1
|
Lee HK, Ismail T, Kim C, Kim Y, Park JW, Kwon OS, Kang BS, Lee DS, Kwon T, Park TJ, Lee HS. Lysine demethylase 3a in craniofacial and neural development during Xenopus embryogenesis. Int J Mol Med 2018; 43:1105-1113. [PMID: 30569092 DOI: 10.3892/ijmm.2018.4024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 12/05/2018] [Indexed: 11/05/2022] Open
Abstract
Epigenetic modifier lysine demethylase 3a (Kdm3a) specifically demethylates mono‑ and di‑methylated ninth lysine of histone 3 and belongs to the Jumonji domain‑containing group of demethylases. Kdm3a serves roles during various biological and pathophysiological processes, including spermatogenesis and metabolism, determination of sex, androgen receptor‑mediated transcription and embryonic carcinoma cell differentiation. In the present study, physiological functions of Kdm3a were evaluated during embryogenesis of Xenopus laevis. Spatiotemporal expression pattern indicated that kdm3a exhibited its expression from early embryonic stages until tadpole stage, however considerable increase of kdm3a expression was observed during the neurula stage of Xenopus development. Depleting kdm3a using kdm3a antisense morpholino oligonucleotides induced anomalies, including head deformities, small‑sized eyes and abnormal pigmentation. Whole‑mount in situ hybridization results demonstrated that kdm3a knockdown was associated with defects in neural crest migration. Further, quantitative polymerase chain reaction revealed abnormal expression of neural markers in kdm3a morphants. RNA sequencing of kdm3a morphants indicated that kdm3a was implicated in mesoderm formation, cell adhesion and metabolic processes of embryonic development. In conclusion, the results of the present study indicated that Kdm3a may serve a role in neural development during Xenopus embryogenesis and may be targeted for treatment of developmental disorders. Further investigation is required to elucidate the molecular mechanism underlying the regulation of neural development by Kdm3a.
Collapse
Affiliation(s)
- Hyun-Kyung Lee
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Tayaba Ismail
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Chowon Kim
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Youni Kim
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Jeen-Woo Park
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Oh-Shin Kwon
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Beom-Sik Kang
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Dong-Seok Lee
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Taejoon Kwon
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Tae Joo Park
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Hyun-Shik Lee
- Cell and Matrix Research Institute, Kyungpook National University‑Center for Nonlinear Dynamics, School of Life Sciences, Brain Korea 21 Plus Kyungpook National University Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
| |
Collapse
|
2
|
Curran KL, Allen L, Porter BB, Dodge J, Lope C, Willadsen G, Fisher R, Johnson N, Campbell E, VonBergen B, Winfrey D, Hadley M, Kerndt T. Circadian genes, xBmal1 and xNocturnin, modulate the timing and differentiation of somites in Xenopus laevis. PLoS One 2014; 9:e108266. [PMID: 25238599 PMCID: PMC4169625 DOI: 10.1371/journal.pone.0108266] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Accepted: 08/20/2014] [Indexed: 02/06/2023] Open
Abstract
We have been investigating whether xBmal1 and xNocturnin play a role in somitogenesis, a cyclic developmental process with an ultradian period. Previous work from our lab shows that circadian genes (xPeriod1, xPeriod2, xBmal1, and xNocturnin) are expressed in developing somites. Somites eventually form the vertebrae, muscles of the back, and dermis. In Xenopus, a pair of somites is formed about every 50 minutes from anterior to posterior. We were intrigued by the co-localization of circadian genes in an embryonic tissue known to be regulated by an ultradian clock. Cyclic expression of genes involved in Notch signaling has been implicated in the somite clock. Disruption of Notch signaling in humans has been linked to skeletal defects in the vertebral column. We found that both depletion (morpholino) and overexpression (mRNA) of xBMAL1 protein (bHLH transcription factor) or xNOCTURNIN protein (deadenylase) on one side of the developing embryo led to a significant decrease in somite number with respect to the untreated side (p<0.001). These manipulations also significantly affect expression of a somite clock component (xESR9; p<0.05). We observed opposing effects on somite size. Depletion of xBMAL1 or xNOCTURNIN caused a statistically significant decrease in somite area (quantified using NIH ImageJ; p<0.002), while overexpression of these proteins caused a significant dose dependent increase in somite area (p<0.02; p<0.001, respectively). We speculate that circadian genes may play two separate roles during somitogenesis. Depletion and overexpression of xBMAL1 and NOCTURNIN both decrease somite number and influence expression of a somite clock component, suggesting that these proteins may modulate the timing of the somite clock in the undifferentiated presomitic mesoderm. The dosage dependent effects on somite area suggest that xBMAL1 and xNOCTURNIN may also act during somite differentiation to promote myogenesis.
