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Jalvy S, Veschambre P, Fédou S, Rezvani HR, Thézé N, Thiébaud P. Leukemia inhibitory factor signaling in Xenopus embryo: Insights from gain of function analysis and dominant negative mutant of the receptor. Dev Biol 2019; 447:200-213. [DOI: 10.1016/j.ydbio.2018.12.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 10/05/2018] [Accepted: 12/18/2018] [Indexed: 01/19/2023]
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Hardwick LJA, Philpott A. Xenopus Models of Cancer: Expanding the Oncologist's Toolbox. Front Physiol 2018; 9:1660. [PMID: 30538639 PMCID: PMC6277521 DOI: 10.3389/fphys.2018.01660] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023] Open
Abstract
The use of the Xenopus model system has provided diverse contributions to cancer research, not least because of the striking parallels between tumour pathogenesis and early embryo development. Cell cycle regulation, signalling pathways, and cell behaviours such as migration are frequently perturbed in cancers; all have been investigated using Xenopus, and these developmental events can additionally act as an assay for drug development studies. In this mini-review, we focus our discussion primarily on whole embryo Xenopus models informing cancer biology; the contributions to date and future potential. Insights into tumour immunity, oncogene function, and visualisation of vascular responses during tumour formation have all been achieved with naturally occurring tumours and induced-tumour-like-structures in Xenopus. Finally, as we are now entering the era of genetically modified Xenopus models, we can harness genome editing techniques to recapitulate human disease through creating embryos with analogous genetic abnormalities. With the speed, versatility and accessibility that epitomise the Xenopus system, this new range of pre-clinical Xenopus models has great potential to advance our mechanistic understanding of oncogenesis and provide an early in vivo model for chemotherapeutic development.
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Affiliation(s)
- Laura J A Hardwick
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.,Peterhouse, University of Cambridge, Cambridge, United Kingdom
| | - Anna Philpott
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
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3
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Use of genetically encoded, light-gated ion translocators to control tumorigenesis. Oncotarget 2017; 7:19575-88. [PMID: 26988909 PMCID: PMC4991402 DOI: 10.18632/oncotarget.8036] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Accepted: 02/11/2016] [Indexed: 01/01/2023] Open
Abstract
It has long been known that the resting potential of tumor cells is depolarized relative to their normal counterparts. More recent work has provided evidence that resting potential is not just a readout of cell state: it regulates cell behavior as well. Thus, the ability to control resting potential in vivo would provide a powerful new tool for the study and treatment of tumors, a tool capable of revealing living-state physiological information impossible to obtain using molecular tools applied to isolated cell components. Here we describe the first use of optogenetics to manipulate ion-flux mediated regulation of membrane potential specifically to prevent and cause regression of oncogene-induced tumors. Injection of mutant-KRAS mRNA induces tumor-like structures with many documented similarities to tumors, in Xenopus tadpoles. We show that expression and activation of either ChR2D156A, a blue-light activated cation channel, or Arch, a green-light activated proton pump, both of which hyperpolarize cells, significantly lowers the incidence of KRAS tumor formation. Excitingly, we also demonstrate that activation of co-expressed light-activated ion translocators after tumor formation significantly increases the frequency with which the tumors regress in a process called normalization. These data demonstrate an optogenetic approach to dissect the biophysics of cancer. Moreover, they provide proof-of-principle for a novel class of interventions, directed at regulating cell state by targeting physiological regulators that can over-ride the presence of mutations.
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Moore D, Walker SI, Levin M. Cancer as a disorder of patterning information: computational and biophysical perspectives on the cancer problem. CONVERGENT SCIENCE PHYSICAL ONCOLOGY 2017. [DOI: 10.1088/2057-1739/aa8548] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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5
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Naert T, Van Nieuwenhuysen T, Vleminckx K. TALENs and CRISPR/Cas9 fuel genetically engineered clinically relevant Xenopus tropicalis tumor models. Genesis 2017; 55. [PMID: 28095622 DOI: 10.1002/dvg.23005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 11/18/2016] [Accepted: 11/19/2016] [Indexed: 12/12/2022]
Abstract
The targeted nuclease revolution (TALENs, CRISPR/Cas9) now allows Xenopus researchers to rapidly generate custom on-demand genetic knockout models. These novel methods to perform reverse genetics are unprecedented and are fueling a wide array of human disease models within the aquatic diploid model organism Xenopus tropicalis (X. tropicalis). This emerging technology review focuses on the tools to rapidly generate genetically engineered X. tropicalis models (GEXM), with a focus on establishment of genuine genetic and clinically relevant cancer models. We believe that due to particular advantageous characteristics, outlined within this review, GEXM will become a valuable alternative animal model for modeling human cancer. Furthermore, we provide perspectives of how GEXM will be used as a platform for elucidation of novel therapeutic targets and for preclinical drug validation. Finally, we also discuss some future prospects on how the recent expansions and adaptations of the CRISPR/Cas9 toolbox might influence and push forward X. tropicalis cancer research.
