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Moreno-Oñate M, Gallardo-Fuentes L, Martínez-García PM, Naranjo S, Jiménez-Gancedo S, Tena JJ, Santos-Pereira JM. Rewiring of the epigenome and chromatin architecture by exogenously induced retinoic acid signaling during zebrafish embryonic development. Nucleic Acids Res 2024; 52:3682-3701. [PMID: 38321954 PMCID: PMC11040003 DOI: 10.1093/nar/gkae065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 01/15/2024] [Accepted: 01/24/2024] [Indexed: 02/08/2024] Open
Abstract
Retinoic acid (RA) is the ligand of RA receptors (RARs), transcription factors that bind to RA response elements. RA signaling is required for multiple processes during embryonic development, including body axis extension, hindbrain antero-posterior patterning and forelimb bud initiation. Although some RA target genes have been identified, little is known about the genome-wide effects of RA signaling during in vivo embryonic development. Here, we stimulate the RA pathway by treating zebrafish embryos with all-trans-RA (atRA) and use a combination of RNA-seq, ATAC-seq, ChIP-seq and HiChIP to gain insight into the molecular mechanisms by which exogenously induced RA signaling controls gene expression. We find that RA signaling is involved in anterior/posterior patterning, central nervous system development, and the transition from pluripotency to differentiation. AtRA treatment also alters chromatin accessibility during early development and promotes chromatin binding of RARαa and the RA targets Hoxb1b, Meis2b and Sox3, which cooperate in central nervous system development. Finally, we show that exogenous RA induces a rewiring of chromatin architecture, with alterations in chromatin 3D interactions involving target genes. Altogether, our findings identify genome-wide targets of RA signaling and provide a molecular mechanism by which developmental signaling pathways regulate target gene expression by altering chromatin topology.
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Affiliation(s)
- Marta Moreno-Oñate
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Lourdes Gallardo-Fuentes
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Pedro M Martínez-García
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Silvia Naranjo
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Sandra Jiménez-Gancedo
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - Juan J Tena
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas/Universidad Pablo de Olavide, 41013 Sevilla, Spain
| | - José M Santos-Pereira
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Sevilla, Spain
- Departamento de Biología Celular, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
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Sone R, Taimatsu K, Ohga R, Nishimura T, Tanaka M, Kawahara A. Critical roles of the ddx5 gene in zebrafish sex differentiation and oocyte maturation. Sci Rep 2020; 10:14157. [PMID: 32873816 PMCID: PMC7463030 DOI: 10.1038/s41598-020-71143-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 08/07/2020] [Indexed: 02/04/2023] Open
Abstract
DEAD-box helicase 5 (Ddx5) functions as an ATP-dependent RNA helicase and as a transcriptional coactivator for several transcription factors; however, the developmental function of the ddx5 gene in vertebrates is not fully understood. We found that the zebrafish ddx5 gene was expressed in developing gonads. Using the genome editing technology transcription activator-like effector nuclease, we established a ddx5-disrupted zebrafish and examined the morphological phenotypes of the mutant. We found that the majority of ddx5-deficient mutants developed as fertile males with normal testes and a small number of ddx5-deficient mutants developed as infertile females with small ovaries. Apoptotic cell death at 31 days post fertilization was increased in thick immature gonads (presumptive developing ovaries) of the ddx5-deficient mutant compared to those of heterozygous wild-type fish, while the number of apoptotic cells in thin immature gonads (presumptive developing testes) was comparable between the mutant and wild-type animals. Histological analysis revealed that ovaries of adult ddx5-deficient females had fewer vitellogenic oocytes and a larger number of stage I and II oocytes. The amount of cyclic adenosine monophosphate in the ddx5-deficient ovaries was high compared to that of wild-type ovaries, presumably leading to the mitotic arrest of oocyte maturation. Therefore, the ddx5 gene is dispensable for testis development, but it is essential for female sex differentiation and oocyte maturation in zebrafish.
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Affiliation(s)
- Ryota Sone
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Kiyohito Taimatsu
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Rie Ohga
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Toshiya Nishimura
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan.,Faculty of Fisheries Science, Hokkaido University, Sapporo, 041-8611, Japan
| | - Minoru Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Atsuo Kawahara
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan.
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Ye C, Xu S, Hu Q, Hu M, Zhou L, Qin X, Jia J, Hu G. Structure and function analysis of various brain subregions and pituitary in grass carp (Ctenopharyngodon idellus). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2020; 33:100653. [PMID: 31923798 DOI: 10.1016/j.cbd.2019.100653] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 11/25/2022]
Abstract
It has been generally acknowledged that environment could alter the morphology and functional differentiation of vertebrate brain. However, as the largest group of all vertebrates, studies about the structures and functions of various brain subregions in teleost are still scarce. In this study, using grass carp as a model, histology method and RNA-sequencing were recruited to examine the microstructure and transcript levels among different brain subregions and pituitary. Histological results showed that the grass carp brain was composed of six parts, including olfactory bulb, telencephalon, hypothalamus, optic tectum, cerebellum, and medulla oblongata. In addition, compared to elasmobranchs and non-teleost bony ray-finned fishes, grass carp lost the hypothalamo-hypophyseal portal system, instead the hypophysiotropic neurons were directly terminated in the pituitary cells. At the transcriptomic level, our results suggested that the olfactory bulb might be related to reproduction and immune function. The telencephalon was deemed to be involved in the regulation of appetite and reproduction. The optic tectum might play important roles in the vision system and feeding. The hypothalamus could regulate feeding, and reproduction process. The medulla oblongata was related with the auditory system. The pituitary seemed to play pivotal roles in energy metabolism, organ development and reproduction. Finally, the correlation analysis suggested that the hypothalamus and the telencephalon were highly related, and close anatomical connection and overlapping functions suggested that the telencephalon and hypothalamus might be the regulation center of feeding and reproduction among teleost brain. This study provided a global view of the microstructures and specific functions of various brain subregions and pituitary in teleost. These results will be very helpful for further study in the neuroendocrinology regulation of growth and reproduction in teleost brain-pituitary axis.
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Affiliation(s)
- Cheng Ye
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Shaohua Xu
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Qiongyao Hu
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Minqiang Hu
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Lingling Zhou
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Xiangfeng Qin
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Jingyi Jia
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China
| | - Guangfu Hu
- College of Fisheries, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Huazhong Agricultural University, Wuhan 430070, China.
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Yanagi K, Sone R, Ohga R, Kawahara A. Involvement of the centrosomal protein 55 (cep55) gene in zebrafish head formation. Genes Cells 2019; 24:642-649. [PMID: 31365163 DOI: 10.1111/gtc.12715] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 07/17/2019] [Accepted: 07/22/2019] [Indexed: 12/14/2022]
Abstract
Mammalian CEP55 (centrosomal protein 55 kDa) is a coiled-coil protein localized to the centrosome in interphase cells and is required for cytokinesis. A homozygous non-sense mutation in human CEP55 has been recently identified in perinatal lethal MARCH (multinucleated neurons, anhydramnios, renal dysplasia, cerebellar hypoplasia and hydranencephaly) syndrome. We have isolated zebrafish cep55 mutants defective in head morphology. The zebrafish cep55 gene was expressed in the head including the retina and the pectoral fin at 1 day post-fertilization (dpf), and extensive cell death was widely observed in the head and tail of the cep55 mutant. In the cep55 mutant, the anterior-posterior distance of the ventral pharyngeal arches was short, and retinal lamination was disorganized. Neural cells, such as islet1-positive cells and pax2-positive cells, and fli1b-positive vascular cells were reduced in the head of the cep55 mutant. Thus, we propose that the zebrafish cep55 mutant is a model organism for human MARCH syndrome.
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Affiliation(s)
- Kanoko Yanagi
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Chuo, Japan
| | - Ryota Sone
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Chuo, Japan
| | - Rie Ohga
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Chuo, Japan
| | - Atsuo Kawahara
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Chuo, Japan
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Slota LA, Miranda EM, McClay DR. Spatial and temporal patterns of gene expression during neurogenesis in the sea urchin Lytechinus variegatus. EvoDevo 2019; 10:2. [PMID: 30792836 PMCID: PMC6371548 DOI: 10.1186/s13227-019-0115-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 01/30/2019] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND The sea urchin is a basal deuterostome that is more closely related to vertebrates than many organisms traditionally used to study neurogenesis. This phylogenetic position means that the sea urchin can provide insights into the evolution of the nervous system by helping resolve which developmental processes are deuterostome innovations, which are innovations in other clades, and which are ancestral. However, the nervous system of echinoderms is one of the least understood of all major metazoan phyla. To gain insights into echinoderm neurogenesis, spatial and temporal gene expression data are essential. Then, functional data will enable the building of a detailed gene regulatory network for neurogenesis in the sea urchin that can be compared across metazoans to resolve questions about how nervous systems evolved. RESULTS Here, we analyze spatiotemporal gene expression during sea urchin neurogenesis for genes that have been shown to be neurogenic in one or more species. We report the expression of 21 genes expressed in areas of neurogenesis in the sea urchin embryo from blastula stage (just before neural progenitors begin their specification sequence) through pluteus larval stage (when much of the nervous system has been patterned). Among those 21 gene expression patterns, we report expression of 11 transcription factors and 2 axon guidance genes, each expressed in discrete domains in the neuroectoderm or in the endoderm. Most of these genes are expressed in and around the ciliary band. Some including the transcription factors Lv-mbx, Lv-dmrt, Lv-islet, and Lv-atbf1, the nuclear protein Lv-prohibitin, and the guidance molecule Lv-semaa are expressed in the endoderm where they are presumably involved in neurogenesis in the gut. CONCLUSIONS This study builds a foundation to study how neurons are specified and evolved by analyzing spatial and temporal gene expression during neurogenesis in a basal deuterostome. With these expression patterns, we will be able to understand what genes are required for neural development in the sea urchin. These data can be used as a starting point to (1) build a spatial gene regulatory network for sea urchin neurogenesis, (2) identify how subtypes of neurons are specified, (3) perform comparative studies with the sea urchin, protostome, and vertebrate organisms.
