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Kumar S, Umair Z, Kumar V, Kumar S, Lee U, Kim J. Foxd4l1.1 negatively regulates transcription of neural repressor ventx1.1 during neuroectoderm formation in Xenopus embryos. Sci Rep 2020; 10:16780. [PMID: 33033315 PMCID: PMC7545198 DOI: 10.1038/s41598-020-73662-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Accepted: 09/16/2020] [Indexed: 11/09/2022] Open
Abstract
Neuroectoderm formation is the first step in development of a proper nervous system for vertebrates. The developmental decision to form a non-neural ectoderm versus a neural one involves the regulation of BMP signaling, first reported many decades ago. However, the precise regulatory mechanism by which this is accomplished has not been fully elucidated, particularly for transcriptional regulation of certain key transcription factors. BMP4 inhibition is a required step in eliciting neuroectoderm from ectoderm and Foxd4l1.1 is one of the earliest neural genes highly expressed in the neuroectoderm and conserved across vertebrates, including humans. In this work, we focused on how Foxd4l1.1 downregulates the neural repressive pathway. Foxd4l1.1 inhibited BMP4/Smad1 signaling and triggered neuroectoderm formation in animal cap explants of Xenopus embryos. Foxd4l1.1 directly bound within the promoter of endogenous neural repressor ventx1.1 and inhibited ventx1.1 transcription. Foxd4l1.1 also physically interacted with Xbra in the nucleus and inhibited Xbra-induced ventx1.1 transcription. In addition, Foxd4l1.1 also reduced nuclear localization of Smad1 to inhibit Smad1-mediated ventx1.1 transcription. Foxd4l1.1 reduced the direct binding of Xbra and Smad1 on ventx1.1 promoter regions to block Xbra/Smad1-induced synergistic activation of ventx1.1 transcription. Collectively, Foxd4l1.1 negatively regulates transcription of a neural repressor ventx1.1 by multiple mechanisms in its exclusively occupied territory of neuroectoderm, and thus leading to primary neurogenesis. In conjunction with the results of our previous findings that ventx1.1 directly represses foxd4l1.1, the reciprocal repression of ventx1.1 and foxd4l1.1 is significant in at least in part specifying the mechanism for the non-neural versus neural ectoderm fate determination in Xenopus embryos.
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Affiliation(s)
- Shiv Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea
| | - Zobia Umair
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea
| | - Vijay Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea
| | - Santosh Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea
| | - Unjoo Lee
- Department of Electrical Engineering, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea.
| | - Jaebong Kim
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do, Chuncheon, 24252, Republic of Korea.
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Umair Z, Kumar S, Kim DH, Rafiq K, Kumar V, Kim S, Park JB, Lee JY, Lee U, Kim J. Ventx1.1 as a Direct Repressor of Early Neural Gene zic3 in Xenopus laevis. Mol Cells 2018; 41:1061-1071. [PMID: 30590909 PMCID: PMC6315313 DOI: 10.14348/molcells.2018.0341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 09/14/2018] [Indexed: 01/07/2023] Open
Abstract
From Xenopus embryo studies, the BMP4/Smad1-targeted gene circuit is a key signaling pathway for specifying the cell fate between the ectoderm and neuro-ectoderm as well as the ventral and dorsal mesoderm. In this context, several BMP4/Smad1 target transcriptional factors have been identified as repressors of the neuro-ectoderm. However, none of these direct target transcription factors in this pathway, including GATA1b, Msx1 and Ventx1.1 have yet been proven as direct repressors of early neuro-ectodermal gene expression. In order to demonstrate that Ventx1.1 is a direct repressor of neuro-ectoderm genes, a genome-wide Xenopus ChIP-Seq of Ventx1.1 was performed. In this study, we demonstrated that Ventx1.1 bound to the Ventx1.1 response cis-acting element 1 and 2 (VRE1 and VRE2) on the promoter for zic3, which is a key early neuro-ectoderm gene, and this Ventx1.1 binding led to repression of zic3 transcription. Site-directed mutagenesis of VRE1 and VRE2 within zic3 promoter completely abolished the repression caused by Ventx1.1. In addition, we found both the positive and negative regulation of zic3 promoter activity by FoxD5b and Xcad2, respectively, and that these occur through the VREs and via modulation of Ventx1.1 levels. Taken together, the results demonstrate that the BMP4/Smad1 target gene, Ventx1.1, is a direct repressor of neuro-ectodermal gene zic3 during early Xenopus embryogenesis.
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Affiliation(s)
- Zobia Umair
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Shiv Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Daniel H. Kim
- Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 03722,
Korea
| | - Khezina Rafiq
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Vijay Kumar
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - SungChan Kim
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Jae-Bong Park
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Jae-Yong Lee
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
| | - Unjoo Lee
- Department of Electrical Engineering, Hallym University, Gangwon-Do 24252,
Korea
| | - Jaebong Kim
- Department of Biochemistry, Institute of Cell Differentiation and Aging, College of Medicine, Hallym University, Gangwon-Do 24252,
Korea
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Amber S, Zahid S. Data integration for functional annotation of regulatory single nucleotide polymorphisms associated with Alzheimer's disease susceptibility. Gene 2018; 672:115-125. [PMID: 29883757 DOI: 10.1016/j.gene.2018.06.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 05/30/2018] [Accepted: 06/04/2018] [Indexed: 01/10/2023]
Abstract
BACKGROUND Alzheimer's disease (AD), the most common form of dementia affects 24.3 million people worldwide. More than twenty genetic loci have been associated with AD and a significant number of genetic variants were mapped within these loci. A large proportion of genome wide significant variants lie outside the coding region. However, the plausible function of these variants is still unexplored. OBJECTIVE The present study aimed to unravel the regulatory role of proxy single nucleotide polymorphisms (SNPs), to determine their risk of developing AD. METHODS The RegulomeDB was employed to predict the regulatory role of proxy SNPs. Protein association network and functional enrichment analysis was performed using String10.5 and gene ontology, respectively. RESULTS A total of 451 SNPs were examined through SNAP web portal (r2 ≤ 0.80) which returned 2186 proxy SNPs in linkage disequilibrium (LD) with genome wide significant SNPs for AD. Out of 2186 SNPs analyzed in RegulomeDB, 151 had the scores < 3 that indicates the high degree of their potential regulatory function. Further analysis revealed that out of these 151 SNPs, 37 were genome wide significant for AD, 17 were significantly associated with diseases other than AD, 89 were proxy SNPs (not genome wide significant) for various diseases including AD while 8 SNPs were novel proxy SNPs for AD. CONCLUSION These findings support the notion that the non-coding variants can be strongly associated with disease risk. Further validation through genome wide association studies will be helpful for the elucidation of their regulatory potential.
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Affiliation(s)
- Sanila Amber
- Neurobiology Research Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan
| | - Saadia Zahid
- Neurobiology Research Laboratory, Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan.
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Watanabe M, Yasuoka Y, Mawaribuchi S, Kuretani A, Ito M, Kondo M, Ochi H, Ogino H, Fukui A, Taira M, Kinoshita T. Conservatism and variability of gene expression profiles among homeologous transcription factors in Xenopus laevis. Dev Biol 2017; 426:301-324. [DOI: 10.1016/j.ydbio.2016.09.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 07/27/2016] [Accepted: 09/19/2016] [Indexed: 12/11/2022]
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Shah RR, Koniski A, Shinde M, Blythe SA, Fass DM, Haggarty SJ, Palis J, Klein PS. Regulation of primitive hematopoiesis by class I histone deacetylases. Dev Dyn 2013; 242:108-21. [PMID: 23184530 PMCID: PMC3553261 DOI: 10.1002/dvdy.23906] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Revised: 10/16/2012] [Accepted: 11/08/2012] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Histone deacetylases (HDACs) regulate multiple developmental processes and cellular functions. However, their roles in blood development have not been determined, and in Xenopus laevis a specific function for HDACs has yet to be identified. Here, we employed the class I selective HDAC inhibitor, valproic acid (VPA), to show that HDAC activity is required for primitive hematopoiesis. RESULTS VPA treatment during gastrulation resulted in a complete absence of red blood cells (RBCs) in Xenopus tadpoles, but did not affect development of other mesodermal tissues, including myeloid and endothelial lineages. These effects of VPA were mimicked by Trichostatin A (TSA), a well-established pan-HDAC inhibitor, but not by valpromide, which is structurally similar to VPA but does not inhibit HDACs. VPA also caused a marked, dose-dependent loss of primitive erythroid progenitors in mouse yolk sac explants at clinically relevant concentrations. In addition, VPA treatment inhibited erythropoietic development downstream of bmp4 and gata1 in Xenopus ectodermal explants. CONCLUSIONS These findings suggest an important role for class I HDACs in primitive hematopoiesis. Our work also demonstrates that specific developmental defects associated with exposure to VPA, a significant teratogen in humans, arise through inhibition of class I HDACs.
