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The neural plate in the amphibian embryo is induced in the ectoderm by signals from the dorsal mesoderm. In the extensively studied species Xenopus laevis, such signals are believed to proceed along two alternate pathways, defined as vertical and planar induction. We have studied the relative importance of these pathways in Rana pipiens. In the embryo of this frog, dorsal mesoderm involution can be diverted from its normal course by injection of peptides that inhibit interaction of fibronectin with its receptor. In such embryos, dorsal mesoderm failed to migrate across the blastocoel roof but moved bilaterally along the equator, leading to the formation of two notochords. Neural tissue differentiation occurred in close association with each notochord, but no neural tissue formed along the dorsal midline as might have been predicted by a predominantly planar induction model. While in X. laevis planar induction has been reported to be a major pathway in neuralizing the ecoderm, the results presented here indicate that vertical induction predominates in initiating neural development in R. pipiens embryos.
FIG. 1. Development of embryos injected at the blastula stage
with 200 nl of GRGDS peptide at 50 mg/ml. At the early gastrula
stage both control (A) and injected embryos (B) display an apparently
normal blastopore lip (arrow) as viewed from the vegetal pole. At late
gastrula, blastopore closure in the control embryo (C) is almost
complete (arrow), but the injected embryo (D) shows a large yolk
plug. By stage 20 [control at tailbud stage (E)], the endomesoderm
of the injected embryo (F) protrudes from the blastopore that
remains largely open. In E and F, anterior is to the right and dorsal
is up. (Bar = 1 mm.)
FiG. 2. Expression of differentiation markers visualized by whole-mount immunostaining in intact and GRGDS embryos. Control embryos
at stage 18 (A, D, and G); GRGDS embryos at equivalent stage 18 (B, E, and H), stage 20 (C, F, I, andJ), and stage 21 (K and L). Muscle-specific
12/101 monoclonal antibody (39) stains somites in control (A) and GRGDS embryos (B and C); note two sets of somites in B and C. Tor 70
monoclonal antibody specifically stains the notochord inR. pipiens, as in other amphibians (40) (D). In GRGDS embryos, two distinct notochords
appear at lateral positions (Eand F). 4d monoclonal antibody, raised against chicken NCAM 180 kDa (36, 37), strongly stains the central nervous
system (CNS) of control embryos (G). NCAM staining was detected as early as stage 18 (H) in GRGDS embryos along both sides of the embryo
and intensified at stage 20 (I). B, C, E, F, and Hare dorsal views, I is ventral, anterior is up in all cases. (J) Lateral view of a GRGDS embryo
stained with LINC antibody (38) (anterior to the right) shows very similar pattern to NCAM staining (Hand I). (K) This ventral view ofaGRGDS
embryo doubly stained with LINC (brown) and 12/101 (blue) shows that segmented somites are associated with LINC-positive tubular
structures; anterior is up. (L) GRGDS embryo doubly stained with Tor 70 (brown) and 4d-NCAM (blue) antibodies; anterior is to the left.
NCAM-positive cells are localized in the vicinity of each notochord while the midline of the ectoderm is unstained; note the apparent segmented
spinal nerves. (A-I, bar = 1 mm; J-L, bar = 1 mm.)
FIG. 3. Schematic representation of 32-cell stage blastomeres (Upper)
and their contribution to notochord and CNS in normal (Lower
Left) and GRGDS-injected (Lower Right) embryos. The notochord
(arrowheads, Not) arise from blastomeres B1 andC1 in both normal and
GRGDS embryos. Shading is proportionate to the contribution of each
blastomere to the CNS; whereas the CNS originates from A and B tier
blastomeres in control embryos, it originates exclusively from B and C
tier blastomeres in GRGDS embryos. Asterisks indicate blastomeres
whose fate was not determined.