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Affiliation(s)
- Leslie A. Slota
- Department of Biology, Duke University, 124 Science Dr., Box 90338, Durham, NC 27708 USA
| | - Esther M. Miranda
- Department of Biology, Duke University, 124 Science Dr., Box 90338, Durham, NC 27708 USA
| | - David R. McClay
- Department of Biology, Duke University, 124 Science Dr., Box 90338, Durham, NC 27708 USA
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McClay DR, Miranda E, Feinberg SL. Neurogenesis in the sea urchin embryo is initiated uniquely in three domains. Development 2018; 145:dev167742. [PMID: 30413529 PMCID: PMC6240313 DOI: 10.1242/dev.167742] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 09/25/2018] [Indexed: 12/23/2022]
Abstract
Many marine larvae begin feeding within a day of fertilization, thus requiring rapid development of a nervous system to coordinate feeding activities. Here, we examine the patterning and specification of early neurogenesis in sea urchin embryos. Lineage analysis indicates that neurons arise locally in three regions of the embryo. Perturbation analyses showed that when patterning is disrupted, neurogenesis in the three regions is differentially affected, indicating distinct patterning requirements for each neural domain. Six transcription factors that function during proneural specification were identified and studied in detail. Perturbations of these proneural transcription factors showed that specification occurs differently in each neural domain prior to the Delta-Notch restriction signal. Though gene regulatory network state changes beyond the proneural restriction are largely unresolved, the data here show that the three neural regions already differ from each other significantly early in specification. Future studies that define the larval nervous system in the sea urchin must therefore separately characterize the three populations of neurons that enable the larva to feed, to navigate, and to move food particles through the gut.
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Affiliation(s)
- David R McClay
- Department of Biology, 124 Science Drive, Duke University, Durham, NC 27708, USA
| | - Esther Miranda
- Department of Biology, 124 Science Drive, Duke University, Durham, NC 27708, USA
| | - Stacy L Feinberg
- Department of Biology, 124 Science Drive, Duke University, Durham, NC 27708, USA
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7
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Mwacharo JM, Kim ES, Elbeltagy AR, Aboul-Naga AM, Rischkowsky BA, Rothschild MF. Genomic footprints of dryland stress adaptation in Egyptian fat-tail sheep and their divergence from East African and western Asia cohorts. Sci Rep 2017; 7:17647. [PMID: 29247174 PMCID: PMC5732286 DOI: 10.1038/s41598-017-17775-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 11/20/2017] [Indexed: 01/08/2023] Open
Abstract
African indigenous sheep are classified as fat-tail, thin-tail and fat-rump hair sheep. The fat-tail are well adapted to dryland environments, but little is known on their genome profiles. We analyzed patterns of genomic variation by genotyping, with the Ovine SNP50K microarray, 394 individuals from five populations of fat-tail sheep from a desert environment in Egypt. Comparative inferences with other East African and western Asia fat-tail and European sheep, reveal at least two phylogeographically distinct genepools of fat-tail sheep in Africa that differ from the European genepool, suggesting separate evolutionary and breeding history. We identified 24 candidate selection sweep regions, spanning 172 potentially novel and known genes, which are enriched with genes underpinning dryland adaptation physiology. In particular, we found selection sweeps spanning genes and/or pathways associated with metabolism; response to stress, ultraviolet radiation, oxidative stress and DNA damage repair; activation of immune response; regulation of reproduction, organ function and development, body size and morphology, skin and hair pigmentation, and keratinization. Our findings provide insights on the complexity of genome architecture regarding dryland stress adaptation in the fat-tail sheep and showcase the indigenous stocks as appropriate genotypes for adaptation planning to sustain livestock production and human livelihoods, under future climates.
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Affiliation(s)
- Joram M Mwacharo
- Small Ruminant Genomics Group, International Center for Agricultural Research in the Dry Areas (ICARDA), P. O. Box 5689, Addis Ababa, Ethiopia.
| | - Eui-Soo Kim
- Department of Animal Science, Iowa State University, 2255 Kildee Hall, Ames, IA, 50011-3150, USA
| | - Ahmed R Elbeltagy
- Animal Production Research Institute (APRI), Agriculture Research Centre (ARC), Ministry of Agriculture, Nadi Elsaid Street, Dokki, Cairo, Egypt
| | - Adel M Aboul-Naga
- Animal Production Research Institute (APRI), Agriculture Research Centre (ARC), Ministry of Agriculture, Nadi Elsaid Street, Dokki, Cairo, Egypt
| | - Barbara A Rischkowsky
- Small Ruminant Genomics Group, International Center for Agricultural Research in the Dry Areas (ICARDA), P. O. Box 5689, Addis Ababa, Ethiopia
| | - Max F Rothschild
- Department of Animal Science, Iowa State University, 2255 Kildee Hall, Ames, IA, 50011-3150, USA
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Miles A, Tropepe V. Coordinating progenitor cell cycle exit and differentiation in the developing vertebrate retina. NEUROGENESIS 2016; 3:e1161697. [PMID: 27604453 PMCID: PMC4974023 DOI: 10.1080/23262133.2016.1161697] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 01/09/2016] [Accepted: 02/29/2016] [Indexed: 02/06/2023]
Abstract
The proper development of the vertebrate retina relies heavily on producing the correct number and type of differentiated retinal cell types. To achieve this, proliferating retinal progenitor cells (RPCs) must exit the cell cycle at an appropriate time and correctly express a subset of differentiation markers that help specify retinal cell fate. Homeobox genes, which encode a family of transcription factors, have been accredited to both these processes, implicated in the transcriptional regulation of important cell cycle components, such as cyclins and cyclin-dependent kinases, and proneural genes. This dual regulation of homeobox genes allows these factors to help co-ordinate the transition from the proliferating RPC to postmitotic, differentiated cell. However, understanding the exact molecular targets of these factors remains a challenging task. This commentary highlights the current knowledge we have about how these factors regulate cell cycle progression and differentiation, with particular emphasis on a recent discovery from our lab demonstrating an antagonistic relationship between Vsx2 and Dmbx1 to control RPC proliferation. Future studies should aim to further understand the direct transcriptional targets of these genes, additional co-factors/interacting proteins and the possible recruitment of epigenetic machinery by these homeobox genes.
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Affiliation(s)
- Amanda Miles
- Department of Cell & Systems Biology, University of Toronto , Toronto, Ontario, Canada
| | - Vincent Tropepe
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada; Department of Ophthalmology & Vision Sciences; Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
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10
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Kotani H, Taimatsu K, Ohga R, Ota S, Kawahara A. Efficient Multiple Genome Modifications Induced by the crRNAs, tracrRNA and Cas9 Protein Complex in Zebrafish. PLoS One 2015; 10:e0128319. [PMID: 26010089 PMCID: PMC4444095 DOI: 10.1371/journal.pone.0128319] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/26/2015] [Indexed: 12/22/2022] Open
Abstract
The type II clustered regularly interspaced short palindromic repeats (CRISPR) associated with Cas9 endonuclease (CRISPR/Cas9) has become a powerful genetic tool for understanding the function of a gene of interest. In zebrafish, the injection of Cas9 mRNA and guide-RNA (gRNA), which are prepared using an in vitro transcription system, efficiently induce DNA double-strand breaks (DSBs) at the targeted genomic locus. Because gRNA was originally constructed by fusing two short RNAs CRISPR RNA (crRNA) and trans-activating crRNA (tracrRNA), we examined the effect of synthetic crRNAs and tracrRNA with Cas9 mRNA or Cas9 protein on the genome editing activity. We previously reported that the disruption of tyrosinase (tyr) by tyr-gRNA/Cas9 mRNA causes a retinal pigment defect, whereas the disruption of spns2 by spns2-gRNA1/Cas9 mRNA leads to a cardiac progenitor migration defect in zebrafish. Here, we found that the injection of spns2-crRNA1, tyr-crRNA and tracrRNA with Cas9 mRNA or Cas9 protein simultaneously caused a migration defect in cardiac progenitors and a pigment defect in retinal epithelial cells. A time course analysis demonstrated that the injection of crRNAs and tracrRNA with Cas9 protein rapidly induced genome modifications compared with the injection of crRNAs and tracrRNA with Cas9 mRNA. We further show that the crRNA-tracrRNA-Cas9 protein complex is functional for the visualization of endogenous gene expression; therefore, this is a very powerful, ready-to-use system in zebrafish.
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Affiliation(s)
- Hirohito Kotani
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi, Japan
| | - Kiyohito Taimatsu
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi, Japan
| | - Rie Ohga
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi, Japan
| | - Satoshi Ota
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi, Japan
| | - Atsuo Kawahara
- Laboratory for Developmental Biology, Center for Medical Education and Sciences, Graduate School of Medical Science, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi, Japan
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Wong L, Power N, Miles A, Tropepe V. Mutual antagonism of the paired-type homeobox genes, vsx2 and dmbx1, regulates retinal progenitor cell cycle exit upstream of ccnd1 expression. Dev Biol 2015; 402:216-28. [PMID: 25872183 DOI: 10.1016/j.ydbio.2015.03.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 03/17/2015] [Accepted: 03/25/2015] [Indexed: 01/04/2023]
Abstract
Understanding the mechanisms that regulate the transition between the proliferative and a post-mitotic state of retinal progenitor cells (RPCs) is key to advancing our knowledge of retinal growth and maturation. In the present study we determined that during zebrafish embryonic retinal neurogenesis, two paired-type homeobox genes - vsx2 and dmbx1 - function in a mutually antagonistic manner. We demonstrate that vsx2 gene expression requires active Fgf signaling and that this in turn suppresses dmbx1 expression and maintains cells in an undifferentiated, proliferative RPC state. This vsx2-dependent RPC state can be prolonged cell-autonomously by knockdown of dmbx1, or it can be suppressed prematurely by the over-expression of dmbx1, which we show can inhibit vsx2 expression and lead to precocious neuronal differentiation. dmbx1 loss of function also results in altered expression of canonical cell cycle genes, and in particular up-regulation of ccnd1, which correlates with our previous finding of a prolonged RPC cell cycle. By knocking down ccnd1 and dmbx1 simultaneously, we show that RPCs can overcome this phenotype to exit the cell cycle on time and differentiate normally into retinal neurons. Collectively, our data provide novel insight into the mechanism that enables RPCs to exit the cell cycle through a previously unrecognized antagonistic interaction of two paired-type homeobox genes that are central regulators of an Fgf-vsx2-dmbx1-ccnd1 signaling axis.
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Affiliation(s)
- Loksum Wong
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
| | - Namita Power
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
| | - Amanda Miles
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
| | - Vincent Tropepe
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5; Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada M5T 3A9; Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada M5S 3B2.
