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Abstract
TGF-β family ligands function in inducing and patterning many tissues of the early vertebrate embryonic body plan. Nodal signaling is essential for the specification of mesendodermal tissues and the concurrent cellular movements of gastrulation. Bone morphogenetic protein (BMP) signaling patterns tissues along the dorsal-ventral axis and simultaneously directs the cell movements of convergence and extension. After gastrulation, a second wave of Nodal signaling breaks the symmetry between the left and right sides of the embryo. During these processes, elaborate regulatory feedback between TGF-β ligands and their antagonists direct the proper specification and patterning of embryonic tissues. In this review, we summarize the current knowledge of the function and regulation of TGF-β family signaling in these processes. Although we cover principles that are involved in the development of all vertebrate embryos, we focus specifically on three popular model organisms: the mouse Mus musculus, the African clawed frog of the genus Xenopus, and the zebrafish Danio rerio, highlighting the similarities and differences between these species.
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Affiliation(s)
- Joseph Zinski
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
| | - Benjamin Tajer
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
| | - Mary C Mullins
- University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104-6058
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2
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Klein SL, Moody SA. Early neural ectodermal genes are activated by Siamois and Twin during blastula stages. Genesis 2015; 53:308-20. [PMID: 25892704 PMCID: PMC8943805 DOI: 10.1002/dvg.22854] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 04/13/2015] [Accepted: 04/14/2015] [Indexed: 12/13/2022]
Abstract
BMP signaling distinguishes between neural and non-neural fates by activating epidermis-specific transcription and repressing neural-specific transcription. The neural ectoderm forms after the Organizer secrets antagonists that prevent these BMP-mediated activities. However, it is not known whether neural genes also are transcriptionally activated. Therefore, we tested the ability of nine Organizer transcription factors to ectopically induce the expression of four neural ectodermal genes in epidermal precursors. We found evidence for two pathways: Foxd4 and Sox11 were only induced by Sia and Twn, whereas Gmnn and Zic2 were induced by Sia, Twn, as well as seven other Organizer transcription factors. The induction of Foxd4, Gmnn and Zic2 by Sia/Twn was both non-cell autonomous (requiring an intermediate protein) and cell autonomous (direct), whereas the induction of Sox11 required Foxd4 activity. Because direct induction by Sia/Twn could occur endogenously in the dorsal-equatorial blastula cells that give rise to both the Organizer mesoderm and the neural ectoderm, we knocked down Sia/Twn in those cells. This prevented the blastula expression of Foxd4 and Sox11, demonstrating that Sia/Twn directly activate some neural genes before the separation of the Organizer mesoderm and neural ectoderm lineages.
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Affiliation(s)
- Steven L. Klein
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, 2300 I Street, Northwest, Washington, DC
| | - Sally A. Moody
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, 2300 I Street, Northwest, Washington, DC
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3
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Rankin SA, Kormish J, Kofron M, Jegga A, Zorn AM. A gene regulatory network controlling hhex transcription in the anterior endoderm of the organizer. Dev Biol 2011; 351:297-310. [PMID: 21215263 DOI: 10.1016/j.ydbio.2010.11.037] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 11/15/2010] [Accepted: 11/17/2010] [Indexed: 10/18/2022]
Abstract
The homeobox gene hhex is one of the earliest markers of the anterior endoderm, which gives rise to foregut organs such as the liver, ventral pancreas, thyroid, and lungs. The regulatory networks controlling hhex transcription are poorly understood. In an extensive cis-regulatory analysis of the Xenopus hhex promoter, we determined how the Nodal, Wnt, and BMP pathways and their downstream transcription factors regulate hhex expression in the gastrula organizer. We show that Nodal signaling, present throughout the endoderm, directly activates hhex transcription via FoxH1/Smad2 binding sites in the proximal -0.44 Kb promoter. This positive action of Nodal is suppressed in the ventral-posterior endoderm by Vent 1 and Vent2, homeodomain repressors that are induced by BMP signaling. Maternal Wnt/β-catenin on the dorsal side of the embryo cooperates with Nodal and indirectly activates hhex expression via the homeodomain activators Siamois and Twin. Siamois/Twin stimulate hhex transcription through two mechanisms: (1) they induce the expression of Otx2 and Lim1 and together Siamois, Twin, Otx2, and Lim1 appear to promote hhex transcription through homeobox sites in a Wnt-responsive element located between -0.65 to -0.55 Kb of the hhex promoter. (2) Siamois/Twin also induce the expression of the BMP-antagonists Chordin and Noggin, which are required to exclude Vents from the organizer allowing hhex transcription. This study reveals a complex network regulating anterior endoderm transcription in the early embryo.