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Affiliation(s)
- Thomas Naert
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium
| | - Tom Van Nieuwenhuysen
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium
| | - Kris Vleminckx
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium.,Center for Medical Genetics, Ghent University and Ghent University Hospital, Belgium
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Espín-Palazón R, Traver D. The NF-κB family: Key players during embryonic development and HSC emergence. Exp Hematol 2016; 44:519-27. [PMID: 27132652 DOI: 10.1016/j.exphem.2016.03.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 03/24/2016] [Accepted: 03/26/2016] [Indexed: 02/07/2023]
Abstract
The nuclear factor-κB (NF-κB) family is a crucial transcription factor group known mainly for its role in the regulation of the immune system and its response to infection in vertebrates. The signaling pathway leading to NF-κB activation and translocation to the nucleus to exert its function as a transcription factor is well conserved among Kingdom Animalia, which has helped to elucidate other roles that NF-κB plays in other biological contexts such as developmental biology. The manipulation of NF-κB members in a diverse range of animal models results in severe developmental defects during embryogenesis, very often leading to embryonic lethality. Defects include dorsal-ventral patterning and limb, liver, skin, lung, neural, notochord, muscle, skeletal, and hematopoietic defects. Here, we recapitulate the research that has been done to address the role that NF-κB plays during embryonic development, in particular to emphasize its recently discovered role in the specification of hematopoietic stem cells (HSCs), the foundation of the hematopoietic system in vertebrates.
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Affiliation(s)
- Raquel Espín-Palazón
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA
| | - David Traver
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA.
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Hardwick LJA, Philpott A. An oncologist׳s friend: How Xenopus contributes to cancer research. Dev Biol 2015; 408:180-7. [PMID: 25704511 PMCID: PMC4684227 DOI: 10.1016/j.ydbio.2015.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 01/27/2015] [Accepted: 02/10/2015] [Indexed: 01/10/2023]
Abstract
One of the most striking features of the Xenopus system is the versatility in providing a unique range of both in vitro and in vivo models that are rapid, accessible and easily manipulated. Here we present an overview of the diverse contribution that Xenopus has made to advance our understanding of tumour biology and behaviour; a contribution that goes beyond the traditional view of Xenopus as a developmental model organism. From the utility of the egg and oocyte extract system to the use of whole embryos as developmental or induced tumour models, the Xenopus system has been fundamental to investigation of cell cycle mechanisms, cell metabolism, cell signalling and cell behaviour, and has allowed an increasing appreciation of the parallels between early development and the pathogenesis of tumour progression and metastasis. Although not the prototypical oncological model system, we propose that Xenopus is an adaptable and multifunctional tool in the oncologist׳s arsenal.
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Affiliation(s)
- Laura J A Hardwick
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Anna Philpott
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK.
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Chernet BT, Levin M. Transmembrane voltage potential of somatic cells controls oncogene-mediated tumorigenesis at long-range. Oncotarget 2015; 5:3287-306. [PMID: 24830454 PMCID: PMC4102810 DOI: 10.18632/oncotarget.1935] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The microenvironment is increasingly recognized as a crucial aspect of cancer. In contrast and complement to the field's focus on biochemical factors and extracellular matrix, we characterize a novel aspect of host:tumor interaction - endogenous bioelectric signals among non-excitable somatic cells. Extending prior work focused on the bioelectric state of cancer cells themselves, we show for the first time that the resting potentials of distant cells are critical for oncogene-dependent tumorigenesis. In the Xenopus laevis tadpole model, we used human oncogenes such as mutant KRAS to drive formation of tumor-like structures that exhibited overproliferation, increased nuclear size, hypoxia, acidity, and leukocyte attraction. Remarkably, misexpression of hyperpolarizing ion channels at distant sites within the tadpole significantly reduced the incidence of these tumors. The suppression of tumorigenesis could also be achieved by hyperpolarization using native CLIC1 chloride channels, suggesting a treatment modality not requiring gene therapy. Using a dominant negative approach, we implicate HDAC1 as the mechanism by which resting potential changes affect downstream cell behaviors. Based on published data on the voltage-mediated changes of butyrate flux through the SLC5A8 transporter, we present a model linking resting potentials of host cells to the ability of oncogenes to initiate tumorigenesis. Antibiotic data suggest that the relevant butyrate is generated by a native bacterial species, identifying a novel link between the microbiome and cancer that is mediated by alterations in bioelectric signaling.
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Affiliation(s)
- Brook T Chernet
- Center for Regenerative and Developmental Biology and Department of Biology Tufts University 200 Boston Avenue,Suite 4600 Medford, MA 02155 U.S.A
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Chernet BT, Levin M. Transmembrane voltage potential is an essential cellular parameter for the detection and control of tumor development in a Xenopus model. Dis Model Mech 2013; 6:595-607. [PMID: 23471912 PMCID: PMC3634644 DOI: 10.1242/dmm.010835] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Understanding mechanisms that orchestrate cell behavior into appropriately patterned tissues and organs within the organism is an essential element of preventing, detecting and treating cancer. Bioelectric signals (resting transmembrane voltage potential gradients in all cells) underlie an important and broadly conserved set of control mechanisms that regulate pattern formation. We tested the role of transmembrane potential in tumorigenesis mediated by canonical oncogenes in Xenopus laevis. Depolarized membrane potential (Vmem) was a characteristic of induced tumor-like structures (ITLSs) generated by overexpression of Gli1, KrasG12D, Xrel3 or p53Trp248. This bioelectric signature was also present in precursor ITLS sites. Vmem is a bioelectric marker that reveals ITLSs before they become histologically and morphologically apparent. Moreover, voltage was functionally important: overexpression of hyperpolarizing ion transporters caused a return to normal Vmem and significantly reduced ITLS formation in vivo. To characterize the molecular mechanism by which Vmem change regulates ITLS phenotypes, we performed a suppression screen. Vmem hyperpolarization was transduced into downstream events via Vmem-regulated activity of SLC5A8, a sodium-butyrate exchanger previously implicated in human cancer. These data indicate that butyrate, a histone deacetylase (HDAC) inhibitor, might be responsible for transcriptional events that mediate suppression of ITLSs by hyperpolarization. Vmem is a convenient cellular parameter by which tumors induced by human oncogenes can be detected in vivo and represents a new diagnostic modality. Moreover, control of resting membrane potential is functionally involved in the process by which oncogene-bearing cells depart from normal morphogenesis programs to form tumors. Modulation of Vmem levels is a novel and promising strategy for tumor normalization.
