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Abstract
5-methylcytosine (5mC) is an epigenetic modification to DNA which modulates transcription. 5mC can be sequentially oxidized to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). Collectively, these marks are referred to as the oxidized derivatives of 5mC (i.e., oxi-mCs). Their formation is catalyzed by the ten-eleven translocation methylcytosine dioxygenases (TETs 1, 2 and 3). Various techniques have been developed for the detection of oxi-mCs. The following chapter describes an immunochemical protocol for the simultaneous detection of 5hmC and 5caC in embryonic zebrafish tissue sections. The embryos are fixed, permeabilized and embedded in paraffin blocks. The blocks are cut into sections that are mounted onto slides. Depurination of the DNA is performed to allow immunodetection of the oxi-mCs. The 5hmC is detected with the help of a mouse anti-5hmC monoclonal primary antibody and a goat anti-mouse Alexa Fluor 633-conjugated secondary antibody. The weak 5caC signal requires enzymatic amplification. Its detection involves a rabbit anti-5caC polyclonal primary antibody and a goat anti-rabbit secondary antibody that is conjugated to horseradish peroxidase (HRP). HRP amplifies the 5caC signal by catalyzing the deposition of large quantities of fluorescein-labeled tyramide. Sections immunostained for 5hmC and 5caC are analyzed by fluorescent light or confocal laser scanning microscopy. This immunochemical method allows for highly sensitive detection of 5hmC and 5caC in zebrafish tissues.
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Affiliation(s)
- Peter Jessop
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - Martin Gering
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
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Moore C, Richens JL, Hough Y, Ucanok D, Malla S, Sang F, Chen Y, Elworthy S, Wilkinson RN, Gering M. Gfi1aa and Gfi1b set the pace for primitive erythroblast differentiation from hemangioblasts in the zebrafish embryo. Blood Adv 2018; 2:2589-2606. [PMID: 30309860 PMCID: PMC6199651 DOI: 10.1182/bloodadvances.2018020156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 09/07/2018] [Indexed: 12/14/2022] Open
Abstract
The transcriptional repressors Gfi1(a) and Gfi1b are epigenetic regulators with unique and overlapping roles in hematopoiesis. In different contexts, Gfi1 and Gfi1b restrict or promote cell proliferation, prevent apoptosis, influence cell fate decisions, and are essential for terminal differentiation. Here, we show in primitive red blood cells (prRBCs) that they can also set the pace for cellular differentiation. In zebrafish, prRBCs express 2 of 3 zebrafish Gfi1/1b paralogs, Gfi1aa and Gfi1b. The recently identified zebrafish gfi1aa gene trap allele qmc551 drives erythroid green fluorescent protein (GFP) instead of Gfi1aa expression, yet homozygous carriers have normal prRBCs. prRBCs display a maturation defect only after splice morpholino-mediated knockdown of Gfi1b in gfi1aa qmc551 homozygous embryos. To study the transcriptome of the Gfi1aa/1b double-depleted cells, we performed an RNA-Seq experiment on GFP-positive prRBCs sorted from 20-hour-old embryos that were heterozygous or homozygous for gfi1aa qmc551 , as well as wt or morphant for gfi1b We subsequently confirmed and extended these data in whole-mount in situ hybridization experiments on newly generated single- and double-mutant embryos. Combined, the data showed that in the absence of Gfi1aa, the synchronously developing prRBCs were delayed in activating late erythroid differentiation, as they struggled to suppress early erythroid and endothelial transcription programs. The latter highlighted the bipotent nature of the progenitors from which prRBCs arise. In the absence of Gfi1aa, Gfi1b promoted erythroid differentiation as stepwise loss of wt gfi1b copies progressively delayed Gfi1aa-depleted prRBCs even further, showing that Gfi1aa and Gfi1b together set the pace for prRBC differentiation from hemangioblasts.