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Affiliation(s)
- Scott A Rankin
- Division of Developmental Biology, Cincinnati Children's Research Foundation and Department of Pediatrics, College of Medicine, University of Cincinnati, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
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4
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Haldin CE, Massé KL, Bhamra S, Simrick S, Kyuno JI, Jones EA. The lmx1b gene is pivotal in glomus development in Xenopus laevis. Dev Biol 2008; 322:74-85. [PMID: 18687324 DOI: 10.1016/j.ydbio.2008.07.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 07/03/2008] [Accepted: 07/07/2008] [Indexed: 12/31/2022]
Abstract
We have previously shown that lmx1b, a LIM homeodomain protein, is expressed in the pronephric glomus. We now show temporal and spatial expression patterns of lmx1b and its potential binding partners in both dissected pronephric anlagen and in individual dissected components of stage 42 pronephroi. Morpholino oligonucleotide knock-down of lmx1b establishes a role for lmx1b in the development of the pronephric components. Depletion of lmx1b results in the formation of a glomus with reduced size. Pronephric tubules were also shown to be reduced in structure and/or coiling whereas more distal tubule structure was unaffected. Over-expression of lmx1b mRNA resulted in no significant phenotype. Given that lmx1b protein is known to function as a heterodimer, we have over-expressed lmx1b mRNA alone or in combination with potential interacting molecules and analysed the effects on kidney structures. Phenotypes observed by over-expression of lim1 and ldb1 are partially rescued by co-injection with lmx1b mRNA. Animal cap experiments confirm that co-injection of lmx1b with potential binding partners can up-regulate pronephric molecular markers suggesting that lmx1b lies upstream of wt1 in the gene network controlling glomus differentiation. This places lmx1b in a genetic hierarchy involved in pronephros development and suggests that it is the balance in levels of binding partners together with restricted expression domains of lmx1b and lim1 which influences differentiation into glomus or tubule derivatives in vivo.
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Affiliation(s)
- Caroline E Haldin
- Department of Biological Sciences, Warwick University, Coventry, CV4 7AL, UK
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5
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Abstract
Xenopus embryos are particularly suited for functional experiments to investigate vertebrate embryonic development. Due to the large size of embryos and their development outside of the mother organism, they are very accessible, easy to manipulate, and allow for immediate observation of developmental phenotypes. Powerful methods have been established for both gain- and loss-of-function strategies, which build on these inherent advantages. This chapter describes injection methods used to overexpress gene products and inhibit gene expression as well as pharmacological approaches to manipulate Wnt signaling in Xenopus embryos.
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Affiliation(s)
- Danielle L Lavery
- School of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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6
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Abstract
Mesoderm and endoderm formation in Xenopus involves the coordinated efforts of maternally and zygotically expressed transcription factors together with growth factor signalling, including members of the TGFbeta and wnt families. In this review we discuss our current state of knowledge of these pathways, and describe in more detail some of the transcription factor-DNA interactions that are involved in mesendoderm formation.
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Affiliation(s)
- Fiona C Wardle
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
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7
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Ilia M, Sugiyama Y, Price J. Gender and age related expression of Oct-6--a POU III domain transcription factor, in the adult mouse brain. Neurosci Lett 2003; 344:138-40. [PMID: 12782346 DOI: 10.1016/s0304-3940(03)00445-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Oct-6 is a POU III domain transcription factor whose primary role is thought to be developmental. It is expressed in embryonic stem cells, Schwann cells, and in neuronal subpopulations during telencephalic development. Its best characterised role is in Schwann cells where it is thought to regulate myelin specific gene expression. Expression of Oct-6 was recently discovered in neurons in post-mortem human schizophrenic specimens while being undetectable in matched controls. This study of human tissue contrasted in a number of regards with earlier studies of rodent brain, and questioned what we can consider to be normal adult expression of this gene. In this study, we have investigated Oct-6 expression via in situ hybridisation and Western blot analysis in normal adult female mice of different ages. We show that both RNA and protein levels of Oct-6 expression are highly sustained in the adult and aging cerebellum, whereas they are attenuated in the telencephalon by PW30 (postnatal week 30). These observations suggest that Oct-6 expression takes place in a sex and age dependent way.
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Affiliation(s)
- Maria Ilia
- Department of Neuroscience, Institute of Psychiatry, P039, 1 Windsor Walk Ground, London SE5 8AF, UK.