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Affiliation(s)
- Brook T Chernet
- Center for Regenerative and Developmental Biology and Department of Biology, Tufts University, 200 Boston Avenue, Medford, MA 02155, USA
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Lobikin M, Chernet B, Lobo D, Levin M. Resting potential, oncogene-induced tumorigenesis, and metastasis: the bioelectric basis of cancer in vivo. Phys Biol 2012. [PMID: 23196890 DOI: 10.1088/1478-3975/9/6/065002] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cancer may result from localized failure of instructive cues that normally orchestrate cell behaviors toward the patterning needs of the organism. Steady-state gradients of transmembrane voltage (V(mem)) in non-neural cells are instructive, epigenetic signals that regulate pattern formation during embryogenesis and morphostatic repair. Here, we review molecular data on the role of bioelectric cues in cancer and present new findings in the Xenopus laevis model on how the microenvironment's biophysical properties contribute to cancer in vivo. First, we investigated the melanoma-like phenotype arising from serotonergic signaling by 'instructor' cells-a cell population that is able to induce a metastatic phenotype in normal melanocytes. We show that when these instructor cells are depolarized, blood vessel patterning is disrupted in addition to the metastatic phenotype induced in melanocytes. Surprisingly, very few instructor cells need to be depolarized for the hyperpigmentation phenotype to occur; we present a model of antagonistic signaling by serotonin receptors that explains the unusual all-or-none nature of this effect. In addition to the body-wide depolarization-induced metastatic phenotype, we investigated the bioelectrical properties of tumor-like structures induced by canonical oncogenes and cancer-causing compounds. Exposure to carcinogen 4-nitroquinoline 1-oxide (4NQO) induces localized tumors, but has a broad (and variable) effect on the bioelectric properties of the whole body. Tumors induced by oncogenes show aberrantly high sodium content, representing a non-invasive diagnostic modality. Importantly, depolarized transmembrane potential is not only a marker of cancer but is functionally instructive: susceptibility to oncogene-induced tumorigenesis is significantly reduced by forced prior expression of hyperpolarizing ion channels. Importantly, the same effect can be achieved by pharmacological manipulation of endogenous chloride channels, suggesting a strategy for cancer suppression that does not require gene therapy. Together, these data extend our understanding of the recently demonstrated role of transmembrane potential in tumor formation and metastatic cell behavior. V(mem) is an important non-genetic biophysical aspect of the microenvironment that regulates the balance between normally patterned growth and carcinogenesis.
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Affiliation(s)
- Maria Lobikin
- Biology Department and Tufts Center for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA 02155, USA
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11
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Armstrong NJ, Fagotto F, Prothmann C, Rupp RAW. Maternal Wnt/β-catenin signaling coactivates transcription through NF-κB binding sites during Xenopus axis formation. PLoS One 2012; 7:e36136. [PMID: 22590521 PMCID: PMC3348924 DOI: 10.1371/journal.pone.0036136] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 03/31/2012] [Indexed: 12/20/2022] Open
Abstract
Maternal Wnt/β-Catenin signaling establishes a program of dorsal-specific gene expression required for axial patterning in Xenopus. We previously reported that a subset of dorsally expressed genes depends not only on Wnt/β-Catenin stimulation, but also on a MyD88-dependent Toll-like receptor/IL1-receptor (TLR/IL1-R) signaling pathway. Here we show that these two signal transduction cascades converge in the nucleus to coactivate gene transcription in blastulae through a direct interaction between β-Catenin and NF-κB proteins. A transdominant inhibitor of NF-κB, ΔNIκBα, phenocopies loss of MyD88 protein function, implicating Rel/NF-κB proteins as selective activators of dorsal-specific gene expression. Sensitive axis formation assays in the embryo demonstrate that dorsalization by Wnt/β-Catenin requires NF-κB protein activity, and vice versa. Xenopus nodal-related 3 (Xnr3) is one of the genes with dual β-Catenin/NF-κB input, and a proximal NF-κB consensus site contributes to the regional activity of its promoter. We demonstrate in vitro binding of Xenopus β-Catenin to several XRel proteins. This interaction is observed in vivo upon Wnt-stimulation. Finally, we show that a synthetic luciferase reporter gene responds to both endogenous and exogenous β-Catenin levels in an NF-κB motif dependent manner. These results suggest that β-Catenin acts as a transcriptional co-activator of NF-κB-dependent transcription in frog primary embryonic cells.