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Cole GJ, Zhang C, Ojiaku P, Bell V, Devkota S, Mukhopadhyay S. Effects of ethanol exposure on nervous system development in zebrafish. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 299:255-315. [PMID: 22959306 DOI: 10.1016/b978-0-12-394310-1.00007-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Alcohol (ethanol) is a teratogen that adversely affects nervous system development in a wide range of animal species. In humans numerous congenital abnormalities arise as a result of fetal alcohol exposure, leading to a spectrum of disorders referred to as fetal alcohol spectrum disorder (FASD). These abnormalities include craniofacial defects as well as neurological defects that affect a variety of behaviors. These human FASD phenotypes are reproduced in the rodent central nervous system (CNS) following prenatal ethanol exposure. While the study of ethanol effects on zebrafish development has been more limited, several studies have shown that different strains of zebrafish exhibit differential susceptibility to ethanol-induced cyclopia, as well as behavioral deficits. Molecular mechanisms underlying the effects of ethanol on CNS development also appear to be shared between rodent and zebrafish. Thus, zebrafish appear to recapitulate the observed effects of ethanol on human and mouse CNS development, indicating that zebrafish can serve as a complimentary developmental model system to study the molecular basis of FASD. Recent studies examining the effect of ethanol exposure on zebrafish nervous system development are reviewed, with an emphasis on attempts to elucidate possible molecular pathways that may be impacted by developmental ethanol exposure. Recent work from our laboratories supports a role for perturbed extracellular matrix function in the pathology of ethanol exposure during zebrafish CNS development. The use of the zebrafish model to assess the effects of ethanol exposure on adult nervous system function as manifested by changes in zebrafish behavior is also discussed.
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Affiliation(s)
- Gregory J Cole
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
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Posnien N, Koniszewski NDB, Hein HJ, Bucher G. Candidate gene screen in the red flour beetle Tribolium reveals six3 as ancient regulator of anterior median head and central complex development. PLoS Genet 2011; 7:e1002416. [PMID: 22216011 PMCID: PMC3245309 DOI: 10.1371/journal.pgen.1002416] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/13/2011] [Indexed: 11/19/2022] Open
Abstract
Several highly conserved genes play a role in anterior neural plate patterning of vertebrates and in head and brain patterning of insects. However, head involution in Drosophila has impeded a systematic identification of genes required for insect head formation. Therefore, we use the red flour beetle Tribolium castaneum in order to comprehensively test the function of orthologs of vertebrate neural plate patterning genes for a function in insect head development. RNAi analysis reveals that most of these genes are indeed required for insect head capsule patterning, and we also identified several genes that had not been implicated in this process before. Furthermore, we show that Tc-six3/optix acts upstream of Tc-wingless, Tc-orthodenticle1, and Tc-eyeless to control anterior median development. Finally, we demonstrate that Tc-six3/optix is the first gene known to be required for the embryonic formation of the central complex, a midline-spanning brain part connected to the neuroendocrine pars intercerebralis. These functions are very likely conserved among bilaterians since vertebrate six3 is required for neuroendocrine and median brain development with certain mutations leading to holoprosencephaly.
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Affiliation(s)
- Nico Posnien
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
- School of Life Sciences, Oxford Brookes University, Oxford, United Kingdom
| | - Nikolaus Dieter Bernhard Koniszewski
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
| | | | - Gregor Bucher
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
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Hortopan GA, Baraban SC. Aberrant expression of genes necessary for neuronal development and Notch signaling in an epileptic mind bomb zebrafish. Dev Dyn 2011; 240:1964-76. [PMID: 21688347 PMCID: PMC3137702 DOI: 10.1002/dvdy.22680] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/2011] [Indexed: 11/11/2022] Open
Abstract
Mutation within an ubiquitin E3 ligase gene can lead to a failure in Notch signaling, excessive neurons, and depletion of neural progenitor cells in mind bomb mutants. Using mib(hi904) zebrafish, we reported seizures and a down-regulation of γ-aminobutyric acid (GABA) signaling pathway genes. A transcriptome analysis also identified differential expression pattern of genes related to Notch signaling and neurodevelopment. Here, we selected nine of these genes (her4.2, hes5, bhlhb5, hoxa5a, hoxb5b, dmbx1a, dbx1a, nxph1, and plxnd1) and performed a more thorough analysis of expression using conventional polymerase chain reaction, real-time polymerase chain reaction and in situ hybridization. Transgenic reporter fish (Gfap:GFP and Dlx5a-6a:GFP) were used to assess early brain morphology in vivo. Down-regulation of many of these genes was prominent throughout key structures of the developing mib(hi904) zebrafish brain including, but not limited to, the pallium, ventral thalamus, and optic tectum. Brain expression of Dlx5a-6a and Gfap was also reduced. In conclusion, these expression studies indicate a general down-regulation of Notch signaling genes necessary for proper brain development and suggest that these mutant fish could provide valuable insights into neurological conditions, such as Angelman syndrome, associated with ubiquitin E3 ligase mutation.
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Affiliation(s)
- Gabriela A. Hortopan
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California 94143
| | - Scott C. Baraban
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, San Francisco, California 94143
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15
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Stolfi A, Levine M. Neuronal subtype specification in the spinal cord of a protovertebrate. Development 2011; 138:995-1004. [DOI: 10.1242/dev.061507] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The visceral ganglion (VG) comprises the basic motor pool of the swimming ascidian tadpole and has been proposed to be homologous to the spinal cord of vertebrates. Here, we use cis-regulatory modules, or enhancers, from transcription factor genes expressed in single VG neuronal precursors to label and identify morphologically distinct moto- and interneuron subtypes in the Ciona intestinalis tadpole larva. We also show that the transcription factor complement present in each differentiating neuron correlates with its unique morphology. Forced expression of putative interneuron markers Dmbx and Vsx results in ectopic interneuron-like cells at the expense of motoneurons. Furthermore, by perturbing upstream signaling events, we can change the transcription factor expression profile and subsequent identity of the different precursors. Perturbation of FGF signaling transforms the entire VG into Vsx+/Pitx+ putative cholinergic interneurons, while perturbation of Notch signaling results in duplication of Dmbx+ decussating interneurons. These experiments demonstrate the connection between transcriptional regulation and the neuronal subtype diversity underlying swimming behavior in a simple chordate.
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Affiliation(s)
- Alberto Stolfi
- Center for Integrative Genomics, Division of Genetics, Genomics and Development, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Michael Levine
- Center for Integrative Genomics, Division of Genetics, Genomics and Development, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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16
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Cederlund ML, Vendrell V, Morrissey ME, Yin J, Gaora PÓ, Smyth VA, Higgins DG, Kennedy BN. mab21l2 transgenics reveal novel expression patterns of mab21l1 and mab21l2, and conserved promoter regulation without sequence conservation. Dev Dyn 2011; 240:745-54. [PMID: 21360786 DOI: 10.1002/dvdy.22573] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/29/2010] [Indexed: 11/10/2022] Open
Abstract
mab21l1 and mab21l2 paralogs have widespread and dynamic expression patterns during vertebrate development. Both genes are expressed in the developing eye, midbrain, neural tube, and branchial arches. Our goal was to identify promoter regions with activity in mab21l2 expression domains. Assays of mab21l2 promoter-EGFP constructs in zebrafish embryos confirm that constructs containing 7.2 or 4.9 kb of mab21l2 promoter region are sufficient to drive expression in known (e.g., tectum, branchial arches) and unexpected domains (e.g., lens and retinal amacrine cells). A comparative analysis identifies complementary and novel expression domains of endogenous mab21l2 (e.g., lens and ventral iridocorneal canal) and mab21l1 (e.g., retinal amacrine and ganglion cells). Interestingly, therefore, despite the absence of conserved non-coding elements, a 4.9-kb mab21l2 promoter is sufficient to recapitulate expression in tissues unique to mab21l1 or mab21l2.
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Affiliation(s)
- Maria L Cederlund
- UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Dublin, Ireland.
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17
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Zhang C, Turton QM, Mackinnon S, Sulik KK, Cole GJ. Agrin function associated with ocular development is a target of ethanol exposure in embryonic zebrafish. ACTA ACUST UNITED AC 2011; 91:129-41. [PMID: 21308976 DOI: 10.1002/bdra.20766] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 10/25/2010] [Accepted: 10/26/2010] [Indexed: 12/16/2022]
Abstract
BACKGROUND Alcohol (ethanol) is a teratogen known to affect the developing eyes, face, and brain. Among the ocular defects in fetal alcohol spectrum disorder (FASD) are microphthalmia and optic nerve hypoplasia. Employing zebrafish as an FASD model provides an excellent system to analyze the molecular basis of prenatal ethanol exposure-induced defects because embryos can be exposed to ethanol at defined developmental stages and affected genetic pathways can be examined. We have previously shown that disruption of agrin function in zebrafish embryos produces microphthalmia and optic nerve hypoplasia. METHODS Zebrafish embryos were exposed to varying concentrations of ethanol in the absence or presence of morpholino oligonucleotides (MOs) that disrupt agrin function. In situ hybridization was used to analyze ocular gene expression as a consequence of ethanol exposure and agrin knockdown. Morphologic analysis of zebrafish embryos was also conducted. RESULTS Acute ethanol exposure induces diminished agrin gene expression in zebrafish eyes and, importantly, combined treatment with subthreshold levels of agrin MO and ethanol produces pronounced microphthalmia, markedly reduces agrin gene expression, and perturbs Pax6a and Mbx gene expression. Microphthalmia produced by combined agrin MO and ethanol treatment was rescued by sonic hedgehog (Shh) mRNA overexpression, suggesting that ethanol-mediated disruption of agrin expression results in disrupted Shh function. CONCLUSIONS These studies illustrate the strong potential for using zebrafish as a model to aid in defining the molecular basis for ethanol's teratogenic effects. The results of this work suggest that agrin expression and function may be a target of ethanol exposure during embryogenesis.