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Ilia M, Bazigou E, Price J. Expression of the POU domain transcription factor, Oct-6, is attenuated in the adult mouse telencephalon, but increased by neurotoxic damage. Exp Neurol 2003; 181:159-69. [PMID: 12781989 DOI: 10.1016/s0014-4886(03)00047-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Oct-6 is a POU III domain transcription factor expressed in embryonic stem cells, Schwann cells, and neuronal subpopulations during telencephalic development. Its role is unknown except in Schwann cells where it is thought to regulate myelin-specific gene expression. Expression of Oct-6 was recently discovered in neurons in postmortem human schizophrenic brain while being undetectable in matched controls. This study of human tissue contrasted in a number of regards with earlier studies of rodent brain and questioned what we can consider to be normal adult expression of this gene. In this study, we have investigated Oct-6 expression in normal adult mice and in mice treated with neuractive compounds. We show that Oct-6 is widely expressed in young adults but that its expression subsequently becomes restricted to specific neuronal subpopulations. Contrary to earlier reports, however, this specific expression is transient and is eventually completely lost from telencephalic neurons. The OCT-6 protein, somewhat surprisingly, is found to be cytoplasmic as well as nuclear in certain neuronal subpopulations. Finally, we report that neurotoxic doses of anticonvulsants reactivate OCT-6 expression in adult mouse brain.
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Affiliation(s)
- M Ilia
- Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK.
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9
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Tabata T, Sakaguchi K, Tajima T, Suzuki AS. Comparative study of sequential expression of the organizer-related genes in normal Cynops pyrrhogaster embryos and mesodermalized ectoderm. Dev Growth Differ 2001; 43:351-9. [PMID: 11473542 DOI: 10.1046/j.1440-169x.2001.00581.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An artificially mesodermalized ectoderm (mE) of early Cynops pyrrhogaster gastrula acquires the organizer property; the mE is able to induce the secondary axis. The expression of organizer-related genes was investigated during the mesodermalizing process of the mE. The expression of C. pyrrhogaster organizer-related genes, such as bra, gsc, lim-1, chd and noggin, were analyzed. Cynops pyrrhogaster shh expression was also investigated. The organizer-related genes were activated by 12 h after the mesoderm-inducing stimulus. It was noted that there was a temporal gap in the expression of each gene. The expression of bra and gsc seemed to be more quickly activated during the mesodermalizing process. While expression of lim-1 and noggin was activated later than that of bra and gsc, lim-1 expression was earlier than chd and noggin expression. Shh expression was activated later than lim-1/noggin. The present study suggests the possibility that the bra/gsc, lim-1, chd, noggin and shh genes are expressed one by one in that order during the mesodermalizing of the presumptive ectoderm. It also indicates that the sequence is not always consistent with that of the whole embryo during normal embryogenesis. The meaning of the discrepancy will be discussed in connection with the cascade of certain genes expressed during the mesodermalizing process.
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Affiliation(s)
- T Tabata
- Natural Enviromental Science, Department of Enviromental Science, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
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Hauptmann G, Gerster T. Combinatorial expression of zebrafish Brn-1- and Brn-2-related POU genes in the embryonic brain, pronephric primordium, and pharyngeal arches. Dev Dyn 2000; 218:345-58. [PMID: 10842361 DOI: 10.1002/(sici)1097-0177(200006)218:2<345::aid-dvdy8>3.0.co;2-v] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Vertebrate class III POU genes are widely expressed in the embryonic and adult central nervous system, where they act as transcriptional regulators of cell- and/or region-specific gene expression. We isolated four zebrafish class III POU genes, named zp-12, zp-23, zp-47 and zp-50. In this study, we examined the developmental expression patterns of the Brn-1- and Brn-2-related zp-12, zp-23 and zp-47 genes by means of whole-mount in situ hybridization. Similarly to their mammalian orthologues, the major expression site of all zebrafish zp genes is the CNS. Neurectodermal expression was first detected at the beginning of somitogenesis in spatially restricted segment-like domains in different parts of the neural plate. During somitogenesis transcript distributions changed from highly restricted to widespread but nevertheless distinct patterns found in all major subdivisions of the CNS. While zp-47 expression was detected exclusively in the CNS, localized expression of zp-12 and zp-23 was also found in the pronephric primordium and in cell clusters within the mandibular and hyoid arches. Furthermore, zp-23 transcripts were transiently detected in a restricted region of the paraxial mesendoderm and, at late embryogenesis stages, in the auditory vesicles. The early regionalized expression of all three zp genes is compatible with roles in regional specification of the neural plate. Comparison of the distinct yet overlapping expression of zp-12, zp-23, zp-47 and the previously characterized zp-50 gene implies both unique, as well as redundant functions for each family member. We propose that coordinate expression of particular combinations of class III POU genes contribute to pattern formation or cell fate determination in the developing CNS and other structures.
