1
|
Stepien BK, Pawolski V, Wagner MC, Kurth T, Schmidt MHH, Epperlein HH. The Role of Posterior Neural Plate-Derived Presomitic Mesoderm (PSM) in Trunk and Tail Muscle Formation and Axis Elongation. Cells 2023; 12:cells12091313. [PMID: 37174713 PMCID: PMC10177618 DOI: 10.3390/cells12091313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 04/14/2023] [Accepted: 04/24/2023] [Indexed: 05/15/2023] Open
Abstract
Elongation of the posterior body axis is distinct from that of the anterior trunk and head. Early drivers of posterior elongation are the neural plate/tube and notochord, later followed by the presomitic mesoderm (PSM), together with the neural tube and notochord. In axolotl, posterior neural plate-derived PSM is pushed posteriorly by convergence and extension of the neural plate. The PSM does not go through the blastopore but turns anteriorly to join the gastrulated paraxial mesoderm. To gain a deeper understanding of the process of axial elongation, a detailed characterization of PSM morphogenesis, which precedes somite formation, and of other tissues (such as the epidermis, lateral plate mesoderm and endoderm) is needed. We investigated these issues with specific tissue labelling techniques (DiI injections and GFP+ tissue grafting) in combination with optical tissue clearing and 3D reconstructions. We defined a spatiotemporal order of PSM morphogenesis that is characterized by changes in collective cell behaviour. The PSM forms a cohesive tissue strand and largely retains this cohesiveness even after epidermis removal. We show that during embryogenesis, the PSM, as well as the lateral plate and endoderm move anteriorly, while the net movement of the axis is posterior.
Collapse
Affiliation(s)
- Barbara K Stepien
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, 01062 Dresden, Germany
| | - Verena Pawolski
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, 01062 Dresden, Germany
| | - Marc-Christoph Wagner
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, 01062 Dresden, Germany
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering (CMCB), Technology Platform, Electron Microscopy and Histology Facility, Technische Universität Dresden, 01062 Dresden, Germany
| | - Mirko H H Schmidt
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, 01062 Dresden, Germany
| | - Hans-Henning Epperlein
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, 01062 Dresden, Germany
| |
Collapse
|
2
|
Vasilegina YI, Kremnev SV, Nikishin DA. Effects of mechanical stretching of embryonic tissues on axial structure formation in Xenopus laevis. Russ J Dev Biol 2017. [DOI: 10.1134/s1062360417010118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
3
|
Tanegashima K, Zhao H, Rebbert ML, Dawid IB. Coordinated activation of the secretory pathway during notochord formation in the Xenopus embryo. Development 2009; 136:3543-8. [PMID: 19793890 DOI: 10.1242/dev.036715] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We compared the transcriptome in the developing notochord of Xenopus laevis embryos with that of other embryonic regions. A coordinated and intense activation of a large set of secretory pathway genes was observed in the notochord, but not in notochord precursors in the axial mesoderm at early gastrula stage. The genes encoding Xbp1 and Creb3l2 were also activated in the notochord. These two transcription factors are implicated in the activation of secretory pathway genes during the unfolded protein response, where cells react to the stress of a build-up of unfolded proteins in their endoplasmic reticulum. Xbp1 and Creb3l2 are differentially expressed but not differentially activated in the notochord. Reduction of expression of Xbp1 or Creb3l2 by injection of antisense morpholinos led to strong deficits in notochord but not somitic muscle development. In addition, the expression of some, but not all, genes encoding secretory proteins was inhibited by injection of xbp1 morpholinos. Furthermore, expression of activated forms of Xbp1 or Creb3l2 in animal explants could activate a similar subset of secretory pathway genes. We conclude that coordinated activation of a battery of secretory pathway genes mediated by Xbp1 and Creb/ATF factors is a characteristic and necessary feature of notochord formation.