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Affiliation(s)
- Neil J Armstrong
- Department of Molecular Biology, Adolf-Butenandt-Institute, Ludwig-Maximilians-University, Munich, Germany
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12
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Robert J, Cohen N. The genus Xenopus as a multispecies model for evolutionary and comparative immunobiology of the 21st century. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2011; 35:916-923. [PMID: 21277325 PMCID: PMC3109137 DOI: 10.1016/j.dci.2011.01.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The Xenopus model for immunological research offers a collection of invaluable research tools including MHC-defined clones, inbred strains, cell lines, and monoclonal antibodies. Further, the annotated full genome sequence of Xenopus tropicalis and its remarkable conservation of gene organization with mammals, as well as ongoing genome mapping and mutagenesis studies in X. tropicalis, add a new dimension to the study of immunity. In this paper, we review uses of this amphibian model to study: the development of the immune system; vascular and lymphatic regeneration; immune tolerance; tumor immunity; immune responses to important emerging infectious diseases; and the evolution of classical and non-classical MHC class I genes. We also discuss the rich potential of the species with different degrees of polypoidy resulting from whole genome-wide duplication of the Xenopodinae subfamily as a model to study regulation at the genome level.
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Affiliation(s)
- Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, United States.
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Xrel3/XrelA attenuates β-catenin-mediated transcription during mesoderm formation in Xenopus embryos. Biochem J 2011; 435:247-57. [PMID: 21214516 DOI: 10.1042/bj20101801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In Xenopus laevis embryonic development, activation of the Wnt/β-catenin pathway promotes mesoderm cell fate determination via Xnr (Xenopus nodal-related) expression. We have demonstrated previously that Rel/NF-κB (nuclear factor κB) proteins expressed in presumptive ectoderm limit the activity of Xnrs to the marginal zone of embryos during mesoderm induction, which assists to distinguish mesoderm from ectoderm. The mechanism of this regulation, however, is unknown. In the present study, we investigated whether Rel/NF-κB proteins are able to modulate mesoderm formation by mediating Wnt/β-catenin signalling. We determined that ectopic expression of XrelA or Xrel3 in the dorsal marginal zone perturbed dorsal mesoderm formation by down-regulating multiple Wnt/β-catenin target genes including Xnr3, Xnr5 and Xnr6. Ventral co-expression of XrelA or Xrel3 with either wild-type β-catenin or constitutively active β-cateninS37A abrogated β-catenin-induced axis duplication and attenuated β-catenin-stimulated reporter transcription. Lastly, we provide evidence that Xrel3, but not XrelA, can interact with β-catenin without affecting the association of β-catenin with other transcriptional co-activators in vitro. Both Xrel3 and XrelA, however, prevented the accumulation, in nuclei, of exogenously expressed and endogenous β-catenin in vivo. These results suggest that Rel proteins are able to bind β-catenin and attenuate β-catenin-mediated transcription by nuclear exclusion.
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Abstract
Despite intense study, the role of the immune system in detecting (immunosurveillance), controlling and remodeling (immunoediting) neoplasia remains elusive. We present here a comparative view of the complex interactions between neoplasia and the host immune system. We provide evidence, in the amphibian Xenopus laevis, consistent with an evolutionarily conserved and crucial role of the immune system in controlling neoplasia, which involves a striking variety of anti-tumoral immune effectors including conventional CTLs, classical MHC class Ia unrestricted CTLs (CCU-CTLs) that interact with nonclassical MHC class Ib molecules, CD8 NKT-like cells and NK cells. We also review the tumors found in X. laevis with an emphasis on thymic lymphoid tumors and a rare ovarian dysgerminoma. Finally, we consider the use of X. laevis for in vivo study of tumorigenesis. Given our current knowledge, the experimental systems already established in X. laevis, and the rapid accumulation of genetic resources for the sister species Silurana (Xenopus) tropicalis, it is our conviction that these species provide an ideal alternative to the murine system for studying tumorigenesis and tumor immunity.
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Affiliation(s)
- Ana Goyos
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA
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Kennedy MW, Green KA, Ford RL, Andrews PG, Paterno GD, Gillespie LL, Kao KR. Regulation of the response to Nodal-mediated mesoderm induction by Xrel3. Dev Biol 2007; 311:383-95. [PMID: 17920056 DOI: 10.1016/j.ydbio.2007.08.040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 08/20/2007] [Accepted: 08/22/2007] [Indexed: 11/15/2022]
Abstract
The Xenopus egg has a yolk-laden vegetal hemisphere juxtaposed to a darkly pigmented animal hemisphere. Mesoderm is derived from the marginal zone, located at the interface between the two hemispheres. The vegetal-most cells become endoderm and release TGF-beta-related factors, including the Xenopus Nodal related (Xnr) proteins, which diffuse to induce the marginal zone to form mesoderm. The remaining animal cells become ectoderm, but our understanding of the mechanisms that limit the response to induction is incomplete. In this study, we provide evidence to suggest that Xrel3, a member of the Rel/NF-kappaB family, plays a role in defining the boundary separating induced from uninduced cells by regulating Xnr-responsive gene transcription. Ectopic Xrel3 expressed in prospective mesoderm caused repression of mesoderm-specific genes resulting in loss-of-function phenotypes that were rescued by co-expression of Xnr2. Depletion of Xrel3 from embryos with antisense morpholinos increased Xnr-dependent transcription, broadened expression of the pan-mesoderm marker Xbra and sensitized animal cells to mesoderm induction by Xnr2. We propose that an additional component to the mechanism that differentiates the ectoderm from the mesoderm involves regulation of nodal-dependent gene transcription by Xrel3.
