Planar and vertical signals in the induction and patterning of the Xenopus nervous system

Development ◽  
1992 ◽  
Vol 116 (1) ◽  
pp. 67-80 ◽  
Author(s):  
A. Ruiz i Altaba
Keyword(s):  
Nervous System ◽  
Neural Tube ◽  
Neural Tissue ◽  
Cell Types ◽  
Cell Group ◽  
Ventral Region ◽  
Cellular Mechanisms ◽  
Anteroposterior Axis ◽  
Cell Groups ◽  
Neural Ectoderm

The cellular mechanisms responsible for the formation of the Xenopus nervous system have been examined in total exogastrula embryos in which the axial mesoderm appears to remain segregated from prospective neural ectoderm and in recombinates of ectoderm and mesoderm. Posterior neural tissue displaying anteroposterior pattern develops in exogastrula ectoderm. This effect may be mediated by planar signals that occur in the absence of underlying mesoderm. The formation of a posterior neural tube may depend on the notoplate, a midline ectodermal cell group which extends along the anteroposterior axis. The induction of neural structures characteristic of the forebrain and of cell types normally found in the ventral region of the posterior neural tube requires additional vertical signals from underlying axial mesoderm. Thus, the formation of the embryonic Xenopus nervous system appears to involve the cooperation of distinct planar and vertical signals derived from midline cell groups.

scholarly journals Dorsalization of the neural tube by the non-neural ectoderm

Development ◽  
1995 ◽  
Vol 121 (7) ◽  
pp. 2099-2106 ◽  
Author(s):  
M.E. Dickinson ◽  
M.A. Selleck ◽  
A.P. McMahon ◽  
M. Bronner-Fraser
Keyword(s):  
Neural Crest ◽  
Neural Tube ◽  
Cell Formation ◽  
Neural Crest Cell ◽  
Neural Tissue ◽  
Cell Types ◽  
Stage 4 ◽  
Slug Expression ◽  
Neural Ectoderm ◽  
Crest Cell

The patterning of cell types along the dorsoventral axis of the spinal cord requires a complex set of inductive signals. While the chordamesoderm is a well-known source of ventralizing signals, relatively little is known about the cues that induce dorsal cell types, including neural crest. Here, we demonstrate that juxtaposition of the non-neural and neural ectoderm is sufficient to induce the expression of dorsal markers, Wnt-1, Wnt-3a and Slug, as well as the formation of neural crest cells. In addition, the competence of neural plate to express Wnt-1 and Wnt-3a appears to be stage dependent, occurring only when neural tissue is taken from stage 8–10 embryos but not from stage 4 embryos, regardless of the age of the non-neural ectoderm. In contrast to the induction of Wnt gene expression, neural crest cell formation and Slug expression can be induced when either stage 4 or stage 8–10 neural plates are placed in contact with the non-neural ectoderm. These data suggest that the non-neural ectoderm provides a signal (or signals) that specifies dorsal cell types within the neural tube, and that the response is dependent on the competence of the neural tissue.

Control of dorsoventral pattern in vertebrate neural development: induction and polarizing properties of the floor plate

Development ◽  
1991 ◽  
Vol 113 (Supplement_2) ◽  
pp. 105-122 ◽  
Author(s):  
Marysia Placzek ◽  
Toshiya Yamada ◽  
Marc Tessier-Lavigne ◽  
Thomas Jessell ◽  
Jane Dodd
Keyword(s):  
Neural Tube ◽  
Neural Development ◽  
Cell Types ◽  
Floor Plate ◽  
Neural Cells ◽  
Dorsoventral Patterning ◽  
Cellular Mechanisms ◽  
Cell Position

Distinct classes of neural cells differentiate at specific locations within the embryonic vertebrate nervous system. To define the cellular mechanisms that control the identity and pattern of neural cells we have used a combination of functional assays and antigenic markers to examine the differentiation of cells in the developing spinal cord and hindbrain in vivo and in vitro. Our results suggest that a critical step in the dorsoventral patterning of the embryonic CNS is the differentiation of a specialized group of midline neural cells, termed the floor plate, in response to local inductive signals from the underlying notochord. The floor plate and notochord appear to control the pattern of cell types that appear along the dorsoventral axis of the neural tube. The fate of neuroepithelial cells in the ventral neural tube may be defined by cell position with respect to the ventral midline and controlled by polarizing signals that originate from the floor plate and notochord.

