Regional expression, pattern and timing of convergence and extension during gastrulation of Xenopus laevis

We show with time-lapse micrography that narrowing in the circumblastoporal dimension (convergence) and lengthening in the animal-vegetal dimension (extension) of the involuting marginal zone (IMZ) and the noninvoluting marginal zone (NIMZ) are the major tissue movements driving blastopore closure and involution of the IMZ during gastrulation in the South African clawed frog, Xenopus laevis. Analysis of blastopore closure shows that the degree of convergence is uniform from dorsal to ventral sides, whereas the degree of extension is greater on the dorsal side of the gastrula. Explants of the gastrula show simultaneous convergence and extension in the dorsal IMZ and NIMZ. In both regions, convergence and extension are most pronounced at their common boundary, and decrease in both animal and vegetal directions. Convergent extension is autonomous to the IMZ and begins at stage 10.5, after the IMZ has involuted. In contrast, expression of convergent extension in the NIMZ appears to be dependent on basal contact with chordamesoderm or with itself. The degree of extension decreases progressively in lateral and ventral sectors. Isolated ventral sectors show convergence without a corresponding degree of extension, perhaps reflecting the transient convergence and thickening that occurs in this region of the intact embryo. We present a detailed mechanism of how these processes are integrated with others to produce gastrulation. The significance of the regional expression of convergence and extension in Xenopus is discussed and compared to gastrulation in other amphibians.

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Faculty Opinions recommendation of Formation of the dorsal marginal zone in Xenopus laevis analyzed by time-lapse microscopic magnetic resonance imaging.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1085816.538735 ◽

2007 ◽

Author(s):

Lance Davidson

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Xenopus Laevis ◽

Marginal Zone ◽

Time Lapse ◽

Resonance Imaging

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Morphological polarity of intercalating deep mesodermal cells in the organzer of Xenopus laevis gastrulae

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156183 ◽

1989 ◽

Vol 47 ◽

pp. 840-841

Author(s):

Ray Keller ◽

John Shih ◽

Paul Wilson

Keyword(s):

Xenopus Laevis ◽

Time Lapse ◽

Light Level ◽

Cell Labelling ◽

Fluorescent Compound ◽

Morphogenetic Movements ◽

Tissue Interactions ◽

Convergence And Extension ◽

Morphological Polarity ◽

Cell Intercalation

The dorsal lip of the blastopore constitutes the “organizer” of the amphibian body plan, both in terms of its tissue interactions and its morphogenetic movements of convergence and extension during gastrulation. This tissue autonomously narrows (converges) and lengthens (extends) during early development, functioning prominently in the morphogenetic movements of both gastrulation and neurulation Xenopus laevis. High resolution time-lapse recording of cell behavior in cultured explants and cell labelling studies have shown that the movements of convergence and extension are produced by radial intercalation of cells, in which several layers rearrange to produce fewer layers of greater area, and by mediolateral intercalation of cells, in which several rows of cells rearrange to produce a narrower, longer array. By labelling individual cells with the fluorescent compound, DiI, and making low light level recordings, we found that cells of the notochord intercalate mediolaterally using polarized protrusive activity at their internal medial or lateral ends. Thus polarized protrusive activity appears to play a major role in mediolateral cell intercalation after the boundary between the notochord and somites forms in the late gastrula stage.We examine further the morphology of the deep mesodermal cells with scanning electron microscopy at earlier stages, to search for morphological manifestations of a similar polarity of protrusive activity. The dorsal deep mesodermal cells of early gastrulae were exposed by rapidly pulling the. epithelial endoderm off the deep cells with forceps, in Danilchik's solution, and fixing the embryo within 15 seconds in 2% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4) as described previously. The dorsal deep cells adjacent to the epithelium are elongate and aligned parallel to one another and to the circumference of the glastopore (Fig. 1). The medial and lateral ends bear broad, lamelliform protrusions (large pointers, Fig. 1, 2) whereas the anterior and posterior ends bear numerous small filiform protrusions (small pointers, Fig. 1, 2). This characteristic morphology is found only in the dorsal marginal zone, which undergoes convergence and extension by mediolateral intercalation.