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Affiliation(s)
- Mark W Kennedy
- Terry Fox Cancer Research Labs, Memorial University of Newfoundland, St. John's, NL, Canada
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Zhang C, Carl TF, Trudeau ED, Simmet T, Klymkowsky MW. An NF-kappaB and slug regulatory loop active in early vertebrate mesoderm. PLoS One 2006; 1:e106. [PMID: 17205110 PMCID: PMC1762408 DOI: 10.1371/journal.pone.0000106] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 11/23/2006] [Indexed: 01/11/2023] Open
Abstract
Background In both Drosophila and the mouse, the zinc finger transcription factor Snail is required for mesoderm formation; its vertebrate paralog Slug (Snai2) appears to be required for neural crest formation in the chick and the clawed frog Xenopus laevis. Both Slug and Snail act to induce epithelial to mesenchymal transition (EMT) and to suppress apoptosis. Methodology & Principle Findings Morpholino-based loss of function studies indicate that Slug is required for the normal expression of both mesodermal and neural crest markers in X. laevis. Both phenotypes are rescued by injection of RNA encoding the anti-apoptotic protein Bcl-xL; Bcl-xL's effects are dependent upon IκB kinase-mediated activation of the bipartite transcription factor NF-κB. NF-κB, in turn, directly up-regulates levels of Slug and Snail RNAs. Slug indirectly up-regulates levels of RNAs encoding the NF-κB subunit proteins RelA, Rel2, and Rel3, and directly down-regulates levels of the pro-apopotic Caspase-9 RNA. Conclusions/Significance These studies reveal a Slug/Snail–NF-κB regulatory circuit, analogous to that present in the early Drosophila embryo, active during mesodermal formation in Xenopus. This is a regulatory interaction of significance both in development and in the course of inflammatory and metastatic disease.
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Affiliation(s)
- Chi Zhang
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Timothy F. Carl
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Evan D. Trudeau
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Thomas Simmet
- Institute of Pharmacology of Natural Products and Clinical Pharmacology, University of Ulm, Ulm, Germany
| | - Michael W. Klymkowsky
- Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
- * To whom correspondence should be addressed. E-mail:
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Tseng AS, Adams DS, Qiu D, Koustubhan P, Levin M. Apoptosis is required during early stages of tail regeneration in Xenopus laevis. Dev Biol 2006; 301:62-9. [PMID: 17150209 PMCID: PMC3136124 DOI: 10.1016/j.ydbio.2006.10.048] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Revised: 10/27/2006] [Accepted: 10/31/2006] [Indexed: 01/16/2023]
Abstract
The Xenopus tadpole is able to regenerate its tail, including skin, muscle, notochord, spinal cord and neurons and blood vessels. This process requires rapid tissue growth and morphogenesis. Here we show that a focus of apoptotic cells appears in the regeneration bud within 12 h of amputation. Surprisingly, when caspase-3 activity is specifically inhibited, regeneration is abolished. This is true of tails both before and after the refractory period. Programmed cell death is only required during the first 24 h after amputation, as later inhibition has no effect on regeneration. Inhibition of caspase-dependent apoptosis results in a failure to induce proliferation in the growth zone, a mispatterning of axons in the regenerate, and the appearance of ectopic otoliths in the neural tube, in the context of otherwise normal continued development of the larva. Larvae amputated during the refractory stage exhibit a much broader domain of caspase-3-positive cells, suggesting a window for the amount of apoptosis that is compatible with normal regeneration. These data reveal novel roles for apoptosis in development and indicate that a degree of apoptosis is an early and obligate component of normal tail regeneration, suggesting the possibility of the existence of endogenous inhibitory cells that must be destroyed by programmed cell death for regeneration to occur.
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Affiliation(s)
| | | | | | | | - Michael Levin
- Corresponding author. Fax: +1 617 892 8597. (M. Levin)
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Abstract
ErbB signaling has long been implicated in cancer formation and progression and is shown to regulate cell division, migration, and death during tumorigenesis. The functions of the ErbB pathway during early vertebrate embryogenesis, however, are not well understood. Here we report characterization of ErbB activities during early frog development. Gain-of-function analyses show that EGFR, ErbB2, and ErbB4 induce ectopic tumor-like cell mass that contains increased numbers of mitotic cells. Both the muscle and the neural markers are expressed in these ectopic protrusions. ErbBs also induce mesodermal markers in ectodermal explants. Loss-of-function studies using carboxyl terminal-truncated dominant-negative ErbB receptors demonstrate that blocking ErbB signals leads to defective gastrulation movements and malformation of the embryonic axis with a reduction in the head structures in early frog embryos. These data, together with the observation that ErbBs are expressed early during frog embryogenesis, suggest that ErbBs regulate cell proliferation, movements, and embryonic patterning during early Xenopus development.