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Affiliation(s)
| | | | | | | | - Sunir Malla
- Deep Seq, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Fei Sang
- Deep Seq, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Yan Chen
- Department of Infection, Immunity & Cardiovascular Disease, Medical School, and
- Bateson Centre, University of Sheffield, Sheffield, United Kingdom
| | - Stone Elworthy
- Department of Infection, Immunity & Cardiovascular Disease, Medical School, and
- Bateson Centre, University of Sheffield, Sheffield, United Kingdom
| | - Robert N Wilkinson
- Department of Infection, Immunity & Cardiovascular Disease, Medical School, and
- Bateson Centre, University of Sheffield, Sheffield, United Kingdom
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3
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Jessop P, Ruzov A, Gering M. Developmental Functions of the Dynamic DNA Methylome and Hydroxymethylome in the Mouse and Zebrafish: Similarities and Differences. Front Cell Dev Biol 2018; 6:27. [PMID: 29616219 PMCID: PMC5869911 DOI: 10.3389/fcell.2018.00027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 03/05/2018] [Indexed: 12/25/2022] Open
Abstract
5-methylcytosine (5mC) is the best understood DNA modification and is generally believed to be associated with repression of gene expression. Over the last decade, sequentially oxidized forms of 5mC (oxi-mCs) have been discovered within the genomes of vertebrates. Their discovery was accompanied by that of the ten-eleven translocation (TET) methylcytosine dioxygenases, the enzymes that catalyze the formation of the oxi-mCs. Although a number of studies performed on different vertebrate models and embryonic stem cells demonstrated that both TET enzymes and oxi-mCs are likely to be important for several developmental processes it is currently unclear whether their developmental roles are conserved among vertebrates. Here, we summarize recent developments in this field suggesting that biological roles of TETs/oxi-mCs may significantly differ between mice and zebrafish. Thus, although the role of TET proteins in late organogenesis has been documented for both these systems; unlike in mice the enzymatic oxidation of 5mC does not seem to be involved in zygotic reprogramming or gastrulation in zebrafish. Our analysis may provide an insight into the general principles of epigenetic regulation of animal development and cellular differentiation.
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Affiliation(s)
- Peter Jessop
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Alexey Ruzov
- Division of Cancer and Stem Cells, Centre for Biomolecular Sciences, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Martin Gering
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
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Thambyrajah R, Ucanok D, Jalali M, Hough Y, Wilkinson RN, McMahon K, Moore C, Gering M. A gene trap transposon eliminates haematopoietic expression of zebrafish Gfi1aa, but does not interfere with haematopoiesis. Dev Biol 2016; 417:25-39. [PMID: 27432513 PMCID: PMC5003831 DOI: 10.1016/j.ydbio.2016.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/10/2016] [Accepted: 07/15/2016] [Indexed: 11/02/2022]
Abstract
A transposon-mediated gene trap screen identified the zebrafish line qmc551 that expresses a GFP reporter in primitive erythrocytes and also in haemogenic endothelial cells, which give rise to haematopoietic stem and progenitor cells (HSPCs) that seed sites of larval and adult haematopoiesis. The transposon that mediates this GFP expression is located in intron 1 of the gfi1aa gene, one of three zebrafish paralogs that encode transcriptional repressors homologous to mammalian Gfi1 and Gfi1b proteins. In qmc551 transgenics, GFP expression is under the control of the endogenous gfi1aa promoter, recapitulates early gfi1aa expression and allows live observation of gfi1aa promoter activity. While the transposon integration interferes with the expression of gfi1aa mRNA in haematopoietic cells, homozygous qmc551 fish are viable and fertile, and display normal primitive and definitive haematopoiesis. Retained expression of Gfi1b in primitive erythrocytes and up-regulation of Gfi1ab at the onset of definitive haematopoiesis in homozygous qmc551 carriers, are sufficient to allow normal haematopoiesis. This finding contradicts previously published morpholino data that suggested an essential role for zebrafish Gfi1aa in primitive erythropoiesis.
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Affiliation(s)
- Roshana Thambyrajah
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Deniz Ucanok
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Maryam Jalali
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Yasmin Hough
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Robert Neil Wilkinson
- Department of Infection, Immunity & Cardiovascular Disease, University of Sheffield, Medical School, Beech Hill Road, Sheffield S10 2RX, UK; Bateson Centre, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
| | - Kathryn McMahon
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Chris Moore
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Martin Gering
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK.
