Identification of early developing axon projections from spinal interneurons in the chick embryo with a neuron specific beta-tubulin antibody: evidence for a new ‘pioneer’ pathway in the spinal cord

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 705-716 ◽  
Author(s):  
H. Yaginuma ◽  
T. Shiga ◽  
S. Homma ◽  
R. Ishihara ◽  
R.W. Oppenheim
Keyword(s):  
Spinal Cord ◽  
Chick Embryo ◽  
Neural Tube ◽  
Floor Plate ◽  
C Cells ◽  
Beta Tubulin ◽  
Cell Groups ◽  
Neuronal Processes ◽  
Longitudinal Association ◽  
Chick Spinal Cord

The early development of interneurons in the chick embryo spinal cord was studied using a monoclonal antibody against a neuron-specific beta-tubulin isoform. Early developing interneurons were divided into two cell groups on the basis of their location and the pattern of growth of their axons. One group is composed of cells that establish a primitive longitudinal pathway (PL-cells), whereas the other group contains cells constituting a circumferential pathway (C-cells). The onset of axonal development in both cell groups occurs at stage (st.) 15 (embryonic day, (E), 2) in the branchial segments, which is prior to axonogenesis of motoneurons. PL-cells develop in the region between the floor plate and the motoneuron nucleus. Their axons are the first neuronal processes (‘pioneer axons’) to arrive in the ventrolateral marginal zone and they project both rostrally and caudally to establish a primitive longitudinal association pathway at the ventrolateral surface of the neural tube. This pathway is formed before axons of C-cells arrive in the ventrolateral region. The first C-cells are initially located in the most dorsal portion of the neural tube, whereas later appearing C-cells are also located in both intermediate and ventral regions of the neural tube. The axons of C-cells project ventrally, without fasciculating, along the lateral border of the neural tube. Some of their axons enter the ipsilateral ventrolateral longitudinal pathway at st. 17. We often observed apparent contacts and interactions between preexisting axons of PL-cells and newly arriving axons of C-cells. The axons of commissural C-cells first enter the floor plate at st. 17 and cross the midline at st. 18. Axons of C cells begin to join the contralateral ventrolateral longitudinal pathway at st. 18+ to st. 19. In the floor plate region, contacts between growth cones and axons were often observed. However, axons in the floor plate at these stages were not fasciculated. These observations establish the timing and pattern of growth of axons from two specific populations of early developing interneurons in the chick spinal cord. Additionally, we have identified an early and apparently previously undescribed ‘pioneer’ pathway that constitutes the first longitudinal pathway in the chick spinal cord.

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.

scholarly journals Signals from the notochord and floor plate regulate the region-specific expression of two Pax genes in the developing spinal cord

Development ◽  
1993 ◽  
Vol 117 (3) ◽  
pp. 1001-1016 ◽  
Author(s):  
M.D. Goulding ◽  
A. Lumsden ◽  
P. Gruss
Keyword(s):  
Gene Expression ◽  
Spinal Cord ◽  
Neural Tube ◽  
Neural Progenitor Cells ◽  
Expression Patterns ◽  
Primitive Streak ◽  
Floor Plate ◽  
Neural Patterning ◽  
Specific Expression ◽  
Early Effect

Members of the paired box (Pax) gene family are expressed in discrete regions of the developing central nervous system, suggesting a role in neural patterning. In this study, we describe the isolation of the chicken homologues of Pax-3 and Pax-6. Both genes are very highly conserved and share extensive homology with the mouse Pax-3 and Pax-6 genes. Pax-3 is expressed in the primitive streak and in two bands of cells at the lateral extremity of the neural plate. In the spinal cord, Pax-6 is expressed later than Pax-3 with the first detectable expression preceding closure of the neural tube. When the neural tube closes, transcripts of both genes become dorsoventrally restricted in the undifferentiated mitotic neuroepithelium. We show that the removal of the notochord, or implantation of an additional notochord, dramatically alter the dorsoventral (DV) expression patterns of Pax-3 and Pax-6. These manipulations suggest that signals from the notochord and floor plate regulate the establishment of the dorsoventrally restricted expression domains of Pax-3 and Pax-6 in the spinal cord. The rapid changes to Pax gene expression that occur in neural progenitor cells following the grafting of an ectopic notochord suggest that changes to Pax gene expression are an early effect of the notochord on spinal cord patterning.