Collapse
Affiliation(s)
- Kristen L. Curran
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Latoya Allen
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Brittany Bronson Porter
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Joseph Dodge
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Chelsea Lope
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Gail Willadsen
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Rachel Fisher
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Nicole Johnson
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Elizabeth Campbell
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Brett VonBergen
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Devon Winfrey
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Morgan Hadley
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| | - Thomas Kerndt
- University of Wisconsin-Whitewater, Department of Biological Sciences, Whitewater, Wisconsin, United States of America
| |
Collapse
|
3
|
Schmidt R, Strähle U, Scholpp S. Neurogenesis in zebrafish - from embryo to adult. Neural Dev 2013; 8:3. [PMID: 23433260 PMCID: PMC3598338 DOI: 10.1186/1749-8104-8-3] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 01/17/2013] [Indexed: 01/19/2023] Open
Abstract
Neurogenesis in the developing central nervous system consists of the induction and proliferation of neural progenitor cells and their subsequent differentiation into mature neurons. External as well as internal cues orchestrate neurogenesis in a precise temporal and spatial way. In the last 20 years, the zebrafish has proven to be an excellent model organism to study neurogenesis in the embryo. Recently, this vertebrate has also become a model for the investigation of adult neurogenesis and neural regeneration. Here, we summarize the contributions of zebrafish in neural development and adult neurogenesis.
Collapse
Affiliation(s)
- Rebecca Schmidt
- Karlsruhe Institute of Technology, Institute of Toxicology and Genetics, 76021, Karlsruhe, Germany
| | | | | |
Collapse
|
4
|
Curran KL, LaRue S, Bronson B, Solis J, Trow A, Sarver N, Zhu H. Circadian genes are expressed during early development in Xenopus laevis. PLoS One 2008; 3:e2749. [PMID: 18716681 PMCID: PMC2518526 DOI: 10.1371/journal.pone.0002749] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Accepted: 06/23/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Circadian oscillators are endogenous time-keeping mechanisms that drive twenty four hour rhythmic changes in gene expression, metabolism, hormone levels, and physical activity. We have examined the developmental expression of genes known to regulate circadian rhythms in order to better understand the ontogeny of the circadian clock in a vertebrate. METHODOLOGY/PRINCIPAL FINDINGS In this study, genes known to function together in part of the core circadian oscillator mechanism (xPeriod1, xPeriod2, and xBmal1) as well as a rhythmic, clock-controlled gene (xNocturnin) were analyzed using in situ hybridization in embryos from neurula to late tailbud stages. Each transcript was present in the developing nervous system in the brain, eye, olfactory pit, otic vesicle and at lower levels in the spinal cord. These genes were also expressed in the developing somites and heart, but at different developmental times in peripheral tissues (pronephros, cement gland, and posterior mesoderm). No difference was observed in transcript levels or localization when similarly staged embryos maintained in cyclic light were compared at two times of day (dawn and dusk) by in situ hybridization. Quantitation of xBmal1 expression in embryonic eyes was also performed using qRT-PCR. Eyes were isolated at dawn, midday, dusk, and midnight (cylic light). No difference in expression level between time-points was found in stage 31 eyes (p = 0.176) but stage 40 eyes showed significantly increased levels of xBmal1 expression at midnight (RQ = 1.98+/-0.094) when compared to dawn (RQ = 1+/-0.133; p = 0.0004). CONCLUSIONS/SIGNIFICANCE We hypothesize that when circadian genes are not co-expressed in the same tissue during development that it may indicate pleiotropic functions of these genes that are separate from the timing of circadian rhythm. Our results show that all circadian genes analyzed thus far are present during early brain and eye development, but rhythmic gene expression in the eye is not observed until after stage 31 of development.
Collapse
Affiliation(s)
- Kristen L Curran
- Department of Biological Sciences, University of Wisconsin-Whitewater, Wisconsin, USA.
| | | | | | | | | | | | | |
Collapse
|
5
|
Koga M, Kudoh T, Hamada Y, Watanabe M, Kageura H. A new triple staining method for double in situ hybridization in combination with cell lineage tracing in whole-mount Xenopus embryos. Dev Growth Differ 2007; 49:635-45. [PMID: 17711476 DOI: 10.1111/j.1440-169x.2007.00958.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To analyze cell to cell interaction effects on cell differentiation, we developed a new triple staining method for double in situ hybridization with cell lineage tracing in whole-mount Xenopus embryos. The method provides high color contrast views, and also enabled us to examine inside the embryos. Wild-type embryos whose blastomere(s) had been injected with a cell lineage tracer were cultured, fixed, hemisectioned when necessary, and first served for the double in situ hybridization, with two sequential chromogenic reactions. They were postfixed, and the labeled cells were retraced immunohistochemically. Finally, the pigment of the embryos was bleached to obtain a clear view. We applied this method to a blastomere transplantation experiment to examine whether the spatial gene expression patterns along the anteroposterior axis can be induced by cell to cell interactions. The presumptive organizer of a 32-cell embryo was replaced by the labeled presumptive epidermis of another synchronous embryo. The resultant triple-stained late gastrula showed quite similar anteroposterior expression patterns of gsc and Xbra to those of a normal embryo in the axial mesoderm derived from the transplanted presumptive epidermis, indicating that cell to cell interactions had induced these patterns.