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Almeida RD, Loose M, Sottile V, Matsa E, Denning C, Young L, Johnson AD, Gering M, Ruzov A. 5-hydroxymethyl-cytosine enrichment of non-committed cells is not a universal feature of vertebrate development. Epigenetics 2014; 7:383-9. [DOI: 10.4161/epi.19375] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Watson O, Novodvorsky P, Gray C, Rothman AMK, Lawrie A, Crossman DC, Haase A, McMahon K, Gering M, Van Eeden FJM, Chico TJA. Blood flow suppresses vascular Notch signalling via dll4 and is required for angiogenesis in response to hypoxic signalling. Cardiovasc Res 2013; 100:252-61. [PMID: 23812297 PMCID: PMC3797625 DOI: 10.1093/cvr/cvt170] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Aims The contribution of blood flow to angiogenesis is incompletely understood. We examined the effect of blood flow on Notch signalling in the vasculature of zebrafish embryos, and whether blood flow regulates angiogenesis in zebrafish with constitutively up-regulated hypoxic signalling. Methods and results Developing zebrafish (Danio rerio) embryos survive via diffusion in the absence of circulation induced by knockdown of cardiac troponin T2 or chemical cardiac cessation. The absence of blood flow increased vascular Notch signalling in 48 h post-fertilization old embryos via up-regulation of the Notch ligand dll4. Despite this, patterning of the intersegmental vessels is not affected by absent blood flow. We therefore examined homozygous vhl mutant zebrafish that have constitutively up-regulated hypoxic signalling. These display excessive and aberrant angiogenesis from 72 h post-fertilization, with significantly increased endothelial number, vessel diameter, and length. The absence of blood flow abolished these effects, though normal vessel patterning was preserved. Conclusion We show that blood flow suppresses vascular Notch signalling via down-regulation of dll4. We have also shown that blood flow is required for angiogenesis in response to hypoxic signalling but is not required for normal vessel patterning. These data indicate important differences in hypoxia-driven vs. developmental angiogenesis.
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Affiliation(s)
- Oliver Watson
- Lab D38, MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Firth Court, Sheffield S10 2TN, UK
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Ketley A, Warren A, Holmes E, Gering M, Aboobaker AA, Brook JD. The miR-30 microRNA family targets smoothened to regulate hedgehog signalling in zebrafish early muscle development. PLoS One 2013; 8:e65170. [PMID: 23755189 PMCID: PMC3673911 DOI: 10.1371/journal.pone.0065170] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 04/22/2013] [Indexed: 11/18/2022] Open
Abstract
The importance of microRNAs in development is now widely accepted. However, identifying the specific targets of individual microRNAs and understanding their biological significance remains a major challenge. We have used the zebrafish model system to evaluate the expression and function of microRNAs potentially involved in muscle development and study their interaction with predicted target genes. We altered expression of the miR-30 microRNA family and generated phenotypes that mimicked misregulation of the Hedgehog pathway. Inhibition of the miR-30 family increases activity of the pathway, resulting in elevated ptc1 expression and increased numbers of superficial slow-muscle fibres. We show that the transmembrane receptor smoothened is a target of this microRNA family. Our results indicate that fine coordination of smoothened activity by the miR-30 family allows the correct specification and differentiation of distinct muscle cell types during zebrafish embryonic development.
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Affiliation(s)
- Ami Ketley
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - Anne Warren
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - Emily Holmes
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - Martin Gering
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - A. Aziz Aboobaker
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - J. David Brook
- Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
- * E-mail:
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Gray C, Bratt D, Lees J, daCosta M, Plant K, Watson OJ, Solaymani-Kohal S, Tazzyman S, Serbanovic-Canic J, Crossman DC, Keavney BD, Haase A, McMahon K, Gering M, Roehl H, Evans PC, Chico TJA. Loss of function of parathyroid hormone receptor 1 induces Notch-dependent aortic defects during zebrafish vascular development. Arterioscler Thromb Vasc Biol 2013; 33:1257-63. [PMID: 23559631 DOI: 10.1161/atvbaha.112.300590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Coarctation of the aorta is rarely associated with known gene defects. Blomstrand chondrodysplasia, caused by mutations in the parathyroid hormone receptor 1 (PTHR1) is associated with coarctation of the aorta in some cases, although it is unclear whether PTHR1 deficiency causes coarctation of the aorta directly. The zebrafish allows the study of vascular development using approaches not possible in other models. We therefore examined the effect of loss of function of PTHR1 or its ligand parathyroid hormone-related peptide (PTHrP) on aortic formation in zebrafish. APPROACH AND RESULTS Morpholino antisense oligonucleotide knockdown of either PTHR1 or PTHrP led to a localized occlusion of the mid-aorta in developing zebrafish. Confocal imaging of transgenic embryos showed that these defects were caused by loss of endothelium, rather than failure to lumenize. Using a Notch reporter transgenic ([CSL:Venus]qmc61), we found both PTHR1 and PTHrP knockdown-induced defective Notch signaling in the hypochord at the site of the aortic defect before onset of circulation, and the aortic occlusion was rescued by inducible Notch upregulation. CONCLUSIONS Loss of function of either PTHR1 or PTHrP leads to a localized aortic defect that is Notch dependent. These findings may underlie the aortic defect seen in Blomstrand chondrodysplasia, and reveal a link between parathyroid hormone and Notch signaling during aortic development.