Analysis of clonal restriction of cell mingling in Xenopus

1985 ◽  
Vol 312 (1153) ◽  
pp. 57-65 ◽  
Keyword(s):  
Horseradish Peroxidase ◽  
Cell Types ◽  
Cell Group ◽  
Cell Stage ◽  
Wide Range ◽  
Cell Groups ◽  
Cell Layers ◽  
Single Blastomeres

Cell fates were traced by injecting horseradish peroxidase into single blastomeres of Xenopus embryos at 2- to 512-cell stages. At later stages the number, types and locations of all labelled progeny were observed. Progeny of a single labelled ancestral cell divided coherently until the 12th cell generation, the onset of gastrulation, and then dispersed and mingled with unlabelled cells. Cell mingling was restricted at mediolateral and anterior—posterior boundaries. These boundaries were always respected by progeny of any blastomere labelled at the 512-cell stage but they were frequently crossed by progeny of blastomeres labelled at the 256-cell or earlier stages. The boundaries defined seven morphological compartments each populated exclusively by a group of ancestral cells at the 512-cell stage. Each blastomere that contributed progeny to the nervous system also gave rise to a wide range of cell types in all three primary germ cell layers but the clone was restricted to a single compartment. Analysis of clonal restriction of cell mingling was done in vitro . Twenty to thirty blastomeres were excised from one ancestral cell group at the 512-cell stage and combined in vitro with 20-30 blastomeres from another group. One group of blastomeres labelled with horseradish peroxidase was placed in contact with another group of unlabelled blastomeres, maintained in vitro for up to 2 days, and then processed histologically to show the distribution of labelled and unlabelled cells. Mingling was significantly greater in combinations of two of the same ancestral cell groups than in combinations of two different ancestral cell groups. A similar result was observed when a single labelled cell was combined with either the same or different ancestral cells. In all experiments the cells were significantly larger in combinations of different ancestral cell groups, indicating that they had undergone fewer divisions. These results are consistent with the hypothesis that boundaries observed in vivo are lines of clonal restriction formed by mutual inhibition of cell motility and cell division following contact between progeny of different ancestral cell groups.

Hox-7 expression during murine craniofacial development

Development ◽  
1991 ◽  
Vol 113 (2) ◽  
pp. 601-611 ◽  
Author(s):  
A. MacKenzie ◽  
M.W. Ferguson ◽  
P.T. Sharpe
Keyword(s):  
Nervous System ◽  
Choroid Plexus ◽  
Expression Pattern ◽  
Neural Tube ◽  
Anterior Pituitary ◽  
Expression Patterns ◽  
In Situ Hybridisation ◽  
Cell Types ◽  
Subsequent Formation ◽  
Dorsal Midline