FIG. 4. Examples of lineage tracing of 32-cell stage blastomeres in control (A, C, and F) and GRGDS-injected embryos (B, D, E, G, H, and
I), sectioned at stage 21. (A and B) Bi and Cl blastomeres were injected with FLDX (green) and TRLDX (red), respectively. Transverse section
of a control embryo (A) shows Bi progeny in the spinal cord (n) and notochord (arrow); in this section Cl progeny does not appear in the
notochord but in somites and mesenchyme. The notochord (arrow) of GRGDS embryo (B) contains Bi- and Cl-derived cells, and neural tissue
(arrowhead) contains Bi-derived cells. Blue staining in the ventolateral aspects of the neural tube (A; also in C) corresponds to immunostaining
with a mix of 4d-NCAM and LINC antibodies visualized with AMCA fluorochrome. (C-E) Both Al blastomeres were injected with FLDX.
Transverse section of normal embryo (C) shows Al progeny in the spinal cord (n) and the epidermis, while in the GRGDS embryo (D,
phase-contrast; E, fluorescence), Al progeny is restricted to the apical epidermal region; no labeled cells can be detected in a lateral position
where neural tissue is located (see I and Fig. 2 H-J and L). Arrows in D point to the dual notochords. (F-I) The progeny of B2 (FLDX) and
C2 (TRLDX) blastomeres in a normal (F) and a GRGDS (G-I) embryo. (F) In this section, B2 progeny is almost exclusively restricted to one
half of the rhombencephalon (n). C2-derived cells form the pharynx and mesenchyme but are virtually absent from the rhombencephalon (n)
and the notochord (arrow). (G) Phase-contrast image of an oblique transverse section of a GRGDS embryo showing only one of the two axes
(arrow). (H and I) Higher magnification of the axis indicated in G. The neural tube-like structure (n) is composed of cells originating from B2
(green) and C2 (red) blastomeres, while the notochord (arrows in Hand I) is not labeled. (D and E, bar = 0.3 mm; A, F, and G, bar = 0.2 mm;
C, B, H, and I, bar = 0.1 mm.)
Bolce,
Ventral ectoderm of Xenopus forms neural tissue, including hindbrain, in response to activin.
1992, Pubmed,
Xenbase
Bolce,
Ventral ectoderm of Xenopus forms neural tissue, including hindbrain, in response to activin.
1992,
Pubmed
,
Xenbase
Boucaut,
Prevention of gastrulation but not neurulation by antibodies to fibronectin in amphibian embryos.
,
Pubmed
Boucaut,
Biologically active synthetic peptides as probes of embryonic development: a competitive peptide inhibitor of fibronectin function inhibits gastrulation in amphibian embryos and neural crest cell migration in avian embryos.
1984,
Pubmed
Boucaut,
Fibronectin-rich fibrillar extracellular matrix controls cell migration during amphibian gastrulation.
1990,
Pubmed
,
Xenbase
Brivanlou,
Expression of an engrailed-related protein is induced in the anterior neural ectoderm of early Xenopus embryos.
1989,
Pubmed
,
Xenbase
Dirksen,
A novel, activin-inducible, blastopore lip-specific gene of Xenopus laevis contains a fork head DNA-binding domain.
1992,
Pubmed
,
Xenbase
Dixon,
Cellular contacts required for neural induction in Xenopus embryos: evidence for two signals.
1989,
Pubmed
,
Xenbase
Doniach,
Planar and vertical induction of anteroposterior pattern during the development of the amphibian central nervous system.
1993,
Pubmed
,
Xenbase
Doniach,
Planar induction of anteroposterior pattern in the developing central nervous system of Xenopus laevis.
1992,
Pubmed
,
Xenbase
Elinson,
Two UV-sensitive targets in dorsoanterior specification of frog embryos.
1989,
Pubmed
,
Xenbase
Frelinger,
Topography of N-CAM structural and functional determinants. II. Placement of monoclonal antibody epitopes.
1986,
Pubmed
Gilbert,
Spemann's organizer: models and molecules.
1993,
Pubmed
Guthrie,
Horizontal and vertical pathways in neural induction.