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Affiliation(s)
- Caroline Gray
- MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Sheffield, UK
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9
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Bratt DG, Lees J, Crossman DC, Gering M, Chico TJA. 18 Parathyroid hormone receptor 1 knockdown induces localised aortic occlusion by down regulating notch signalling in zebrafish. Heart 2011. [DOI: 10.1136/heartjnl-2011-300920b.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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10
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Abstract
The Notch signalling pathway is repeatedly employed during embryonic development and adult homeostasis of a variety of tissues. In particular, its frequent involvement in the regulation of stem and progenitor cell maintenance and proliferation, as well as its role in binary fate decisions in cells that are destined to differentiate, is remarkable. Here, we review its role in the development of haematopoietic stem cells during vertebrate embryogenesis and put it into the context of Notch's functions in arterial specification, angiogenic vessel sprouting and vessel maintenance. We further discuss interactions with other signalling cascades, and pinpoint open questions and some of the challenges that lie ahead.
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Affiliation(s)
- Martin Gering
- Institute of Genetics, School of Biology, Queen's Medical Centre, University of Nottingham, Nottingham, UK
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11
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Wilkinson RN, Pouget C, Gering M, Russell AJ, Davies SG, Kimelman D, Patient R. Hedgehog and Bmp polarize hematopoietic stem cell emergence in the zebrafish dorsal aorta. Dev Cell 2009; 16:909-16. [PMID: 19531361 DOI: 10.1016/j.devcel.2009.04.014] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Revised: 03/02/2009] [Accepted: 04/29/2009] [Indexed: 01/09/2023]
Abstract
Hematopoietic stem cells (HSCs) are first detected in the floor of the embryonic dorsal aorta (DA), and we investigate the signals that induce the HSC program there. We show that while continued Hedgehog (Hh) signaling from the overlying midline structures maintains the arterial program characteristic of the DA roof, a ventral Bmp4 signal induces the blood stem cell program in the DA floor. This patterning of the DA by Hh and Bmp is the mirror image of that in the neural tube, with Hh favoring dorsal rather than ventral cell types, and Bmp favoring ventral rather than dorsal. With the majority of current data supporting a model whereby HSCs derive from arterial endothelium, our data identify the signal driving this conversion. These findings are important for the study of the production of HSCs from embryonic stem cells and establish a paradigm for the development of adult stem cells.
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Affiliation(s)
- Robert N Wilkinson
- MRC Molecular Hematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
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12
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Hsu JC, Gering M. Transcriptional regulation of the c-myb gene in zebrafish embryogenesis. Dev Biol 2009. [DOI: 10.1016/j.ydbio.2009.05.173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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13
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Abstract
Notch signaling is essential for hematopoietic stem cell (HSC) formation during embryogenesis, and hitherto it was also thought to be required for HSC maintenance. However, in this issue of Cell Stem Cell, Maillard et al. (2008) demonstrate rather conclusively that inactivation of the Notch pathway in HSCs does not interfere with their self-renewal.
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Affiliation(s)
- Martin Gering
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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14
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Meier N, Krpic S, Rodriguez P, Strouboulis J, Monti M, Krijgsveld J, Gering M, Patient R, Hostert A, Grosveld F. Novel binding partners of Ldb1 are required for haematopoietic development. Blood Cells Mol Dis 2007. [DOI: 10.1016/j.bcmd.2006.10.093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Meier N, Krpic S, Rodriguez P, Strouboulis J, Monti M, Krijgsveld J, Gering M, Patient R, Hostert A, Grosveld F. Novel binding partners of Ldb1 are required for haematopoietic development. Development 2006; 133:4913-23. [PMID: 17108004 DOI: 10.1242/dev.02656] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ldb1, a ubiquitously expressed LIM domain binding protein, is essential in a number of tissues during development. It interacts with Gata1, Tal1, E2A and Lmo2 to form a transcription factor complex regulating late erythroid genes. We identify a number of novel Ldb1 interacting proteins in erythroleukaemic cells, in particular the repressor protein Eto-2 (and its family member Mtgr1), the cyclin-dependent kinase Cdk9, and the bridging factor Lmo4. MO-mediated knockdowns in zebrafish show these factors to be essential for definitive haematopoiesis. In accordance with the zebrafish results these factors are coexpressed in prehaematopoietic cells of the early mouse embryo, although we originally identified the complex in late erythroid cells. Based on the change in subcellullar localisation of Eto-2 we postulate that it plays a central role in the transition from the migration and expansion phase of the prehaematopoietic cells to the establishment of definitive haematopoietic stem cells.
