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Journal ArticleDOI

Expression of a type II collagen gene in the zebrafish embryonic axis

01 Jul 1995-Developmental Dynamics (Wiley Subscription Services, Inc., A Wiley Company)-Vol. 203, Iss: 3, pp 363-376
TL;DR: The cloning and expression pattern of a type II collagen (col2a1) gene from the zebrafish Danio rerio is reported, showing that the spatial and temporal pattern of col2a 1 expression in axial mesoderm follows the expression of twist closer than other genes tested.
Abstract: To understand the hierarchy of developmental controls underlying axis specification in vertebrate embryos, it is helpful to identify relationships between regulatory molecules and the genes that given axial cells their differentiated phenotypes. This work reports the cloning and expression pattern of one of these differentiation genes, a type II collagen (col2a1) gene from the zebrafish Danio rerio. Along th8e embryonic axis, col2a1 is expressed dynamically in three rows that are each a single cell wide: the notochord and the rows of cells immediately dorsal and ventral to it—the floor plate of the central nervous system, and the hypochord. In addition, col2a1 is expressed in the pharyngeal arches, the epithelium of the otic capsule, and in the mesenchyme of the neurocranium. Experiments probed the expression pattern of col2a1 relative to that of known or potential regulators of axis development, including axial, sonic hedgehog, twist, and cyclops. The results showed that the spatial and temporal pattern of col2a1 expression in axial mesoderm follows the expression of twist closer than other genes tested. In cyclops embryos, which lack an intact floor plate, col2a1 expression was usually low, but not missing in cells in the ventral spinal cord. Because col2a1 expression reveals abnormalities in the notochord of cyclopsb16 embryos, and less col2a1-expressing mesenchyme accumulates rostral to the notochord in cyclops embryos, the effects of the cyclopsb16 mutation are not confined to the central nervous system. ©1995 Wiley-Liss, Inc.
Citations
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Journal ArticleDOI
09 Nov 1995-Nature
TL;DR: It is shown that floating head is the zebrafish homologue of Xnot, a homeobox gene expressed in the amphibian organizer and notochord, and it is proposed that flh regulates notochords precursor cell fate.
Abstract: The notochord is a midline mesodermal structure with an essential patterning function in all vertebrate embryos. Zebrafish floating head (flh) mutants lack a notochord, but develop with prechordal plate and other mesodermal derivatives, indicating that flh functions specifically in notochord development. We show that floating head is the zebrafish homologue of Xnot, a homeobox gene expressed in the amphibian organizer and notochord. We propose that flh regulates notochord precursor cell fate.

471 citations

Journal ArticleDOI
TL;DR: The embryonic origin, signalling roles and ultimate fate of the notochord are discussed, with an emphasis on structural aspects ofNotochord biology.
Abstract: The notochord is the defining structure of the chordates, and has essential roles in vertebrate development. It serves as a source of midline signals that pattern surrounding tissues and as a major skeletal element of the developing embryo. Genetic and embryological studies over the past decade have informed us about the development and function of the notochord. In this review, I discuss the embryonic origin, signalling roles and ultimate fate of the notochord, with an emphasis on structural aspects of notochord biology.

408 citations


Cites background from "Expression of a type II collagen ge..."

  • ...Consistent with this structural role, both the floor plate and the hypochord express a variety of cartilage proteins, such as type II collagen (Yan et al., 1995)....

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  • ...(C) As well as the notochord, the floor plate and hypochord express type II collagen (Yan et al., 1995)....

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Journal ArticleDOI
TL;DR: It is reported that the cyclops locus encodes the nodal-related protein Ndr2, a member of the transforming growth factor type beta superfamily of factors, which is required for ventral midline patterning of the embryonic central nervous system.
Abstract: Ventral structures in the central nervous system are patterned by signals emanating from the underlying mesoderm as well as originating within the neuroectoderm. Mutations in the zebrafish, Danio rerio, are proving instrumental in dissecting these midline signals. The cyclops mutation leads to a loss of medial floor plate and to severe deficits in ventral forebrain development, leading to cyclopia. Here, we report that the cyclops locus encodes the nodal-related protein Ndr2, a member of the transforming growth factor type β superfamily of factors. The evidence includes identification of a missense mutation in the initiation codon and rescue of the cyclops phenotype by expression of ndr2 RNA, here renamed “cyclops.” Thus, in interaction with other molecules implicated in these processes such as sonic hedgehog and one-eyed-pinhead, cyclops is required for ventral midline patterning of the embryonic central nervous system.

371 citations

Journal ArticleDOI
TL;DR: It is concluded that shh is neither required nor sufficient to induce this cell type in the zebrafish, and ectopic overexpression of shh in zebra fish embryos does not induce ectopic medial floor plate cells.
Abstract: Sonic hedgehog (Shh) is a secreted protein that is involved in the organization and patterning of several tissues in vertebrates. We show that the zebrafish sonic-you (syu) gene, a member of a group of five genes required for somite patterning, is encoding Shh. Embryos mutant for a deletion of syu display defects in patterning of the somites, the lateral floor plate cells, the pectoral fins, the axons of motorneurons and the retinal ganglion cells. In contrast to mouse embryos lacking Shh activity, syu mutant embryos do form medial floor plate cells and motorneurons. Since ectopic overexpression of shh in zebrafish embryos does not induce ectopic medial floor plate cells, we conclude that shh is neither required nor sufficient to induce this cell type in the zebrafish.