Collapse
Affiliation(s)
- Masaaki Koga
- Department of Earth System Science, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan.
| | | | | | | | | |
Collapse
|
6
|
Gross JB, Hanken J. Use of fluorescent dextran conjugates as a long-term marker of osteogenic neural crest in frogs. Dev Dyn 2004; 230:100-6. [PMID: 15108313 DOI: 10.1002/dvdy.20036] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The neural crest is a population of multipotent stem cells unique to vertebrates. In the head, cranial neural crest (CNC) cells make an assortment of differentiated cell types and tissues, including neurons, melanocytes, cartilage, and bone. The earliest understanding of the developmental potentiality of CNC cells came from classic studies using amphibian embryos. Fate maps generated from these studies have been largely validated in recent years. However, a fate map for the most late-developing structures in amphibians, and especially anurans (frogs), has never been produced. One such tissue type, skull bone, has been among the most difficult tissues to study due to the long time required for its development during anuran metamorphosis, which in some species may not occur until several months, or even years, after hatching. We report a relatively simple technique for studying this elusive population of neural crest-derived osteogenic (bone-forming) cells in Xenopus laevis by using fluorescently labeled dextran conjugates.
Collapse
Affiliation(s)
- Joshua B Gross
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
| | | |
Collapse
|
7
|
Myers AP, Corson LB, Rossant J, Baker JC. Characterization of mouse Rsk4 as an inhibitor of fibroblast growth factor-RAS-extracellular signal-regulated kinase signaling. Mol Cell Biol 2004; 24:4255-66. [PMID: 15121846 PMCID: PMC400469 DOI: 10.1128/mcb.24.10.4255-4266.2004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Receptor tyrosine kinase (RTK) signals regulate the specification of a varied array of tissue types by utilizing distinct modules of proteins to elicit diverse effects. The RSK proteins are part of the RTK signal transduction pathway and are thought to relay these signals by acting downstream of extracellular signal-regulated kinase (ERK). In this study we report the identification of ribosomal S6 kinase 4 (Rsk4) as an inhibitor of RTK signals. Among the RSK proteins, RTK inhibition is specific to RSK4 and, in accordance, is dependent upon a region of the RSK4 protein that is divergent from other RSK family members. We demonstrate that Rsk4 inhibits the transcriptional activation of specific targets of RTK signaling as well as the activation of ERK. Developmentally, Rsk4 is expressed in extraembryonic tissue, where RTK signals are known to have critical roles. Further examination of Rsk4 expression in the extraembryonic tissues demonstrates that its expression is inversely correlated with the presence of activated ERK 1/2. These studies demonstrate a new and divergent function for RSK4 and support a role for RSK proteins in the specification of RTK signals during early mouse development.
Collapse
Affiliation(s)
- Andrea Pomrehn Myers
- Department of Genetics, Stanford Medical School, Stanford, California 94305, USA
| | | | | | | |
Collapse
|
8
|
Davidson G, Mao B, del Barco Barrantes I, Niehrs C. Kremen proteins interact with Dickkopf1 to regulate anteroposterior CNS patterning. Development 2002; 129:5587-96. [PMID: 12421700 DOI: 10.1242/dev.00154] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A gradient of Wnt/beta-catenin signalling formed by posteriorising Wnts and anteriorising Wnt antagonists regulates anteroposterior (AP) patterning of the central nervous system (CNS) during Xenopus gastrulation. In this process, the secreted Wnt antagonist Dkk1 functions in the Spemann organiser and its anterior derivatives by blocking Wnt receptors of the lipoprotein receptor-related protein (LRP) 5 and 6 class. In addition to LRP6, Dkk1 interacts with another recently identified receptor class, the transmembrane proteins Kremen1 (Krm1) and Kremen2 (Krm2) to synergistically inhibit LRP6. We have investigated the role of Krm1 and Krm2 during early Xenopus embryogenesis. Consistent with a role in zygotic Wnt inhibition, overexpressed Krm anteriorises embryos and rescues embryos posteriorised by Wnt8. Antisense morpholino oligonucleotide (Mo) knockdown of Krm1 and Krm2 leads to deficiency of anterior neural development. In this process, Krm proteins functionally interact with Dkk1: (1) in axis duplication assays krm2 synergises with dkk1 in inhibiting Wnt/LRP6 signalling; (2) krm2 rescues microcephalic embryos induced by injection of inhibitory anti-Dkk1 antibodies; and (3) injection of krm1/2 antisense Mo enhances microcephaly induced by inhibitory anti-Dkk1 antibodies. The results indicate that Krm proteins function in a Wnt inhibition pathway regulating early AP patterning of the CNS.