Collapse
Affiliation(s)
- Kosuke Tanegashima
- Laboratory of Molecular Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
4
|
Jessell TM, Bovolenta P, Placzek M, Tessier-Lavigne M, Dodd J. Polarity and patterning in the neural tube: the origin and function of the floor plate. CIBA FOUNDATION SYMPOSIUM 2007; 144:255-76; discussion 276-80, 290-5. [PMID: 2673681 DOI: 10.1002/9780470513798.ch15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Little is known about the cellular and molecular mechanisms that determine neuronal cell fate and the patterning of neuronal connections in the vertebrate central nervous system. In this paper we summarize evidence which indicates that some aspects of neuronal differentiation and axon guidance are regulated by specialized epithelial cells that occupy the medial region of the neural plate and, later, the ventral midline of the spinal cord. This cell group, termed the notoplate/floor plate appears to constitute a distinct compartment within the neural plate that is more closely related in lineage and perhaps also in function to axial mesodermal cells of the underlying notochord than to other neural plate cells. Cells of the notoplate exhibit specialized mechanical and adhesive properties that may contribute to neurulation. At later stages of development, the floor plate appears to guide developing axons in the embryonic spinal cord by releasing a diffusible chemoattractant factor and by virtue of its specialized cell surface properties. The floor plate may also play a role in the determination of cell identity and patterning at earlier stages of neural tube development.
Collapse
Affiliation(s)
- T M Jessell
- Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, NY 10032
| | | | | | | | | |
Collapse
|
5
|
Platz F. Structural and experimental investigations of the functional anatomy and the turgor of the notochord in the larval tail of anuran tadpoles. Ann Anat 2006; 188:289-302. [PMID: 16856594 DOI: 10.1016/j.aanat.2006.01.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The premetamorphotic morphology and metamorphotic degeneration of the tail notochord of anuran tadpoles has been investigated. For this purpose the functional anatomy and origin of the notochord turgor was analysed in 10 species macroscopically and using light, transmission and scanning electron microscopic techniques. The notochord consists of the fibrous notochord sheath, which surrounds the notochord cells. Within the sheath these cells form a net-like unit. The inner cells are derived from the marginal notochord cells (chordoblasts). They are protected from mechanical overload by intracellular filaments and desmosomes. Due to their vacuoles, which are filled with a hyaline liquid, they have a constant volume but are deformable. Dissolved substances may pass from the vascularized fin to the notochord cells. The transport from marginal to inner cells occurs via cytopempsis and micropinocytosis. The morphological correlation of this process consists of multiple membrane invaginations and intracellular vesicles. Within the notochord cells a high turgor pressure has been observed. During metamorphosis the membrane vesiculation persists and the notochord cells degenerate. Due to the loss of turgor pressure the tight consistency of the notochord is lost. The collagen filaments and the elastic membrane of the notochord sheath dissolve. Notochord cells with their filaments, high turgor pressure and their central vacuole can function as a combined mechanical and physiological system, which is adaptable to the needs of pressure, compression, tensile and bending forces.
Collapse
Affiliation(s)
- Franz Platz
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, University of Freiburg, Albertstr. 17, D-79104 Freiburg, Germany.
| |
Collapse
|
6
|
Dingwell KS, Smith JC. Tes regulates neural crest migration and axial elongation in Xenopus. Dev Biol 2006; 293:252-67. [PMID: 16554046 DOI: 10.1016/j.ydbio.2006.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Accepted: 02/03/2006] [Indexed: 11/20/2022]
Abstract
Tes is a member of an emerging family of proteins sharing a set of protein motifs referred to as PET-LIM domains. PET-LIM proteins such as Prickle regulate cell behavior during gastrulation in Xenopus and zebrafish, and to ask whether Tes is also involved in controlling cell behavior, we isolated its Xenopus orthologue. Xtes is expressed as a maternal transcript that is maintained at low levels until neurula stages when expression is elevated in the head and axial structures. Depletion of Xtes leads to a foreshortened head and severe defects in axis elongation. The anterior defect is due in part to the inhibition of cranial neural crest migration while the defects in elongation may be due to perturbation of expression of XFGF8, Xdelta-1 and Xcad-3 and thereby to disruption of posterior somitogenesis. Finally, we note that simultaneous depletion of Xtes and Xenopus Prickle results in axial defects that are more severe than those resulting from depletion of Xtes alone, suggesting that the two proteins act together to control axial elongation.