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Affiliation(s)
- Chengjin Zhang
- Julius L. Chambers Biomedical/Biotechnology Research Institute, Department of Biology, North Carolina Central University, Durham, North Carolina 27707, USA
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18
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Wong L, Weadick CJ, Kuo C, Chang BSW, Tropepe V. Duplicate dmbx1 genes regulate progenitor cell cycle and differentiation during zebrafish midbrain and retinal development. BMC DEVELOPMENTAL BIOLOGY 2010; 10:100. [PMID: 20860823 PMCID: PMC2954992 DOI: 10.1186/1471-213x-10-100] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 09/22/2010] [Indexed: 01/03/2023]
Abstract
Background The Dmbx1 gene is important for the development of the midbrain and hindbrain, and mouse gene targeting experiments reveal that this gene is required for mediating postnatal and adult feeding behaviours. A single Dmbx1 gene exists in terrestrial vertebrate genomes, while teleost genomes have at least two paralogs. We compared the loss of function of the zebrafish dmbx1a and dmbx1b genes in order to gain insight into the molecular mechanism by which dmbx1 regulates neurogenesis, and to begin to understand why these duplicate genes have been retained in the zebrafish genome. Results Using gene knockdown experiments we examined the function of the dmbx1 gene paralogs in zebrafish, dmbx1a and dmbx1b in regulating neurogenesis in the developing retina and midbrain. Dose-dependent loss of dmbx1a and dmbx1b function causes a significant reduction in growth of the midbrain and retina that is evident between 48-72 hpf. We show that this phenotype is not due to patterning defects or persistent cell death, but rather a deficit in progenitor cell cycle exit and differentiation. Analyses of the morphant retina or anterior hindbrain indicate that paralogous function is partially diverged since loss of dmbx1a is more severe than loss of dmbx1b. Molecular evolutionary analyses of the Dmbx1 genes suggest that while this gene family is conservative in its evolution, there was a dramatic change in selective constraint after the duplication event that gave rise to the dmbx1a and dmbx1b gene families in teleost fish, suggestive of positive selection. Interestingly, in contrast to zebrafish dmbx1a, over expression of the mouse Dmbx1 gene does not functionally compensate for the zebrafish dmbx1a knockdown phenotype, while over expression of the dmbx1b gene only partially compensates for the dmbx1a knockdown phenotype. Conclusion Our data suggest that both zebrafish dmbx1a and dmbx1b genes are retained in the fish genome due to their requirement during midbrain and retinal neurogenesis, although their function is partially diverged. At the cellular level, Dmbx1 regulates cell cycle exit and differentiation of progenitor cells. The unexpected observation of putative post-duplication positive selection of teleost Dmbx1 genes, especially dmbx1a, and the differences in functionality between the mouse and zebrafish genes suggests that the teleost Dmbx1 genes may have evolved a diverged function in the regulation of neurogenesis.
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Affiliation(s)
- Loksum Wong
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
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19
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Abstract
For more than a decade, the zebrafish has proven to be an excellent model organism to investigate the mechanisms of neurogenesis during development. The often cited advantages, namely external development, genetic, and optical accessibility, have permitted direct examination and experimental manipulations of neurogenesis during development. Recent studies have begun to investigate adult neurogenesis, taking advantage of its widespread occurrence in the mature zebrafish brain to investigate the mechanisms underlying neural stem cell maintenance and recruitment. Here we provide a comprehensive overview of the tools and techniques available to study neurogenesis in zebrafish both during development and in adulthood. As useful resources, we provide tables of available molecular markers, transgenic, and mutant lines. We further provide optimized protocols for studying neurogenesis in the adult zebrafish brain, including in situ hybridization, immunohistochemistry, in vivo lipofection and electroporation methods to deliver expression constructs, administration of bromodeoxyuridine (BrdU), and finally slice cultures. These currently available tools have put zebrafish on par with other model organisms used to investigate neurogenesis.
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Affiliation(s)
- Prisca Chapouton
- Institute of Developmental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
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20
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Abstract
The zebrafish is one of the leading models for the analysis of the vertebrate visual system. A wide assortment of molecular, genetic, and cell biological approaches is available to study zebrafish visual system development and function. As new techniques become available, genetic analysis and imaging continue to be the strengths of the zebrafish model. In particular, recent developments in the use of transposons and zinc finger nucleases to produce new generations of mutant strains enhance both forward and reverse genetic analysis. Similarly, the imaging of developmental and physiological processes benefits from a wide assortment of fluorescent proteins and the ways to express them in the embryo. The zebrafish is also highly attractive for high-throughput screening of small molecules, a promising strategy to search for compounds with therapeutic potential. Here we discuss experimental approaches used in the zebrafish model to study morphogenetic transformations, cell fate decisions, and the differentiation of fine morphological features that ultimately lead to the formation of the functional vertebrate visual system.
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Affiliation(s)
- Andrei Avanesov
- Division of Craniofacial and Molecular Genetics, Tufts University, Boston, Massachusetts, USA
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21
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Embree LJ, Azuma M, Hickstein DD. Ewing sarcoma fusion protein EWSR1/FLI1 interacts with EWSR1 leading to mitotic defects in zebrafish embryos and human cell lines. Cancer Res 2009; 69:4363-71. [PMID: 19417137 DOI: 10.1158/0008-5472.can-08-3229] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanism whereby the fusion of EWSR1 with the ETS transcription factor FLI1 contributes to malignant transformation in Ewing sarcoma remains unclear. We show that injection of human or zebrafish EWSR1/FLI1 mRNA into developing zebrafish embryos leads to mitotic defects with multipolar and disorganized mitotic spindles. Expression of human EWSR1/FLI1 in HeLa cells also results in mitotic defects, along with mislocalization of Aurora kinase B, a key regulator of mitotic progression. Because these mitotic abnormalities mimic those observed with the knockdown of EWSR1 in zebrafish embryos and HeLa cells, we investigated whether EWSR1/FLI1 interacts with EWSR1 and interferes with its function. EWSR1 coimmunoprecipitates with EWSR1/FLI1, and overexpression of EWSR1 rescues the mitotic defects in EWSR1/FLI1-transfected HeLa cells. This interaction between EWSR1/FLI1 and EWSR1 in Ewing sarcoma may induce mitotic defects leading to genomic instability and subsequent malignant transformation.
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Affiliation(s)
- Lisa J Embree
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
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22
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Transcriptional regulation of a myeloid-lineage specific gene lysozyme C during zebrafish myelopoiesis. Mech Dev 2009; 126:314-23. [PMID: 19275935 DOI: 10.1016/j.mod.2009.02.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 02/26/2009] [Accepted: 02/27/2009] [Indexed: 11/24/2022]
Abstract
lysozyme C (lyz), a glycoside hydrolase expressed exclusively in myeloid cells, is involved in the host defense against bacterial infection. We isolated a 2.4kb zebrafish lyz promoter region and established transgenic lines that drive enhanced green fluorescent protein (EGFP) to examine how lyz expression is regulated during myelopoiesis. We found that the 2.4kb lyz promoter is sufficient to drive myeloid-specific expression of EGFP in zebrafish. We identified potential transcriptional regulatory elements including a Runx element (TGTGGT at -1.70kb) and a C/ebp element (TTTGGCAAT at -1.46kb) in the lyz promoter, and showed that they are required for myeloid-specific expression of EGFP. We found that the myeloid-lineage transcription factors C/ebp1, Runx1 and Pu.1 can bind to the 2.4kb lyz promoter. Forced expression of runx1, c/ebp1 and pu.1 together induced ectopic lyz expression in the intermediated cell mass (ICM). Thus, we propose that c/ebp1 and runx1 presumably cooperated with pu.1 in the transcriptional regulation of lyz during zebrafish myelopoiesis.
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23
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Menelaou E, Svoboda KR. Secondary motoneurons in juvenile and adult zebrafish: axonal pathfinding errors caused by embryonic nicotine exposure. J Comp Neurol 2009; 512:305-22. [PMID: 19006183 PMCID: PMC2798059 DOI: 10.1002/cne.21903] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Nicotine is a drug of abuse that has been reported to have many adverse effects on the developing nervous system. We previously demonstrated that embryonic exposure to nicotine alters axonal pathfinding of spinal secondary motoneurons in zebrafish. We hypothesize that these changes will persist into adulthood. The Tg(isl1:GFP) line of zebrafish, which expresses green fluorescent protein (GFP) in a subtype of spinal secondary motoneurons, was used to investigate potential long-term consequences of nicotine exposure on motoneuron development. Anatomical characterization of Tg(isl1:GFP) zebrafish ranging between 3 and 30 days postfertilization (dpf) was initially performed in fixed tissue to characterize axonal trajectories in larval and juvenile fish. Tg(isl1:GFP) embryos were transiently exposed to 5–30 μM nicotine. They were then rescued from nicotine and raised into later stages of life (3–30 dpf) and fixed for microscopic examination. Morphological analysis revealed that nicotine-induced abnormalities in secondary motoneuron anatomy were still evident in juvenile fish. Live imaging of Tg(isl1:GFP) zebrafish using fluorescent stereomicroscopy revealed that the nicotine-induced changes in motoneuron axonal pathfinding persisted into adulthood. We detected abnormalities in 37-dpf fish that were transiently exposed to nicotine as embryos. These fish were subsequently imaged over a 7-week period of time until they were ≈3 months of age. These pathfinding errors of spinal secondary motoneuron axons detected at 37 dpf persisted within the same fish until 86 dpf, the latest age analyzed. These findings indicate that exposure to nicotine during embryonic development can have permanent consequences for motoneuron anatomy in zebrafish. J. Comp. Neurol. 512:305–322, 2009. © 2008 Wiley-Liss, Inc.
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Affiliation(s)
- Evdokia Menelaou
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Menelaou E, Husbands EE, Pollet RG, Coutts CA, Ali DW, Svoboda KR. Embryonic motor activity and implications for regulating motoneuron axonal pathfinding in zebrafish. Eur J Neurosci 2008; 28:1080-96. [PMID: 18823502 PMCID: PMC2741004 DOI: 10.1111/j.1460-9568.2008.06418.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Zebrafish embryos exhibit spontaneous contractions of the musculature as early as 18-19 h post fertilization (hpf) when removed from their protective chorion. These movements are likely initiated by early embryonic central nervous system activity. We have made the observation that narrowminded mutant embryos (hereafter, nrd(-/-)) lack normal embryonic motor output upon dechorionation. However, these mutants can swim and respond to tactile stimulation by larval stages of development. nrd(-/-) embryos exhibit defects in neural crest development, slow muscle development and also lack spinal mechanosensory neurons known as Rohon-Beard (RB) neurons. At early developmental stages (i.e. 21-22 hpf) and while still in their chorions, nrd siblings (nrd(+/?)) exhibited contractions of the musculature at a rate similar to wild-type embryos. Anatomical analysis indicated that RB neurons were present in the motile embryos, but absent in the non-motile embryos, indicating that the non-motile embryos were nrd(-/-) embryos. Further anatomical analysis of nrd(-/-) embryos revealed errors in motoneuron axonal pathfinding that persisted into the larval stage of development. These errors were reversed when nrd(-/-) embryos were raised in high [K(+)] beginning at 21 hpf, indicating that the abnormal axonal phenotypes may be related to a lack of depolarizing activity early in development. When activity was blocked with tricaine in wild-type embryos, motoneuron phenotypes were similar to the motoneuron phenotypes in nrd(-/-) embryos. These results implicate early embryonic activity in conjunction with other factors as necessary for normal motoneuron development.
