an expression profile of cells undergoing cornea-lens transdifferentiation ("lens regeneration") and corneal wound healing (the latter representing a consequence of the surgery required to trigger transdifferentiation). Screens were undertaken to search for genes expressed during both transdifferentiation and embryonic lens development. Significantly, new genes were recovered that are also expressed during embryonic lens development. The expression of these genes, as well as others known to be expressed during embryonic development in Xenopus, can be correlated with different periods of embryonic lens induction and development, in an attempt to define these events in a molecular context. This information is considered in light of our current working model of embryonic lens induction, in which specific tissue properties and phases of induction have been previously defined in an experimental context. Expression data reveal the existence of further levels of complexity in this process and suggests that individual phases of lens induction and specific tissue properties are not strictly characterized or defined by expression of individual genes.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois 61801, USA.
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Montalta-He H, Leemans R, Loop T, Strahm M, Certa U, Primig M, Acampora D, Simeone A, Reichert H. Evolutionary conservation of otd/Otx2 transcription factor action: a genome-wide microarray analysis in Drosophila. Genome Biol 2002; 3:RESEARCH0015. [PMID: 11983056 PMCID: PMC115189 DOI: 10.1186/gb-2002-3-4-research0015] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2002] [Revised: 02/05/2002] [Accepted: 02/13/2002] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Homeobox genes of the orthodenticle (otd)/Otx family have conserved roles in the embryogenesis of head and brain. Gene replacement experiments show that the Drosophila otd gene and orthologous mammalian Otx genes are functionally equivalent, in that overexpression of either gene in null mutants of Drosophila or mouse can restore defects in cephalic and brain development. This suggests that otd and Otx genes control a comparable subset of downstream target genes in either organism. Here we use quantitative transcript imaging to analyze this equivalence of otd and Otx gene action at a genomic level. RESULTS Oligonucleotide arrays representing 13,400 annotated Drosophila genes were used to study differential gene expression in flies in which either the Drosophila otd gene or the human Otx2 gene was overexpressed. Two hundred and eighty-seven identified transcripts showed highly significant changes in expression levels in response to otd overexpression, and 682 identified transcripts showed highly significant changes in expression levels in response to Otx2 overexpression. Among these, 93 showed differential expression changes following overexpression of either otd or Otx2, and for 90 of these, comparable changes were observed under both experimental conditions. We postulate that these transcripts are common downstream targets of the fly otd gene and the human Otx2 gene in Drosophila. CONCLUSION Our experiments indicate that approximately one third of the otd-regulated transcripts also respond to overexpression of the human Otx2 gene in Drosophila. These common otd/Otx2 downstream genes are likely to represent the molecular basis of the functional equivalence of otd and Otx2 gene action in Drosophila.
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Affiliation(s)
- Haiqiong Montalta-He
- Institute of Zoology, Biozentrum/Pharmazentrum, Klingelbergstrasse 50, University of Basel, CH-4056 Basel, Switzerland.
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Kenyon KL, Zaghloul N, Moody SA. Transcription factors of the anterior neural plate alter cell movements of epidermal progenitors to specify a retinal fate. Dev Biol 2001; 240:77-91. [PMID: 11784048 DOI: 10.1006/dbio.2001.0464] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The embryonic progenitors that give rise to the vertebrate retina acquire their cell fate identity through a series of transitions that ultimately determine their final, differentiated retinal cell fates. In Xenopus, these transitions have been broadly defined as competence, specification, and determination. The expression of several transcription factors within the anterior neural plate at the time when the presumptive eye field separates from other neural derivatives suggests that these genes function to specify competent embryonic progenitors toward a retinal fate. In support of this, we demonstrate that some transcription factors expressed in the anterior neural ectoderm and/or presumptive eye field (otx2, pax6, and rx1) change the fate of competent, ventral progenitors, which normally do not contribute to the retina, from an epidermal to a retinal fate. Furthermore, the expression of these factors changes the morphogenetic movements of progenitors during gastrulation, causing ventral cells to populate the native anterior neural plate. In addition, we experimentally demonstrate that the efficacy of pax6 to specify retinal cells depends on the position of the affected cell relative to the field of neural induction. Thereby, otx2, pax6, and rx1 mediate early steps of retinal specification, including the regulation of morphogenetic cell movements, that are dependent on the level of neural-inductive signaling.