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Affiliation(s)
- Rishita R. Shah
- Cell and Molecular Biology Graduate Group, University of Pennsylvania Philadelphia, PA USA 19104
| | - Anne Koniski
- Department of Pediatrics Center for Pediatric Biomedical Research University of Rochester Medical Center 601 Elmwood Ave. Rochester, NY 14642
| | - Mansi Shinde
- Pharmacology Graduate Group, University of Pennsylvania Philadelphia, PA USA 19104
| | - Shelby A. Blythe
- Cell and Molecular Biology Graduate Group, University of Pennsylvania Philadelphia, PA USA 19104
| | - Daniel M. Fass
- Stanley Center for Psychiatric Research Broad Institute of Harvard and MIT Cambridge, MA USA 02142
- Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School Boston, MA USA 02114
| | - Stephen J. Haggarty
- Stanley Center for Psychiatric Research Broad Institute of Harvard and MIT Cambridge, MA USA 02142
- Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School Boston, MA USA 02114
| | - James Palis
- Department of Pediatrics Center for Pediatric Biomedical Research University of Rochester Medical Center 601 Elmwood Ave. Rochester, NY 14642
| | - Peter S. Klein
- Cell and Molecular Biology Graduate Group, University of Pennsylvania Philadelphia, PA USA 19104
- Pharmacology Graduate Group, University of Pennsylvania Philadelphia, PA USA 19104
- Department of Medicine (Hematology/Oncology) University of Pennsylvania School of Medicine Philadelphia, PA USA 19104
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Pieper M, Ahrens K, Rink E, Peter A, Schlosser G. Differential distribution of competence for panplacodal and neural crest induction to non-neural and neural ectoderm. Development 2012; 139:1175-87. [PMID: 22318231 DOI: 10.1242/dev.074468] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It is still controversial whether cranial placodes and neural crest cells arise from a common precursor at the neural plate border or whether placodes arise from non-neural ectoderm and neural crest from neural ectoderm. Using tissue grafting in embryos of Xenopus laevis, we show here that the competence for induction of neural plate, neural plate border and neural crest markers is confined to neural ectoderm, whereas competence for induction of panplacodal markers is confined to non-neural ectoderm. This differential distribution of competence is established during gastrulation paralleling the dorsal restriction of neural competence. We further show that Dlx3 and GATA2 are required cell-autonomously for panplacodal and epidermal marker expression in the non-neural ectoderm, while ectopic expression of Dlx3 or GATA2 in the neural plate suppresses neural plate, border and crest markers. Overexpression of Dlx3 (but not GATA2) in the neural plate is sufficient to induce different non-neural markers in a signaling-dependent manner, with epidermal markers being induced in the presence, and panplacodal markers in the absence, of BMP signaling. Taken together, these findings demonstrate a non-neural versus neural origin of placodes and neural crest, respectively, strongly implicate Dlx3 in the regulation of non-neural competence, and show that GATA2 contributes to non-neural competence but is not sufficient to promote it ectopically.
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Affiliation(s)
- Mareike Pieper
- Brain Research Institute, University of Bremen, FB2, PO Box 330440, 28334 Bremen, Germany
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Voumvourakis KI, Antonelou RC, Kitsos DK, Stamboulis E, Tsiodras S. TGF-β/BMPs: crucial crossroad in neural autoimmune disorders. Neurochem Int 2011; 59:542-50. [PMID: 21718734 DOI: 10.1016/j.neuint.2011.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Revised: 05/15/2011] [Accepted: 06/05/2011] [Indexed: 01/12/2023]
Abstract
Transforming growth factor beta (TGF-β) has a crucial role in the differentiation of ectodermal cells to neural or epidermal precursors. TGF-β and bone morphogenetic protein molecules (BMPs) are involved in many developmental processes, including cell proliferation and differentiation, apoptosis, mitotic arrest and intercellular interactions during morphogenesis. Additionally, the failure of central thymic tolerance mechanisms, leading to T cells with a skewed autoreactive response, is being described as a contributor in inflammatory processes in autoimmune diseases such as multiple sclerosis. Since TGF-β and BMP proteins are crucial for the development of the neural system and the thymus, as well as for the differentiation of T cells, it is essential to further investigate their role in the pathophysiology of this disorder by using references from embryonic experimental research. Available literature in the TGF/BMP signalling cascade, mostly during embryonic development of the nervous system is being reviewed. An attempt is made to further elucidate a potential role of TGF/BMP signalling in the pathophysiology of MS. During demyelination, BMP signaling, through various molecular mechanisms, directs the development of the adult neural stem cell in the astrocyte rather than the oligodendrocyte direction, therefore inhibiting the repair process. Further understanding of the above relationships could lead to the development of potentially efficient therapies for MS in the future.
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Affiliation(s)
- Konstantine I Voumvourakis
- 2nd Department of Neurology, Attikon University Hospital, University of Athens Medical School, Athens, Greece
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Schlosser G. Making senses development of vertebrate cranial placodes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 283:129-234. [PMID: 20801420 DOI: 10.1016/s1937-6448(10)83004-7] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cranial placodes (which include the adenohypophyseal, olfactory, lens, otic, lateral line, profundal/trigeminal, and epibranchial placodes) give rise to many sense organs and ganglia of the vertebrate head. Recent evidence suggests that all cranial placodes may be developmentally related structures, which originate from a common panplacodal primordium at neural plate stages and use similar regulatory mechanisms to control developmental processes shared between different placodes such as neurogenesis and morphogenetic movements. After providing a brief overview of placodal diversity, the present review summarizes current evidence for the existence of a panplacodal primordium and discusses the central role of transcription factors Six1 and Eya1 in the regulation of processes shared between different placodes. Upstream signaling events and transcription factors involved in early embryonic induction and specification of the panplacodal primordium are discussed next. I then review how individual placodes arise from the panplacodal primordium and present a model of multistep placode induction. Finally, I briefly summarize recent advances concerning how placodal neurons and sensory cells are specified, and how morphogenesis of placodes (including delamination and migration of placode-derived cells and invagination) is controlled.
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Affiliation(s)
- Gerhard Schlosser
- Zoology, School of Natural Sciences & Martin Ryan Institute, National University of Ireland, Galway, Ireland
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9
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Zheng C, Zhu Q, Sankoff D. Descendants of Whole Genome Duplication within Gene Order Phylogeny. J Comput Biol 2008; 15:947-64. [DOI: 10.1089/cmb.2008.0118] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Chunfang Zheng
- Departments of Biology, Biochemistry, and Mathematics and Statistics, University of Ottawa, Ottawa, Canada
| | - Qian Zhu
- Departments of Biology, Biochemistry, and Mathematics and Statistics, University of Ottawa, Ottawa, Canada
| | - David Sankoff
- Departments of Biology, Biochemistry, and Mathematics and Statistics, University of Ottawa, Ottawa, Canada
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Hutton JF, Rozenkov V, Khor FSL, D'Andrea RJ, Lewis ID. Bone morphogenetic protein 4 contributes to the maintenance of primitive cord blood hematopoietic progenitors in an ex vivo stroma-noncontact co-culture system. Stem Cells Dev 2007; 15:805-13. [PMID: 17253944 DOI: 10.1089/scd.2006.15.805] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Establishment of conditions supporting hematopoietic stem cell (HSC) maintenance and expansion ex vivo is critical for wider clinical application of cord blood (CB) transplantation. AFT024 is a murine fetal liver cell line that expands primitive hematopoietic cells via a process that is not understood. Here we show that bone morphogenic protein 4 (BMP4) is produced by AFT024 and contributes significantly to the maintenance of co-cultured CB-derived primitive cells. Significant amounts of BMP4 mRNA are produced by the supportive AFT024 stromal cell line, and secreted BMP4 protein accumulates in AFT024 conditioned medium. Blockade of BMP4 activity in this coculture model using neutralizing BMP4 monoclonal antibody reduced expansion of primitive CB cells on the basis of phenotypic (CD34(+)CD38(-)) and functional criteria [long-term culture initiating cells (LTC-IC)] and significantly reduced the capacity of the cultured CB stem cells to support repopulation in the nonobese diabetic-severe combined immunodeficiency (NOD-SCID) xenograft model. Therefore, BMP4 is a key growth factor for maintenance of HSC and contributes to the unique properties of the AFT024 stromal noncontact culture.