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MESH Headings
- Amino Acid Sequence
- Animals
- Biomarkers
- Cell Proliferation
- Embryo, Nonmammalian/abnormalities
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/metabolism
- ErbB Receptors/chemistry
- ErbB Receptors/genetics
- ErbB Receptors/metabolism
- Gene Expression Regulation, Developmental/genetics
- Head/abnormalities
- Head/embryology
- Humans
- Molecular Sequence Data
- Phylogeny
- Receptor, ErbB-2/chemistry
- Receptor, ErbB-2/genetics
- Receptor, ErbB-2/metabolism
- Receptor, ErbB-3/chemistry
- Receptor, ErbB-3/genetics
- Receptor, ErbB-3/metabolism
- Receptor, ErbB-4
- Sequence Alignment
- Sequence Homology, Amino Acid
- Signal Transduction
- Time Factors
- Xenopus laevis/abnormalities
- Xenopus laevis/embryology
- Xenopus laevis/metabolism
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Affiliation(s)
| | - Chenbei Chang
- Corresponding author. ; Phone: 205-975-7229; Fax: 205-975-5648
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19
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Vonica A, Brivanlou AH. An obligatory caravanserai stop on the silk road to neural induction: Inhibition of BMP/GDF signaling. Semin Cell Dev Biol 2006; 17:117-32. [PMID: 16516504 DOI: 10.1016/j.semcdb.2005.11.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Work in Xenopus laevis produced the first molecular explanation for neural specification, the default model, where inactivation of the BMP pathway in ectodermal cells changes fates from epidermal to neural. This review covers the present status of our understanding of neural specification, with emphasis on Xenopus, but including relevant facts in other model systems. While recent experiments have increased the complexity of the molecular picture, they have also provided additional support for the default model and the central position of the BMP pathway. We conclude that synergy between accumulated knowledge and technical progress will maintain Xenopus at the forefront of research in neural development.
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Affiliation(s)
- Alin Vonica
- Laboratory of Molecular Embryology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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20
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Agudo D, Agudo Garcillán D, Gómez-Esquer F, Díaz-Gil G, Martínez-Arribas F, Delcán J, Schneider J, Palomar MA, Linares R. Proteomic analysis of the Gallus gallus embryo at stage-29 of development. Proteomics 2006; 5:4946-57. [PMID: 16287166 DOI: 10.1002/pmic.200402056] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The chicken (Gallus gallus) is one of the primary models for embryological and developmental studies. In order to begin to understand the molecular mechanisms underlying the normal and abnormal development of the chicken, we used 2-DE to construct a whole-embryo proteome map. Proteins were separated by IEF on IPG strips, and by 11% SDS-PAGE) gels. Protein identification was performed by means of PMF with MALDI-TOF-MS. In all, 105 protein spots were identified, 35 of them implicated in embryo development, 10 related with some diseases, and 16, finally, being proteins that have never been identified, purified or characterized in the chicken before. This map will be updated continuously and will serve as a reference database for investigators, studying changes at the protein level under different physiological conditions.
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Affiliation(s)
- David Agudo
- Departamento de Ciencias de la Salud III, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Avenida de Atenas, S/N E28922 Alcorcón, Madrid, Spain.
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21
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Prothmann C, Armstrong NJ, Roth S, Rupp RAW. Vertebrate rel proteins exhibit dorsal-like activities in earlyDrosophila embryogenesis. Dev Dyn 2006; 235:949-57. [PMID: 16493693 DOI: 10.1002/dvdy.20713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Drosophila, the Toll/Dorsal pathway triggers the nuclear entry of the Rel protein Dorsal, which controls dorsoventral patterning in early embryogenesis and plays an important role in innate immunity of the adult fly. In vertebrates, the homologous Toll/IL-1 receptor signaling pathway directs the nuclear localization of Rel/NF-kappaB complexes, which activate genes involved in proliferation, apoptosis, and immune response. Recently, first evidence has been reported for the activity of vertebrate Rel proteins and a Toll-like signaling pathway in the dorsoventral patterning process of Xenopus laevis embryos. Given the evolutionary divergence of the fly and frog model organisms, these findings raise the question, to what extent the effector functions of this pathway have been conserved? Here, we report the ability of two Xenopus Rel proteins to partially substitute for several, but not all, functions of the Dorsal protein in Drosophila embryos. Our results suggest the interaction between Rel proteins and their cytoplasmic inhibitors as an important interface of evolutionary adaptation.
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Affiliation(s)
- Christian Prothmann
- Adolf-Butenandt-Institut, Ludwif-Maximilians-Universität München, Schillerstrasse 44, D-80336 Munich, Germany
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22
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Abstract
We have identified two Xenopus mRNAs that encode proteins homologous to a component of the Wnt/beta-catenin transcriptional machinery known as Pygopus. The predicted proteins encoded by both mRNAs share the same structural properties with human Pygo-2, but with Xpygo-2alpha having an additional 21 N-terminal residues. Xpygo-2alpha messages accumulate in the prospective anterior neural plate after gastrulation and then are localized to the nervous system, rostral to and including the hindbrain. Xpygo-2beta mRNA is expressed in oocytes and early embryos but declines in level before and during gastrulation. In late neurula, Xpygo-2beta mRNA is restricted to the retinal field, including eye primordia and prospective forebrain. A C-terminal truncated mutant of Xpygo-2 containing the N-terminal Homology Domain (NHD) caused both axis duplication when injected at the 2-cell stage and inhibition of anterior neural development when injected in the prospective head, mimicking the previously described effects of Wnt-signaling activators. Inhibition of Xpygo-2alpha and Xpygo-2beta by injection of gene-specific antisense morpholino oligonucleotides into prospective anterior neurectoderm caused brain defects that were prevented by coinjection of Xpygo-2 mRNA. Both Xpygo-2alpha and Xpygo-2beta morpholinos reduced the eye and forebrain markers Xrx-1, Xpax-6, and XBF-1, while the Xpygo-2alpha morpholino also eliminated expression of the mid-hindbrain marker En-2. The differential expression and regulatory activities of Xpygo-2alpha/beta in rostral neural tissue indicate that they represent essential components of a novel mechanism for Wnt signaling in regionalization of the brain.