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The function and mechanism of convergent extension during gastrulation of Xenopus laevis

Development ◽

10.1242/dev.89.supplement.185 ◽

1985 ◽

Vol 89 (Supplement) ◽

pp. 185-209

Author(s):

R. E. Keller ◽

Michael Danilchik ◽

Robert Gimlich ◽

John Shih

Keyword(s):

Marginal Zone ◽

Cell Formation ◽

Cell Lineage ◽

Time Lapse ◽

Convergent Extension ◽

A Cell ◽

Tissue Recombination ◽

Migration Of Cells ◽

Time Lapse Video

The processes thought to function in Xenopus gastrulation include bottle cell formation, migration of cells on the roof of the blastocoel, and autonomous convergent extension of the circumblastoporal region. A review of recent and classical results shows that only the last accounts for the bulk of the tissue displacement of gastrulation, including spreading of the marginal zone toward the blastopore, involution of the marginal zone, and closure of the blastopore. Microsurgical manipulation and explantation studies, analysed by time-lapse video and cine microscopy, shows that the dorsal circumblastoporal region contains two regions which show either autonomous or semiautonomous convergent extension. The dorsal involuting marginal zone (IMZ) undergoes convergence (narrowing) and extension (lengthening) after its involution, beginning at the midgastrula stage and continuing through neurulation, such that it simultaneously extends posteriorly across the yolk plug and narrows the blastoporal circumference. Concurrently, the corresponding region of the overlying non-involuting marginal zone (NIMZ) begins a complementary convergent extension, but at a greater rate, which spreads vegetally to occupy surface area vacated by the IMZ. Tissue recombination experiments show that the deep cells of the dorsal IMZ bring about convergent extension. Labelling of small populations of these cells with a cell lineage tracer shows that convergent extension involves intercalation of deep cells to form a longer, narrower array. Direct time-lapse video and cine micrography of deep cells in cultured explants show that convergent extension involves radial and circumferential intercalation. Removal of the entire blastocoel roof of the early gastrula, including all or part of the NIMZ, shows that convergent extension of the IMZ alone can bring about its involution and blastopore closure. The role of convergent extension in gastrulation of other amphibians and other metazoans and its significance to related problems in early development are discussed.

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Cell movements during epiboly and gastrulation in zebrafish

Development ◽

10.1242/dev.108.4.569 ◽

1990 ◽

Vol 108 (4) ◽

pp. 569-580 ◽

Cited By ~ 69

Author(s):

R.M. Warga ◽

C.B. Kimmel

Keyword(s):

Dorsal Side ◽

Epithelial Layer ◽

Convergent Extension ◽

Blastula Stage ◽

Cell Movements ◽

Yolk Cell ◽

Radial Cell ◽

Convergence And Extension ◽

Embryonic Ectoderm ◽

Anterior Posterior

Beginning during the late blastula stage in zebrafish, cells located beneath a surface epithelial layer of the blastoderm undergo rearrangements that accompany major changes in shape of the embryo. We describe three distinctive kinds of cell rearrangements. (1) Radial cell intercalations during epiboly mix cells located deeply in the blastoderm among more superficial ones. These rearrangements thoroughly stir the positions of deep cells, as the blastoderm thins and spreads across the yolk cell. (2) Involution at or near the blastoderm margin occurs during gastrulation. This movement folds the blastoderm into two cellular layers, the epiblast and hypoblast, within a ring (the germ ring) around its entire circumference. Involuting cells move anteriorwards in the hypoblast relative to cells that remain in the epiblast; the movement shears the positions of cells that were neighbors before gastrulation. Involuting cells eventually form endoderm and mesoderm, in an anterior-posterior sequence according to the time of involution. The epiblast is equivalent to embryonic ectoderm. (3) Mediolateral cell intercalations in both the epiblast and hypoblast mediate convergence and extension movements towards the dorsal side of the gastrula. By this rearrangement, cells that were initially neighboring one another become dispersed along the anterior-posterior axis of the embryo. Epiboly, involution and convergent extension in zebrafish involve the same kinds of cellular rearrangements as in amphibians, and they occur during comparable stages of embryogenesis.