368 citations


Cites background from "Expression of a type II collagen ge..."

  • ...In the weak alleles, syutq252and syutbq70, expression of shhis reduced, in embryos that carry syutbx392over the shhdeletion (syut4), it is barely detectable and no shhexpression is seen in syut4 mutant embryos. et al., 1992; Krauss et al., 1993; Yan et al., 1995)....

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  • ...Antisense probes were made f shh (Krauss et al., 1993), twhh (Ekker et al., 1995), collagen2a1(Yan et al., 1995), F-spondin2(Higashijima et al., 1997; Klar et al., 1992) myoD (Weinberg et al., 1996), twist (B. Riggleman unpubl., MorinKensicki and Eisen, 1997), fkd4 (Odenthal and Nüsslein-Volhard,…...

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Journal ArticleDOI
TL;DR: The zebrafish locus one-eyed pinhead (oep) gene is essential for the formation of anterior axial mesoderm, endoderm and ventral neuroectoderm as well as the floor plate, and it is suggested that oep is required downstream or in parallel to shh signaling in gastrulation.
Abstract: The zebrafish locus one-eyed pinhead (oep) is essential for the formation of anterior axial mesoderm, endoderm and ventral neuroectoderm. At the beginning of gastrulation anterior axial mesoderm cells form the prechordal plate and express goosecoid (gsc) in wild-type embryos. In oep mutants the prechordal plate does not form and gsc expression is not maintained. Exposure to lithium, a dorsalizing agent, leads to the ectopic induction and maintenance of gsc expression in wild-type embryos. Lithium treatment of oep mutants still leads to ectopic gsc induction but not maintenance, suggesting that oep acts downstream of inducers of dorsal mesoderm. In genetic mosaics, wild-type cells are capable of forming anterior axial mesoderm in oep embryos, suggesting that oep is required in prospective anterior axial mesoderm cells before gastrulation. The oep gene is also essential for endoderm formation and the early development of ventral neuroectoderm, including the floor plate. The loss of endoderm is already manifest during gastrulation by the absence of axial-expressing cells in the hypoblast of oep mutants. These findings suggest that oep is also required in lateral and ventral regions of the gastrula margin. The sonic hedgehog (shh).gene is expressed in the notochord of oep animals. Therefore, the impaired floor plate development in oep mutants is not caused by the absence of the floor plate inducer shh. This suggests that oep is required downstream or in parallel to shh signaling. The ventral region of the forebrain is also absent in oep mutants, leading to severe cyclopia. In contrast, anterior-posterior brain patterning appears largely unaffected, suggesting that underlying prechordal plate is not required for anterior-posterior pattern formation but might be involved in dorsoventral brain patterning. To test if oep has a wider, partially redundant role, we constructed double mutants with two other zebrafish loci essential for patterning during gastrulation. Double mutants with floating head, the zebrafish Xnot homologue, display enhanced floor plate and adaxial muscle phenotypes. Double mutants with no tail (ntl), the zebrafish homologue of the mouse Brachyury locus, display severe defects in midline and mesoderm formation including absence of most of the somitic mesoderm. These results reveal a redundant function of oep and ntl in mesoderm formation. Our data suggest that both oep and ntl act in the blastoderm margin to specify mesendodermal cell fates.

360 citations


Cites background from "Expression of a type II collagen ge..."

  • ...To determine when the endoderm is abnormal, we analyzed the expression of collagen type II (Yan et al., 1995) during the segmentation period....

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References
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Journal ArticleDOI
TL;DR: A series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio is described, providing for flexibility and continued evolution of the staging series as the authors learn more about development in this species.
Abstract: We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis--the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the changing spectrum of major developmental processes that occur during the first 3 days after fertilization, and we review some of what is known about morphogenesis and other significant events that occur during each of the periods. Stages subdivide the periods. Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope. The descriptions also fully utilize the optical transparancy of the live embryo, which provides for visibility of even very deep structures when the embryo is examined with the compound microscope and Nomarski interference contrast illumination. Photomicrographs and composite camera lucida line drawings characterize the stages pictorially. Other figures chart the development of distinctive characters used as staging aid signposts.

10,612 citations

Journal ArticleDOI
31 Dec 1993-Cell
TL;DR: Three members of a mouse gene family related to the Drosophila segment polarity gene, hedgehog (hh), are identified and it is suggested that Shh may play a role in the normal inductive interactions that pattern the ventral CNS.

2,259 citations

Journal ArticleDOI
04 Sep 1992-Cell
TL;DR: The activity of exogenous noggin RNA in embryonic axis induction and the localized expression of endogenous noggan transcripts suggest that noggins plays a role in normal dorsal development.

1,200 citations

Journal ArticleDOI
31 Dec 1993-Cell
TL;DR: The existence of an hh-related gene family in the zebrafish, Brachydanio rerio, that is expressed in the notochord, floor plate, and posterior fin mesoderm, tissues associated with polarizing activities in various vertebrate embryos is described.

1,186 citations

Journal ArticleDOI
04 Oct 1991-Cell
TL;DR: This paper describes the cloning and expression of a Xenopus homolog of Brachyury, Xbra, and shows that expression of Xbra occurs as a result of mesoderm induction in Xenopus, both in Response to the natural signal and in response to the Mesoderm-inducing factors activin A and basic FGF.

983 citations