Collapse
Affiliation(s)
- Kevin S Dingwell
- Wellcome Trust and Cancer Research UK Gurdon Institute of Cancer and Developmental Biology, and Department of Zoology, University of Cambridge, Cambridge CB2 1QR, UK
| | | |
Collapse
|
7
|
Bocina I, Saraga-Babić M. Immunohistochemical study of cytoskeletal and extracellular matrix components in the notochord and notochordal sheath of amphioxus. Int J Biol Sci 2006; 2:73-8. [PMID: 16733537 PMCID: PMC1458430 DOI: 10.7150/ijbs.2.73] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Accepted: 03/10/2006] [Indexed: 11/05/2022] Open
Abstract
A major cytoskeletal and extracellular matrix proteins of the amphioxus notochordal cells and sheath were detected by immunohistochemical techniques. The three-layered amphioxus notochordal sheath strongly expressed fish collagen type I in its outer and middle layers, while in the innermost layer expression did not occur. The amphioxus notochordal sheath was reactive to applied anti-human antibodies for intermediate filament proteins such as cytokeratins, desmin and vimentin, as well as to microtubule components (beta-tubulin), particularly in the area close to the epipharyngeal groove. Alpha-smooth muscle actin was expressed in some notochordal cells and in the area of the notochordal attachment to the sheath. Thus muscular nature of notochordal cells was shown by immunohistochemistry in tissue section. Our results confirm that genes encoding intermediate filament proteins, microtubules and microfilaments are highly conserved during evolution. Collagen type I was proven to be the key extracellular matrix protein that forms the amphioxus notochordal sheath.
Collapse
Affiliation(s)
- Ivana Bocina
- Department of Biology, Faculty of Natural Scieneces, University of Split, Teslina 12, 21000 Split, Croatia.
| | | |
Collapse
|
8
|
Abstract
In vertebrates, the paraxial mesoderm corresponds to the bilateral strips of mesodermal tissue flanking the notochord and neural tube and which are delimited laterally by the intermediate mesoderm and the lateral plate. The paraxial mesoderm comprises the head or cephalic mesoderm anteriorly and the somitic region throughout the trunk and the tail of the vertebrates. Soon after gastrulation, the somitic region of vertebrates starts to become segmented into paired blocks of mesoderm, termed somites. This process lasts until the number of somites characteristic of the species is reached. The somites later give rise to all skeletal muscles of the body, the axial skeleton, and part of the dermis. In this review I discuss the processes involved in the formation of the paraxial mesoderm and its segmentation into somites in vertebrates.
Collapse
Affiliation(s)
- O Pourquié
- Laboratoire de génétique et de physiologie du développement, Developmental Biology Institute of Marseille (IBDM), CNRS-INSERM-Université de la méditerranée-AP de Marseille, France.
| |
Collapse
|
9
|
Abstract
The origin and development of the amphibian somitic mesoderm is summarized and reviewed with the goal of identifying issues most profitably pursued in these organisms. The location of the prospective somitic mesoderm as well as the cell movements bringing this tissue into its definitive position varies among amphibians. These variations have implications for the tissue interactions patterning the embryo, the design of the gastrulation movements, the role of the somitic mesoderm in early patterning and morphogenic processes, and the nature of the developmental pathway leading to somites. The presegmentation morphogenesis, the process of segmentation, and the subsequent, postsegmentation morphogenesis of the somitic mesoderm also varies considerably among amphibians. Although segmentation in amphibians shares what may be highly conserved and general patterning mechanisms with other vertebrates, the somitic developmental pathway as a whole is not conservative and has been capable of accommodating the use of a number of quite different morphogenic processes, all leading to very similar ends. The major challenges in studying amphibian somitogenesis are to develop molecular markers for major components of the somite, to determine the derivatives of the somite with better cell tracing experiments, and learning to work with the small dermatomal and sclerotomal cell populations found in most species. A potential advantage is that the diversity of somitogenesis among the amphibians makes this group ideal for studying the evolution of developmental processes. In addition, many amphibians allow direct observation of somitogenesis with great resolution and permit biomechanical analysis of tissues participating in morphogenesis, thus making it possible to analyze cellular mechanisms of morphogenesis in ways not possible in most other systems.