Collapse
Affiliation(s)
- Gary Davidson
- Division of Molecular Embryology, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | | | | | | |
Collapse
|
9
|
Khokha MK, Chung C, Bustamante EL, Gaw LWK, Trott KA, Yeh J, Lim N, Lin JCY, Taverner N, Amaya E, Papalopulu N, Smith JC, Zorn AM, Harland RM, Grammer TC. Techniques and probes for the study of Xenopus tropicalis development. Dev Dyn 2002; 225:499-510. [PMID: 12454926 DOI: 10.1002/dvdy.10184] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The frog Xenopus laevis has provided significant insights into developmental and cellular processes. However, X. laevis has an allotetraploid genome precluding its use in forward genetic analysis. Genetic analysis may be applicable to Xenopus (Silurana) tropicalis, which has a diploid genome and a shorter generation time. Here, we show that many tools for the study of X. laevis development can be applied to X. tropicalis. By using the developmental staging system of Nieuwkoop and Faber, we find that X. tropicalis embryos develop at similar rates to X. laevis, although they tolerate a narrower range of temperatures. We also show that many of the analytical reagents available for X. laevis can be effectively transferred to X. tropicalis. The X. laevis protocol for whole-mount in situ hybridization to mRNA transcripts can be successfully applied to X. tropicalis without alteration. Additionally, X. laevis probes often work in X. tropicalis--alleviating the immediate need to clone the X. tropicalis orthologs before initiating developmental studies. Antibodies that react against X. laevis proteins can effectively detect the X. tropicalis protein by using established immunohistochemistry procedures. Antisense morpholino oligonucleotides (MOs) offer a new alternative to study loss of gene activity during development. We show that MOs function in X. tropicalis. Finally, X. tropicalis offers the possibility for forward genetics and genomic analysis.
Collapse
Affiliation(s)
- Mustafa K Khokha
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Fernández-Garre P, Rodríguez-Gallardo L, Gallego-Díaz V, Alvarez IS, Puelles L. Fate map of the chicken neural plate at stage 4. Development 2002; 129:2807-22. [PMID: 12050131 DOI: 10.1242/dev.129.12.2807] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
A detailed fate map was obtained for the early chick neural plate (stages 3d/4). Numerous overlapping plug grafts were performed upon New-cultured chick embryos, using fixable carboxyfluorescein diacetate succinimidyl ester to label donor chick tissue. The specimens were harvested 24 hours after grafting and reached in most cases stages 9-11 (early neural tube). The label was detected immunocytochemically in wholemounts, and cross-sections were later obtained. The positions of the graft-derived cells were classified first into sets of purely neural, purely non-neural and mixed grafts. Comparisons between these sets established the neural plate boundary at stages 3d/4. Further analysis categorized graft contributions to anteroposterior and dorsoventral subdivisions of the early neural tube, including data on the floor plate and the eye field. The rostral boundary of the neural plate was contained within the earliest expression domain of the Ganf gene, and the overall shape of the neural plate was contrasted and discussed with regard to the expression patterns of the genes Plato, Sox2, Otx2 and Dlx5 (and others reported in the literature) at stages 3d/4.
Collapse
Affiliation(s)
- Pedro Fernández-Garre
- Department of Morphological Sciences, Faculty of Medicine, University of Murcia, 30100, Murcia, Spain
| | | | | | | | | |
Collapse
|
11
|
Kiecker C, Niehrs C. A morphogen gradient of Wnt/β-catenin signalling regulates anteroposterior neural patterning in Xenopus. Development 2001; 128:4189-201. [PMID: 11684656 DOI: 10.1242/dev.128.21.4189] [Citation(s) in RCA: 343] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Anteroposterior (AP) patterning of the vertebrate neural plate is initiated during gastrulation and is regulated by Spemann’s organizer and its derivatives. The prevailing model for AP patterning predicts a caudally increasing gradient of a ‘transformer’ which posteriorizes anteriorly specified neural cells. However, the molecular identity of the transforming gradient has remained elusive. We show that in Xenopus embryos (1) dose-dependent Wnt signalling is both necessary and sufficient for AP patterning of the neuraxis, (2) Wnt/β-catenin signalling occurs in a direct and long-range fashion within the ectoderm, and (3) that there is an endogenous AP gradient of Wnt/β-catenin signalling in the presumptive neural plate of the Xenopus gastrula. Our results indicate that an activity gradient of Wnt/β-catenin signalling acts as transforming morphogen to pattern the Xenopus central nervous system.
Collapse
Affiliation(s)
- C Kiecker
- Division of Molecular Embryology, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | | |
Collapse
|
12
|
Darras S, Nishida H. The BMP/CHORDIN antagonism controls sensory pigment cell specification and differentiation in the ascidian embryo. Dev Biol 2001; 236:271-88. [PMID: 11476571 DOI: 10.1006/dbio.2001.0339] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated the role of the bone morphogenetic protein (BMP) pathway during neural tissue formation in the ascidian embryo. The orthologue of the BMP antagonist, chordin, was isolated from the ascidian Halocynthia roretzi. While both the expression pattern and the phenotype observed by overexpressing chordin or BMPb (the dpp-subclass BMP) do not suggest a role for these factors in neural induction, BMP/CHORDIN antagonism was found to affect neural patterning. Overexpression of BMPb induced ectopic sensory pigment cells in the brain lineages that do not normally form pigment cells and suppressed pressure organ formation within the brain. Reciprocally, overexpressing chordin suppressed pigment cell formation and induced ectopic pressure organ. We show that pigment cell formation occurs in three steps. (1) During cleavage stages ectodermal cells are neuralized by a vegetal signal that can be substituted by bFGF. (2) At the early gastrula stage, BMPb secreted from the lateral nerve cord blastomeres induces those neuralized blastomeres in close proximity to adopt a pigment cell fate. (3) At the tailbud stage, among these pigment cell precursors, BMPb induces the differentiation of specifically the anterior type of pigment cell, the otolith; while posteriorly, CHORDIN suppresses BMP activity and allows ocellus differentiation.