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Affiliation(s)
- Jonathon F Hutton
- Haematology and Oncology Program, Child Health Research Institute, The Queen Elizabeth Hospital and the Schools of Paediatrics and Reproductive Health and Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, 5006
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11
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Gillis WJ, Bowerman B, Schneider SQ. Ectoderm- and endomesoderm-specific GATA transcription factors in the marine annelid Platynereis dumerilli. Evol Dev 2007; 9:39-50. [PMID: 17227365 DOI: 10.1111/j.1525-142x.2006.00136.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The GATA family of transcription factors appears to retain conserved roles in early germ layer patterning in most, if not all, animals; however, the number and structure of GATA factor genes varies substantially when different animal genomes are compared. Thus, the origin and relationships of invertebrate and vertebrate GATA factors, and their involvement in animal germ layer evolution, are unclear. We identified two highly conserved GATA factor genes in a marine annelid, the polychaete Platynereis dumerilii. A phylogenetic analysis indicates that the two Platynereis GATA factors are orthologous to the GATA1/2/3 and GATA4/5/6 subfamilies present in vertebrates. We also identified conserved motifs within each GATA class, and assigned the divergent Caenorhabditiselegans and Drosophila melanogaster GATA factor genes to the vertebrate classes. Similar to their vertebrate homologs, PdGATA123 mRNA expression was restricted to ectoderm, whereas PdGATA456 was detected only in endomesoderm. Finally, we identified in genome databases one GATA factor gene in each of two distantly related cnidarians that include motifs from both bilaterian GATA factor classes. Our results show that distinct orthologs of the two vertebrate GATA factor classes exist in a protostome invertebrate, suggesting that bilaterian GATA factors originated from GATA1/2/3 and 4/5/6 ancestral orthologs. Moreover, our results indicate that the GATA gene duplication and the functional divergence that led to these two ancestral GATA factor genes occurred after the split of the bilaterian stem group from the cnidarians.
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Affiliation(s)
- William J Gillis
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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12
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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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Sadlon TJ, Lewis ID, D'Andrea RJ. BMP4: Its Role in Development of the Hematopoietic System and Potential as a Hematopoietic Growth Factor. Stem Cells 2004; 22:457-74. [PMID: 15277693 DOI: 10.1634/stemcells.22-4-457] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Blood formation occurs throughout the life of an individual in a process driven by hematopoietic stem cells (HSCs). The ability of bone marrow (BM) and cord blood (CB) HSC to undergo self-renewal and develop into multiple blood lineages has made these cells an important clinical resource. Transplantation with BM- and CB-derived HSCs is now used extensively for treatment of hematological disorders, malignancies, and immunodeficiencies. An understanding of the embryonic origin of HSC and the factors regulating their generation and expansion in vivo will provide important information for the manipulation of these cells ex vivo. This is critical for the further development of CB transplantation, the potential of which is limited by small numbers of HSC in the donor population. Although the origins of HSCs have become clearer and progress has been made in identifying genes that are critical for the formation and maintenance of HSCs, less is known about the signals that commit specific populations of mesodermal precursors to hematopoietic cell fate. Critical signals acting on these precursor cells are likely to be derived from visceral endoderm in yolk sac and from underlying stroma in the aorta-gonad-mesonephros region. Here we summarize briefly the origin of yolk sac and embryonic HSCs before detailing evidence that bone morphogenic protein-4 (BMP4) has a crucial role in Xenopus and mammalian HSC development. We discuss evidence that BMP4 acts as a hematopoietic growth factor and review its potential to modulate HSC in ex vivo expansion cultures from cord blood.
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Affiliation(s)
- Timothy J Sadlon
- Immunology Program, Child Health Research Institute, North Adelaide, South Australia
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Parlakian A, Tuil D, Hamard G, Tavernier G, Hentzen D, Concordet JP, Paulin D, Li Z, Daegelen D. Targeted inactivation of serum response factor in the developing heart results in myocardial defects and embryonic lethality. Mol Cell Biol 2004; 24:5281-9. [PMID: 15169892 PMCID: PMC419888 DOI: 10.1128/mcb.24.12.5281-5289.2004] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Serum response factor (SRF) is at the confluence of multiple signaling pathways controlling the transcription of immediate-early response genes and muscle-specific genes. There are active SRF target sequences in more than 50 genes expressed in the three muscle lineages including normal and diseased hearts. However, the role of SRF in heart formation has not been addressed in vivo thus far due to the early requirement of SRF for mesoderm formation. We have generated a conditional mutant of SRF by using Cre-LoxP strategy that will be extremely useful to study the role of SRF in embryonic and postnatal cardiac functions, as well as in other tissues. This report shows that heart-specific deletion of SRF in the embryo by using a new beta MHC-Cre transgenic mouse line results in lethal cardiac defects between embryonic day 10.5 (E10.5) and E13.5, as evidenced by abnormally thin myocardium, dilated cardiac chambers, poor trabeculation, and a disorganized interventricular septum. At E9.5, we found a marked reduction in the expression of essential regulators of heart development, including Nkx2.5, GATA4, myocardin, and the SRF target gene c-fos prior to overt maldevelopment. We conclude that SRF is crucial for cardiac differentiation and maturation, acting as a global regulator of multiple developmental genes.
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Affiliation(s)
- Ara Parlakian
- Laboratoire de Biologie Moléculaire de la Différenciation, Université Paris 7, 75005 Paris, France
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Peng Y, Jiang BH, Yang PH, Cao Z, Shi X, Lin MCM, He ML, Kung HF. Phosphatidylinositol 3-kinase signaling is involved in neurogenesis during Xenopus embryonic development. J Biol Chem 2004; 279:28509-14. [PMID: 15123704 DOI: 10.1074/jbc.m402294200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol 3-kinase (PI3K) has numerous cellular functions, including cell survival and proliferation. In this study, we demonstrated that the expression of the active form of PI3K induced dorsal differentiation and axis duplication and strongly induced the expression of neural markers. In contrast, the inhibition of PI3K activity by its dominant negative mutant induced the phenotype of losing posterior structures and the expression of ventral markers. Akt is an essential target of PI3K for neurogenesis. The expression of the active form of Akt induced axis duplication and increased the expression of neural markers. Inhibition of the Akt activity abolished the PI3K-induced double heads and axes. This signal transmits through its target, glycogen synthase kinase 3beta, which is known to mediate Wnt signaling for Xenopus development. These results identify a new function of PI3K/Akt signaling in axis formation and neurogenesis during Xenopus embryonic development and provide a direct link between growth factor-mediated PI3K/Akt signaling and Wnt signaling during embryonic development.
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Affiliation(s)
- Ying Peng
- Department of Neurology, Nanfang Hospital, The First Military Medical University, Guangzhou 510515, China
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16
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Bertrand V, Hudson C, Caillol D, Popovici C, Lemaire P. Neural Tissue in Ascidian Embryos Is Induced by FGF9/16/20, Acting via a Combination of Maternal GATA and Ets Transcription Factors. Cell 2003; 115:615-27. [PMID: 14651852 DOI: 10.1016/s0092-8674(03)00928-0] [Citation(s) in RCA: 242] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In chordates, formation of neural tissue from ectodermal cells requires an induction. The molecular nature of the inducer remains controversial in vertebrates. Here, using the early neural marker Otx as an entry point, we dissected the neural induction pathway in the simple embryos of Ciona intestinalis. We first isolated the regulatory element driving Otx expression in the prospective neural tissue, showed that this element directly responds to FGF signaling and that FGF9/16/20 acts as an endogenous neural inducer. Binding site analysis and gene loss of function established that FGF9/16/20 induces neural tissue in the ectoderm via a synergy between two maternal response factors. Ets1/2 mediates general FGF responsiveness, while the restricted activity of GATAa targets the neural program to the ectoderm. Thus, our study identifies an endogenous FGF neural inducer and its early downstream gene cascade. It also reveals a role for GATA factors in FGF signaling.
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Affiliation(s)
- Vincent Bertrand
- Laboratoire de Génétique et Physiologie du Développement, IBDM, CNRS/INSERM, Université de la Méditerranée/AP de Marseille, Parc Scientifique de Luminy, Case 907, F-13288, Marseille Cedex 9, France.
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17
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Hwang YS, Lee HS, Roh DH, Cha SW, Lee SY, Seo JJ, Kim J, Park MJ. Active repression of organizer genes by C-terminal domain of PV.1. Biochem Biophys Res Commun 2003; 308:79-86. [PMID: 12890483 DOI: 10.1016/s0006-291x(03)01321-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PV.1, a homeotic protein, ventralizes dorsal mesoderm and inhibits neuralization by mediating BMP-4 signaling in Xenopus embryo. In our previous report antimorphic PV.1 causes a secondary axis by inducing the ectopic organizer. We analyzed the structure of this transcription factor through domain level assessment. In a phenotype-inducing test, half of the N-terminus at the N-terminal side was unessential for inducing ventralization of embryos. We examined the transacting activity of several regions of PV.1 utilizing GAL4 hybrid system. The C-terminal region/GAL4DBD (DNA binding domain) exhibited strong repressive activity on a reporter gene (operator/promoter/reporter; Gal4-TK-luc) as much as the whole polypeptide/GAL4DBD, whereas the N-terminal region/GAL4DBD showed only modest repression. The results suggest that PV.1 functions as a transcriptional repressor and this repressive activity is localized mostly to the C-terminal region. Additional characterizations of N- and C-terminus with respect to the effects on the expression of other genes are described.