Collapse
Affiliation(s)
- R Keller
- Department of Biology, University of Virginia, Charlottesville 22903, USA
| |
Collapse
|
10
|
Sausedo RA, Schoenwolf GC. Cell behaviors underlying notochord formation and extension in avian embryos: quantitative and immunocytochemical studies. Anat Rec (Hoboken) 1993; 237:58-70. [PMID: 8214642 DOI: 10.1002/ar.1092370107] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Formation and extension of the notochord is one of the earliest and most obvious events of axis development in vertebrate embryos. In birds, prospective notochord cells arise from Hensen's node and come to lie beneath the midline of the neural plate, where they assist in the process of neurulation and initiate the dorsoventral patterning of the neural tube through sequential inductive interactions. In the present study, we examined notochord development in avian embryos with quantitative and immunological procedures. Extension of the notochord occurs principally through accretion, that is, the addition of cells to its caudal end, a process that involves considerable cell rearrangement at the notochord-Hensen's node interface. In addition, cell division and cell rearrangement within the notochord proper contribute to notochord extension. Thus, extension of the notochord occurs in a manner that is significantly different from that of the adjacent, overlying, midline region of the neural plate (i.e., the median hinge-point region or future floor plate of the neural tube), which as shown in one of the previous studies from our laboratory (Schoenwolf and Alvarez: Development 106:427-439, 1989), extends caudally as its cells undergo two rounds of mediolateral cell-cell intercalation and two-three rounds of cell division.
Collapse
Affiliation(s)
- R A Sausedo
- Department of Anatomy, School of Medicine, University of Utah, Salt Lake City 84132
| | | |
Collapse
|
11
|
Alvarez IS, Schoenwolf GC. Expansion of surface epithelium provides the major extrinsic force for bending of the neural plate. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1992; 261:340-8. [PMID: 1629665 DOI: 10.1002/jez.1402610313] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neurulation, formation of the neural tube, requires both intrinsic forces (i.e., those generated within the neural plate) and extrinsic forces (i.e., those generated outside the neural plate in adjacent tissues), but the precise origin of these forces is unclear. In this study, we addressed the question of which tissue produces the major extrinsic force driving bending of the neural plate. We have previously shown that 1) extrinsic forces are required for bending and 2) such forces are generated lateral to the neural plate. Three tissues flank the neural plate prior to its bending: surface epithelium, mesoderm, and endoderm. In the present study, we removed two of these layers, namely, the endoderm and mesoderm, underlying and lateral to the neural plate; bending still occurred, often with complete formation of a neural tube, although the latter usually rotated toward the side of tissue depletion. These results suggest that the surface epithelium, the only tissue remaining after microsurgery, provides the major extrinsic force for bending of the neural plate and that the mesoderm (and perhaps endoderm) stabilizes the neuraxis, maintaining its proper orientation and position on the midline.