Collapse
Affiliation(s)
- S Darras
- Department of Biological Sciences, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
| | | |
Collapse
|
13
|
Curran KL, Grainger RM. Expression of activated MAP kinase in Xenopus laevis embryos: evaluating the roles of FGF and other signaling pathways in early induction and patterning. Dev Biol 2000; 228:41-56. [PMID: 11087625 DOI: 10.1006/dbio.2000.9917] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
FGF signaling has been implicated in germ layer formation and axial determination. An antibody specific for the activated form of mitogen-activated protein kinase (MAPK) was used to monitor FGF signaling in vivo during early Xenopus development. Activation of MAPK in young embryos is abolished by injection of a dominant negative FGF receptor (XFD) RNA, suggesting that MAPK is activated primarily by FGF in this context. A transition from cytoplasmic to nuclear localization of activated MAPK occurs in morula/blastula stage embryo animal and marginal zones coinciding with the proposed onset of mesodermal competence. Activated MAPK delineates the region of the dorsal marginal zone before blastopore formation and persists in this region during gastrulation, indicating an early role for FGF signaling in dorsal mesoderm. Activated MAPK was also found in posterior neural tissue from late gastrulation onward. Inhibition of FGF signaling does not block posterior neural gene expression (HoxB9) or activation of MAPK; however, inhibition of FGF signaling does cause a statistically significant decrease in the level of activated MAPK. These results point toward the involvement of other receptor tyrosine kinase signaling pathways in posterior neural patterning.
Collapse
MESH Headings
- Active Transport, Cell Nucleus
- Animals
- Blastocyst/enzymology
- Blastocyst/metabolism
- Body Patterning
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/enzymology
- Embryo, Nonmammalian/metabolism
- Embryonic Induction
- Enzyme Activation
- Fibroblast Growth Factors/physiology
- Gastrula/enzymology
- Gastrula/metabolism
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Histocytochemistry
- In Situ Hybridization
- Mesoderm/drug effects
- Mesoderm/enzymology
- Mesoderm/metabolism
- Microinjections
- Mitogen-Activated Protein Kinases/genetics
- Mitogen-Activated Protein Kinases/metabolism
- Nervous System/embryology
- Nervous System/enzymology
- Nervous System/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Fibroblast Growth Factor/genetics
- Receptors, Fibroblast Growth Factor/physiology
- Signal Transduction
- Xenopus laevis/embryology
- Xenopus laevis/metabolism
Collapse
Affiliation(s)
- K L Curran
- Department of Biology, University of Virginia, Charlottesville, Virginia, 22903, USA
| | | |
Collapse
|
14
|
Abstract
Choroid plexus lipocalin 1 (Cpl1) has been isolated from the African clawed toad (Xenopus laevis) and the cane toad (Bufo marinus). Xcpl1 has been used as a marker for studying early neural development. Due to its retinoid binding properties and the fact that it causes dysmorphogenesis when overexpressed in the early embryo, the protein product is considered to be part of the retinoic acid signalling pathway. Later in development and during adulthood, the epithelial cell sheet of the choroid plexus which forms the blood-cerebrospinal fluid barrier expresses cpl1 as the predominant secretory protein. These data, the similarity of Cpl1 to prostaglandin D(2) synthase and its functional homology to transthyretin will be discussed.
Collapse
Affiliation(s)
- G Lepperdinger
- Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, A-5020 Salzburg, Austria.
| |
Collapse
|
15
|
Grainger RM, Mannion JE, Cook TL, Zygar CA. Defining intermediate stages in cell determination: acquisition of a lens-forming bias in head ectoderm during lens determination. DEVELOPMENTAL GENETICS 2000; 20:246-57. [PMID: 9216064 DOI: 10.1002/(sici)1520-6408(1997)20:3<246::aid-dvg7>3.0.co;2-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Cell determination in vertebrates requires integration of many events, although the mechanisms controlling the different stages in this process are poorly understood. While studies of lens determination have helped define some of these stages, we know very little about the intermediate steps involved in the commitment of ectoderm to lens formation. Lens determination begins during gastrulation when ectoderm is briefly competent to respond to lens-inducing signals and progresses to a point, at the neural tube stage, when the presumptive lens ectoderm is specified. Between these two stages important regulatory genes are activated in the presumptive lens ectoderm, including the transcription factor Pax-6, and transplantation experiments presented here suggest that the presumptive lens ectoderm is becoming "biased" toward lens formation. We show that competent ectoderm from Xenopus laevis embryos forms well-differentiated lenses in most cases when transplanted to the presumptive lens area of neural plate stage hosts, where the lens-inductive environment is strong. When placed into later, neural tube stage hosts, optimally competent ectoderm does form small lenses in about half the cases, but the overall response is much weaker. Even in this weakly inducing environment, however, lens ectoderm that is part way through the inductive process (at the neural plate stage) is shown to have a lens-forming bias, since it forms well differentiated lenses in nearly all cases. While we find that ectoderm surrounding the lens-forming area at neural plate stages does not have a lens-forming bias, non-lens head ectoderm at the neural tube stage does, suggesting that a large region of head ectoderm is biased during neurulation. Using Rana palustris embryos, a species used in the earliest lens induction studies, we were also able to show that the optic vesicle can induce lenses in non-lens head ectoderm at neural tube stages. These results lead us to refine the definition of lens cell determination and provide a context that should allow clarification of determination mechanisms.