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A temporally resolved transcriptome for developing “Keller” explants of the Xenopus laevis dorsal marginal zone

10.1101/2020.09.22.308312 ◽

2020 ◽

Author(s):

Anneke D. Kakebeen ◽

Robert Huebner ◽

Asako Shindo ◽

Kujin Kwon ◽

Taejoon Kwon ◽

...

Keyword(s):

Gene Expression ◽

Xenopus Laevis ◽

Marginal Zone ◽

Model System ◽

Extensive Study ◽

Convergent Extension ◽

Time Resolved ◽

Vertebrate Embryos ◽

Global Patterns ◽

Central Paradigm

AbstractExplanted tissues from vertebrate embryos reliably develop in culture and have provided essential paradigms for understanding embryogenesis, from early embryological investigations of induction, to the extensive study of Xenopus animal caps, to the current studies of mammalian gastruloids. Cultured explants of the Xenopus dorsal marginal zone (“Keller” explants) serve as a central paradigm for studies of convergent extension cell movements, yet we know little about the global patterns of gene expression in these explants. In an effort to more thoroughly develop this important model system, we provide here a time-resolved bulk transcriptome for developing Keller explants.

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The dorsal involuting marginal zone stiffens anisotropically during its convergent extension in the gastrula of Xenopus laevis

Development ◽

10.1242/dev.121.10.3131 ◽

1995 ◽

Vol 121 (10) ◽

pp. 3131-3140 ◽

Cited By ~ 7

Author(s):

S.W. Moore ◽

R.E. Keller ◽

M.A. Koehl

Keyword(s):

Extracellular Matrix ◽

Xenopus Laevis ◽

Marginal Zone ◽

Force Production ◽

Special Property ◽

Testing Procedure ◽

Materials Testing ◽

Convergent Extension ◽

Cell Matrix ◽

Prechordal Mesoderm

Physically, the course of morphogenesis is determined by the distribution and timing of force production in the embryo and by the mechanical properties of the tissues on which these forces act. We have miniaturized a standard materials-testing procedure (the stress-relaxation test) to measure the viscoelastic properties of the dorsal involuting marginal zone, prechordal mesoderm, and vegetal endoderm of Xenopus laevis embryos during gastrulation. We focused on the involuting marginal zone, because it undergoes convergent extension (an important and wide-spread morphogenetic process) and drives involution, blastopore closure and elongation of the embryonic axis. We show that the involuting marginal zone stiffens during gastrulation, stiffening is a special property of this region rather than a general property of the whole embryo, stiffening is greater along the anteroposterior axis than the mediolateral axis and changes in the cytoskeleton or extracellular matrix are necessary for stiffening, although changes in cell-cell adhesions or cell-matrix adhesions are not ruled out. These findings provide a baseline of data on which future experiments can be designed and make specific, testable predictions about the roles of the cytoskeleton, extracellular matrix and intercellular adhesion in convergent extension, as well as predictions about the morphogenetic role of convergent extension in early development.

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Lithium dorsalizes but also mechanically disrupts gastrulation of Xenopus laevis

Development ◽

10.1242/dev.102.4.677 ◽

1988 ◽

Vol 102 (4) ◽

pp. 677-686 ◽

Cited By ~ 1

Author(s):

C.M. Regen ◽

R.A. Steinhardt

Keyword(s):

Xenopus Laevis ◽

Marginal Zone ◽

Lithium Treatment ◽

Leading Edge ◽

Spatial Layout ◽

Cell Group ◽

Axis Formation ◽

Convergent Extension ◽

Distinct Effect ◽

Group Movements

The discovery that lithium treatment at blastula stages can induce axis formation suggested that it might act by respecifying the cytoplasmic rearrangement-generated dorsoventral pattern, so that ventral cells behave like their dorsal counterparts. We have studied the effects of Li+ treatment on the spatial layout of the cell-group movements of gastrulation to see whether this is the case. We find that involution of the chordamesoderm and associated archenteron roof is retarded by Li+, an effect which does not suggest dorsal respecification. However, in both migration of the leading edge mesoderm and convergent extension of the marginal zone, ventral regions clearly do show dorsal-type movement. Because of this, and because of examples where disruption of involution and effects on axis differentiation do not correlate, we propose that failure of involution represents a distinct effect of Li+ involving disruption of mechanical relationships at the blastopore. Thus archenteron formation poorly reflects the dorsoventral pattern. Extension of sandwich explants of the ventral marginal zone is proposed as a reliable quantitative assay for alterations to the dorsoventral pattern.