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Affiliation(s)
- Natalia Meier
- Department of Cell Biology and Genetics, Erasmus MC, PO Box 2040, 3000 CA, Rotterdam, The Netherlands
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Patterson LJ, Gering M, Eckfeldt CE, Green AR, Verfaillie CM, Ekker SC, Patient R. The transcription factors Scl and Lmo2 act together during development of the hemangioblast in zebrafish. Blood 2006; 109:2389-98. [PMID: 17090656 DOI: 10.1182/blood-2006-02-003087] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe transcription factors Scl and Lmo2 are crucial for development of all blood. An important early requirement for Scl in endothelial development has also been revealed recently in zebrafish embryos, supporting previous findings in scl−/− embryoid bodies. Scl depletion culminates most notably in failure of dorsal aorta formation, potentially revealing a role in the formation of hemogenic endothelium. We now present evidence that the requirements for Lmo2 in zebrafish embryos are essentially the same as for Scl. The expression of important hematopoietic regulators is lost, reduced, or delayed, panendothelial gene expression is down-regulated, and aorta-specific marker expression is lost. The close similarity of the phenotypes for Scl and Lmo2 suggest that they perform these early functions in hemangioblast development within a multiprotein complex, as shown for erythropoiesis. Consistent with this, we find that scl morphants cannot be rescued by a non-Lmo2–binding form of Scl but can be rescued by non-DNA–binding forms, suggesting tethering to target genes through DNA-binding partners linked via Lmo2. Interestingly, unlike other hematopoietic regulators, the Scl/Lmo2 complex does not appear to autoregulate, as neither gene's expression is affected by depletion of the other. Thus, expression of these critical regulators is dependent on continued expression of upstream regulators, which may include cell-extrinsic signals.
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Affiliation(s)
- Lucy J Patterson
- Weatherall Institute of Molecular Medicine, Oxford University, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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17
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Abstract
AbstractBlood and endothelial cells arise in close association in developing embryos, possibly from a shared precursor, the hemangioblast, or as hemogenic endothelium. The transcription factor, Scl/Tal1 (stem cell leukemia protein), is essential for hematopoiesis but thought to be required only for remodeling of endothelium in mouse embryos. By contrast, it has been implicated in hemangioblast formation in embryoid bodies. To resolve the role of scl in endothelial development, we knocked down its synthesis in zebrafish embryos where early precursors and later phenotypes can be more easily monitored. With respect to blood, the zebrafish morphants phenocopied the mouse knockout and positioned scl in the genetic hierarchy. Importantly, endothelial development was also clearly disrupted. Dorsal aorta formation was substantially compromised and gene expression in the posterior cardinal vein was abnormal. We conclude that scl is especially critical for the development of arteries where adult hematopoietic stem cells emerge, implicating scl in the formation of hemogenic endothelium.
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Affiliation(s)
- Lucy J Patterson
- Weatherall Institute of Molecular Medicine, Oxford University, John Radcliffe Hospital, Headington, Oxford, OX3 9DS, United Kingdom
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18
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Gering M, Patient R. Hedgehog Signaling Is Required for Adult Blood Stem Cell Formation in Zebrafish Embryos. Dev Cell 2005; 8:389-400. [PMID: 15737934 DOI: 10.1016/j.devcel.2005.01.010] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Revised: 11/25/2004] [Accepted: 01/04/2005] [Indexed: 11/19/2022]
Abstract
Studies with embryonic explants and embryonic stem cells have suggested a role for Hedgehog (Hh) signaling in hematopoiesis. However, targeted deletion of Hh pathway components in the mouse has so far failed to provide in vivo evidence. Here we show that zebrafish embryos mutant in the Hh pathway or treated with the Hh signaling inhibitor cyclopamine display defects in adult hematopoietic stem cell (HSC) formation but not in primitive hematopoiesis. Hh is required in the trunk at three consecutive stages during vascular development: for the medial migration of endothelial progenitors of the dorsal aorta (DA), for arterial gene expression, and for the formation of intersomitic vessel sprouts. Interference with Hh signaling during the first two stages also interferes with HSC formation. Furthermore, HSC and DA formation also share Vegf and Notch requirements, which further distinguishes them from primitive hematopoiesis and underlines their close relationship during vertebrate development.