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Affiliation(s)
- Evdokia Menelaou
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
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Bonkowsky JL, Wang X, Fujimoto E, Lee JE, Chien CB, Dorsky RI. Domain-specific regulation of foxP2 CNS expression by lef1. BMC DEVELOPMENTAL BIOLOGY 2008; 8:103. [PMID: 18950487 PMCID: PMC2579431 DOI: 10.1186/1471-213x-8-103] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 10/24/2008] [Indexed: 11/22/2022]
Abstract
Background FOXP2 is a forkhead transcription factor critical for normal development of language in humans, but little is known of its broader function and regulation during central nervous system (CNS) development. We report here that lef1, a member of the Lef/Tcf family of transcription factors activated by Wnt signaling, regulates foxP2 during embryogenesis, and we isolate novel foxP2 enhancers which are lef1-dependent. Results Loss, knock down, or inhibition of lef1 led to loss of foxP2 expression. We isolated DNA fragments from the foxP2 genomic region that function as enhancers to drive GFP expression in the CNS during development, including in the telencephalon, diencephalon, eye, tectum, and hindbrain. Three of these enhancers, foxP2-enhancerA.1, foxP2-enhancerB, and foxP2-enhancerD, contain putative Lef1 binding sites, and are regulated by lef1. However, two other genomic fragments containing Lef1 sites failed to function in vivo as enhancers. Chromatin immunoprecipitation confirmed that Lef1 binds to sites in foxP2-enhancerA.1 and foxP2-enhancerB. Conclusion This work shows that lef1 is necessary for expression of foxP2 in the tectum, mid-hindbrain boundary, and hindbrain during CNS development, and is the first insight into the upstream regulation of foxP2 during development. We also demonstrate that in silico prediction of potential lef1 binding sites poorly predicts their ability to function in vivo as enhancers. The foxP2 enhancers we identified will allow dissection of foxP2's role during CNS development.
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Affiliation(s)
- Joshua L Bonkowsky
- Division of Pediatric Neurology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah 84108, USA.
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26
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Liu IH, Zhang C, Kim MJ, Cole GJ. Retina development in zebrafish requires the heparan sulfate proteoglycan agrin. Dev Neurobiol 2008; 68:877-98. [PMID: 18327763 DOI: 10.1002/dneu.20625] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recent studies from our laboratory have begun to elucidate the role of agrin in zebrafish development. One agrin morphant phenotype that results from agrin knockdown is microphthalmia (reduced eye size). To begin to understand the mechanisms underlying the role of agrin in eye development, we have analyzed retina development in agrin morphants. Retinal differentiation is impaired in agrin morphants, with retinal lamination being disrupted following agrin morpholino treatment. Pax 6.1 and Mbx1 gene expression, markers of eye development, are markedly reduced in agrin morphants. Formation of the optic fiber layer of the zebrafish retina is also impaired, exhibited as both reduced size of the optic fiber layer, and disruption of retinal ganglion cell axon growth to the optic tectum. The retinotectal topographic projection to the optic tectum is perturbed in agrin morphants in association with a marked loss of heparan sulfate expression in the retinotectal pathway, with this phenotype resembling retinotectal phenotypes observed in mutant zebrafish lacking enzymes for heparan sulfate synthesis. Treatment of agrin morphants with a fibroblast growth factor (Fgf) receptor inhibitor, rescue of the retinal lamination phenotype by transplantation of Fgf8-coated beads, and disruption of both the expression of Fgf-dependent genes and activation of ERK in agrin morphants provides evidence that agrin modulation of Fgf function contributes to retina development. Collectively, these agrin morphant phenotypes provide support for a crucial role of agrin in retina development and formation of an ordered retinotectal topographic map in the optic tectum of zebrafish.
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Affiliation(s)
- I-Hsuan Liu
- Julius L. Chambers Biomedical/Biotechnology Research Institute, Durham, North Carolina 27707, USA
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27
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Uncoupling nicotine mediated motoneuron axonal pathfinding errors and muscle degeneration in zebrafish. Toxicol Appl Pharmacol 2008; 237:29-40. [PMID: 18694773 DOI: 10.1016/j.taap.2008.06.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 06/16/2008] [Accepted: 06/16/2008] [Indexed: 11/23/2022]
Abstract
Zebrafish embryos offer a unique opportunity to investigate the mechanisms by which nicotine exposure impacts early vertebrate development. Embryos exposed to nicotine become functionally paralyzed by 42 hpf suggesting that the neuromuscular system is compromised in exposed embryos. We previously demonstrated that secondary spinal motoneurons in nicotine-exposed embryos were delayed in development and that their axons made pathfinding errors (Svoboda, K.R., Vijayaraghaven, S., Tanguay, R.L., 2002. Nicotinic receptors mediate changes in spinal motoneuron development and axonal pathfinding in embryonic zebrafish exposed to nicotine. J. Neurosci. 22, 10731-10741). In that study, we did not consider the potential role that altered skeletal muscle development caused by nicotine exposure could play in contributing to the errors in spinal motoneuron axon pathfinding. In this study, we show that an alteration in skeletal muscle development occurs in tandem with alterations in spinal motoneuron development upon exposure to nicotine. The alteration in the muscle involves the binding of nicotine to the muscle-specific AChRs. The nicotine-induced alteration in muscle development does not occur in the zebrafish mutant (sofa potato, [sop]), which lacks muscle-specific AChRs. Even though muscle development is unaffected by nicotine exposure in sop mutants, motoneuron axonal pathfinding errors still occur in these mutants, indicating a direct effect of nicotine exposure on nervous system development.
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Hong SK, Tsang M, Dawid IB. The mych gene is required for neural crest survival during zebrafish development. PLoS One 2008; 3:e2029. [PMID: 18446220 PMCID: PMC2323570 DOI: 10.1371/journal.pone.0002029] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Accepted: 03/14/2008] [Indexed: 12/01/2022] Open
Abstract
Background Among Myc family genes, c-Myc is known to have a role in neural crest specification in Xenopus and in craniofacial development in the mouse. There is no information on the function of other Myc genes in neural crest development, or about any developmental role of zebrafish Myc genes. Principal Findings We isolated the zebrafish mych (myc homologue) gene. Knockdown of mych leads to severe defects in craniofacial development and in certain other tissues including the eye. These phenotypes appear to be caused by cell death in the neural crest and in the eye field in the anterior brain. Significance Mych is a novel factor required for neural crest cell survival in zebrafish.
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Affiliation(s)
- Sung-Kook Hong
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America.
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Ikuta T, Saiga H. Dynamic change in the expression of developmental genes in the ascidian central nervous system: revisit to the tripartite model and the origin of the midbrain-hindbrain boundary region. Dev Biol 2007; 312:631-43. [PMID: 17996862 DOI: 10.1016/j.ydbio.2007.10.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 10/03/2007] [Accepted: 10/04/2007] [Indexed: 12/01/2022]
Abstract
Comparative studies on expression patterns of developmental genes along the anterior-posterior axis of the embryonic central nervous system (CNS) between vertebrates and ascidians led to the notion of "tripartite organization," a common ground plan of the CNS, consisting of the anterior, central and posterior regions expressing Otx, Pax2/5/8 and Hox genes, respectively. In ascidians, however, descriptions and interpretations about expression of the developmental genes regarded as region specific have become not necessarily consistent. To address this issue, we examined detailed expression of key developmental genes for the ascidian CNS, including Otx, Pax2/5/8a, En, Fgf8/17/18, Dmbx, Lhx3 and Hox genes, in the CNS around the junction of the trunk and tail of three different tailbud-stage embryos of Ciona intestinalis, employing double-fluorescence in situ hybridization, followed by staining with DAPI to precisely locate expressing cells for each gene. Based on these observations, we have constructed detailed gene expression maps of the region at the tailbud stages. Our analysis shows that expression of several genes regarded as markers for specific domains in the ascidian CNS changes dynamically within a relatively short period. This motivates us to revisit to the tripartite ground plan and the origin of the midbrain-hindbrain boundary (MHB) region.
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Affiliation(s)
- Tetsuro Ikuta
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachiohji, Tokyo 192-0397, Japan
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30
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Azuma M, Embree LJ, Sabaawy H, Hickstein DD. Ewing sarcoma protein ewsr1 maintains mitotic integrity and proneural cell survival in the zebrafish embryo. PLoS One 2007; 2:e979. [PMID: 17912356 PMCID: PMC1991596 DOI: 10.1371/journal.pone.0000979] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Accepted: 09/11/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The Ewing sarcoma breakpoint region 1 gene (EWSR1), also known as EWS, is fused to a number of different partner genes as a result of chromosomal translocation in diverse sarcomas. Despite the involvement of EWSR1 in these diverse sarcomas, the in vivo function of wild type EWSR1 remains unclear. PRINCIPAL FINDINGS We identified two zebrafish EWSR1 orthologues, ewsr1a and ewsr1b, and demonstrate that both genes are expressed maternally, and are expressed ubiquitously throughout zebrafish embryonic development. Morpholino induced knockdown of both zebrafish ewsr1 genes led to mitotic defects with multipolar or otherwise abnormal mitotic spindles starting from the bud stage (10 hour post-fertilization (hpf)). The abnormalities in mitotic spindles were followed by p53-mediated apoptosis in the developing central nervous system (CNS) leading to a reduction in the number of proneural cells, disorganization of neuronal networks, and embryonic lethality by 5 days post-fertilization. siRNA silencing of EWSR1 in Hela cells resulted in mitotic defects accompanied by apoptotic cell death, indicating that the role of EWSR1 is conserved between zebrafish and human. CONCLUSIONS Ewsr1 maintains mitotic integrity and proneural cell survival in early zebrafish development.
