scholarly journals The presumptive floor plate (notoplate) induces behaviors associated with convergent extension in medial but not lateral neural plate cells of Xenopus

2006 ◽  
Vol 300 (2) ◽  
pp. 670-686 ◽  
Author(s):  
Akouavi M. Ezin ◽  
Paul Skoglund ◽  
Ray Keller
Keyword(s):  
Floor Plate ◽  
Neural Plate ◽  
Convergent Extension

scholarly journals Multiple morphogens and rapid elongation promote segmental patterning during development

2021 ◽  
Vol 17 (6) ◽  
pp. e1009077
Author(s):  
Yuchi Qiu ◽  
Lianna Fung ◽  
Thomas F. Schilling ◽  
Qing Nie
Keyword(s):  
Cell Fate ◽  
Gene Regulatory Networks ◽  
Cell Sorting ◽  
Short Range ◽  
Regulatory Networks ◽  
Neural Plate ◽  
Convergent Extension ◽  
Simultaneous Formation ◽  
Gene Regulatory ◽  
Rapid Elongation

The vertebrate hindbrain is segmented into rhombomeres (r) initially defined by distinct domains of gene expression. Previous studies have shown that noise-induced gene regulation and cell sorting are critical for the sharpening of rhombomere boundaries, which start out rough in the forming neural plate (NP) and sharpen over time. However, the mechanisms controlling simultaneous formation of multiple rhombomeres and accuracy in their sizes are unclear. We have developed a stochastic multiscale cell-based model that explicitly incorporates dynamic morphogenetic changes (i.e. convergent-extension of the NP), multiple morphogens, and gene regulatory networks to investigate the formation of rhombomeres and their corresponding boundaries in the zebrafish hindbrain. During pattern initiation, the short-range signal, fibroblast growth factor (FGF), works together with the longer-range morphogen, retinoic acid (RA), to specify all of these boundaries and maintain accurately sized segments with sharp boundaries. At later stages of patterning, we show a nonlinear change in the shape of rhombomeres with rapid left-right narrowing of the NP followed by slower dynamics. Rapid initial convergence improves boundary sharpness and segment size by regulating cell sorting and cell fate both independently and coordinately. Overall, multiple morphogens and tissue dynamics synergize to regulate the sizes and boundaries of multiple segments during development.

scholarly journals Differential patterning of ventral midline cells by axial mesoderm is regulated by BMP7 and chordin

Development ◽  
1999 ◽  
Vol 126 (2) ◽  
pp. 397-408 ◽  
Author(s):  
K. Dale ◽  
N. Sattar ◽  
J. Heemskerk ◽  
J.D. Clarke ◽  
M. Placzek ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Floor Plate ◽  
Neural Plate ◽  
Ventral Midline ◽  
Molecular Events ◽  
Morphogenetic Protein ◽  
Explant Cultures ◽  
Prechordal Mesoderm ◽  
Midline Cells ◽  
Bmp Antagonist

Ventral midline cells in the neural tube have distinct properties at different rostrocaudal levels, apparently in response to differential signalling by axial mesoderm. Floor plate cells are induced by sonic hedgehog (SHH) secreted from the notochord whereas ventral midline cells of the rostral diencephalon (RDVM cells) appear to be induced by the dual actions of SHH and bone morphogenetic protein 7 (BMP7) from prechordal mesoderm. We have examined the cellular and molecular events that govern the program of differentiation of RDVM cells under the influence of the axial mesoderm. By fate mapping, we show that prospective RDVM cells migrate rostrally within the neural plate, passing over rostral notochord before establishing register with prechordal mesoderm at stage 7. Despite the co-expression of SHH and BMP7 by rostral notochord, prospective RDVM cells appear to be specified initially as caudal ventral midline neurectodermal cells and to acquire RDVM properties only at stage 7. We provide evidence that the signalling properties of axial mesoderm over this period are regulated by the BMP antagonist, chordin. Chordin is expressed throughout the axial mesoderm as it extends, but is downregulated in prechordal mesoderm coincident with the onset of RDVM cell differentiation. Addition of chordin to conjugate explant cultures of prechordal mesoderm and neural tissue prevents the rostralization of ventral midline cells by prechordal mesoderm. Chordin may thus act to refine the patterning of the ventral midline along the rostrocaudal axis.