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Affiliation(s)
- Blue B Lake
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, A1B 3V6 Newfoundland, Canada.
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23
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Koebernick K, Hollemann T, Pieler T. A restrictive role for Hedgehog signalling during otic specification in Xenopus. Dev Biol 2003; 260:325-38. [PMID: 12921735 DOI: 10.1016/s0012-1606(03)00242-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Vertebrate inner ear development is initiated by the specification of the otic placode, an ectodermal structure induced by signals from neighboring tissue. Although several signaling molecules have been identified as candidate otic inducers, many details of the process of inner ear induction remain elusive. Here, we report that otic induction is responsive to the level of Hedgehog (Hh) signaling activity in Xenopus, making use of both gain- and loss-of-function approaches. Ectopic activation of Hedgehog signaling resulted in the development of ectopic vesicular structures expressing the otic marker genes XPax-2, Xdll-3, and Xwnt-3A, thus revealing otic identity. Induction of ectopic otic vesicles was also achieved by misexpression of two different inhibitors of Hh signaling: the putative Hh antagonist mHIP and XPtc1deltaLoop2, a dominant-negative form of the Hh receptor Patched. In addition, misexpression of XPtc1deltaLoop2 as well as treatment of Xenopus embryos with the specific Hh signaling antagonist cyclopamine resulted in the formation of enlarged otic vesicles. In summary, our observations suggest that a defined level of Hh signaling provides a restrictive environment for otic fate in Xenopus embryos.
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Affiliation(s)
- Katja Koebernick
- Institute of Biochemistry and Molecular Cell Biology, Georg-August-Universität Göttingen, Justus-von-Liebig-Weg 11, D-37077 Göttingen, Germany
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24
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Muñoz-Sanjuán I, Bell E, Altmann CR, Vonica A, Brivanlou AH. Gene profiling during neural induction in Xenopus laevis: regulation of BMP signaling by post-transcriptional mechanisms and TAB3, a novel TAK1-binding protein. Development 2002; 129:5529-40. [PMID: 12403722 DOI: 10.1242/dev.00097] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The earliest decision in vertebrate neural development is the acquisition of a neural identity by embryonic ectodermal cells. The default model for neural induction postulates that neural fate specification in the vertebrate embryo occurs by inhibition of epidermal inducing signals in the gastrula ectoderm. Bone morphogenetic proteins (BMPs) act as epidermal inducers, and all identified direct neural inducers block BMP signaling either intra- or extracellularly. Although the mechanism of action of the secreted neural inducers has been elucidated, the relevance of intracellular BMP inhibitors in neural induction is not clear. In order to address this issue and to identify downstream targets after BMP inhibition, we have monitored the transcriptional changes in ectodermal explants neuralized by Smad7 using a Xenopus laevis 5000-clone gastrula-stage cDNA microarray. We report the identification and initial characterization of 142 genes whose transcriptional profiles change in the neuralized explants. In order to address the potential involvement during neural induction of genes identified in the array, we performed gain-of-function studies in ectodermal explants. This approach lead to the identification of four genes that can function as neural inducers in Xenopus and three others that can synergize with known neural inducers in promoting neural fates. Based on these studies, we propose a role for post-transcriptional control of gene expression during neural induction in vertebrates and present a model whereby sustained BMP inhibition is promoted partly through the regulation of TGFbeta activated kinase (TAK1) activity by a novel TAK1-binding protein (TAB3).
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Affiliation(s)
- Ignacio Muñoz-Sanjuán
- The Laboratory of Vertebrate Embryology, The Rockefeller University, New York, NY, USA
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25
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Maeda R, Mood K, Jones TL, Aruga J, Buchberg AM, Daar IO. Xmeis1, a protooncogene involved in specifying neural crest cell fate in Xenopus embryos. Oncogene 2001; 20:1329-42. [PMID: 11313877 DOI: 10.1038/sj.onc.1204250] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2000] [Revised: 01/05/2001] [Accepted: 01/09/2001] [Indexed: 02/03/2023]
Abstract
Meis1 (Myeloid Ecotropic viral Integration Site 1) is a homeobox gene that was originally isolated as a common site of viral integration in myeloid tumors of the BXH-2 recombinant inbred mice strain. We previously isolated a Xenopus homolog of Meis1 (Xmeis1). Here we show that Xmeis1 may play a significant role in neural crest development. In developing Xenopus embryos, Xmeis1 displays a broad expression pattern, but strong expression is observed in tissue of neural cell fate, such as midbrain, hindbrain, the dorsal portion of the neural tube, and neural crest derived branchial arches. In animal cap explants, overexpression of Xmeis1b, an alternatively spliced form of Xmeis1, induces expression of neural crest marker genes in the absence of mesoderm. Moreover, Xmeis1b induces XGli-3 and XZic3, pre-pattern genes involved at the earliest stages of neural crest development, and like these two genes, can induce ectopic pigmented cell masses when overexpressed in developing embryos. Misexpression of Xmeis1b also induces ectopic expression of neural crest markers along the antero-posterior axis of the neural tube in developing Xenopus embryos. In contrast, Xmeis1a, another splice variant, is much less effective at inducing these effects. These data suggest that Xmeis1b is involved in neural crest cell fate specification during embryogenesis, and can functionally intersect with the Gli/Zic signal transduction pathway.