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Affiliation(s)
- Mizuki Azuma
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
| | - Lisa J. Embree
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hatem Sabaawy
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Dennis D. Hickstein
- Experimental Transplantation and Immunology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
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Sherwood NM, Adams BA, Isaac ER, Wu S, Fradinger EA. Knocked down and out: PACAP in development, reproduction and feeding. Peptides 2007; 28:1680-7. [PMID: 17467121 DOI: 10.1016/j.peptides.2007.03.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Accepted: 03/15/2007] [Indexed: 11/20/2022]
Abstract
One approach to understanding the role of PACAP in vivo is to knockdown the translation of PACAP mRNA to protein or to knock out the PACAP gene by targeted disruption. In this paper, we review the effect of PACAP knockdown with morpholinos on early brain development in zebrafish. Also reviewed is the role of PACAP at several stages of reproduction as assessed in mice with a disrupted PACAP gene. New data are presented to analyze PACAP's action in energy homeostasis (body mass, food intake, endocrine parameters) using female PACAP-null mice. The evidence suggests PACAP is important for brain development in zebrafish and is required for normal reproduction, but not for body mass or food intake in mice maintained near thermoneutrality.
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Affiliation(s)
- Nancy M Sherwood
- Department of Biology, University of Victoria, Victoria, BC V8W 3N5, Canada.
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32
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Campbell DS, Stringham SA, Timm A, Xiao T, Law MY, Baier H, Nonet ML, Chien CB. Slit1a inhibits retinal ganglion cell arborization and synaptogenesis via Robo2-dependent and -independent pathways. Neuron 2007; 55:231-45. [PMID: 17640525 DOI: 10.1016/j.neuron.2007.06.034] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 05/30/2007] [Accepted: 06/28/2007] [Indexed: 01/20/2023]
Abstract
Upon arriving at their targets, developing axons cease pathfinding and begin instead to arborize and form synapses. To test whether CNS arborization and synaptogenesis are controlled by Slit-Robo signaling, we followed single retinal ganglion cell (RGC) arbors over time. ast (robo2) mutant and slit1a morphant arbors had more branch tips and greater arbor area and complexity compared to wild-type and concomitantly more presumptive presynaptic sites labeled with YFP-Rab3. Increased arborization in ast was phenocopied by dominant-negative Robo2 expressed in single RGCs and rescued by full-length Robo2, indicating that Robo2 acts cell-autonomously. Time-lapse imaging revealed that ast and slit1a morphant arbors stabilized earlier than wild-type, suggesting a role for Slit-Robo signaling in preventing arbor maturation. Genetic analysis showed that Slit1a acts both through Robo2 and Robo2-independent mechanisms. Unlike previous PNS studies showing that Slits promote branching, our results show that Slits inhibit arborization and synaptogenesis in the CNS.
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Affiliation(s)
- Douglas S Campbell
- Department of Neurobiology and Anatomy, University of Utah Medical Center, Salt Lake City, UT 84132, USA.
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33
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Scholpp S, Foucher I, Staudt N, Peukert D, Lumsden A, Houart C. Otx1l, Otx2 and Irx1b establish and position the ZLI in the diencephalon. Development 2007; 134:3167-76. [PMID: 17670791 PMCID: PMC7116068 DOI: 10.1242/dev.001461] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The thalamic complex is the major sensory relay station in the vertebrate brain and comprises three developmental subregions: the prethalamus, the thalamus and an intervening boundary region - the zona limitans intrathalamica (ZLI). Shh signalling from the ZLI confers regional identity of the flanking subregions of the ZLI, making it an important local signalling centre for regional differentiation of the diencephalon. However, our understanding of the mechanisms responsible for positioning the ZLI along the neural axis is poor. Here we show that, before ZLI formation, both Otx1l and Otx2 (collectively referred to as Otx1l/2) are expressed in spatially restricted domains. Formation of both the ZLI and the Irx1b-positive thalamus require Otx1l/2; embryos impaired in Otx1l/2 function fail to form these areas, and, instead, the adjacent pretectum and, to a lesser extent, the prethalamus expand into the mis-specified area. Conditional expression of Otx2 in these morphant embryos cell-autonomously rescues the formation of the ZLI at its correct location. Furthermore, absence of thalamic Irx1b expression, in the presence of normal Otx1l/2 function, leads to a substantial caudal broadening of the ZLI by transformation of thalamic precursors. We therefore propose that the ZLI is induced within the competence area established by Otx1l/2, and is posteriorly restricted by Irx1b.
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Affiliation(s)
- Steffen Scholpp
- MRC Centre for Developmental Neurobiology, New Hunt's House, Guy's Campus, King's College London, London SE1 1UL, UK.
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34
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Hanaoka R, Dawid IB, Kawahara A. Cloning and expression of zebrafish genes encoding the heme synthesis enzymes uroporphyrinogen III synthase (UROS) and protoporphyrinogen oxidase (PPO). ACTA ACUST UNITED AC 2007; 18:54-60. [PMID: 17364814 DOI: 10.1080/10425170601060848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Heme is synthesized from glycine and succinyl CoA by eight heme synthesis enzymes. Although genetic defects in any of these enzymes are known to cause severe human blood diseases, their developmental expression in mammals is unknown. In this paper, we report two zebrafish heme synthesis enzymes, uroporphyrinogen III synthase (UROS) and protoporphyrinogen oxidase (PPO) that are well conserved in comparison to their human counterparts. Both UROS and PPO formed pairs of bilateral stripes in the lateral plate mesoderm at the 15-somite stage. At 24 h post-fertilization (hpf), UROS and PPO were predominantly expressed in the intermediate cell mass (ICM) that is the major site of primitive hematopoiesis. The expression of UROS and PPO was drastically suppressed in the bloodless mutants cloche and vlad tepes/gata 1 from 15-somite to 24hpf stages, indicating that both cloche and vlad tepes/gata 1 are required for the induction and maintenance of UROS and PPO expression in the ICM.
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Affiliation(s)
- Ryuki Hanaoka
- Laboratory of Developmental Molecular Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-Ku, Kyoto, Japan
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35
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Mann CJ, Hinits Y, Hughes SM. Comparison of neurolin (ALCAM) and neurolin-like cell adhesion molecule (NLCAM) expression in zebrafish. Gene Expr Patterns 2006; 6:952-63. [PMID: 16750657 DOI: 10.1016/j.modgep.2006.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 03/19/2006] [Accepted: 03/24/2006] [Indexed: 11/24/2022]
Abstract
Many immunoglobulin (Ig)-superfamily cell adhesion molecules influence skeletal muscle formation. In Drosophila, dumbfounded (duf/kirre), irreC, sticks and stones and hibris encode related Ig-family proteins expressed in subsets of neurons and muscle precursor cells. The family mediates cell migration, axon guidance and fusion of myoblasts. Despite the importance of these genes in invertebrate myogenesis, no obvious functional parallels are known in vertebrate myogenesis. Here we investigate the gene expression pattern and phylogenetic and protein-structural relationships of the duf-related molecules neurolin and neurolin-like cell adhesion molecule (NLCAM), members of the activated leukocyte cell adhesion molecule (ALCAM) sub-family of Ig-molecules. These proteins are among the closest to Duf/Kirre by sequence. During zebrafish development, neurolin is expressed in subsets of somite and muscle cells, heart and numerous sites of neuronal maturation. The new ALCAM-family member, NLCAM, appears to have arisen by duplication of neurolin/ALCAM. NLCAM is expressed widely during gastrulation, particularly in the nascent neural plate, but later becomes predominantly expressed in sites of muscle and nerve maturation and in the fin fold. The expression of each gene is often in groups of cells in similar parts of the embryo; for example, in the region of Rohon Beard neurons, trigeminal ganglion and fusing fast and migrating slow muscle fibres. However, expression can also be distinct and dynamic; for example, muscle pioneer fibres express neurolin but not NLCAM at high level. Both molecules are expressed in subsets of muscle precursors at times prior to fusion.
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Affiliation(s)
- Christopher J Mann
- MRC Centre for Developmental Neurobiology and Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, King's College London, London SE1 1UL, UK
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36
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Chang L, Khoo B, Wong L, Tropepe V. Genomic sequence and spatiotemporal expression comparison of zebrafish mbx1 and its paralog, mbx2. Dev Genes Evol 2006; 216:647-54. [PMID: 16733737 DOI: 10.1007/s00427-006-0082-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Accepted: 05/01/2006] [Indexed: 11/30/2022]
Abstract
The expression of midbrain homeobox-1 (mbx1) defines a discrete region in the vertebrate neural plate that will give rise to the mesencephalon, as well as subregions of the diencephalon and retinal field. Here, we report on the identification and cloning of a second Mbx gene in zebrafish, termed mbx2. Genomic sequence comparison suggests that mbx1 and mbx2 are derived from the duplication of a single putative ancestral gene that is conserved in other vertebrates as a single copy gene. Furthermore, phylogenetic analyses indicate that the mbx genes belong to a novel subgroup of paired-like homeobox genes. Finally, quantitative reverse transcriptase-PCR and whole mount in situ hybridization experiments revealed a pattern of partial spatiotemporal expression divergence between the mbx paralogs that correlates with sequence divergence in noncoding regulatory domains. Our data support a subfunctionalization model that may explain the retention of duplicate mbx genes in teleosts.
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Affiliation(s)
- Lou Chang
- Department of Cell & Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 3G5, Canada
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37
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Foucher I, Mione M, Simeone A, Acampora D, Bally-Cuif L, Houart C. Differentiation of cerebellar cell identities in absence of Fgf signalling in zebrafish Otx morphants. Development 2006; 133:1891-900. [PMID: 16611693 DOI: 10.1242/dev.02352] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although the secreted molecule Fgf8 is a key player of the isthmic organiser function, the mechanisms by which it acts remain unclear. Here, we present evidence indicating that Fgf8 is not instructive in establishing zebrafish cerebellar cell identities, although it is required for proliferation and morphogenesis of this territory. We first show that, as in mouse, lack of Otx function in zebrafish leads to transformation of the presumptive mesencephalon into an extended rhombomere 1 (r1). Expanded Fgf8 expression was proposed to be the cause of this fate transformation. However, this report demonstrates that zebrafish embryos lacking both Otx and fgf8 functions retain an extended r1 and display differentiation of at least two cerebellar cell fates. We show that this is not caused by presence of other Fgfs, which implies that in absence of Otx, Fgf function is not necessary for the differentiation of cerebellar cell types. Otx proteins are therefore potent repressors of cerebellar fates, kept out of r1 progeny by Fgf8. Because Otx transcripts are not present in presumptive r1 territory prior to fgf8 expression, Fgf8 is required to maintain, rather than induce, the posterior boundary of Otx expression. This maintenance is enough to allow cerebellar differentiation.