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Affiliation(s)
- Yoo-Seok Hwang
- Department of Anatomy, School of Medicine, Kyungpook National University, Taegu 700-422, South Korea
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18
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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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19
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Shim S, Bae N, Han JK. Bone morphogenetic protein-4-induced activation of Xretpos is mediated by Smads and Olf-1/EBF associated zinc finger (OAZ). Nucleic Acids Res 2002; 30:3107-17. [PMID: 12136093 PMCID: PMC135757 DOI: 10.1093/nar/gkf437] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have previously isolated Xretpos, a novel family of long terminal repeat (LTR)-retrotransposons in Xenopus laevis, whose transcript is restricted to ventro-posterior-specific regions and induced by bone morphogenetic protein-4 (BMP-4) signaling. To explore the molecular mechanism of the transcriptional regulation, we identified and characterized Xretpos promoter regions consisting of LTRs and a 5'-untranslated region. We demonstrated that this promoter region contains all the necessary regulatory elements for the spatial and temporal expression of XRETPOS: Sequence analysis of the Xretpos promoter revealed multiple Smad-binding elements and Olf-1/EBF-associated zinc finger (OAZ) binding sites similar to BMP-4 response element, which were identified and proved to be required for BMP-4 induction in the Xvent2 promoter. We further demonstrated that Smads and OAZ proteins bind to their response elements in the promoter and these bindings are essential for the BMP-4-induced activation of the Xretpos promoter. Furthermore, we showed that the endogenous expression of Xretpos protein indeed occurred and was temporally regulated and BMP-4-inducible during the early Xenopus development. Finally, overexpression and partial loss-of-function study revealed that Xretpos has a posterio-ventralizing activity. Together, our results place Xretpos downstream of BMP-4 and provide evidence for the conserved mechanism of transcriptional regulation of the BMP-4 target genes.
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Affiliation(s)
- Sangwoo Shim
- Laboratory of Developmental Biology, Department of Life Science and Division of Molecular and Life Sciences, Pohang University of Science and Technology, San 31 Hyoja-Dong, Pohang, Kyungbuk, 790-784, South Korea
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20
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Peng Y, Xu RH, Mei JM, Li XP, Yan D, Kung HF, Phang JM. Neural inhibition by c-Jun as a synergizing factor in bone morphogenetic protein 4 signaling. Neuroscience 2002; 109:657-64. [PMID: 11927148 DOI: 10.1016/s0306-4522(01)00526-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The transcription factor, activator protein 1 (AP-1) complexes (c-Jun and c-Fos heterodimers) has been shown to interact with transforming growth factor beta signaling in mammalian cells and Drosophila embryo. Here we show that c-Jun alone is involved in the anti-neuralizing activity of bone morphogenetic protein 4, a transforming growth factor beta superfamily member, in Xenopus neurogenesis. Co-injection of mRNAs encoding c-jun and a dominant negative bone morphogenetic protein receptor completely inhibits dominant negative bone morphogenetic protein receptor-induced neuralization and reverses the epidermal fate in the animal cap. Surprisingly, a dominant negative c-Jun does not induce neural tissue in the animal cap, but it synergizes with dominant negative bone morphogenetic protein receptor for neural induction. Temporal analysis using a dexamethasone-inducible c-Jun shows that exogenous c-Jun activity must be turned on before or at stage 11 to fulfill the anti-neuralizing effect. Neural inhibition by c-Jun does not occur until stage 13 suggesting that c-Jun probably acts by suppressing neural maintenance rather than neural initiation. This is also supported by the fact that c-Jun does not inhibit expression of the neural-initializing gene Zic-r1 but the neural cofactor Sox2, and that ectopic expression of Sox2 attenuates the anti-neuralizing effect of c-Jun. Finally, we display that the c-Jun effect is enhanced by an auto-regulatory loop between c-Jun and bone morphogenetic protein. These studies suggest that c-Jun/AP-1 is a converging point in both the fibroblast growth factor and transforming growth factor beta signaling pathways. Based on our findings, we propose that c-Jun synergizes with bone morphogenetic protein 4 signaling to inhibit neural development in Xenopus ectoderm.
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Affiliation(s)
- Y Peng
- Metabolism and Cancer Susceptibility Section, Basic Research Laboratory, NCI-FCRDC, National Institutes of Health, Frederick, MD 21702-1201, USA
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21
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Hwang YS, Seo JJ, Cha SW, Lee HS, Lee SY, Roh DH, Kung Hf HF, Kim J, Ja Park M. Antimorphic PV.1 causes secondary axis by inducing ectopic organizer. Biochem Biophys Res Commun 2002; 292:1081-6. [PMID: 11944926 DOI: 10.1006/bbrc.2002.6740] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Xenopus homeobox gene, PV.1 ventralizes activin-induced dorsal mesoderm and inhibits neuralization of ectoderm in animal cap when overexpressed. Here we generated PV.1/engrailed fusion construct (N-PV1-EnR) to perform loss-of-function study for this transcription factor. N-PV1-EnR showed an extremely antimorphic effect, causing a partial secondary embryonic axis when expressed at ventral marginal zone of blastula. In ventral marginal zone cells, this chimeric protein induced organizer genes and suppressed ventral markers mimicking those effects reported for dominant negative BMP-4 receptor (DNBR). Moreover, N-PV1-EnR rescued the ventralized embryos caused by the ectopic dorsal expression of PV.1 but not by that of Xvent-2. These results suggested that PV.1 functions at downstream of BMP-4 as a ventralizing effector which acts separately from Xvent-2 and the dominant negative effect gained by this specific mutant is applicable for the further studies of BMP-4 downstream pathway.
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MESH Headings
- Activin Receptors, Type I/genetics
- Activin Receptors, Type I/metabolism
- Animals
- Body Patterning/drug effects
- Body Patterning/physiology
- Bone Morphogenetic Protein Receptors, Type I
- Embryo, Nonmammalian/drug effects
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/physiology
- Embryonic Induction/drug effects
- Genes, Dominant
- Homeodomain Proteins/antagonists & inhibitors
- Homeodomain Proteins/genetics
- Homeodomain Proteins/pharmacology
- In Vitro Techniques
- Microinjections
- Organizers, Embryonic/drug effects
- Organizers, Embryonic/metabolism
- Phenotype
- Protein Serine-Threonine Kinases
- RNA, Messenger/administration & dosage
- RNA, Messenger/genetics
- Receptors, Growth Factor
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/pharmacology
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Transcription Factors
- Xenopus
- Xenopus Proteins
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Affiliation(s)
- Yoo-Seok Hwang
- Department of Anatomy, School of Medicine, Kyungpook National University, Taegu, 700-422, South Korea
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22
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Moroni E, Dell'Era P, Rusnati M, Presta M. Fibroblast growth factors and their receptors in hematopoiesis and hematological tumors. JOURNAL OF HEMATOTHERAPY & STEM CELL RESEARCH 2002; 11:19-32. [PMID: 11847001 DOI: 10.1089/152581602753448513] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Fibroblast growth factors (FGFs) belong to a family of pleiotropic heparin-binding growth factors. They exert multiple functions on various cell types of mesodermal and neuroectodermal origin, affecting cell proliferation, motility, survival, and differentiation. FGF's exert their activity by interacting with tyrosine kinase receptors (FGFRs) and cell-surface heparan sulfate proteoglycans. This article reviews recent studies on the role of the FGF/FGFR system in embryonic hematopoietic development, hematopoiesis, and hematological tumors. FGFs exert both autocrine and paracrine functions in these biological processes by acting on blood cells and their precursors and accessory cells in the bone marrow, including stromal and endothelial cells.
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Affiliation(s)
- Emanuela Moroni
- Unit of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology, School of Medicine, University of Brescia, Via Valsabbina 19, 25123 Brescia, Italy
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23
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Chen HD, Huang YK, Ault K, Wong GW, Lin MC, Chen HC, Kung HF. Molecular basis for differing antineurogenic effects of GATA-1a and GATA-1b in Xenopus. Biochem Biophys Res Commun 2000; 273:614-20. [PMID: 10873654 DOI: 10.1006/bbrc.2000.2988] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The erythroid transcription factor GATA-1 in Xenopus has been cloned as a pair of presumably duplicated genes designated as xGATA-1a and xGATA-1b. Although both xGATA-1a and xGATA-1b are able to stimulate erythropoiesis, only xGATA-1b is capable of inhibiting neurogenesis in Xenopus embryos. Chimeras of these two genes were constructed by permuting coding and untranslated regions (UTR) on both ends of these two xGATA-1, and their neurogenesis-inhibitory effects were studied. These results reveal that (1) sequence variations between the coding regions alone do not account for the neurogenesis effect; (2) 3' UTR of xGATA-1a causes the loss of the neurogenesis inhibition of xGATA-1b; (3) 3' UTR of xGATA-1b is essential to inhibit neurogenesis. In addition, the presence of either UTR does not affect the stability of the mRNA in vitro. These observations suggest the influence of 3' UTR in xGATA-1 on the inhibition of neurogenesis.