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Affiliation(s)
- R Maeda
- Regulation of Cell Growth Laboratory, National Cancer Institute-Frederick, Frederick, Maryland, MD 21702, USA
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26
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Abstract
The Rel/NF-kappa B gene family encodes a large group of transcriptional activators involved in myriad differentiation events, including embryonic development. We have shown previously that Xrel3, a Xenopus Rel/NF-kappa B-related gene, is expressed in the forebrain, dorsal aspect of the mid- and hindbrain, the otocysts and notochord of neurula and larval stage embryos. Overexpression of Xrel3 causes formation of embryonic tumours. We now show that Xrel3-induced tumours and animal caps from embryos injected with Xrel3 RNA express Otx2, Shh and Gli1. Heterodimerisation of a C-terminally deleted mutant of Xrel3 with wild-type Xrel3 inhibits in vitro binding of wild-type Xrel3 to Rel/NF-kappa B consensus DNA sequences. This dominant interference mutant disrupts Shh, Gli1 and Otx2 mRNA patterning and inhibits anterior development when expressed in the dorsal side of zygotes, which is rescued by co-injecting wild-type Xrel3 mRNA. In chick development, Rel activates Shh signalling, which is required for normal limb formation; Shh, Gli1 and Otx2 encode important neural patterning elements in vertebrates. The activation of these genes in tumours by Xrel3 overexpression and the inhibition of their expression and head development by a dominant interference mutant of Xrel3 indicates that Rel/NF-kappa B is required for activation of these genes and for anterior neural patterning in Xenopus.
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Affiliation(s)
- B B Lake
- Terry Fox Cancer Research Laboratories, Faculty of Medicine, Memorial University of Newfoundland, St John's, Newfoundland A1B 3V6, Canada
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27
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Paterno GD, Ryan PJ, Kao KR, Gillespie LL. The VT+ and VT- isoforms of the fibroblast growth factor receptor type 1 are differentially expressed in the presumptive mesoderm of Xenopus embryos and differ in their ability to mediate mesoderm formation. J Biol Chem 2000; 275:9581-6. [PMID: 10734108 DOI: 10.1074/jbc.275.13.9581] [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: 11/06/2022] Open
Abstract
Previously, we cloned a variant form of the type 1 fibroblast growth factor receptor (FGFR1), FGFR-VT-, from Xenopus embryos (Gillespie, L. L., Chen, G., and Paterno, G. D. (1995) J. Biol. Chem. 270, 22758-22763). This isoform differed from the reported FGFR1 sequence (FGFR-VT+) by a 2-amino acid deletion, Val(423)-Thr(424), in the juxtamembrane region. This deletion arises from the use of an alternate 5' splice donor site, and the activity of the VT+ and VT- forms of the FGFR1 was regulated by phosphorylation at this site. We have now investigated the expression pattern and function of these two isoforms in mesoderm formation in Xenopus embryos. Cells within the marginal zone are induced to form mesoderm during blastula stages. RNase protection analysis of blastula stage embryos revealed that the VT+ isoform was expressed throughout the embryo but that the VT- isoform was expressed almost exclusively in the marginal zone. The ratio of VT+:VT- transcripts in the marginal zone indicated that the VT+ form was predominant throughout blastula stages except for a brief interval, coinciding with the start of zygotic transcription, when a dramatic increase in VT- expression levels was detected. This increase could be mimicked in part by treatment of animal cap explants with FGF-2. Overexpression of the VT+ isoform in Xenopus embryos resulted in development of tadpoles with severe reductions in trunk and tail structures, while embryos overexpressing the VT- isoform developed normally. A standard mesoderm induction assay revealed that a 10-fold higher concentration of FGF-2 was required to reach 50% induction in VT+-overexpressing animal cap explants compared with those overexpressing the VT- isoform. Furthermore, little or no expression of the panmesodermal marker Brachyury (Xbra) was detected in VT+-overexpressing embryos, while VT--overexpressing embryos showed normal staining. This demonstrates that VT+ overexpression had a negative effect on mesoderm formation in vivo. These data are consistent with a model in which mesoderm formation in vivo is regulated, at least in part, by the relative expression levels of the VT+ and VT- isoforms.
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Affiliation(s)
- G D Paterno
- Terry Fox Cancer Research Laboratories, Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3V6, Canada
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28
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Wallingford JB. Tumors in tadpoles: the Xenopus embryo as a model system for the study of tumorigenesis. Trends Genet 1999; 15:385-8. [PMID: 10498932 DOI: 10.1016/s0168-9525(99)01800-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- J B Wallingford
- Department of Molecular and Cell Biology, 401 Barker Hall, University of California, Berkeley, CA 94720, USA.
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