Development of the central nervous system

2013 ◽  
Author(s):  
Martin E. Atkinson
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Neural Tube ◽  
Large Diameter ◽  
Floor Plate ◽  
Neural Plate ◽  
Ependymal Cells ◽  
High Dose ◽  
Neuronal Processes ◽  
Mantle Layer

The early development of the nervous system, the process of neurulation, has already been outlined in Chapter 8 and illustrated in Figure 8.4. To briefly recap, an area of dorsal ectoderm is induced by the underlying notochord to form the neural plate during the third week of development. The lateral edges of the neural plate rise to form the neural folds which eventually fold over and unite in the midline by the end of the fourth week to produce the neural tube. A distinct cell population on the crest of the neural folds, the neural crest, migrates from the forming neural tube to form various structures, including components of the peripheral nervous system. The closed neural tube consists of a large diameter anterior portion that will become the brain and a longer cylindrical posterior section, the future spinal cord. Initially, the neural plate is a single cell layer, but concentric layers of cells can be recognized by the time the neural tube has closed. An inner layer of ependymal cells surrounds the central spinal canal. Neuroblasts, the precursors of neurons, make up the bulk of the neural tube called the mantle layer; this will become the grey matter of the spinal cord. Neuroblasts do not extend processes until they have completed their differentiation. When the cells in a particular location are fully differentiated, the neuronal processes emerging from the neuroblasts form an outer marginal layer which ultimately becomes the white matter of the spinal cord. Figure 19.1B shows that the neural tube changes shape due to proliferation of cells in the mantle layer. This figure also indicates two midline structures in the roof and floor of the tube, known as the roof plate and floor plate. They are important in the determination of the types of neurons that develop from the mantle layer. The floor plate is induced by the expression of a protein product of a gene called sonic hedgehog (SHH) produced by the underlying notochord; the floor plate then expresses the same gene itself. Neuroblasts nearest to the floor plate receive a high dose of SHH protein and respond by differentiating into motor neurons; as seen in Figure 19.1B, these cells group together to form bilateral ventrolateral basal plates.

Induction of floor plate differentiation by contact-dependent, homeogenetic signals

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 205-218 ◽  
Author(s):  
M. Placzek ◽  
T.M. Jessell ◽  
J. Dodd
Keyword(s):  
Axon Guidance ◽  
Neural Tube ◽  
Floor Plate ◽  
Cell Patterning ◽  
Neural Plate ◽  
Neural Cells ◽  
Cellular Mechanisms ◽  
Prechordal Mesoderm ◽  
Specific Antigens ◽  
Inductive Signals

The floor plate is located at the ventral midline of the neural tube and has been implicated in neural cell patterning and axon guidance. To address the cellular mechanisms involved in floor plate differentiation, we have used an assay that monitors the expression of floor-plate-specific antigens in neural plate explants cultured in the presence of inducing tissues. Contact-mediated signals from both the notochord and the floor plate act directly on neural plate cells to induce floor plate differentiation. Floor plate induction is initiated medially by a signal from the notochord, but appears to be propagated to more lateral cells by homeogenetic signals that derive from medial floor plate cells. The response of neural plate cells to inductive signals declines with embryonic age, suggesting that the mediolateral extent of the floor plate is limited by a loss of competence of neural cells. The rostral boundary of the floor plate at the midbrain-forebrain junction appears to result from the lack of inducing activity in prechordal mesoderm and the inability of rostral neural plate cells to respond to inductive signals.

Caudalization by the amphibian organizer: brachyury, convergent extension and retinoic acid

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3051-3062 ◽  
Author(s):  
T. Yamada
Keyword(s):  
Cell Motility ◽  
Neural Development ◽  
Marginal Zone ◽  
Floor Plate ◽  
Convergent Extension ◽  
Neural Tissues ◽  
Dorsal Mesoderm ◽  
The One ◽  
Cell Intercalation ◽  
Morphogenetic Effects