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Affiliation(s)
- Martin Gering
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, United Kingdom
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19
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Pinheiro P, Gering M, Patient R. The basic helix-loop-helix transcription factor, Tal2, marks the lateral floor plate of the spinal cord in zebrafish. Gene Expr Patterns 2004; 4:85-92. [PMID: 14678833 DOI: 10.1016/s1567-133x(03)00145-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Basic helix-loop-helix (bHLH) transcription factors play key roles in the development of the central nervous system. Here we report the isolation of a zebrafish gene that encodes a homologue of the mammalian bHLH transcription factor, Tal2. In zebrafish embryos, tal2, like its mammalian homologue, is strongly expressed in the diencephalon and the mesencephalon, with the latter expression located in post-mitotic cells of the tectum. However, in addition to this conserved brain expression, we also detect expression in the floor plate of the spinal cord. By the location of this expression relative to other genes expressed in the floor plate and by analysing expression in a selection of midline mutants, we reveal that tal2 is expressed within the lateral floor plate as opposed to the medial floor plate, and also in more dorsal cells which are distinct from motorneurons and depend on either sonic hedgehog signalling or a signal coming from the lateral floor plate. This is to our knowledge the first report of a gene expressed specifically in lateral cells of the floor plate in the spinal cord.
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Affiliation(s)
- Philip Pinheiro
- Institute of Genetics, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK
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Gering M, Yamada Y, Rabbitts TH, Patient RK. Lmo2 and Scl/Tal1 convert non-axial mesoderm into haemangioblasts which differentiate into endothelial cells in the absence of Gata1. Development 2003; 130:6187-99. [PMID: 14602685 DOI: 10.1242/dev.00875] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The LIM domain protein Lmo2 and the basic helix-loop-helix transcription factor Scl/Tal1 are expressed in early haematopoietic and endothelial progenitors and interact with each other in haematopoietic cells. While loss-of-function studies have shown that Lmo2 and Scl/Tal1 are essential for haematopoiesis and angiogenic remodelling of the vasculature, gain-of-function studies have suggested an earlier role for Scl/Tal1 in the specification of haemangioblasts, putative bipotential precursors of blood and endothelium. In zebrafish embryos, Scl/Tal1 can induce these progenitors from early mesoderm mainly at the expense of the somitic paraxial mesoderm. We show that this restriction to the somitic paraxial mesoderm correlates well with the ability of Scl/Tal1 to induce ectopic expression of its interaction partner Lmo2. Co-injection of lmo2 mRNA with scl/tal1 dramatically extends its effect to head, heart, pronephros and pronephric duct mesoderm inducing early blood and endothelial genes all along the anteroposterior axis. Erythroid development, however, is expanded only into pronephric mesoderm,remaining excluded from head, heart and somitic paraxial mesoderm territories. This restriction correlates well with activation of gata1transcription and co-injection of gata1 mRNA along with scl/tal1 and lmo2 induces erythropoiesis more broadly without ventralising or posteriorising the embryo. While no ectopic myeloid development from the Scl/Tal1-Lmo2-induced haemangioblasts was observed, a dramatic increase in the number of endothelial cells was found. These results suggest that, in the absence of inducers of erythroid or myeloid haematopoiesis, Scl/Tal1-Lmo2-induced haemangioblasts differentiate into endothelial cells.
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Affiliation(s)
- Martin Gering
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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Barton LM, Gottgens B, Gering M, Gilbert JG, Grafham D, Rogers J, Bentley D, Patient R, Green AR. Regulation of the stem cell leukemia (SCL) gene: a tale of two fishes. Proc Natl Acad Sci U S A 2001; 98:6747-52. [PMID: 11381108 PMCID: PMC34424 DOI: 10.1073/pnas.101532998] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2000] [Indexed: 11/18/2022] Open
Abstract
The stem cell leukemia (SCL) gene encodes a tissue-specific basic helix-loop-helix (bHLH) protein with a pivotal role in hemopoiesis and vasculogenesis. Several enhancers have been identified within the murine SCL locus that direct reporter gene expression to subdomains of the normal SCL expression pattern, and long-range sequence comparisons of the human and murine SCL loci have identified additional candidate enhancers. To facilitate the characterization of regulatory elements, we have sequenced and analyzed 33 kb of the SCL genomic locus from the pufferfish Fugu rubripes, a species with a highly compact genome. Although the pattern of SCL expression is highly conserved from mammals to teleost fish, the genes flanking pufferfish SCL were unrelated to those known to flank both avian and mammalian SCL genes. These data suggest that SCL regulatory elements are confined to the region between the upstream and downstream flanking genes, a region of 65 kb in human and 8.5 kb in pufferfish. Consistent with this hypothesis, the entire 33-kb pufferfish SCL locus directed appropriate expression to hemopoietic and neural tissue in transgenic zebrafish embryos, as did a 10.4-kb fragment containing the SCL gene and extending to the 5' and 3' flanking genes. These results demonstrate the power of combining the compact genome of the pufferfish with the advantages that zebrafish provide for studies of gene regulation during development. Furthermore, the pufferfish SCL locus provides a powerful tool for the manipulation of hemopoiesis and vasculogenesis in vivo.