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Affiliation(s)
- H D Chen
- Endocrinology and Reproduction Research Branch, NICHD, Bethesda, Maryland 20892, USA.
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24
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Liu W, Ren C, Shi J, Feng X, He Z, Xu L, Lan K, Xie L, Peng Y, Fan J, Kung HF, Yao KT, Xu RH. Characterization of the functionally related sites in the neural inducing gene noggin. Biochem Biophys Res Commun 2000; 270:293-7. [PMID: 10733942 DOI: 10.1006/bbrc.2000.2415] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previously we have shown that blocking bone morphogenetic protein (BMP) receptor signaling by a dominant negative BMP receptor causes neurogenesis in Xenopus animal caps (ACs), whereas the physiological neural inducer noggin acts as a homodimer physically binding to BMP-4 and disrupting its signaling at the ligand level. The present study attempted to elucidate the relationship between the structure and function of noggin. By replacing some cysteine residues with serine residues through a site-directed mutagenesis strategy, we generated three noggin mutants, C145S, C205S, and C(218, 220, 222)S (3CS). Although mRNAs encoded by these mutants were translated as efficiently as wild-type (WT) noggin mRNA, they behaved differently when expressed in vivo. Expression of WT noggin or C205S in Xenopus ACs converted the explants (prospective ectoderm) into neural tissue, indicated by the neural-like morphology and expression of the pan neural marker NCAM in the ACs. In contrast, ACs expressing C145S or 3CS sustained an epidermal fate like the control caps. Similar results were observed in the mesoderm where C205S (but not C145S and 3CS) displayed dorsalizing activity as well as WT noggin. Altogether, our results suggest that Cys145 alone or Cys(218, 220, 222) as a whole in noggin protein is required for the biological activities of noggin, probably participating in the dimerization of noggin with BMP-4 or itself.
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Affiliation(s)
- W Liu
- Cancer Research Institute, Hunan Medical University, Changsha, Hunan, 410078, China
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25
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Kishi M, Mizuseki K, Sasai N, Yamazaki H, Shiota K, Nakanishi S, Sasai Y. Requirement of Sox2-mediated signaling for differentiation of early Xenopus neuroectoderm. Development 2000; 127:791-800. [PMID: 10648237 DOI: 10.1242/dev.127.4.791] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
From early stages of development, Sox2-class transcription factors (Sox1, Sox2 and Sox3) are expressed in neural tissues and sensory epithelia. In this report, we show that Sox2 function is required for neural differentiation of early Xenopus ectoderm. Microinjection of dominant-negative forms of Sox2 (dnSox2) mRNA inhibits neural differentiation of animal caps caused by attenuation of BMP signals. Expression of dnSox2 in developing embryos suppresses expression of N-CAM and regional neural markers. We have analyzed temporal requirement of Sox2-mediated signaling by using an inducible dnSox2 construct fused to the ligand-binding domain of the glucocorticoid receptor. Attenuation of Sox2 function both from the late blastula stage and from the late gastrula stage onwards causes an inhibition of neural differentiation in animal caps and in whole embryos. Additionally, dnSox2-injected cells that fail to differentiate into neural tissues are not able to adopt epidermal cell fate. These data suggest that Sox2-class genes are essential for early neuroectoderm cells to consolidate their neural identity during secondary steps of neural differentiation.
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Affiliation(s)
- M Kishi
- Department of Biological Sciences, Institute for Frontier Medical Sciences, Kyoto University, Sakyo, Kyoto 606-8397, Japan
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26
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Abstract
The formation of the vertebrate nervous system is initiated at gastrula stages of development, when signals from a specialized cluster of cells (the organizer) trigger neural development in the ectoderm. This process, termed neural induction, was first described in 1924 and stemmed from experiments on amphibia (Spemann & Mangold 1924). In recent years, the molecular mechanisms underlying neural induction in the amphibian have been elucidated. Surprisingly, neuralizing agents secreted by the organizer do not act via receptor-mediated signaling events; rather, these factors antagonize local epidermal inducers within the cells of the dorsal ectoderm and function to uncover the latent neural fate of these cells. Many of the recent advances in our understanding of vertebrate neural induction come from studies on the frog, Xenopus laevis. It is now clear that a blockade of signaling of the bone morphogenetic proteins (BMPs) during gastrula stages is sufficient to initiate neuralization of the ectoderm in this species. Thus this review first details our current understanding of neural induction, using the amphibian as a model. We then use data emerging from other systems to examine the extent to which the Xenopus studies can be applied to other vertebrate species. The initiation of the neurectoderm-specific gene expression program and subsequent steps in patterning and neuronal development are only touched on here. We focus primarily on the initial establishment of the neural fate in the vertebrate gastrula ectoderm.
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Affiliation(s)
- D C Weinstein
- Department of Molecular Vertebrate Embryology, Rockefeller University, New York, New York 10021, USA
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27
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Deblandre GA, Wettstein DA, Koyano-Nakagawa N, Kintner C. A two-step mechanism generates the spacing pattern of the ciliated cells in the skin of Xenopus embryos. Development 1999; 126:4715-28. [PMID: 10518489 DOI: 10.1242/dev.126.21.4715] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The skin of Xenopus embryos contains a population of specialized ciliated cells that are distributed in an evenly spaced pattern. Here we describe two successive steps that govern the differentiation and the generation of the spacing pattern of these ciliated cells. The first step occurs in the inner or sensorial layer of the non-neural ectoderm where a subset of cells are chosen to differentiate into ciliated-cell precursors. This choice is under the control of lateral inhibition mediated by a Suppressor of Hairless-dependent Notch signaling pathway, in which X-Delta-1 is the putative ligand driving the selection process, and a new Enhancer-of-Split-related gene is an epidermal target of Notch signaling. Because nascent ciliated-cell precursors prevent neighboring cells from taking on the same fate, a scattered pattern of these precursors is generated within the deep layer of the non-neural ectoderm. Ciliated-cell precursors then intercalate into the outer layer of cells in the epidermis. We show that the intercalation event acts as a second step to regulate the spacing of the mature ciliated cells. We propose that the differentiation of the ciliated cells is not only regulated by Notch-mediated lateral inhibition, but is also an example where differentiation is coupled to the movement of cells from one cell layer to another.
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Affiliation(s)
- G A Deblandre
- Salk Institute for Biological Studies, PO Box 85800, San Diego, CA 92186, USA.
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28
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Feledy JA, Beanan MJ, Sandoval JJ, Goodrich JS, Lim JH, Matsuo-Takasaki M, Sato SM, Sargent TD. Inhibitory patterning of the anterior neural plate in Xenopus by homeodomain factors Dlx3 and Msx1. Dev Biol 1999; 212:455-64. [PMID: 10433834 DOI: 10.1006/dbio.1999.9374] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patterning of the embryonic ectoderm is dependent upon the action of negative (antineural) and positive (neurogenic) transcriptional regulators. Msx1 and Dlx3 are two antineural genes for which the anterior epidermal-neural boundaries of expression differ, probably due to differential sensitivity to BMP signaling in the ectoderm. In the extreme anterior neural plate, Dlx3 is strongly expressed while Msx1 is silent. While both of these factors prevent the activation of genes specific to the nascent central nervous system, Msx1 inhibits anterior markers, including Otx2 and cement gland-specific genes. Dlx3 has little, if any, effect on these anterior neural plate genes, instead providing a permissive environment for their expression while repressing more panneural markers, including prepattern genes belonging to the Zic family and BF-1. These properties define a molecular mechanism for translating the organizer-dependent morphogenic gradient of BMP activity into spatially restricted gene expression in the prospective anterior neural plate.
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Affiliation(s)
- J A Feledy
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, 20892, USA
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29
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Melby AE, Clements WK, Kimelman D. Regulation of dorsal gene expression in Xenopus by the ventralizing homeodomain gene Vox. Dev Biol 1999; 211:293-305. [PMID: 10395789 DOI: 10.1006/dbio.1999.9296] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Patterning in the vertebrate embryo is controlled by an interplay between signals from the dorsal organizer and the ventrally expressed BMPs. Here we examine the function of Vox, a homeodomain-containing gene that is activated by the ventralizing signal BMP-4. Inhibition of BMP signaling using a dominant negative BMP receptor (DeltaBMPR) leads to the ectopic activation of dorsal genes in the ventral marginal zone, and this activation is prevented by co-injection of Vox. chordin is the most strongly activated of those genes that are up-regulated by DeltaBMPR and is the gene most strongly inhibited by Vox expression. We demonstrate that Vox acts as a transcriptional repressor, showing that the activity of native Vox is mimicked by a Vox-repressor fusion (VoxEnR) and that a Vox-activator fusion (VoxG4A) acts as an antimorph, causing the formation of a partial secondary axis when expressed on the ventral side of the embryo. Although Vox can ectopically activate BMP-4 expression in whole embryos, we see no activation of BMP-4 by VoxG4A, demonstrating that this activation is indirect. Using a hormone-inducible version of VoxG4A, we find that a critical time window for Vox function is during the late blastula period. Using this construct, we demonstrate that only a subset of dorsal genes is directly repressed by Vox, revealing that there are different modes of regulation for organizer genes. Since the major direct target for Vox repression is chordin, we propose that Vox acts in establishing a BMP-4 morphogen gradient by restricting the expression domain of chordin.