Collapse
Affiliation(s)
- I S Alvarez
- Department of Anatomy, University of Utah, School of Medicine, Salt Lake City 84132
| | | |
Collapse
|
12
|
Abstract
The cell junctions of the notochord of Xenopus laevis tadpoles were examined with the electron microscope using thin sections, lanthanum tracer experiments, and freeze-fracture replicas. Both the peripheral and vacuolated cells of the notochord are connected by numerous spot desmosomes characterized by an intercellular desmogloea and intermediate filaments on the cytoplasmic sides. The peripheral cells also display numerous hemidesmosomes facing the underlying basal lamina. Staining with rhodamine-phalloidin for F-actin yielded negative results and suggested that adhaerens-type junctions are absent. Tracer experiments with lanthanum and freeze-fracture replicas clearly revealed the presence of gap junctions between both cell types but no indications of tight junctions were found and no intercellular barrier existed for tracer infiltration of the notochord.
Collapse
Affiliation(s)
- W Honer
- Institute of Cytology, University of Bonn, Federal Republic of Germany
| | | |
Collapse
|
13
|
Keller R, Cooper MS, Danilchik M, Tibbetts P, Wilson PA. Cell intercalation during notochord development in Xenopus laevis. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1989; 251:134-54. [PMID: 2769201 DOI: 10.1002/jez.1402510204] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Morphometric data from scanning electron micrographs (SEM) of cells in intact embryos and high-resolution time-lapse recordings of cell behavior in cultured explants were used to analyze the cellular events underlying the morphogenesis of the notochord during gastrulation and neurulation of Xenopus laevis. The notochord becomes longer, narrower, and thicker as it changes its shape and arrangement and as more cells are added at the posterior end. The events of notochord development fall into three phases. In the first phase, occurring in the late gastrula, the cells of the notochord become distinct from those of the somitic mesoderm on either side. Boundaries form between the two tissues, as motile activity at the boundary is replaced by stabilizing lamelliform protrusions in the plane of the boundary. In the second phase, spanning the late gastrula and early neurula, cell intercalation causes the notochord to narrow, thicken, and lengthen. Its cells elongate and align mediolaterally as they rearrange. Both protrusive activity and its effectiveness are biased: the anterioposterior (AP) margins of the cells advance and retract but produce much less translocation than the more active left and right ends. The cell surfaces composing the lateral boundaries of the notochord remain inactive. In the last phase, lasting from the mid- to late neurula stage, the increasingly flattened cells spread at all their interior margins, transforming the notochord into a cylindrical structure resembling a stack of pizza slices. The notochord is also lengthened by the addition of cells to its posterior end from the circumblastoporal ring of mesoderm. Our results show that directional cell movements underlie cell intercalation and raise specific questions about the cell polarity, contact behavior, and mechanics underlying these movements. They also demonstrate that the notochord is built by several distinct but carefully coordinated processes, each working within a well-defined geometric and mechanical environment.
Collapse
Affiliation(s)
- R Keller
- Department of Zoology, University of California, Berkeley 94720
| | | | | | | | | |
Collapse
|
14
|
Schoenwolf GC, Everaert S, Bortier H, Vakaet L. Neural plate- and neural tube-forming potential of isolated epiblast areas in avian embryos. ANATOMY AND EMBRYOLOGY 1989; 179:541-9. [PMID: 2751116 DOI: 10.1007/bf00315697] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Formation, shaping, and bending of the neural plate and closure of the neural groove are complex processes resulting in formation of the neural tube. Two experiments were performed using avian embryos as model systems to examine these events. First, we transected blastoderms near the level of Hensen's node to determine the potential of prenodal neural plate to form neural tube in isolation from primitive streak regression. Our results demonstrate that shaping and bending of the prenodal neural plate occur under these conditions, but neural groove closure is inhibited. Second, we isolated various areas of postnodal epiblasts to determine their potential to form neural plate. Our results suggest that the area of the postnodal epiblast that can form neural plate consists of paired tracts lying adjacent to the definitive primitive streak and extending caudally at least 1 mm from its cranial end.