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Affiliation(s)
- L M Barton
- Department of Hematology, Cambridge Institute for Medical Research, University of Cambridge, Addenbrookes Hospital, Cambridge CB2 2XY, United Kingdom
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Durbin L, Sordino P, Barrios A, Gering M, Thisse C, Thisse B, Brennan C, Green A, Wilson S, Holder N. Anteroposterior patterning is required within segments for somite boundary formation in developing zebrafish. Development 2000; 127:1703-13. [PMID: 10725246 DOI: 10.1242/dev.127.8.1703] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Somite formation involves the establishment of a segmental prepattern in the presomitic mesoderm, anteroposterior patterning of each segmental primordium and formation of boundaries between adjacent segments. How these events are co-ordinated remains uncertain. In this study, analysis of expression of zebrafish mesp-a reveals that each segment acquires anteroposterior regionalisation when located in the anterior presomitic mesoderm. Thus anteroposterior patterning is occurring after the establishment of a segmental prepattern in the paraxial mesoderm and prior to somite boundary formation. Zebrafish fss(−), bea(−), des(−) and aei(−) embryos all fail to form somites, yet we demonstrate that a segmental prepattern is established in the presomitic mesoderm of all these mutants and hox gene expression shows that overall anteroposterior patterning of the mesoderm is also normal. However, analysis of various molecular markers reveals that anteroposterior regionalisation within each segment is disturbed in the mutants. In fss(−), there is a loss of anterior segment markers, such that all segments appear posteriorized, whereas in bea(−), des(−) and aei(−), anterior and posterior markers are expressed throughout each segment. Since somite formation is disrupted in these mutants, correct anteroposterior patterning within segments may be a prerequisite for somite boundary formation. In support of this hypothesis, we show that it is possible to rescue boundary formation in fss(−) through the ectopic expression of EphA4, an anterior segment marker, in the paraxial mesoderm. These observations indicate that a key consequence of the anteroposterior regionalisation of segments may be the induction of Eph and ephrin expression at segment interfaces and that Eph/ephrin signalling subsequently contributes to the formation of somite boundaries.
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Affiliation(s)
- L Durbin
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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Sinclair AM, Göttgens B, Barton LM, Stanley ML, Pardanaud L, Klaine M, Gering M, Bahn S, Sanchez M, Bench AJ, Fordham JL, Bockamp E, Green AR. Distinct 5' SCL enhancers direct transcription to developing brain, spinal cord, and endothelium: neural expression is mediated by GATA factor binding sites. Dev Biol 1999; 209:128-42. [PMID: 10208748 DOI: 10.1006/dbio.1999.9236] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The SCL gene encodes a basic helix-loop-helix transcription factor with a pivotal role in the development of endothelium and of all hematopoietic lineages. SCL is also expressed in the central nervous system, although its expression pattern has not been examined in detail and its function in neural development is unknown. In this article we present the first analysis of SCL transcriptional regulation in vivo. We have identified three spatially distinct regulatory modules, each of which was both necessary and sufficient to direct reporter gene expression in vivo to three different regions within the normal SCL expression domain, namely, developing endothelium, midbrain, and hindbrain/spinal cord. In addition we have demonstrated that GATA factor binding sites are essential for neural expression of the SCL constructs. The midbrain element was particularly powerful and axonal lacZ expression revealed the details of axonal projections, thus implicating SCL in the development of occulomotor, pupillary, or retinotectal pathways. The neural expression pattern of the SCL gene was highly conserved in mouse, chicken, and zebrafish embryos and the 5' region of the chicken SCL locus exhibited a striking degree of functional conservation in transgenic mice. These data suggest that SCL performs critical functions in neural development. The regulatory elements identified here provide important tools for analyzing these functions.