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Affiliation(s)
- Isabelle Foucher
- MRC Centre for Developmental Neurobiology, New Hunt's House, King's College London, London SE1 9RT, UK
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38
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Muto A, Arai KI, Watanabe S. Rab11-FIP4 is predominantly expressed in neural tissues and involved in proliferation as well as in differentiation during zebrafish retinal development. Dev Biol 2006; 292:90-102. [PMID: 16457799 DOI: 10.1016/j.ydbio.2005.12.050] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Revised: 12/21/2005] [Accepted: 12/22/2005] [Indexed: 12/30/2022]
Abstract
Rab11 family interacting protein 4 (Rab11-FIP4) was initially identified in humans as an Rab11-binding protein, but its biological function has remained unknown. We cloned the zebrafish orthologue of Rab11-FIP4 (zRab11-FIP4) and analyzed its function in vivo by using antisense morpholino. zRab11-FIP4 was expressed as 2 alternative transcripts, i.e., the longer A-form predominantly expressed in neural tissues and the shorter B-form expressed ubiquitously; and in situ hybridization revealed that the A-form was the dominant form. In the developing retina, zRab11-FIP4 was expressed in progenitors throughout the retina at early stages; and then, along with the differentiation, the expression became gradually restricted to the ganglion cell layer and ciliary marginal zone. zRab11-FIP4A knockdown embryos exhibited eye phenotypes similar to those of the shh mutant, such as a small eye with impaired cell proliferation and the delay in cell-cycle exit and differentiation of retinal progenitors. The lack of induction of p57kip2 and enhanced expression of cyclin D1 were observed in the morphant retina. Importantly, the delay in cell-cycle exit was rescued by ectopic expression of either p57Kip2 or dominant-negative PKA, suggesting that Rab11-FIP4A plays pivotal roles in retinal development by regulating Shh signaling and a mechanism acting in parallel with Shh signaling in the control of cell-cycle exit.
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Affiliation(s)
- Akihiko Muto
- Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan
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39
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Holland PWH, Takahashi T. The evolution of homeobox genes: Implications for the study of brain development. Brain Res Bull 2006; 66:484-90. [PMID: 16144637 DOI: 10.1016/j.brainresbull.2005.06.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The homeobox gene superfamily includes many genes implicated in brain development in vertebrates; for example, the Otx, Emx, Dmbx, Gbx, En and Hox gene families. We describe the evolutionary history of the homeobox gene superfamily, as inferred from molecular phylogenetics and chromosomal mapping. Studies of amphioxus, a close relative of vertebrates, have proven particularly informative because it has a genome uncomplicated by recent lineage-specific gene duplications and because in situ hybridisation techniques exist for mapping gene positions and gene expression patterns. We describe an ancient subdivision into gene classes (ANTP, PRD, LIM, POU, SIN, TALE), each containing multiple gene families. The original ANTP class gene duplicated to give distinct NK-like and Hox/ParaHox-related genes, both of which underwent tandem duplication, before the expanding Hox gene cluster duplicated to give Hox and ParaHox clusters. A chromosomal breakage event probably occurred to separate the NK-like and extended Hox genes. Finally, there was additional and extensive gene duplication and gene loss in the vertebrate lineage. We argue that understanding evolutionary history is important for establishing consistent gene nomenclature, and for comparing gene expression patterns and gene functions between species and between gene families.
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Miyake A, Nakayama Y, Konishi M, Itoh N. Fgf19 regulated by Hh signaling is required for zebrafish forebrain development. Dev Biol 2005; 288:259-75. [PMID: 16256099 DOI: 10.1016/j.ydbio.2005.09.042] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Revised: 09/16/2005] [Accepted: 09/27/2005] [Indexed: 01/21/2023]
Abstract
Fibroblast growth factor (Fgf) signaling plays important roles in brain development. Fgf3 and Fgf8 are crucial for the formation of the forebrain and hindbrain. Fgf8 is also required for the midbrain to form. Here, we identified zebrafish Fgf19 and examined its roles in brain development by knocking down Fgf19 function. We found that Fgf19 expressed in the forebrain, midbrain and hindbrain was involved in cell proliferation and cell survival during embryonic brain development. Fgf19 was also essential for development of the ventral telencephalon and diencephalon. Regional specification is linked to cell type specification. Fgf19 was also essential for the specification of gamma-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes generated in the ventral telencephalon and diencephalon. The cross talk between Fgf and Hh signaling is critical for brain development. In the forebrain, Fgf19 expression was down-regulated on inhibition of Hh but not of Fgf3/Fgf8, and overexpression of Fgf19 rescued partially the phenotype on inhibition of Hh. The present findings indicate that Fgf19 signaling is crucial for forebrain development by interacting with Hh and provide new insights into the roles of Fgf signaling in brain development.
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Affiliation(s)
- Ayumi Miyake
- Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto 606-8501, Japan
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41
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Cañestro C, Bassham S, Postlethwait J. Development of the central nervous system in the larvacean Oikopleura dioica and the evolution of the chordate brain. Dev Biol 2005; 285:298-315. [PMID: 16111672 DOI: 10.1016/j.ydbio.2005.06.039] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Revised: 06/11/2005] [Accepted: 06/17/2005] [Indexed: 11/22/2022]
Abstract
In non-vertebrate chordates, central nervous system (CNS) development has been studied in only two taxa, the Cephalochordata and a single Class (Ascidiacea) of the morphologically diverse Urochordata. To understand development and molecular regionalization of the brain in a different deeply diverging chordate clade, we isolated and determined the expression patterns of orthologs of vertebrate CNS markers (otxa, otxb, otxc, pax6, pax2/5/8a, pax2/5/8b, engrailed, and hox1) in Oikopleura dioica (Subphylum Urochordata, Class Larvacea). The three Oikopleura otx genes are expressed similarly to vertebrate Otx paralogs, demonstrating that trans-homologs converged on similar evolutionary outcomes by independent neo- or subfunctionalization processes during the evolution of the two taxa. This work revealed that the Oikopleura CNS possesses homologs of the vertebrate forebrain, hindbrain, and spinal cord, but not the midbrain. Comparing larvacean gene expression patterns to published results in ascidians disclosed important developmental differences and similarities that suggest mechanisms of development likely present in their last common ancestor. In contrast to ascidians, the lack of a radical reorganization of the CNS as larvaceans become adults allows us to relate embryonic gene expression patterns to three subdivisions of the adult anterior brain. Our study of the Oikopleura brain provides new insights into chordate CNS evolution: first, the absence of midbrain is a urochordate synapomorphy and not a peculiarity of ascidians, perhaps resulting from their drastic CNS metamorphosis; second, there is no convincing evidence for a homolog of a midbrain-hindbrain boundary (MHB) organizer in urochordates; and third, the expression pattern of "MHB-genes" in the urochordate hindbrain suggests that they function in the development of specific neurons rather than in an MHB organizer.
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Affiliation(s)
- Cristian Cañestro
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
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42
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Takahashi T. The evolutionary origins of vertebrate midbrain and MHB: insights from mouse, amphioxus and ascidian Dmbx homeobox genes. Brain Res Bull 2005; 66:510-7. [PMID: 16144640 DOI: 10.1016/j.brainresbull.2005.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Indexed: 12/25/2022]
Abstract
Comparative studies on developmental gene expression suggest that the ancestral chordate central nervous system comprised anterior, midbrain-hindbrain boundary (MHB) and posterior regions. The most anterior region consists of both forebrain and midbrain in vertebrates. It remains, however, unresolved when or how the vertebrate midbrain was established from this anterior zone. I previously reported a mouse PRD-class homeobox gene, Dmbx1, expressed in the presumptive midbrain at early developmental stages, and in the hindbrain at later stages, with exclusion from the MHB. To investigate the evolution of midbrain development, I have cloned Dmbx genes from amphioxus and from Ciona, representing the two most closely related lineages to the vertebrates, and examined embryonic Dmbx expression in these species. In amphioxus, no Dmbx expression is observed in the neural tube, supporting previous arguments that the MHB equivalent region has been secondarily lost in evolution. In Ciona, the CiDmbx gene is detected in neural cells posterior to Pax-2/5/8-positive cells (MHB homologue), but not in any cells anterior to them. These results support the lack of a midbrain homologue in Ciona, and suggest that midbrain development is a vertebrate innovation. Here, I report the full sequences of these genes and discuss the evolution of midbrain development in relation to the tripartite neural ground plan and the origin of the MHB organizer.
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43
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Chitnis AB, Itoh M. Exploring alternative models of rostral-caudal patterning in the zebrafish neurectoderm with computer simulations. Curr Opin Genet Dev 2005; 14:415-21. [PMID: 15261658 DOI: 10.1016/j.gde.2004.06.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The StarLogo and NetLogo programming environments allow developmental biologists to build computer models of cell-cell interactions in an epithelium and visualize emergent properties of hypothetical genetic regulatory networks operating in the cells. These environments were used to explore alternative models that show how a posteriorizing morphogen gradient might define gene-expression domains along the rostral-caudal axis in the zebrafish neurectoderm. The models illustrate how a hypothetical genetic network based on auto-activation and cross-repression could lead to establishment of discrete non-overlapping gene-expression domains.
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Affiliation(s)
- Ajay B Chitnis
- Unit on Vertebrate Neural Development, Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Building 6B, Room 3B 315, 6 Center Drive, Bethesda, Maryland 20892, USA.
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44
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Hislop NR, de Jong D, Hayward DC, Ball EE, Miller DJ. Tandem organization of independently duplicated homeobox genes in the basal cnidarian Acropora millepora. Dev Genes Evol 2005; 215:268-73. [PMID: 15702325 DOI: 10.1007/s00427-005-0468-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Accepted: 12/31/2004] [Indexed: 10/25/2022]
Abstract
A number of examples of independently duplicated regulatory genes have been identified in cnidarians, but the extent of this phenomenon and organization of these duplicated genes are unknown. Here we describe the identification of three pairs of independently duplicated homeobox genes in the anthozoan cnidarian, Acropora millepora. In each case, the pairs of paralogous genes are tightly linked, but the extent of sequence divergence implies that these do not reflect recent duplication events. The phenomenon is likely to be more general, as the examples reported here represent most of the limited number of Acropora homeobox genes for which genomic data are yet available.