We have used in situ hybridisation to establish the temporal and spatial expression patterns of the mouse homeobox-containing gene; Hox-7, in the developing embryonic cranium and nervous system of the mouse between embryonic days 9.5 (E9.5) and E15.5. Hox-7 has previously been associated with areas of mesenchymal-epithelial interaction and cell migration especially in neural crest ectomesenchymal cells. Aside from the expression patterns seen in the facial anlage at E9.5, Hox-7 transcripts were also detected in the neuroepithelium including cells of the dorsal midline of the neural tube. This expression pattern persisted throughout the embryonic time span studied. At E11.5, expression of Hox-7 became obvious in the neuroepithelium of the forming tela choroida and the telencephelii in areas destined to form the choroid plexus before any atrophy of the neuroepithelium took place. High expression of Hox-7 was also present in the mesenchyme cells invading the pouch formed by the involuting choroid plexus neuroepithelium. A second major site where Hox-7 was expressed was the anlage of the anterior pituitary; the Rathke's pouch. Expression became obvious at E10.5 throughout the pouch but by E12.5 became more regionalised in areas of the pouch destined to form the pars distalis. Hox-7 was also expressed in the forming meninges and skull bone precursors from E10.5 onwards. Expression of the Hox-7 gene is also seen in the external ear, the forming eye, the nasal pits and forming Jacobson's organs. When these expression patterns are considered together with characterised human and mouse retinoic acid embryopathies and the congenital malformations seen in human children associated with deletion of chromosome 4p16.1 (Wolf-Hirschhorn syndrome), Hox-7 may be a good candidate as one of the genes involved in the initiation of the choroid plexus phenotype and its subsequent formation, the formation of the outer ear, formation of the dentition and the differentiation of the cell types of the anterior pituitary. The expression pattern of Hox-7 in the dorsal midline of the neural tube further suggests that it may also be involved in the specification of the dorsal-ventral axis of the developing nervous system.

Calcium and neurulation in mammalian embryos

Development ◽  
1985 ◽  
Vol 89 (1) ◽  
pp. 1-14
Author(s):  
Martin J. Smedley ◽  
Martin Stanisstreet
Keyword(s):  
Neural Tube ◽  
Divalent Cations ◽  
Neural Cells ◽  
Cellular Mechanisms ◽  
Rat Embryos ◽  
Transmission Electron ◽  
Mammalian Embryos ◽  
Neural Ectoderm ◽  
Calcium And Magnesium

The role of calcium in neurulation in rat embryos has been studied. Rat embryos at 10·4 days of gestation, when the cephalic neural folds have elevated but not fused, have been cultured in various media, and the effects of these media on the morphology of the cephalic neural folds have been observed by scanning and transmission electron microscopy. Embryos cultured in serum containing EDTA or EGTA, or in saline without divalent cations exhibit opening, then folding back (‘collapse’) of the cephalic neural folds. The neural cells lose their elongated shape and become rounded. Older embryos in which the cephalic neural folds have already fused do not show collapse of the neural tube. Culture of 10·4-day rat embryos with elevated but unfused cephalic neural folds in calcium- and magnesium-free saline to which either calcium or magnesium has been restored shows that calcium is the divalent cation which is essential for the maintenance of the elevated neural folds. In the presence of calcium, lanthanum, which competes for calcium sites, causes opening but not collapse of the elevated cephalic neural folds. Embryos treated with trypsin show dissociation of the lateral (non-neural) ectoderm but the neural folds remain elevated. If embryos in which the cephalic neural folds have been caused to collapse are further cultured in serum the folds re-elevate, although normal neural tube morphology is not completely regained. The possible implications of these observations to the understanding of the cellular mechanisms of normal neurulation, and of neural tube malformations are discussed.

scholarly journals Notch signaling is a critical initiator of roof plate formation as revealed by the use of RNA profiling of the dorsal neural tube

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Shai Ofek ◽  
Sophie Wiszniak ◽  
Sarah Kagan ◽  
Markus Tondl ◽  
Quenten Schwarz ◽  
...  
Keyword(s):  
Nervous System ◽  
Notch Signaling ◽  
Neural Tube ◽  
Cell Types ◽  
Molecular Heterogeneity ◽  
Specific Cell ◽  
Rna Profiling ◽  
Dorsal Neural Tube ◽  
Roof Plate ◽  
The Central Nervous System