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Affiliation(s)
- A M Sinclair
- Department of Haematology, University of Cambridge, MRC Centre, Hills Road, Cambridge, CB2 2QH, United Kingdom
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Abstract
The SCL gene encodes a basic helix-loop-helix (bHLH) transcription factor that is essential for the development of all haematopoietic lineages. SCL is also expressed in endothelial cells, but its function is not essential for specification of endothelial progenitors and the role of SCL in endothelial development is obscure. We isolated the zebrafish SCL homologue and show that it was co-expressed in early mesoderm with markers of haematopoietic, endothelial and pronephric progenitors. Ectopic expression of SCL mRNA in zebrafish embryos resulted in overproduction of common haematopoietic and endothelial precursors, perturbation of vasculogenesis and concomitant loss of pronephric duct and somitic tissue. Notochord and neural tube formation were unaffected. These results provide the first evidence that SCL specifies formation of haemangioblasts, the proposed common precursor of blood and endothelial lineages. Our data also underline the striking similarities between the role of SCL in haematopoiesis/vasculogenesis and the function of other bHLH proteins in muscle and neural development.
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Affiliation(s)
- M Gering
- University of Cambridge, Department of Haematology, MRC Centre, Hills Road, Cambridge CB2 2QH, UK
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Abstract
The region of the 29.5-kb plasmid pSX267 from Staphylococcus xylosus DSM 20267 that is required for autonomous replication in staphylococci was isolated on a 1.8-kb DNA fragment. The sequence analysis of the fragment yielded two open reading frames, repA and orf2, encoding proteins of 37.2 and 13.2 kDa, respectively. The deduced amino acid sequence of repA showed similarity to the replication initiator protein of plasmid pAD1 from Enterococcus faecalis, to two proteins of unknown function encoded by the E. faecalis plasmid pCF10 and the lactobacillus helveticus plasmid pLJ1, and surprisingly to the mouse interferon-response element binding factor 1. The repA gene of pSX267 is indispensable for replication suggesting that it encodes the replication initiator protein of pSX267. Introduction of a frameshift mutation into repA or deletion of 26 codons at its 3'-end resulted in nonreplicative plasmids. Removal of sequences required for repA expression also abolished replication. Complementation experiments with repA in trans identified the ori of pSX267 within the repA coding region. The second orf, which is located downstream of repA, could be deleted without affecting plasmid replication. It seems to be a nonfunctional remainder of a rolling circle plasmid of the pC194/pUB110 family, since its deduced amino acid sequence resembles the pC194/pUB110-type replication proteins. The minimal replicon of pSX267 defined so far comprises 1255 bp. Besides repA, no other plasmid-encoded gene is required to mediate replication in staphylococci.
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Affiliation(s)
- M Gering
- Mikrobielle Genetik, Universität Tübingen, Germany
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Abstract
In Staphylococcus xylosus, scrB is one of two genes necessary for sucrose utilization. It encodes a sucrase that hydrolyzes intracellular sucrose-6-phosphate generated by the uptake of sucrose via the sucrose-specific enzyme II of the phosphotransferase system, the gene product of scrA. ScrB sucrase activity is inducible by the presence of sucrose in the culture medium. Primer extension experiments demonstrated that the observed regulation is achieved at the level of scrB transcription initiation. The protein mediating sucrose-specific regulation of scrB was found to be encoded immediately upstream of the sucrase gene. The nucleotide sequence of the regulatory gene scrR comprises an open reading frame that specifies a protein of 35.8 kDa. This protein exhibits similarity to transcriptional regulators of the GalR-LacI family. Inactivation of the scrR reading frame in the genome of S. xylosus led to the constitutive expression of scrB at a high level, identifying ScrR as a repressor of transcription. Sucrose-specific regulation of scrB was also lost upon deletion of 4 bp of a palindromic sequence (OB) covering positions +6 to +21 downstream of the scrB transcriptional start site. These results suggested a direct interaction of the ScrR repressor and the operator OB. Accordingly, a fusion protein consisting of the maltose-binding protein of Escherichia coli and the ScrR protein was able to interact with an scrB promoter fragment in gel mobility shift experiments but failed to bind an scrB fragment carrying the 4-bp deletion derivative of OB. An scrR promoter fragment, which dose not contain a sequence resembling OB, was not shifted by the fusion protein. This result corroborates scrR primer extension analyses showing that transcription of the repressor gene itself is not regulated. Therefore, the sucrase gene operator OB is the target sequence through which the ScrR protein exerts its negative effect on transcription initiation. In the promoter region of scrA, the gene essential for sucrose transport, two palindromic sequences that are similar to the scrB operator are found. Their presence in scrA suggests that ScrR controls a sucrose-specific regulon in S. xylosus.
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Affiliation(s)
- M Gering
- Mikrobielle Genetik, Universität Tübingen, Germany
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