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Affiliation(s)
- G Hauptmann
- Biozentrum der Universität Basel, Switzerland.
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11
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Brennan HC, Nijjar S, Jones EA. The specification and growth factor inducibility of the pronephric glomus in Xenopus laevis. Development 1999; 126:5847-56. [PMID: 10572058 DOI: 10.1242/dev.126.24.5847] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report a study on the specification of the glomus, the filtration device of the amphibian pronephric kidney, using an explant culturing strategy in Xenopus laevis. Explants of presumptive pronephric mesoderm were dissected from embryos of mid-gastrula to swimming tadpole stages. These explants were cultured within ectodermal wraps and analysed by RT-PCR for the presence of the Wilm's Tumour-1 gene, xWT1, a marker specific for the glomus at the stages analysed, together with other mesodermal markers. We show that the glomus is specified at stage 12.5, the same stage at which pronephric tubules are specified. We have previously shown that pronephric duct is specified somewhat later, at stage 14. Furthermore, we have analysed the growth factor inducibility of the glomus in the presence or absence of retinoic acid (RA) by RT-PCR. We define for the first time the conditions under which these growth factors induce glomus tissue in animal cap tissue. Activin together with high concentrations of RA can induce glomus tissue from animal cap ectoderm. Unlike the pronephric tubules, the glomus can also be induced by FGF and RA.
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Affiliation(s)
- H C Brennan
- Cell and Molecular Development Group, Department of Biological Sciences, Warwick University, Coventry, CV4 7AL, UK
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12
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Abstract
The cAMP signaling system has been postulated to be involved in embryogenesis of many animal species, however, little is known about its role in embryonic axis formation in vertebrates. In this study, the role of the cAMP signaling pathway in patterning the body plan of the Xenopus embryo was investigated by expressing and activating the exogenous human 5-hydroxytryptamine type 1a receptor (5-HT(1a)R) which inhibits adenylyl cyclase through inhibitory G-protein in embryos in a spatially- and temporally-controlled manner. In embryos, ventral, but not dorsal expression and stimulation of this receptor during blastula and gastrula stages induced secondary axes but were lacking anterior structures. At the molecular level, 5-HT(1a)R stimulation induced expression of the dorsal mesoderm marker genes, and downregulated expression of the ventral markers but had no effect on expression of the pan mesodermal marker gene in ventral marginal zone explants. In addition, ventral expression and stimulation of the receptor partially restored dorsal axis of UV-irradiated axis deficient embryo. Finally, the total mass of cAMP differs between dorsal and ventral regions of blastula and gastrula embryos and this is regulated in a temporally-specific manner. These results suggest that the cAMP signaling system may be involved in the transduction of ventral signals in patterning early embryos.
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Affiliation(s)
- M J Kim
- Department of Life Science, Pohang University of Science and Technology, San 31 Hyoja-Dong, Pohang, Kyungbuk, South Korea
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Matsuo-Takasaki M, Lim JH, Sato SM. The POU domain gene, XlPOU 2 is an essential downstream determinant of neural induction. Mech Dev 1999; 89:75-85. [PMID: 10559482 DOI: 10.1016/s0925-4773(99)00204-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The POU domain gene, XlPOU 2, acts as a transcriptional activator during mid-gastrulation in Xenopus. Overexpression or misexpression of VP16-POU-GR, a fusion protein consisting of the strong activator domain of VP16 and the POU domain of XlPOU 2, results in ectopic expression of the neural-specific genes, nrp-1, en-2, and beta-tubulin. In contrast, overexpressing a dominant-inhibitory form of XlPOU 2 inhibits the chordin-induced neuralization of uncommitted ectoderm, and results in a loss of nrp-1 and en-2 expression in embryos. Furthermore, in uncommitted ectoderm, XlPOU 2 regulates the developmental neural program that includes a number of pre-pattern genes and at least one proneural gene, X-ngnr-1, thus playing a key role during neural determination.
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Affiliation(s)
- M Matsuo-Takasaki
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda 20892, USA.
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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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Ryan AK, Rosenfeld MG. POU domain family values: flexibility, partnerships, and developmental codes. Genes Dev 1997; 11:1207-25. [PMID: 9171367 DOI: 10.1101/gad.11.10.1207] [Citation(s) in RCA: 404] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- A K Ryan
- Howard Hughes Medical Institute, Department and School of Medicine, University of California at San Diego, La Jolla 92093-0648, USA
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