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Affiliation(s)
- K L Kenyon
- Department of Anatomy and Cell Biology, Institute for Biomedical Sciences, The George Washington University, Washington, D.C 20037, USA
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Chang T, Mazotta J, Dumstrei K, Dumitrescu A, Hartenstein V. Dpp and Hh signaling in the Drosophila embryonic eye field. Development 2001; 128:4691-704. [PMID: 11731450 DOI: 10.1242/dev.128.23.4691] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have analyzed the function of the Decapentaplegic (Dpp) and Hedgehog (Hh) signaling pathways in partitioning the dorsal head neurectoderm of the Drosophila embryo. This region, referred to as the anterior brain/eye anlage, gives rise to both the visual system and the protocerebrum. The anlage splits up into three main domains: the head midline ectoderm, protocerebral neurectoderm and visual primordium. Similar to their vertebrate counterparts, Hh and Dpp play an important role in the partitioning of the anterior brain/eye anlage. Dpp is secreted in the dorsal midline of the head. Lowering Dpp levels (in dpp heterozygotes or hypomorphic alleles) results in a ‘cyclops’ phenotype, where mid-dorsal head epidermis is transformed into dorsolateral structures, i.e. eye/optic lobe tissue, which causes a continuous visual primordium across the dorsal midline. Absence of Dpp results in the transformation of both dorsomedial and dorsolateral structures into brain neuroblasts. Regulatory genes that are required for eye/optic lobe fate, including sine oculis (so) and eyes absent (eya), are turned on in their respective domains by Dpp. The gene zerknuellt (zen), which is expressed in response to peak levels of Dpp in the dorsal midline, secondarily represses so and eya in the dorsomedial domain. Hh and its receptor/inhibitor, Patched (Ptc), are expressed in a transverse stripe along the posterior boundary of the eye field. As reported previously, Hh triggers the expression of determinants for larval eye (atonal) and adult eye (eyeless) in those cells of the eye field that are close to the Hh source. Eya and So, which are induced by Dpp, are epistatic to the Hh signal. Loss of Ptc, as well as overexpression of Hh, results in the ectopic induction of larval eye tissue in the dorsal midline (cyclopia). We discuss the similarities between vertebrate systems and Drosophila with regard to the fate map of the anterior brain/eye anlage, and its partitioning by Dpp and Hh signaling.
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Affiliation(s)
- T Chang
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
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Hartley KO, Hardcastle Z, Friday RV, Amaya E, Papalopulu N. Transgenic Xenopus embryos reveal that anterior neural development requires continued suppression of BMP signaling after gastrulation. Dev Biol 2001; 238:168-84. [PMID: 11784002 DOI: 10.1006/dbio.2001.0398] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In vertebrates, BMP signaling before gastrulation suppresses neural development. Later in development, BMP signaling specifies a dorsal and ventral fate in the forebrain and dorsal fate in the spinal cord. It is therefore possible that a change in the competence of the ectoderm to respond to BMP signaling occurs at some point in development. We report that exposure of the anterior neural plate to BMP4 before gastrulation causes suppression of all neural markers tested. To determine the effects of BMP4 after gastrulation, we misexpressed BMP4 using a Pax-6 promoter fragment in transgenic frog embryos and implanted beads soaked in BMP4 in the anterior neural plate. Suppression of most anterior neural markers was observed. We conclude that most neural genes continue to require suppression of BMP signaling into the neurula stages. Additionally, we report that BMP4 and BMP7 are abundantly expressed in the prechordal mesoderm of the neurula stage embryo. This poses the paradox of how the expression of most neural genes is maintained if they can be inhibited by BMP signaling. We show that at least one gene in the anterior neural plate suppresses the response of the ectoderm to BMP signaling. We propose that the suppressive effect of BMP signaling on the expression of neural genes coupled with localized suppressors of BMP signaling result in the fine-tuning of gene expression in the anterior neural plate.
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Affiliation(s)
- K O Hartley
- Department of Zoology, Wellcome/CRC Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom
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Germot A, Lecointre G, Plouhinec JL, Le Mentec C, Girardot F, Mazan S. Structural evolution of Otx genes in craniates. Mol Biol Evol 2001; 18:1668-78. [PMID: 11504847 DOI: 10.1093/oxfordjournals.molbev.a003955] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Using a degenerate PCR approach, we performed an exhaustive search of Otx genes in the reedfish Erpetoichthys calabaricus, the dogfish Scyliorhinus canicula, and the hagfish Myxine glutinosa. Three novel Otx genes were identified in each of these species, and their deduced protein sequences were determined over a large C-terminal fragment located immediately downstream of the homeodomain. Like their lamprey and osteichthyan counterparts, these nine genes display a tandem duplication of a 20--25-residue C-terminal domain, which appears to be a hallmark of all craniate Otx genes identified thus far, including the highly divergent Crx gene. Phylogenetic analyses show that, together with their osteichthyan counterparts, the dogfish and reedfish genes can be classified into three gnathostome orthology classes. Two of the three genes identified in each of these species belong to the Otx1 and Otx2 orthology classes previously characterized in osteichthyans. The third one unambiguously clusters with the Otx5/Otx5b genes recently characterized in Xenopus laevis, thus defining a novel orthology class. Our results also strongly suggest that the highly divergent Crx genes identified in humans, rodents, and oxen are the mammalian representatives of this third class. The hagfish genes display no clear relationships to the three gnathostome orthology classes, but one of them appears to be closely related to the LjOtxA gene, previously identified in Lampetra japonica. Taken together, these data support the hypothesis that the Otx multigene families characterized in craniates all derive from duplications of a single ancestral gene which occurred after the splitting of cephalochordates but prior to the gnathostome radiation. Using site-by-site sequence comparisons of the gnathostome Otx proteins, we also identified structural constraints selectively acting on each of the three gnathostome orthology classes. This suggests that specialized functions for each of these orthology classes were fixed in the gnathostome lineage prior to the splitting between osteichthyans and chondrichthyans.