1991,
Pubmed
,
Xenbase
Johnson,
Mesodermal cell adhesion to fibronectin-rich fibrillar extracellular matrix is required for normal Rana pipiens gastrulation.
1993,
Pubmed
Keller,
Xenopus Gastrulation without a blastocoel roof.
1992,
Pubmed
,
Xenbase
Keller,
Vital dye mapping of the gastrula and neurula of Xenopus laevis. I. Prospective areas and morphogenetic movements of the superficial layer.
1975,
Pubmed
,
Xenbase
Keller,
The function and mechanism of convergent extension during gastrulation of Xenopus laevis.
1985,
Pubmed
,
Xenbase
Keller,
Regional expression, pattern and timing of convergence and extension during gastrulation of Xenopus laevis.
1988,
Pubmed
,
Xenbase
Keller,
The cellular basis of the convergence and extension of the Xenopus neural plate.
1992,
Pubmed
,
Xenbase
Keller,
Planar induction of convergence and extension of the neural plate by the organizer of Xenopus.
1992,
Pubmed
,
Xenbase
Kintner,
Monoclonal antibodies identify blastemal cells derived from dedifferentiating limb regeneration.
,
Pubmed
,
Xenbase
Kintner,
Expression of Xenopus N-CAM RNA in ectoderm is an early response to neural induction.
1987,
Pubmed
,
Xenbase
Kintner,
Molecular bases of early neural development in Xenopus embryos.
1992,
Pubmed
,
Xenbase
Mould,
The CS5 peptide is a second site in the IIICS region of fibronectin recognized by the integrin alpha 4 beta 1. Inhibition of alpha 4 beta 1 function by RGD peptide homologues.
1991,
Pubmed
Papalopulu,
Xenopus Distal-less related homeobox genes are expressed in the developing forebrain and are induced by planar signals.
1993,
Pubmed
,
Xenbase
Peng,
Xenopus laevis: Practical uses in cell and molecular biology. Solutions and protocols.
1991,
Pubmed
,
Xenbase
Purcell,
A different type of amphibian mesoderm morphogenesis in Ceratophrys ornata.
1993,
Pubmed
,
Xenbase
Ruiz i Altaba,
Induction and axial patterning of the neural plate: planar and vertical signals.
1993,
Pubmed
Ruiz i Altaba,
Neural expression of the Xenopus homeobox gene Xhox3: evidence for a patterning neural signal that spreads through the ectoderm.
1990,
Pubmed
,
Xenbase
Ruiz i Altaba,
Planar and vertical signals in the induction and patterning of the Xenopus nervous system.
1992,
Pubmed
,
Xenbase
Ruiz i Altaba,
Pintallavis, a gene expressed in the organizer and midline cells of frog embryos: involvement in the development of the neural axis.
1992,
Pubmed
,
Xenbase
Schlichter,
Electrical responses of immature and mature Rana pipiens oocytes to sperm and other activating stimuli.
1981,
Pubmed
Sharpe,
The induction of anterior and posterior neural genes in Xenopus laevis.
1990,
Pubmed
,
Xenbase
Sive,
Progressive determination during formation of the anteroposterior axis in Xenopus laevis.
1989,
Pubmed
,
Xenbase
Smith,
The origin of the mesoderm in an anuran, Xenopus laevis, and a urodele, Ambystoma mexicanum.
1983,
Pubmed
,
Xenbase
Steen,
Monoclonal antibody markers for amphibian oligodendrocytes and neurons.
1989,
Pubmed
,
Xenbase
Watanabe,
Topography of N-CAM structural and functional determinants. I. Classification of monoclonal antibody epitopes.
1986,
Pubmed
,
Xenbase
Yamada,
Adhesive recognition sequences.
1991,
Pubmed
Zimmerman,
XASH-3, a novel Xenopus achaete-scute homolog, provides an early marker of planar neural induction and position along the mediolateral axis of the neural plate.
1993,
Pubmed
,
Xenbase