AbstractBackgroundThe dorsal domain of the neural tube is an excellent model to investigate the generation of complexity during embryonic development. It is a highly dynamic and multifaceted region being first transiently populated by prospective neural crest (NC) cells that sequentially emigrate to generate most of the peripheral nervous system. Subsequently, it becomes the definitive roof plate (RP) of the central nervous system. The RP, in turn, constitutes a patterning center for dorsal interneuron development. The factors underlying establishment of the definitive RP and its segregation from NC and dorsal interneurons are currently unknown.ResultsWe performed a transcriptome analysis at trunk levels of quail embryos comparing the dorsal neural tube at premigratory NC and RP stages. This unraveled molecular heterogeneity between NC and RP stages, and within the RP itself. By implementing these genes, we asked whether Notch signaling is involved in RP development. First, we observed that Notch is active at the RP-interneuron interface. Furthermore, gain and loss of Notch function in quail and mouse embryos, respectively, revealed no effect on early NC behavior. Constitutive Notch activation caused a local downregulation of RP markers with a concomitant development of dI1 interneurons, as well as an ectopic upregulation of RP markers in the interneuron domain. Reciprocally, in mice lacking Notch activity, both the RP and dI1 interneurons failed to form and this was associated with expansion of the dI2 population.ConclusionsCollectively, our results offer a new resource for defining specific cell types, and provide evidence that Notch is required to establish the definitive RP, and to determine the choice between RP and interneuron fates, but not the segregation of RP from NC.

A role for SOX1 in neural determination

Development ◽  
1998 ◽  
Vol 125 (10) ◽  
pp. 1967-1978 ◽  
Author(s):  
L.H. Pevny ◽  
S. Sockanathan ◽  
M. Placzek ◽  
R. Lovell-Badge
Keyword(s):  
Nervous System ◽  
Cell Types ◽  
Cell System ◽  
Specific Gene ◽  
Neural Fate ◽  
Brdu Labeling ◽  
Neural Ectoderm ◽  
Temporal And Spatial ◽  
Vitro Model

In vertebrates, the delineation of the neural plate from a region of the primitive ectoderm is accompanied by the onset of specific gene expression which in turn promotes the formation of the nervous system. Here we show that SOX1, an HMG-box protein related to SRY, is one of the earliest transcription factors to be expressed in ectodermal cells committed to the neural fate: the onset of expression of SOX1 appears to coincide with the induction of neural ectoderm. We demonstrate a role for SOX1 in neural determination and differentiation using an inducible expression P19 cell system as an in vitro model of neurogenesis. Misexpression of SOX1 can substitute for the requirement of retinoic acid to impart neural fate to competent ectodermal P19 cells. Using a series of antigenic markers which identify early neural cell types in combination with BrdU labeling, we demonstrate a temporal and spatial correlation between the differentiation of cell types along the dorsoventral axis of the neural tube and the downregulation of SOX1 expression. SOX1, therefore, defines the dividing neural precursors of the embryonic central nervous system (CNS).

scholarly journals Cell group analysis reveals changes in upper-layer neurons associated with schizophrenia

2020 ◽  
Author(s):  
Rujia Dai ◽  
Lulu Chen ◽  
Sihan Liu ◽  
Yu Chen ◽  
Yi Jiang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Association Studies ◽  
Group Analysis ◽  
Cell Types ◽  
Cell Group ◽  
Specific Gene ◽  
Genome Wide Association Studies ◽  
Cell Type ◽  
Dorsolateral Prefrontal ◽  
Cell Groups

AbstractGenome-wide association studies (GWAS) of schizophrenia (SCZ) have revealed over 100 risk loci. We investigated whether these SCZ-associated variants regulate gene expression by cell type. Using a fully unsupervised deconvolution method, we calculated gene expression by clusters of estimated cell types (cell-groups, CGs). Five CGs emerged in the dorsolateral prefrontal cortices (DLPFC) of 341 donors with and without SCZ. By mapping expression quantitative trait loci (eQTL) per CG, we partitioned the CG-specific heritability of SCZ risk in GWAS. CG-specific expressions and eQTLs were replicated in another independent deconvoluted bulk tissue data and single-cell expression data. Further, we characterized CG-specific gene differential expression and cell proportion changes in SCZ brains. We found upper-layer neurons in the DLPFC to be associated with SCZ based on enrichment of risk heritability in eQTLs, disease-related transcriptional signatures and cell type disproportion. Our study suggests that neurons and related anomalous circuits in upper layers of the DLPFC may have a major contribution to SCZ risk.