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Affiliation(s)
- A E Melby
- Department of Biochemistry, University of Washington, Seattle, Washington, 98195-7350, USA
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30
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Xu RH, Lechleider RJ, Shih HM, Hao CF, Sredni D, Roberts AB, Kung HF. Functional analysis of human Smad1: role of the amino-terminal domain. Biochem Biophys Res Commun 1999; 258:366-73. [PMID: 10329393 DOI: 10.1006/bbrc.1999.0598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The signals originating from transforming growth factor beta/activin/bone morphogenetic proteins (BMPs) are transduced by a set of evolutionarily conserved family of Smad proteins which, upon activation, directly translocate to the nucleus where they may activate transcription. Smad proteins of different species contain conserved amino- (N) and carboxy- (C) terminal domains separated by a proline-rich linker. Human, Drosophila, and Xenopus Smad1 all have been shown to mediate the biological effects of BMP-4 in Xenopus embryos. We have investigated the functional domains of human Smad1 (hSmad1) using the Xenopus embryo system. Dorsal injection of hSmad1 RNA into the 4-cell-stage embryos results in embryonic ventralization. Since the C-terminus of Smads has been shown to mediate the transcriptional activity, whereas this activity is masked by the presence of the N-terminus, we tested the effect of a hSmad1 construct lacking the C-terminal domain [hSmad1(N)] in the Xenopus embryo system. Surprisingly, we found that hSmad1(N) not only synergizes with hSmad1 in embryonic ventralization, but induces ventralization by itself. Ectopic expression of a dominant negative BMP receptor (DN-BR) as well as neural inducers noggin and chordin induce neurogenesis in the animal cap, which is inhibited by co-expression of either hSmad1 or hSmad1(N). Ventral expression of DN-BR induces formation of a second body axis at tailbud stage, which is also prevented by hSmad1 and hSmad1(N). It has recently been reported that calmodulin interacts with the N-terminal domain of Smad proteins. We demonstrate that the ventralizing activity of hSmad1 and hSmad1(N) is markedly inhibited by calmodulin. Thus, calmodulin acts as a Smad1 inhibitor. A model is proposed to accomodate these findings.
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Affiliation(s)
- R H Xu
- Intramural Research Support Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Developmental Center, Frederick, Maryland 21702, USA.
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31
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Affiliation(s)
- S E Juul
- Department of Pediatrics, University of Florida College of Medicine, Gainesville, USA
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32
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Xu RH, Ault KT, Kim J, Park MJ, Hwang YS, Peng Y, Sredni D, Kung HF. Opposite effects of FGF and BMP-4 on embryonic blood formation: roles of PV.1 and GATA-2. Dev Biol 1999; 208:352-61. [PMID: 10191050 DOI: 10.1006/dbio.1999.9205] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In adult vertebrates, fibroblast growth factor (FGF) synergizes with many hematopoietic cytokines to stimulate the proliferation of hematopoietic progenitors. In vertebrate development, the FGF signaling pathway is important in the formation of some derivatives of ventroposterior mesoderm. However, the function of FGF in the specification of the embryonic erythropoietic lineage has remained unclear. Here we address the role of FGF in the specification of the erythropoietic lineage in the Xenopus embryo. We report that ventral injection of embryonic FGF (eFGF) mRNA at as little as 10 pg at the four-cell stage suppresses ventral blood island (VBI) formation, whereas expression of the dominant negative form of the FGF receptor in the lateral mesoderm, where physiologically no blood tissue is formed, results in a dramatic expansion of the VBI. Similar results were observed in isolated ventral marginal zones and animal caps. Bone morphogenetic protein-4 (BMP-4) is known to induce erythropoiesis in the Xenopus embryo. Therefore, we examined how the BMP-4 and FGF signaling pathways might interact in the decision of ventral mesoderm to form blood. We observed that eFGF inhibits BMP-4-induced erythropoiesis by differentially regulating expression of the BMP-4 downstream effectors GATA-2 and PV.1. GATA-2, which stimulates erythropoiesis, is suppressed by FGF. PV.1, which we demonstrate to inhibit blood development, is enhanced by FGF. Additionally, PV.1 and GATA-2 negatively regulate transcription of each other. Thus, BMP-4 induces two transcription factors which have opposing effects on blood development. The FGF and BMP-4 signaling pathways interact to regulate the specification of the erythropoietic lineage.
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Affiliation(s)
- R H Xu
- Intramural Research Support Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland, 21702, USA
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Zhou L, Marzluf GA. Functional analysis of the two zinc fingers of SRE, a GATA-type factor that negatively regulates siderophore synthesis in Neurospora crassa. Biochemistry 1999; 38:4335-41. [PMID: 10194352 DOI: 10.1021/bi982543f] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Multiple GATA factors, zinc finger DNA binding proteins that recognize consensus GATA elements, exist in Neurospora crassa. One of them, SRE, is involved in controlling the iron metabolic pathway of N. crassa. In N. crassa, iron transport is mediated by a number of small cyclic peptides, known as siderophores. The siderophore synthesis pathway is negatively regulated by SRE; a loss-of-function sre mutant strain showed partial constitutive synthesis of siderophore. In the research presented here, the negative function of SRE was further confirmed by a heterokaryon test and by gene complementation. SRE was expressed as a GST fusion protein. In vitro EMSA revealed that SRE binds specifically to DNA molecules containing GATA sequence elements. Autoregulation of sre gene expression appears possible because the sre gene promoter itself contains GATA sequences. Mutations were introduced into sre that lead to amino acid substitutions in each of the zinc fingers that will disrupt their function. In vitro EMSA revealed that both N-terminal and C-terminal zinc fingers of SRE are involved in DNA binding. This feature is different from that found with the vertebrate two zinc finger GATA factors. Invivo tests, accomplished by transforming the mutant sre genes into sre rip mutant, showed that SRE with mutations in either or both zinc fingers still maintained its function under low-iron conditions. In contrast, these mutant SRE proteins fail to function under high-iron conditions. Our results predict the presence of other positive or negative regulators of the siderophore synthetic pathway.
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Affiliation(s)
- L Zhou
- Department of Biochemistry, Program in Molecular, Cellular, and Developmental Biology, The Ohio State University, Columbus 43210, USA
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Mehler MF, Kessler JA. Cytokines in brain development and function. ADVANCES IN PROTEIN CHEMISTRY 1999; 52:223-51. [PMID: 9917922 DOI: 10.1016/s0065-3233(08)60437-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- M F Mehler
- Department of Neurology, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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35
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Abstract
Hematopoietic induction occurs on the ventral side ofXenopus gastrulae and is thought to be triggered by the growth factor bone morphogenetic protein 4 (BMP-4). To characterize this process, we developed a quantitative and sensitive assay for the induction of erythroid cells from totipotent ectoderm of the embryo. When high doses of BMP-4 were used in this explant assay, few erythroid cells were detected. In contrast, large numbers of differentiated erythroid cells were induced when ectoderm was treated with BMP-4 and the mesoderm inducers, activin, or fibroblast growth factor (FGF). Ectopic expression of GATA-1 also induced abundant erythroid cells in ectoderm treated with bFGF. This induction of erythroid cells by GATA-1 was blocked by coexpression with a dominant negative BMP-4 receptor, showing that GATA-1 requires the BMP signaling cascade to function. These results suggest that BMP-4 requires mesoderm induction to generate a program of gene expression, which regulates the specification of hematopoietic mesoderm by GATA factors.
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36
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Abstract
Abstract
Hematopoietic induction occurs on the ventral side ofXenopus gastrulae and is thought to be triggered by the growth factor bone morphogenetic protein 4 (BMP-4). To characterize this process, we developed a quantitative and sensitive assay for the induction of erythroid cells from totipotent ectoderm of the embryo. When high doses of BMP-4 were used in this explant assay, few erythroid cells were detected. In contrast, large numbers of differentiated erythroid cells were induced when ectoderm was treated with BMP-4 and the mesoderm inducers, activin, or fibroblast growth factor (FGF). Ectopic expression of GATA-1 also induced abundant erythroid cells in ectoderm treated with bFGF. This induction of erythroid cells by GATA-1 was blocked by coexpression with a dominant negative BMP-4 receptor, showing that GATA-1 requires the BMP signaling cascade to function. These results suggest that BMP-4 requires mesoderm induction to generate a program of gene expression, which regulates the specification of hematopoietic mesoderm by GATA factors.