Collapse
Affiliation(s)
- R M Grainger
- Department of Biology, University of Virginia, Charlottesville 22903, USA.
| | | | | | | |
Collapse
|
16
|
Abstract
The vitamin A derivative retinoic acid (RA) is necessary for eye development, though its role in signaling within eye tissues is poorly understood. We investigated this question in two transgenic mouse strains carrying a retinoic acid response element (RARE) fused to beta-galactosidase that identify regions of the embryo expressing activated retinoic acid receptors. Retinoid signaling appears in the retina and lens ectoderm of wild-type embryos prior to neural tube closure, when lens induction is under way. To determine if there are interactions between retinoid signaling and the transcription factor Pax-6, also essential for lens development, we examined RARE transgene expression in Small eye (Sey) mice, which carry a Pax-6 mutation. Retinoid signaling in the eye, nose, and forebrain of Sey embryos is decreased, with the most severe effects in the developing lens. In Sey mice the lens anlage cannot respond to exogenous RA after E9, though it is responsive earlier; the retina and other neural ectoderm can respond to RA at any stage. In Sey mice the ability of presumptive lens and retina to produce and/or sequester RA is also decreased, as assayed with a retinoid-reporter cell line. These results implicate retinoid signaling in lens formation and show that RA signaling in the developing eye is dependent upon Pax-6.
Collapse
Affiliation(s)
- J F Enwright
- Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, Virginia 22903, USA
| | | |
Collapse
|
17
|
Holowacz T, Sokol S. FGF is required for posterior neural patterning but not for neural induction. Dev Biol 1999; 205:296-308. [PMID: 9917365 DOI: 10.1006/dbio.1998.9108] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fibroblast growth factor (FGF) has been implicated in a variety of developmental processes including posterior mesoderm and neural patterning. Previous work has led to contradictory roles for FGF in neural induction and anteroposterior neural patterning. Launay et al. (Development 122, 869-880, 1996) suggested a requirement for FGF in anterior neural induction. In contrast, Kroll and Amaya (Development 122, 3173-3183, 1996) and Bang et al. (Development 124, 2075-2085, 1997) proposed that FGF is not required for early neural patterning. Here we use a loss-of-function assay to examine whether FGF is required for neural patterning in three experimental situations: (i) in Xenopus early embryos, (ii) in embryonic explants consisting of presumptive dorsal mesoderm and neurectoderm (Keller explants), and (iii) in explants of dorsal ectoderm and posterior mesoderm in which FGF signaling is specifically blocked in the ectoderm. When cultured until tailbud stages, Keller explants develop neural tissue with normal anteroposterior pattern. Overexpression of the dominant-negative FGF receptor (XFD) in Keller explants inhibited the posterior neural markers En-2, Krox-20, and HoxB9, but not the panneural marker nrp-1 and the anterior neurectodermal markers XAG-1 and Xotx-2. Similar results were seen in whole embryos, but only when XFD RNA was targeted to both the dorsal and lateral regions. In contrast, addition of FGF to Keller explants resulted in a shift of the midbrain-hindbrain boundary marker En-2 to a more anterior position normally fated to become cement gland. We also determined whether FGF is required specifically by the neurectoderm for anteroposterior neural patterning. Recombinants of dorsal ectoderm and posterior mesoderm were made in which FGF was specifically blocked in the ectoderm. Spinal cord and hindbrain markers were inhibited in these recombinants, whereas anterior markers and cement gland development were enhanced. Our results demonstrate that FGF is important for posterior development in both mesoderm and neurectoderm and that neural induction and posteriorization represent separable developmental events.
Collapse
Affiliation(s)
- T Holowacz
- Molecular Medicine Unit, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, Massachusetts, 02215, USA.