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Affiliation(s)
- A Germot
- Equipe ATIPE de l'UPRES-A 8080 Développement et Evolution, Orsay, France
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Hinman VF, Degnan BM. Homeobox Genes, Retinoic Acid and the Development and Evolution of Dual Body Plans in the AscidianHerdmania curvata1. ACTA ACUST UNITED AC 2001. [DOI: 10.1668/0003-1569(2001)041[0664:hgraat]2.0.co;2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Hinman VF, Degnan BM. Homeobox Genes, Retinoic Acid and the Development and Evolution of Dual Body Plans in the AscidianHerdmania curvata. ACTA ACUST UNITED AC 2001. [DOI: 10.1093/icb/41.3.664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Abstract
Proper dorsal--ventral pattern formation of the optic cup is essential for vertebrate eye morphogenesis and retinotectal topographic mapping. Previous studies have suggested that midline tissue-derived Sonic hedgehog (Shh) molecules play critical roles in establishing the bilateral eye fields and in determining the proximal--distal axis of the eye primordium. Here, we have examined the temporal requirements for Shh during the optic vesicle to optic cup transition and after early optic cup formation in chick embryos. Both misexpressing Shh by virus and blocking Shh activity by antibodies resulted in disruption of ventral ocular tissues. Decreasing endogenous Shh signals unexpectedly revealed a sharp morphological boundary subdividing dorsal and ventral portions of the optic cup. In addition, Shh signals differentially influenced expression patterns of genes involved in ocular tissue specification (Pax6, Pax2, and Otx2) and dorsal--ventral patterning (cVax) within the ventral but not dorsal optic cup. Ectopic Shh suppressed expression of Bone Morphogenetic Protein 4 (BMP4) in the dorsal retina, whereas reducing endogenous Sonic hedgehog activity resulted in a ventral expansion of BMP4 territory. These results demonstrate that temporal requirements for Shh signals persist after the formation of the optic cup and suggest that the early vertebrate optic primordium may be subdivided into dorsal and ventral compartments. We propose a model in which ventrally derived Shh signals and dorsally restricted BMP4 signals act antagonistically to regulate the growth and specification of the optic primordium.
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Affiliation(s)
| | - Xian-Jie Yang
- To whom correspondence and reprint requests should be addressed. . Fax: (310) 794-2144
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50
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Abstract
Most of the gene candidates for the control of developmental programmes that underlie brain morphogenesis in vertebrates are the homologues of Drosophila genes coding for signalling molecules or transcription factors. Among these, the orthodenticle group includes the Drosophila orthodenticle (otd) and the vertebrate Otx1 and Otx2 genes, which are mostly involved in fundamental processes of anterior neural patterning. These genes encode transcription factors that recognise specific target sequences through the DNA binding properties of the homeodomain. In Drosophila, mutations of otd cause the loss of the anteriormost head neuromere where the gene is transcribed, suggesting that it may act as a segmentation "gap" gene. In mouse embryos, the expression patterns of Otx1 and Otx2 have shown a remarkable similarity with the Drosophila counterpart. This suggested that they could be part of a conserved control system operating in the brain and different from that coded by the HOX complexes controlling the hindbrain and spinal cord. To verify this hypothesis a series of mouse models have been generated in which the functions of the murine genes were: (i) fully inactivated, (ii) replaced with each others, (iii) replaced with the Drosophila otd gene. Otx1-/- mutants suffer from epilepsy and are affected by neurological, hormonal, and sense organ defects. Otx2-/- mice are embryonically lethal, they show gastrulation impairments and fail in specifying anterior neural plate. Analysis of the Otx1-/-; Otx2+/- double mutants has shown that a minimal threshold level of the proteins they encode is required for the correct positioning of the midbrain-hindbrain boundary (MHB). In vivo otd/Otx reciprocal gene replacement experiments have provided evidence of a general functional equivalence among otd, Otx1 and Otx2 in fly and mouse. Altogether these data highlight a crucial role for the Otx genes in specification, regionalization and terminal differentiation of rostral central nervous system (CNS) and lead to hypothesize that modification of their regulatory control may have influenced morphogenesis and evolution of the brain.
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Affiliation(s)
- D Acampora
- International Institute of Genetics and Biophysics, CNR, Via G. Marconi 12, 80125 Naples, Italy
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