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37
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Shibata K, Ishimura A, Maéno M. GATA-1 inhibits the formation of notochord and neural tissue in Xenopus embryo. Biochem Biophys Res Commun 1998; 252:241-8. [PMID: 9813177 DOI: 10.1006/bbrc.1998.9490] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of GATA-1, which encodes for a hemopoietic transcription factor, initiates at gastrula stage in the Xenopus embryo (1). In order to examine a possible function of GATA-1 in dorso-ventral patterning of mesoderm and ectoderm derivatives, the synthesized RNA of GATA-1 was overexpressed in embryonic cells to assess its biological effects. In the embryos injected with GATA-1 RNA in the dorsal marginal zone at 4-cell stage, dorsal epidermis did not cover the vegetal cells so that the gastrulation was not completed. The same dose of GATA-1 RNA injected into ventral marginal zone did not influence the development, and GATA-2 RNA transcribed from the same vector had little effect, suggesting that this phenomenon is physiologically important. The morphological and immunohistochemical studies revealed that notochord and neural tissue were mostly eliminated in the embryos or the dorsal marginal zone explants after injection of GATA-1 RNA. GATA-1 also inhibited neurogenesis in animal cap explants, which was induced by the injection with noggin RNA. Northern blot analysis using dorsal marginal zone explants showed, however, that only a slight amount of alpha-globin message was induced, and cardiac alpha-actin message was retained. Therefore, GATA-1 did not convert completely the dorsal phenotype to the ventral one. Furthermore, the injection of GATA-1 RNA didnot alter the expression of early dorsal and ventral markers at the onset of gastrulation. These results suggest that GATA-1 is an potential inhibitor of the dorsalization and the neurogenesis, but it affects on the specification of dorsal tissues in relatively later steps.
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Affiliation(s)
- K Shibata
- Department of Biology, Faculty of Science, Niigata University, Ikarashi, Niigata, 950-2181, Japan
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38
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39
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Kim J, Ault KT, Chen HD, Xu RH, Roh DH, Lin MC, Park MJ, Kung HF. Transcriptional regulation of BMP-4 in the Xenopus embryo: analysis of genomic BMP-4 and its promoter. Biochem Biophys Res Commun 1998; 250:516-30. [PMID: 9753664 DOI: 10.1006/bbrc.1998.9280] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent experiments in the Xenopus embryo suggest that proper regulation of BMP-4 signaling is critical to the dorsal ventral specification of both mesoderm and ectoderm. Regulation of BMP-4 signaling is known to occur extracellularly by direct binding with chordin, noggin, and follistatin, and intracellularly through the antagonistic signal interaction with dorsalizing TGF-beta family member activin. However, tight repressional regulation of BMP transcription may also be required to sustain the dorsal and neural status of the induced cells. Here we demonstrate that the dominant negative mutant of the BMP receptor (DN-BR) or the BMP-4 antagonizers, chordin and noggin, negatively regulate BMP-4 transcription in animal cap explants. We suggest that repression of BMP-4 transcription is important in the maintenance of dorsal fate and that continuous input of BMP-4 signaling is required to sustain the expression of BMP-4 transcription in the maintenance of epidermal/ventral fate. Consistent with this postulation, we found that the promoter region of the isolated BMP-4 genomic DNA includes several consensus binding sites for transcriptional regulators functioning under BMP-4 signaling such as GATA binding and ventralizing homeobox genes. In a functional assay we found that the GATA binding and ventral homeobox proteins can positively modulate BMP-4 promoter activity. We also observed that DN-BR decreases BMP-4 promoter activity. This was likely due to a repression of the above-mentioned transcription factors. The significance of these observations to embryonic patterning is discussed.
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Affiliation(s)
- J Kim
- Laboratory of Biochemical Physiology, Frederick Cancer Research and Development Center, National Cancer Institute, Maryland 21702-1201, USA
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40
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Sasai Y. Identifying the missing links: genes that connect neural induction and primary neurogenesis in vertebrate embryos. Neuron 1998; 21:455-8. [PMID: 9768831 DOI: 10.1016/s0896-6273(00)80554-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Affiliation(s)
- Y Sasai
- Department of Medical Embryology and Neurobiology, Institute for Frontier Medical Sciences, Kyoto University, Sakyo, Japan
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41
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Mead PE, Kelley CM, Hahn PS, Piedad O, Zon LI. SCL specifies hematopoietic mesoderm in Xenopus embryos. Development 1998; 125:2611-20. [PMID: 9636076 DOI: 10.1242/dev.125.14.2611] [Citation(s) in RCA: 86] [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
Targeted gene disruption experiments in the mouse have demonstrated an absolute requirement for several transcription factors for the development of hematopoietic progenitors during embryogenesis. Disruption of the basic helix-loop-helix gene SCL (stem cell leukemia) causes a block early in the hematopoietic program with defects in all hematopoietic lineages. To understand how SCL participates in the organogenesis of blood, we have isolated cDNAs encoding Xenopus SCL and characterized the function of SCL during embryogenesis. We demonstrate that SCL is expressed in ventral mesoderm early in embryogenesis. SCL expression is induced by BMP-4, and a dominant negative BMP-4 receptor inhibits SCL expression in the ventral region of the embryo. Expression of SCL in either bFGF-treated animal pole explants or dorsal marginal zone explants leads to the expression of globin protein. Furthermore, over-expression of SCL does not alter normal dorsal-ventral patterning in the embryo, indicating that SCL acts to specify mesoderm to a hematopoietic fate after inductive and patterning events have occurred. We propose that SCL is both necessary and sufficient to specify hematopoietic mesoderm, and that it has a similar role in specifying hematopoietic cell fate as MyoD has in specifying muscle cell fate.
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Affiliation(s)
- P E Mead
- Division of Hematology/Oncology, Howard Hughes Medical Institute, Children's Hospital and Dana-Farber Cancer Institute, Boston, MA, USA
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42
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Takeda K, Ichijo H, Fujii M, Mochida Y, Saitoh M, Nishitoh H, Sampath TK, Miyazono K. Identification of a novel bone morphogenetic protein-responsive gene that may function as a noncoding RNA. J Biol Chem 1998; 273:17079-85. [PMID: 9642273 DOI: 10.1074/jbc.273.27.17079] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bone morphogenetic proteins (BMPs)/osteogenic proteins (OPs), members of the transforming growth factor-beta superfamily, have a wide variety of effects on many cell types including osteoblasts and chondroblasts, and play critical roles in embryonic development. BMPs transduce their effects through binding to two different types of serine/threonine kinase receptors, type I and type II. Signaling by these receptors is mediated by the recently identified Smad proteins. Despite the rapid progress in understanding of the signaling mechanism downstream of BMP receptors, the target genes of BMPs are poorly understood in mammals. Here we identified a novel gene, termed BMP/OP-responsive gene (BORG), in C2C12 mouse myoblast cell line which trans-differentiates into osteoblastic cells in response to BMPs. Expression of BORG was dramatically induced in C2C12 cells by the treatment with BMP-2 or OP-1 within 2 h and peaked at 12-24 h, whereas transforming growth factor-beta had a minimal effect. BMP-dependent expression of BORG was also detected in other cell types which are known to respond to BMPs, suggesting that BORG is a common target gene of BMPs. Cloning and sequence analysis of BORG cDNA and the genomic clones revealed that, unexpectedly, the transcript of BORG lacks any extensive open reading frames and contains a cluster of multiple interspersed repetitive sequences in its middle part. The unusual structural features suggested that BORG may function as a noncoding RNA, although it is spliced and polyadenylated as authentic protein-coding mRNAs. Together with the observation that transfection of antisense oligonucleotides of BORG partially inhibited BMP-induced differentiation in C2C12 cells, it is possible that a new class of RNA molecules may have certain roles in the differentiation process induced by BMPs.
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Affiliation(s)
- K Takeda
- Department of Biochemistry, The Cancer Institute, Tokyo, Japanese Foundation for Cancer Research (JFCR), 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan
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43
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Mizuseki K, Kishi M, Shiota K, Nakanishi S, Sasai Y. SoxD: an essential mediator of induction of anterior neural tissues in Xenopus embryos. Neuron 1998; 21:77-85. [PMID: 9697853 DOI: 10.1016/s0896-6273(00)80516-4] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Vertebrate neurogenesis is initiated by the organizer factors that inhibit antineuralizing activities of bone morphogenetic proteins (BMPs) in the ectoderm. Here, we report a candidate mediator of neuralization, SoxD. Expression of SoxD starts at late blastula stages widely in the prospective ectoderm and becomes restricted to the dorsal ectoderm by mid-gastrula stages. SoxD expression is enhanced by the neural inducer Chordin and is suppressed by BMP4 and its downstream genes. Microinjection of SoxD mRNA causes ectopic formation of neural tissues in vivo and induces neural and neuronal markers in the isolated animal cap. Injection of a dominant-negative form of SoxD mRNA can block neuralization of ectoderm caused by attenuation of BMP signals and can strongly suppress formation of anterior neural tissues in vivo. These data show that SoxD functions as an essential mediator of downstream signaling of neural induction.