| | | |
Collapse
|
18
|
Uzgare AR, Uzman JA, El-Hodiri HM, Sater AK. Mitogen-activated protein kinase and neural specification in Xenopus. Proc Natl Acad Sci U S A 1998; 95:14833-8. [PMID: 9843975 PMCID: PMC24535 DOI: 10.1073/pnas.95.25.14833] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have investigated the activity and function of mitogen-activated protein kinase (MAPK) during neural specification in Xenopus. Ectodermal MAPK activity increased between late blastula and midgastrula stages. At midgastrula, MAPK activity in both newly induced neural ectoderm and ectoderm overexpressing the anterior neural inducer noggin was 5-fold higher than in uninduced ectoderm. Overexpression of MAPK phosphatase-1 (MKP-1) in ectoderm inhibited MAPK activity and prevented neurectoderm-specific gene expression when the ectoderm was recombined with dorsal mesoderm or treated with fibroblast growth factor (FGF). Neurectoderm-specific gene expression was observed, however, in ectoderm overexpressing both noggin and MKP-1. To evaluate the role of MAPK in posterior regionalization, ectodermal isolates were treated with increasing concentrations of FGF and assayed for MAPK activity and neurectoderm-specific gene expression. Although induction of posterior neural ectoderm by FGF was accompanied by an elevation of MAPK activity, relative MAPK activity associated with posterior neural fate was no higher than that of ectoderm specified to adopt an anterior neural fate. Thus, increasingly posterior neural fates are not correlated with quantitative increases in MAPK activity. Because MAPK has been shown to down-regulate Smad1, MAPK may disrupt bone morphogenetic protein 4 (BMP-4) signaling during neural specification. Our results suggest that MAPK plays an essential role in the establishment of neural fate in vivo.
Collapse
Affiliation(s)
- A R Uzgare
- Department of Biology, University of Houston, Houston, TX 77204-5513, USA
| | | | | | | |
Collapse
|
19
|
Zygar CA, Cook TL, Grainger RM. Gene activation during early stages of lens induction in Xenopus. Development 1998; 125:3509-19. [PMID: 9693153 DOI: 10.1242/dev.125.17.3509] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Several stages in the lens determination process have been defined, though it is not known which gene products control these events. At mid-gastrula stages in Xenopus, ectoderm is transiently competent to respond to lens-inducing signals. Between late gastrula and neural tube stages, the presumptive lens ectoderm acquires a lens-forming bias, becomes specified to form lens and begins differentiation. Several genes have been identified, either by expression pattern, mutant phenotype or involvement in crystallin gene regulation, that may play a role in lens bias and specification, and we focus on these roles here. Fate mapping shows that the transcriptional regulators Otx-2, Pax-6 and Sox-3 are expressed in the presumptive lens ectoderm prior to lens differentiation. Otx-2 appears first, followed by Pax-6, during the stages of lens bias (late neural plate stages); expression of Sox-3 follows neural tube closure and lens specification. We also demonstrate the expression of these genes in competent ectoderm transplanted to the lens-forming region. Expression of these genes is maintained or activated preferentially in ectoderm in response to the anterior head environment. Finally, we examined activation of these genes in response to early and late lens-inducing signals. Activation of Otx-2, Pax-6 and Sox-3 in competent ectoderm occurs in response to the early inducing tissue, the anterior neural plate. Since Sox-3 is activated following neural tube closure, we tested its dependence on the later inducing tissue, the optic vesicle, which contacts lens ectoderm at this stage. Sox-3 is not expressed in lens ectoderm, nor does a lens form, when the optic vesicle anlage is removed at late neural plate stages. Expression of these genes demarcates patterning events preceding differentiation and is tightly coupled to particular phases of lens induction.
Collapse
Affiliation(s)
- C A Zygar
- University of Virginia, Department of Biology, Charlottesville, VA, USA
| | | | | |
Collapse
|
20
|
Abstract
We have asked how posterior neural tissue is patterned in Xenopus by assaying the involvement of endogenous retinoic acid (RA) in this process and by using the labial Hox gene, HoxD1, as a posterior marker. Although RA is able to inhibit anterior gene expression and activate expression of more posterior genes, the normal role of retinoids in anteroposterior (A/P) patterning is unclear. HoxD1 is an early posterior neurectodermal marker, expressed from midgastrula with a later anterior expression limit in the future hindbrain. We previously showed that HoxD1 was induced as an immediate early response to retinoic acid in naive ectoderm (animal caps). Here, we use a truncated RARalpha2.2 receptor (RARDelta) to dominantly interfere with retinoid signaling. In embryos injected with RARDelta expression of HoxD1 is eliminated. Conjugates of ectoderm and dorsolateral mesoderm show that retinoid receptors are required in the ectoderm for HoxD1 induction. Further, expression of Krox-20 in r3 and r5 of the presumptive hindbrain is compressed into a single stripe that suggests elimination of r5. RARalpha2.2 expression almost precisely overlaps that of HoxD1, suggesting that this receptor may normally activate HoxD1. Expression of neither more anterior genes including cement gland, forebrain, and midbrain markers nor a more posterior spinal cord marker is affected by RARDelta. These data suggest that the posterior hindbrain is the region of the nervous system most sensitive to retinoid loss. Finally, we compare the ability of RA and fibroblast growth factor (FGF) to posteriorize isolated anterior neurectoderm and show that both factors can act directly on this substrate. RA acts in a more anterior domain than does FGF; however, neither factor is equivalent to the natural posteriorizing capacity of the posterior mesoderm. We propose that endogenous retinoid and FGF signals pattern largely nonoverlapping regions along the A/P axis and that posterior neural patterning requires multiple inducers.