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Affiliation(s)
- Nikki R Hislop
- Comparative Genomics Centre, Molecular Sciences Building 21, James Cook University, Townsville, Queensland 4811, Australia
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Kawahara A, Che YS, Hanaoka R, Takeda H, Dawid IB. Zebrafish GADD45beta genes are involved in somite segmentation. Proc Natl Acad Sci U S A 2005; 102:361-6. [PMID: 15623554 PMCID: PMC544321 DOI: 10.1073/pnas.0408726102] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Somites in vertebrates are periodic segmented structures that give rise to the vertebrae and muscles of body. Somites are generated from presomitic mesoderm (PSM), but it is not fully understood how cellular differentiation and segment formation are achieved in the anterior PSM. We report here that zebrafish gadd45beta1 and gadd45beta2 genes are periodically expressed as paired stripes adjacent to the neural tube in the anterior PSM region where presomitic cells mature. In mammals, it is known that GADD45 (growth arrest and DNA damage) family proteins play a role in cell-cycle control. We found that both knockdown and overexpression of gadd45beta genes caused somite defects with different consequences for marker gene expression. Knockdown of gadd45beta genes with antisense morpholino oligonucleotides caused a broad expansion of mesp-a in the PSM, and both cyclic expression of her1 and segmented expression of MyoD were disorganized. On the other hand, injection of gadd45beta1 or gadd45beta2 suppressed expression of mesp-a and her1 in anterior PSM and MyoD in paraxial mesoderm. These results indicate that regulated expression of gadd45beta genes in the anterior PSM is required for somite segmentation.
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Affiliation(s)
- Atsuo Kawahara
- Laboratory of Developmental Molecular Genetics, Horizontal Medical Research Organization, Kyoto University Faculty of Medicine, Yoshida, Sakyo-Ku, Kyoto 606-8501, Japan.
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Connor RM, Allen CL, Devine CA, Claxton C, Key B. BOC, brother of CDO, is a dorsoventral axon-guidance molecule in the embryonic vertebrate brain. J Comp Neurol 2005; 485:32-42. [PMID: 15776441 DOI: 10.1002/cne.20503] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The early axon scaffolding in the embryonic vertebrate brain consists of a series of ventrally projecting axon tracts that grow into a single major longitudinal pathway connected across the midline by commissures. We have investigated the role of Brother of CDO (BOC), an immunoglobulin (Ig) superfamily member distantly related to the Roundabout (Robo) family of axon-guidance receptors, in the development of this embryonic template of axon tracts in the zebrafish brain. A zebrafish homologue of BOC was isolated and shown to be expressed predominantly in the developing neural plate and later in the neural tube and developing brain. Zebrafish boc was initially highly localized to discrete bands in the mid- and hindbrain, but, as the major brain subdivisions emerged, it became more evenly expressed along the rostrocaudal axis, particularly in dorsal regions. The function of zebrafish boc was examined by a loss-of-function approach. Analysis of embryos injected with antisense morpholinos designed against boc revealed highly selective defects in the development of dorsoventrally projecting axon tracts. Loss of boc caused ventrally projecting axons, particularly those arising from the presumptive telencephalon, to follow aberrant trajectories. These data indicate that boc is an axon-guidance molecule playing a fundamental role in pathfinding during the early patterning of the axon scaffold in the embryonic vertebrate brain.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Axons/physiology
- Brain/embryology
- Brain/metabolism
- CD57 Antigens/genetics
- CD57 Antigens/metabolism
- Cloning, Molecular/methods
- Embryo, Nonmammalian
- Embryonic Induction/drug effects
- Embryonic Induction/physiology
- Gene Expression Regulation, Developmental/physiology
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- Humans
- Immunoglobulin G/physiology
- Immunohistochemistry/methods
- In Situ Hybridization/methods
- Mice
- Microinjections/methods
- Microscopy, Confocal/methods
- Models, Molecular
- Morpholines/pharmacology
- Neural Cell Adhesion Molecules/genetics
- Neural Cell Adhesion Molecules/metabolism
- Neural Networks, Computer
- RNA, Complementary/metabolism
- RNA, Messenger/metabolism
- Receptors, Cell Surface/physiology
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Zebrafish
- Zebrafish Proteins/genetics
- Zebrafish Proteins/metabolism
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Affiliation(s)
- Robin M Connor
- Brain Growth and Regeneration Laboratory, School of Biomedical Sciences, University of Queensland, Brisbane 4072, Queensland, Australia
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Gillhouse M, Wagner Nyholm M, Hikasa H, Sokol SY, Grinblat Y. Two Frodo/Dapper homologs are expressed in the developing brain and mesoderm of zebrafish. Dev Dyn 2004; 230:403-9. [PMID: 15188426 DOI: 10.1002/dvdy.20060] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Members of the Wnt family of extracellular proteins play essential roles during many phases of vertebrate embryonic development. The molecular mechanism of their action involves a complex cascade of intracellular signaling events, which remains to be understood completely. Recently, two novel cytoplasmic modulators of Wnt signaling, Frodo and Dapper, were identified in Xenopus. We report isolation of their homologs in zebrafish, and show that these genes, frd1 and frd2, are expressed in restricted domains during embryogenesis. Both genes are expressed during early gastrulation in the future mesendoderm, and continue to be expressed in distinct patterns in the forming neurectoderm and mesoderm. Comparative sequence analysis and similar expression patterns argue that frd1 is the zebrafish ortholog of Frodo and Dapper, whereas frd2 is a more divergent member of the same family. Our data suggest important roles for zebrafish frd1 and frd2 in patterning the neural plate and several mesodermal derivatives.
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Affiliation(s)
- Matthew Gillhouse
- Department of Zoology, University of Wisconsin, Madison, Wisconsin, USA
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Ohtoshi A, Behringer RR. Neonatal lethality, dwarfism, and abnormal brain development in Dmbx1 mutant mice. Mol Cell Biol 2004; 24:7548-58. [PMID: 15314164 PMCID: PMC507007 DOI: 10.1128/mcb.24.17.7548-7558.2004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Dmbx1 encodes a paired-like homeodomain protein that is expressed in developing neural tissues during mouse embryogenesis. To elucidate the in vivo role of Dmbx1, we generated two Dmbx1 mutant alleles. Dmbx1- lacks the homeobox and Dmbx1z is an insertion of a lacZ reporter gene. Dmbx1z appears to be a faithful reporter of Dmbx1 expression during embryogenesis and after birth. Dmbx1-lacZ expression was detected in the superior colliculus, cerebellar nuclei, and subpopulations of the medulla oblongata and spinal cord. Some Dmbx1 homozygous mutant mice died during the neonatal period, while others survived to adulthood; however, their growth was impaired. Both heterozygous and homozygous mutant offspring from Dmbx1 homozygous mutant females exhibited a low survival rate and poor growth. However, even wild-type pups fostered onto Dmbx1 homozygous mutant females grew poorly, suggesting a Dmbx1-dependent nursing defect. Dmbx1 mutant mice had an aberrant Dmbx1-lacZ expression pattern in the nervous system, indicating that they had abnormal brain development. These results demonstrate that Dmbx1 is required for postnatal survival, growth, and brain development.
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Affiliation(s)
- Akihira Ohtoshi
- Department of Molecular Genetics, University of Texas, M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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Takahashi T, Holland PWH. Amphioxus and ascidian Dmbx homeobox genes give clues to the vertebrate origins of midbrain development. Development 2004; 131:3285-94. [PMID: 15201221 DOI: 10.1242/dev.01201] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The ancestral chordate neural tube had a tripartite structure, comprising anterior, midbrain-hindbrain boundary (MHB) and posterior regions. The most anterior region encompasses both forebrain and midbrain in vertebrates. It is not clear when or how the distinction between these two functionally and developmentally distinct regions arose in evolution. Recently, we reported a mouse PRD-class homeobox gene, Dmbx1, expressed in the presumptive midbrain at early developmental stages, and the hindbrain at later stages,with exclusion from the MHB. This gene provides a route to investigate the evolution of midbrain development. We report the cloning, genomic structure,phylogeny and embryonic expression of Dmbx genes from amphioxus and from Ciona, representing the two most closely related lineages to the vertebrates. Our analyses show that Dmbx genes form a distinct, ancient,homeobox gene family, with highly conserved sequence and genomic organisation,albeit more divergent in Ciona. In amphioxus, no Dmbx expression is observed in the neural tube, supporting previous arguments that the MHB equivalent region has been secondarily modified in evolution. In Ciona, the CiDmbx gene is detected in neural cells caudal to Pax2/5/8-positive cells (MHB homologue), in the Hox-positive region, but,interestingly, not in any cells rostral to them. These results suggest that a midbrain homologue is missing in Ciona, and argue that midbrain development is a novelty that evolved specifically on the vertebrate lineage. We discuss the evolution of midbrain development in relation to the ancestry of the tripartite neural ground plan and the origin of the MHB organiser.
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Affiliation(s)
- Tokiharu Takahashi
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Glass AS, Dahm R. The Zebrafish as a Model Organism for Eye Development. Ophthalmic Res 2004; 36:4-24. [PMID: 15007235 DOI: 10.1159/000076105] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2003] [Accepted: 12/09/2003] [Indexed: 11/19/2022]
Abstract
In recent years, the zebrafish has become a favourite model organism for biologists studying developmental processes in vertebrates. Its rapid embryonic development, the transparency of its embryos, the large number of offspring together with several other advantages make it ideal for discovering and understanding the genes that regulate embryonic development as well as the physiology of the adult organism. Zebrafish are very visually orientated, and their retina and lens show much the same morphology as other vertebrates including humans. For this reason, they are well suited for examining ocular development, function and disease. This review describes the advantages of the zebrafish as a model organism as well as giving an overview of eye development in this species. It has a particular focus on morphological as well as molecular aspects of the development of the lens.
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Affiliation(s)
- Anne S Glass
- Medizinische Genetik, Eberhard-Karls-Universität Tübingen, Germany
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