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Deep cytoplasmic rearrangements during early development in Xenopus laevis

Development ◽

10.1242/dev.111.4.845 ◽

1991 ◽

Vol 111 (4) ◽

pp. 845-856 ◽

Cited By ~ 6

Author(s):

M.V. Danilchik ◽

J.M. Denegre

Keyword(s):

Cell Cycle ◽

Plasma Membrane ◽

Xenopus Laevis ◽

Early Development ◽

Marginal Zone ◽

Dorsal Side ◽

Fluorescent Dye ◽

Entry Point ◽

Sperm Entry ◽

Yolk Platelet

The egg of the frog Xenopus is cylindrically symmetrical about its animal-vegetal axis before fertilization. Midway through the first cell cycle, the yolky subcortical cytoplasm rotates 30 degrees relative to the cortex and plasma membrane, usually toward the side of the sperm entry point. Dorsal embryonic structures always develop on the side away from which the cytoplasm moves. Details of the deep cytoplasmic movements associated with the cortical rotation were studied in eggs vitally stained during oogenesis with a yolk platelet-specific fluorescent dye. During the first cell cycle, eggs labelled in this way develop a complicated swirl of cytoplasm in the animal hemisphere. This pattern is most prominent on the side away from which the vegetal yolk moves, and thus correlates in position with the prospective dorsal side of the embryo. Although the pattern is initially most evident near the egg's equator or marginal zone, extensive rearrangements associated with cleavage furrowing (cytoplasmic ingression) relocate portions of the swirl to vegetal blastomeres on the prospective dorsal side.

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Ryk cooperates with Frizzled 7 to promote Wnt11-mediated endocytosis and is essential for Xenopus laevis convergent extension movements

The Journal of Cell Biology ◽

10.1083/jcb.200710188 ◽

2008 ◽

Vol 182 (6) ◽

pp. 1073-1082 ◽

Cited By ~ 81

Author(s):

Gun-Hwa Kim ◽

Jung-Hyun Her ◽

Jin-Kwan Han

Keyword(s):

Cell Membrane ◽

Membrane Protein ◽

Xenopus Laevis ◽

Tyrosine Kinase ◽

Wnt Signaling ◽

Wnt Pathway ◽

Marginal Zone ◽

Transmembrane Protein ◽

Convergent Extension ◽

Cell Membrane Protein

The single-pass transmembrane protein Ryk (atypical receptor related tyrosine kinase) functions as a Wnt receptor. However, Ryk's correlation with Wnt/Frizzled (Fz) signaling is poorly understood. Here, we report that Ryk regulates Xenopus laevis convergent extension (CE) movements via the β-arrestin 2 (βarr2)-dependent endocytic process triggered by noncanonical Wnt signaling. During X. laevis gastrulation, βarr2-mediated endocytosis of Fz7 and dishevelled (Dvl/Dsh) actually occurs in the dorsal marginal zone tissues, which actively participate in noncanonical Wnt signaling. Noncanonical Wnt11/Fz7-mediated endocytosis of Dsh requires the cell-membrane protein Ryk. Ryk interacts with both Wnt11 and βarr2, cooperates with Fz7 to mediate Wnt11-stimulated endocytosis of Dsh, and signals the noncanonical Wnt pathway in CE movements. Conversely, depletion of Ryk and Wnt11 prevents Dsh endocytosis in dorsal marginal zone tissues. Our study suggests that Ryk functions as an essential regulator for noncanonical Wnt/Fz-mediated endocytosis in the regulation of X. laevis CE movements.

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