Autoregulation and multiple enhancers control Math1 expression in the developing nervous system

Development ◽  
2000 ◽  
Vol 127 (6) ◽  
pp. 1185-1196 ◽  
Author(s):  
A.W. Helms ◽  
A.L. Abney ◽  
N. Ben-Arie ◽  
H.Y. Zoghbi ◽  
J.E. Johnson
Keyword(s):  
Nervous System ◽  
Transgenic Mice ◽  
Neural Tube ◽  
Hair Cells ◽  
Neuronal Cell ◽  
Cell Types ◽  
Regulatory Elements ◽  
Coding Region ◽  
Consensus Binding Site ◽  
Auditory Systems

Development of the vertebrate nervous system requires the actions of transcription factors that establish regional domains of gene expression, which results in the generation of diverse neuronal cell types. MATH1, a transcription factor of the bHLH class, is expressed during development of the nervous system in multiple neuronal domains, including the dorsal neural tube, the EGL of the cerebellum and the hair cells of the vestibular and auditory systems. MATH1 is essential for proper development of the granular layer of the cerebellum and the hair cells of the cochlear and vestibular systems, as shown in mice carrying a targeted disruption of Math1. Previously, we showed that 21 kb of sequence flanking the Math1-coding region is sufficient for Math1 expression in transgenic mice. Here we identify two discrete sequences within the 21 kb region that are conserved between mouse and human, and are sufficient for driving a lacZ reporter gene in these domains of Math1 expression in transgenic mice. The two identified enhancers, while dissimilar in sequence, appear to have redundant activities in the different Math1 expression domains except the spinal neural tube. The regulatory mechanisms for each of the diverse Math1 expression domains are tightly linked, as separable regulatory elements for any given domain of Math1 expression were not found, suggesting that a common regulatory mechanism controls these apparently unrelated domains of expression. In addition, we demonstrate a role for autoregulation in controlling the activity of the Math1 enhancer, through an essential E-box consensus binding site.

The nervous system of amphioxus: structure, development, and evolutionary significance

2005 ◽  
Vol 83 (1) ◽  
pp. 122-150 ◽  
Author(s):  
Helmut Wicht ◽  
Thurston C Lacalli
Keyword(s):  
Nervous System ◽  
Neural Development ◽  
Nerve Cord ◽  
Cell Types ◽  
Evolutionary Significance ◽  
Young Larva ◽  
Vertebrate Brain ◽  
Cell Groups ◽  
Electron Microscopical ◽  
Developing Neurons

Amphioxus neuroanatomy is important not just in its own right but also for the insights it provides regarding the evolutionary origin and basic organization of the vertebrate nervous system. This review summarizes the overall layout of the central nervous system (CNS), peripheral nerves, and nerve plexuses in amphioxus, and what is currently known of their histology and cell types, with special attention to new information on the anterior nerve cord. The intercalated region (IR) is of special functional and evolutionary interest. It extends caudally to the end of somite 4, traditionally considered the limit of the brain-like region of the amphioxus CNS, and is notable for the presence of a number of migrated cell groups. Unlike most other neurons in the cord, these migrated cells detach from the ventricular lumen and move into the adjacent neuropile, much as developing neurons do in vertebrates. The larval nervous system is also considered, as there is a wealth of new data on the organization and cell types of the anterior nerve cord in young larvae, based on detailed electron microscopical analyses and nerve tracing studies, and an emerging consensus regarding how this region relates to the vertebrate brain. Much less is known about the intervening period of the life history, i.e., the period between the young larva and the adult, but a great deal of neural development must occur during this time to generate a fully mature nervous system. It is especially interesting that the vertebrate counterparts of at least some postembryonic events of amphioxus neurogenesis occur, in vertebrates, in the embryo. The implication is that the whole of the postembryonic phase of neural development in amphioxus needs to be considered when making phylogenetic comparisons. Yet this is a period about which almost nothing is known. Considering this, plus the number of new molecular and immunocytochemical techniques now available to researchers, there is no shortage of worthwhile research topics using amphioxus, of whatever stage, as a subject.

Sign in / Sign up

Export Citation Format

Share Document