Collapse
Affiliation(s)
- G C Schoenwolf
- Department of Anatomy, University of Utah, School of Medicine, Salt Lake City 84132
| | | | | | | |
Collapse
|
15
|
Smith JL, Schoenwolf GC. Notochordal induction of cell wedging in the chick neural plate and its role in neural tube formation. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1989; 250:49-62. [PMID: 2723610 DOI: 10.1002/jez.1402500107] [Citation(s) in RCA: 168] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cells in the median hinge point (MHP) of the bending chick neural plate are tightly apposed to the underlying notochord. These cells differ from those in adjacent lateral neuroepithelial areas (L) in that MHP cells are short and mainly wedge-shaped and line a furrow, whereas L cells are tall and mainly spindle-shaped and do not line a furrow. Cell generation time also differs in these regions. These consistent differences are detectable only after the notochord has formed and established contact with the neural plate; it is unclear whether they result from self-differentiation or induction. Two experiments were performed to evaluate the hypothesis that MHP characteristics develop owing to inductive interactions between the notochord and overlying neuroepithelial cells. First, notochordless chick embryos were generated to determine whether midline neuroepithelial cells still developed typical MHP characteristics. In the absence of the notochord, such characteristics did not develop. Second, isolated segments of quail notochord were transplanted subjacent to L of chick hosts to ascertain whether the notochord is capable of inducing MHP characteristics in L cells. When transplanted notochordal segments established apposition with host L cells, the apposing L cells usually developed typical MHP characteristics. Collectively, these results provide strong evidence that the notochord plays an inductive role in the formation of MHP characteristics. This investigation further revealed that bending can occur in the absence of MHP characteristics, forming a neural tube with an abnormal morphology. Thus, the formation of such characteristics, particularly cell wedging, is not required for bending but plays a major role in generating the normal cross-sectional morphology of the neural tube.
Collapse
Affiliation(s)
- J L Smith
- Department of Anatomy, University of Utah, School of Medicine, Salt Lake City 84132
| | | |
Collapse
|
16
|
LaFlamme SE, Jamrich M, Richter K, Sargent TD, Dawid IB. Xenopus endo B is a keratin preferentially expressed in the embryonic notochord. Genes Dev 1988; 2:853-62. [PMID: 2463213 DOI: 10.1101/gad.2.7.853] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Screening of a cDNA library from neurula stage Xenopus laevis for notochord-specific sequences led to the isolation of a cDNA clone, XK endo B (Xenopus keratin endo B), which encodes a nonepidermal type I keratin. In situ and Northern blot hybridizations indicate that expression of XK endo B RNA is concentrated in the notochord, whereas expression in the endoderm is 5-10 times lower. XK endo B mRNA is present in the oocyte and increases from late gastrula. Accumulation peaks by late neurula and is greatly reduced by the tadpole stage; in the adult, a low level of XK endo B RNA is present in the liver. XK endo B shows sequence homology to mouse endo B; genomic Southern blots show that XK endo B is the most similar sequence to mouse endo B in the Xenopus genome, and vice versa, indicating that XK endo B and mouse endo B are homologs. The use of endo B as a marker and the germ layer derivation of the notochord are discussed in light of these results.
Collapse
Affiliation(s)
- S E LaFlamme
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, Maryland 20892
| | | | | | | | | |
Collapse
|
17
|
Abstract
The biochemical composition and biosynthetic activity of Xenopus notochord were examined and compared with those of chick and mouse notochord. The notochords of all three species contain type-II collagen, and the notochords of Xenopus and chick synthesize a soluble glycoprotein with a molecular mass of 86 kilodaltons (kd). Mouse embryos were not tested for this molecule, because their notochords are too small to be dissected out. Most interestingly, Xenopus and chick notochords share a keratan-sulphate-containing proteoglycan which appears to be absent from mouse notochord. The presence or absence of keratan sulphate in the notochords of the different species reflects its presence or absence in cartilage. Since one role of the notochord in vivo is to stimulate chondrogenesis in the sclerotomes of the somites, this result provides support for the view that cells responding to the extracellular matrix produced by one tissue do so by increasing their production of the same matrix components.
Collapse
|