Caudalization, which is proposed to be one of two functions of the amphibian organizer, initiates posterior pathways of neural development in the dorsalized ectoderm. In the absence of caudalization, dorsalized ectoderm only expresses the most anterior (archencephalic) differentiation. In the presence of caudalization, dorsalized ectorderm develops various levels of posterior neural tissues, depending on the extent of caudalization. A series of induction experiments have shown that caudalization is mediated by convergent extension: cell motility that is based on directed cell intercalation, and is essential for the morphogenesis of posterior axial tissues. During amphibian development, convergent extension is first expressed all-over the mesoderm and, after mesoderm involution, it becomes localized to the posterior mid-dorsal mesoderm, which produces notochord. This expression pattern of specific down regulation of convergent extension is also followed by the expression of the brachyury homolog. Furthermore, mouse brachyury has been implicated in the regulation of tissue elongation on the one hand, and in the control of posterior differentiation on the other. These observations suggest that protein encoded by the brachyury homolog controls the expression of convergent extension in the mesoderm. The idea is fully corroborated by a genetic study of mouse brachyury, which demonstrates that the gene product produces elongation of the posterior embryonic axis. However, there exists evidence for the induction of posterior dorsal mesodermal tissues, if brachyury homolog protein is expressed in the ectoderm. In both cases the brachyury homolog contributes to caudalization. A number of other genes appear to be involved in caudalization. The most important of these is pintavallis, which contains a fork-head DNA binding domain. It is first expressed in the marginal zone. After mesoderm involution, it is present not only in the presumptive notochord, but also in the floor plate. This is in contrast to the brachyury homolog, whose expression is restricted to mesoderm. The morphogenetic effects of exogenous RA on anteroposterior specification during amphibian embryogenesis are reviewed. The agent inhibits archencephalic differentiation and enhances differentiation of deuterencephalic and trunk levels. Thus the effect of exogenous RA on morphogenesis of CNS is very similar to that of caudalization, which is proposed to occur through the normal action of the organizer. According to a detailed analysis of the effect of lithium on morphogenesis induced by the Cynops organizer, lithium has a caudalizing effect closely comparable with that of RA. Furthermore, lithium induces convergent extension in the prechordal plate, which normally does not show cell motility.(ABSTRACT TRUNCATED AT 400 WORDS)

Combinatorial Gli gene function in floor plate and neuronal inductions by Sonic hedgehog

Development ◽  
1998 ◽  
Vol 125 (12) ◽  
pp. 2203-2212 ◽  
Author(s):  
A. Ruiz i Altaba
Keyword(s):  
Motor Neurons ◽  
Positional Information ◽  
Floor Plate ◽  
Neural Plate ◽  
Neural Cells ◽  
Spinal Motor Neurons ◽  
Gli Proteins ◽  
Regulatory Feedback Loop ◽  
Midline Cells ◽  
Definition Of

Within the developing vertebrate nervous system, it is not known how progenitor cells interpret the positional information provided by inducing signals or how the domains in which distinct groups of neural cells differentiate are defined. Gli proteins may be involved in these processes. In the frog neural plate, we have previously shown that the zinc finger transcription factor Gli1 is expressed in midline cells and mediates the effects of Shh inducing floor plate differentiation. In contrast, Gli2 and Gli3 are expressed throughout the neural plate except for the midline. Here, it is shown that Gli3 and Shh repress each other whereas Gli2, like Gli1, is a target of Shh signaling. However, only Gli1 can induce the differentiation of floor plate cells. In addition, Gli2 and Gli3 repress the ectopic induction of floor plate cells by Gli1 in co-injection assays and inhibit endogenous floor plate differentiation. The definition of the floor plate domain, therefore, appears to be defined by the antagonizing activities of Gli2 and Gli3 on Gli1 function. Because both Gli1 and Gli2 are induced by Shh, these results establish a regulatory feedback loop triggered by Shh that restricts floor plate cells to the midline. We have also previously shown that the Gli genes induce neuronal differentiation and here it is shown that there is specificity to the types of neurons the Gli proteins induce. Only Gli1 induces Nkx2.1/TTF-1(+) ventral forebrain neurons. Moreover, Gli2 and Gli3 inhibit their differentiation. In contrast, the differentiation of spinal motor neurons can be induced by the two ventrally expressed Gli genes, Gli1 and Gli2, suggesting that Gli2 directly mediates induction of motor neurons by Shh. In addition, Gli3 inhibits motor neuron differentiation by Gli2. Thus, combinatorial Gli function may pattern the neural tube, integrating positional information and cell type differentiation.

scholarly journals Mechanisms of convergence and extension by cell intercalation

2000 ◽  
Vol 355 (1399) ◽  
pp. 897-922 ◽  
Author(s):  
Ray Keller ◽  
Lance Davidson ◽  
Anna Edlund ◽  
Tamira Elul ◽  
Max Ezin ◽  
...  
Keyword(s):  
Essential Elements ◽  
Floor Plate ◽  
Cell Cortex ◽  
Convergent Extension ◽  
Mesoderm Cell ◽  
Mesodermal Cell ◽  
Cell Traction ◽  
Convergence And Extension ◽  
A Cell ◽  
Cell Intercalation