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Affiliation(s)
- K Mizuseki
- Department of Biological Sciences, Kyoto University Faculty of Medicine, Sakyo, Japan
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44
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Gherzi R, Leprini A, Siri A, Zardi L. Structure of 5' region of human tenascin-R gene and characterization of its promoter. DNA Cell Biol 1998; 17:275-82. [PMID: 9539107 DOI: 10.1089/dna.1998.17.275] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The tenascin-R (TN-R) gene encodes a multidomain extracellular matrix protein belonging to the tenascin family, previously detected only in the central nervous system. In this report, we describe the structure of the 5' region of the human TN-R gene and characterize the activity of its promoter. We cloned two previously unreported nontranslated exons (exons 1 and 2, 539 and 101 bp in length, respectively) separated by a large (> or = 40-kb) intron. The intron between exons 2 and 3 (containing the ATG codon) is 122 kb in length. Tenascin-R transcripts in fetal, adult, and neoplastic human brain contain both exons 1 and 2, as demonstrated by S1 nuclease analysis and reverse transcriptase-polymerase chain reaction. The human TN-R promoter displays relatively unusual features in terms of sequence in that it lacks any TATA box, CAAT box, GC-rich regions, or initiator element. The promoter displays its activity only in cultured cells of neural and glial origin, not in transformed epithelial cells and melanoma cells. All the elements required for the full and cell-specific activity of the promoter are contained in the 57-bp sequence closest to the transcription startpoint.
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Affiliation(s)
- R Gherzi
- Laboratory of Cell Biology, Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy
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45
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Mizuseki K, Kishi M, Matsui M, Nakanishi S, Sasai Y. Xenopus Zic-related-1 and Sox-2, two factors induced by chordin, have distinct activities in the initiation of neural induction. Development 1998; 125:579-87. [PMID: 9435279 DOI: 10.1242/dev.125.4.579] [Citation(s) in RCA: 317] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In a differential screen for downstream genes of the neural inducers, we identified two extremely early neural genes induced by Chordin and suppressed by BMP-4: Zic-related-1 (Zic-r1), a zinc finger factor related to the Drosophila pair-rule gene odd-paired, and Sox-2, a Sry-related HMG factor. Expression of the two genes is first detected widely in the prospective neuroectoderm at the beginning of gastrulation, following the onset of Chordin expression and preceding that of Neurogenin (Xngnr-1). Zic-r1 mRNA injection activates the proneural gene Xngnr-1, and initiates neural and neuronal differentiation in isolated animal caps and in vivo. In contrast, Sox-2 alone is not sufficient to cause neural differentiation, but can work synergistically with FGF signaling to initiate neural induction. Thus, Zic-r1 acts in the pathway bridging the neural inducer with the downstream proneural genes, while Sox-2 makes the ectoderm responsive to extracellular signals, demonstrating that the early phase of neural induction involves simultaneous activation of multiple functions.
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Affiliation(s)
- K Mizuseki
- Department of Biological Sciences, Kyoto University Faculty of Medicine, Yoshida, Sakyo, Kyoto 606, Japan
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46
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El-Mabrouk N, Nadeau JH, Sankoff D. Genome halving. COMBINATORIAL PATTERN MATCHING 1998. [DOI: 10.1007/bfb0030793] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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47
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Ault KT, Xu RH, Kung HF, Jamrich M. The homeobox gene PV.1 mediates specification of the prospective neural ectoderm in Xenopus embryos. Dev Biol 1997; 192:162-71. [PMID: 9405105 DOI: 10.1006/dbio.1997.8737] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bone morphogenetic protein 4 (BMP4), a member of the TGF beta superfamily, has been implicated in the dorsoventral specification of both mesoderm and ectoderm. High levels of BMP4 signaling appear to specify ventral lineages, while lower levels are causally associated with the development of dorsal lineages. We have previously identified a homeobox-containing transcription factor (PV. 1) which is a likely mediator of the ventralizing effects of BMP4 in the mesoderm. Here we provide evidence that PV.1 also functions downstream of BMP4 in the patterning of ectoderm, specifying epidermal and suppressing neural gene expression. PV.1 is expressed in the prospective neuroectoderm at the time of ectodermal fate determination. BMP4 and xSmad1 (a downstream effector of BMP4) induce PV.1 in uncommitted ectoderm and the dominant negative form of the BMP4 receptor (DN-BR) blocks PV.1 expression. In animal pole explants PV.1 counteracts the neuralizing effects of chordin and the DN-BR and restores them to their original epidermal fate. To address the physiological significance of these observations we employed an animal cap transplantation system and demonstrated that overexpression of PV.1 in the prospective neuroectoderm specifically blocks neurogenesis in intact embryos. Thus, PV.1 plays an important role in the ventralization of both mesoderm and ectoderm. We have previously shown that PV.1 is also preferentially expressed in the ventral endoderm, suggesting that this transcription factor may be involved in the ventralization of all three germ layers.
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Affiliation(s)
- K T Ault
- Division of Cellular and Gene Therapies, Food and Drug Administration, Bethesda, Maryland 20852-1448, USA.
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48
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Studies on the role of fibroblast growth factor signaling in neurogenesis using conjugated/aged animal caps and dorsal ectoderm-grafted embryos. J Neurosci 1997. [PMID: 9278524 DOI: 10.1523/jneurosci.17-18-06892.1997] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Basic fibroblast growth factor (bFGF) has been shown to induce neural fate in dissociated animal cap (AC) cells or in AC explants cultured in low calcium and magnesium concentrations. However, long-term disclosure of the cap may cause diffusion of the secreted molecule bone morphogenetic protein 4 (BMP-4), a neural inhibitor present in the AC. This may contribute to the subsequent neurogenesis induced by bFGF. Here we used conjugated and aged blastula AC to avoid diffusion of endogenous molecules from the AC. Unlike noggin, bFGF failed to induce neural tissue in this system. However, it enhanced neuralization elicited by a dominant negative BMP receptor (DN-BR) that inhibits the BMP-4 signaling. Posterior neural markers were turned on by bFGF in AC expressing DN-BR or chordin. Blocking the endogenous FGF signal with a dominant negative FGF receptor (XFD) mainly inhibited development of posterior neural tissue in neuralized ACs. These in vitro studies were confirmed in vivo in embryos grafted with XFD-expressing ACs in the place of neuroectoderm. Expression of some regional neural markers was inhibited, although markers for muscle and posterior notochord were still detectable in the grafted embryos, suggesting that XFD specifically affected neurogenesis but not the dorsal mesoderm. The use of these in vitro and in vivo model systems provides new evidence that FGF, although unable to initiate neurogenesis on its own, is required for neural induction as well as for posteriorization.
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49
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Xu RH, Kim J, Taira M, Sredni D, Kung H. Studies on the role of fibroblast growth factor signaling in neurogenesis using conjugated/aged animal caps and dorsal ectoderm-grafted embryos. J Neurosci 1997; 17:6892-8. [PMID: 9278524 PMCID: PMC6573287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Basic fibroblast growth factor (bFGF) has been shown to induce neural fate in dissociated animal cap (AC) cells or in AC explants cultured in low calcium and magnesium concentrations. However, long-term disclosure of the cap may cause diffusion of the secreted molecule bone morphogenetic protein 4 (BMP-4), a neural inhibitor present in the AC. This may contribute to the subsequent neurogenesis induced by bFGF. Here we used conjugated and aged blastula AC to avoid diffusion of endogenous molecules from the AC. Unlike noggin, bFGF failed to induce neural tissue in this system. However, it enhanced neuralization elicited by a dominant negative BMP receptor (DN-BR) that inhibits the BMP-4 signaling. Posterior neural markers were turned on by bFGF in AC expressing DN-BR or chordin. Blocking the endogenous FGF signal with a dominant negative FGF receptor (XFD) mainly inhibited development of posterior neural tissue in neuralized ACs. These in vitro studies were confirmed in vivo in embryos grafted with XFD-expressing ACs in the place of neuroectoderm. Expression of some regional neural markers was inhibited, although markers for muscle and posterior notochord were still detectable in the grafted embryos, suggesting that XFD specifically affected neurogenesis but not the dorsal mesoderm. The use of these in vitro and in vivo model systems provides new evidence that FGF, although unable to initiate neurogenesis on its own, is required for neural induction as well as for posteriorization.
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Affiliation(s)
- R H Xu
- Intramural Research Support Program, Science Applications International Corporation-Frederick, Frederick, Maryland 21702-1201, USA
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