Collapse
Affiliation(s)
- P J Kolm
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
| | | | | |
Collapse
|
21
|
Scholnick J, Sinor C, Oakes J, Outten W, Saha M. Differential expression of Xenopus ribosomal protein gene XlrpS1c. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1354:72-82. [PMID: 9375795 DOI: 10.1016/s0167-4781(97)00101-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Components of the translational machinery of the cell, including ribosomal proteins, are generally considered to be clear examples of housekeeping genes with a spatially ubiquitous distribution of messenger RNA during embryonic development. Here we present data based upon in situ hybridization experiments as well as RNase protection assays, demonstrating that Xenopus ribosomal protein gene S1 is differentially expressed in a complex and spatially distinct pattern during embryogenesis. We observed dramatically high levels of expression in some tissues, such as the branchial arches, otic vesicles, optic vesicles and somites and virtually no expression in other tissues, such as the cement gland, epidermis and notochord. Moreover, ribosomal protein genes S22, L1, and L5 display expression patterns nearly identical to S1. Our data is consistent with a model of ribosomal gene expression according to which ribosomal protein genes (or perhaps a subset of ribosomal protein genes) may be expressed at low levels in all tissues, but are abundantly expressed in other cell types reflecting a dynamic and complex pattern of transcriptional control throughout embryonic development.
Collapse
Affiliation(s)
- J Scholnick
- Department of Biology, The College of William and Mary, Williamsburg, VA 23187, USA
| | | | | | | | | |
Collapse
|
22
|
Saha MS, Miles RR, Grainger RM. Dorsal-ventral patterning during neural induction in Xenopus: assessment of spinal cord regionalization with xHB9, a marker for the motor neuron region. Dev Biol 1997; 187:209-23. [PMID: 9242418 DOI: 10.1006/dbio.1997.8625] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
While the role of the notochord and floor plate in patterning the dorsal-ventral (D/V) axis of the neural tube is clearly established, relatively little is known about the earliest stages of D/V regionalization. In an effort to examine more closely the initial, preneural plate stages of regionalization along the prospective D/V neural axis, we have performed a series of explant experiments employing xHB9, a novel marker of the motor neuron region in Xenopus. Using tissue recombinants and Keller explants we show that direct mesodermal contact is both necessary and sufficient for the initial induction of xHB9 in the motor neuron region. We also show that presumptive neural plate explants removed as early as midgastrulation and cultured in isolation are already specified to express xHB9 but do so in an inappropriate spatial pattern while identical explants are specified to express the floor plate marker vhh-1 with correct spatial patterning. Our data suggest that, in addition to floor plate signaling, continued interactions with the underlying mesoderm through neural tube stages are essential for proper spatial patterning of the motor neuron region.
Collapse
Affiliation(s)
- M S Saha
- Department of Biology, The College of William and Mary, Williamsburg, Virginia 23187, USA.
| | | | | |
Collapse
|
23
|
Artinger M, Blitz I, Inoue K, Tran U, Cho KW. Interaction of goosecoid and brachyury in Xenopus mesoderm patterning. Mech Dev 1997; 65:187-96. [PMID: 9256355 DOI: 10.1016/s0925-4773(97)00073-7] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Detailed in situ analyses reveal overlapping expression of gsc and Xbra in the early Spemann's organizer. Coexpression is lost during gastrulation suggesting an interaction between these genes. Ectopic expression of gsc ventrally suppresses endogenous Xbra expression and transcription from Xbra promoter reporter gene constructs. Suppression is mediated, at least partially, by a gsc-binding site within the first 349 bp of the promoter. Xbra reporter gene transcription is also suppressed in the region of endogenous gsc expression, whereas high-level ectopic Xbra expression has no effect on endogenous gsc expression. We suggest that early patterning of the vertebrate mesoderm, like early patterning of the Drosophila embryo, occurs by first establishing broad domains of gene expression which are subsequently refined by intergenic interactions to further delimit tissue boundaries.
Collapse
Affiliation(s)
- M Artinger
- Department of Developmental & Cell Biology and the Developmental Biology Center, University of California, Irvine 92697-2300, USA.
| | | | | | | | | |
Collapse
|
24
|
Kroll KL, Amaya E. Transgenic Xenopus embryos from sperm nuclear transplantations reveal FGF signaling requirements during gastrulation. Development 1996; 122:3173-83. [PMID: 8898230 DOI: 10.1242/dev.122.10.3173] [Citation(s) in RCA: 547] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have developed a simple approach for large-scale transgenesis in Xenopus laevis embryos and have used this method to identify in vivo requirements for FGF signaling during gastrulation. Plasmids are introduced into decondensed sperm nuclei in vitro using restriction enzyme-mediated integration (REMI). Transplantation of these nuclei into unfertilized eggs yields hundreds of normal, diploid embryos per day which develop to advanced stages and express integrated plasmids nonmosaically. Transgenic expression of a dominant negative mutant of the FGF receptor (XFD) after the mid-blastula stage uncouples mesoderm induction, which is normal, from maintenance of mesodermal markers, which is lost during gastrulation. By contrast, embryos expressing XFD contain well-patterned nervous systems despite a putative role for FGF in neural induction.
Collapse
Affiliation(s)
- K L Kroll
- Department of Cell and Molecular Biology, University of California at Berkeley, 94720, USA.
| | | |
Collapse
|