The cells of many embryonic tissues actively narrow in one dimension (convergence) and lengthen in the perpendicular dimension (extension). Convergence and extension are ubiquitous and important tissue movements in metazoan morphogenesis. In vertebrates, the dorsal axial and paraxial mesodermal tissues, the notochordal and somitic mesoderm, converge and extend. In amphibians as well as a number of other organisms where these movements appear, they occur by mediolateral cell intercalation, the rearrangement of cells along the mediolateral axis to produce an array that is narrower in this axis and longer in the anteroposterior axis. In amphibians, mesodermal cell intercalation is driven by bipolar, mediolaterally directed protrusive activity, which appears to exert traction on adjacent cells and pulls the cells between one another. In addition, the notochordal–somitic boundary functions in convergence and extension by ‘capturing’ notochordal cells as they contact the boundary, thus elongating the boundary. The prospective neural tissue also actively converges and extends parallel with the mesoderm. In contrast to the mesoderm, cell intercalation in the neural plate normally occurs by monopolar protrusive activity directed medially, towards the midline notoplate–floor–plate region. In contrast, the notoplate–floor–plate region appears to converge and extend by adhering to and being towed by or perhaps migrating on the underlying notochord. Converging and extending mesoderm stiffens by a factor of three or four and exerts up to 0.6 μN force. Therefore, active, force–producing convergent extension, the mechanism of cell intercalation, requires a mechanism to actively pull cells between one another while maintaining a tissue stiffness sufficient to push with a substantial force. Based on the evidence thus far, a cell–cell traction model of intercalation is described. The essential elements of such a morphogenic machine appear to be (i) bipolar, mediolaterally orientated or monopolar, medially directed protrusive activity; (ii) this protrusive activity results in mediolaterally orientated or medially directed traction of cells on one another; (iii) tractive protrusions are confined to the ends of the cells; (iv) a mechanically stable cell cortex over the bulk of the cell body which serves as a movable substratum for the orientated or directed cell traction. The implications of this model for cell adhesion, regulation of cell motility and cell polarity, and cell and tissue biomechanics are discussed.

scholarly journals FGF3 in the floor plate directs notochord convergent extension in the Ciona tadpole

Development ◽  
2008 ◽  
Vol 136 (1) ◽  
pp. 23-28 ◽  
Author(s):  
W. Shi ◽  
S. M. Peyrot ◽  
E. Munro ◽  
M. Levine
Keyword(s):  
Floor Plate ◽  
Convergent Extension

Gli1 is a target of Sonic hedgehog that induces ventral neural tube development

Development ◽  
1997 ◽  
Vol 124 (13) ◽  
pp. 2537-2552 ◽  
Author(s):  
J. Lee ◽  
K.A. Platt ◽  
P. Censullo ◽  
A. Ruiz i Altaba
Keyword(s):  
Sonic Hedgehog ◽  
Neural Tube ◽  
Transcriptional Regulator ◽  
Floor Plate ◽  
Neural Plate ◽  
Mouse Embryos ◽  
Human Glioma ◽  
Cubitus Interruptus ◽  
Ventral Neural Tube ◽  
Neural Tube Development

The vertebrate zinc finger genes of the Gli family are homologs of the Drosophila gene cubitus interruptus. In frog embryos, Gli1 is expressed transiently in the prospective floor plate during gastrulation and in cells lateral to the midline during late gastrula and neurula stages. In contrast, Gli2 and Gli3 are absent from the neural plate midline with Gli2 expressed widely and Gli3 in a graded fashion with highest levels in lateral regions. In mouse embryos, the three Gli genes show a similar pattern of expression in the neural tube but are coexpressed throughout the early neural plate. Because Gli1 is the only Gli gene expressed in prospective floor plate cells of frog embryos, we have investigated a possible involvement of this gene in ventral neural tube development. Here we show that Shh signaling activates Gli1 transcription and that widespread expression of endogenous frog or human glioma Gli1, but not Gli3, in developing frog embryos results in the ectopic differentiation of floor plate cells and ventral neurons within the neural tube. Floor-plate-inducing ability is retained when cytoplasmic Gli1 proteins are forced into the nucleus or are fused to the VP16 transactivating domain. Thus, our results identify Gli1 as a midline target of Shh and suggest that it mediates the induction of floor plate cells and ventral neurons by Shh acting as a transcriptional regulator.

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