The role of retinoid-binding proteins in the generation of pattern in the developing limb, the regenerating limb and the nervous system

Development ◽  
1989 ◽  
Vol 107 (Supplement) ◽  
pp. 109-119 ◽  
Author(s):  
M. Maden ◽  
D. E. Ong ◽  
D. Summerbell ◽  
F. Chytil
Keyword(s):  
Nervous System ◽  
Retinoic Acid ◽  
Chick Embryo ◽  
Neural Tube ◽  
Floor Plate ◽  
Limb Bud ◽  
Commissural Axons ◽  
New Information ◽  
Mantle Layer ◽  
Developing Nervous System

We summarise existing data and describe new information on the levels and distribution of cellular retinoic acid-binding protein (CRABP) and cellular retinolbinding protein (CRBP) in the regenerating axolotl limb, the developing chick limb bud and the nervous system of the chick embryo in the light of the known morphogenetic effects of retinoids on these systems. In the regenerating limb, levels of CRABP rise 3- to 4-fold during regeneration, peaking at the time when retinoic acid (RA) is most effective at causing pattern duplications. The levels of CRBP are low. The potency of various retinoids in causing pattern respecification correlates well with the ability of these compounds to bind to CRABP. In the chick limb bud, the levels of CRABP are high and the levels of CRBP are low. Again the binding of various retinoids to CRABP correlates well with their ability to cause pattern duplications. By immunocytochemistry, we show that CRABP is present at high levels in the progress zone of the limb bud and is distributed across the anteroposterior axis in a gradient with the high point at the anterior margin. In the chick embryo, CRABP levels are high and CRBP levels are low. By immunocytochemistry, CRABP is localised primarily to the developing nervous system, labelling cells and axons in the mantle layer of the neural tube. These become the neurons of the commissural system. Also sensory axons label intensely with CRABP whereas motor axons do not and in the mixed nerves at the brachial plexus sensory and motor components can be distinguished on this basis. In the neural tube, CRBP only stains the ventral floor plate. Since the ventral floor plate may be a source of chemoattractant for commissural axons, we suggest on the basis of these staining patterns that RA may fulfill this role and thus be involved morphogenetically in the developing nervous system.

Distribution of glycogen in the floor plate of the chick spinal cord during development

1984 ◽  
Vol 209 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Masato Uehara ◽  
Toshihiko Ueshima
Keyword(s):  
Spinal Cord ◽  
Floor Plate ◽  
Chick Spinal Cord

Effect of the notochord on the differentiation of a floor plate area in the neural tube of the chick embryo

1988 ◽  
Vol 177 (4) ◽  
pp. 317-324 ◽  
Author(s):  
H. W. M. Straaten ◽  
J. W. M. Hekking ◽  
E. J. L. M. Wiertz-Hoessels ◽  
F. Thors ◽  
J. Drukker
Keyword(s):  
Chick Embryo ◽  
Neural Tube ◽  
Floor Plate ◽  
Plate Area

scholarly journals Segmental lineage restrictions in the chick embryo spinal cord depend on the adjacent somites

Development ◽  
1991 ◽  
Vol 113 (1) ◽  
pp. 239-244 ◽  
Author(s):  
C.D. Stern ◽  
K.F. Jaques ◽  
T.M. Lim ◽  
S.E. Fraser ◽  
R.J. Keynes
Keyword(s):  
Spinal Cord ◽  
Chick Embryo ◽  
Single Cell ◽  
Neural Tube ◽  
Fluorescent Tracer ◽  
Anteroposterior Axis ◽  
Somite Formation ◽  
Developing Spinal Cord

We have investigated whether the developing spinal cord is intrinsically segmented in its rostrocaudal (anteroposterior) axis by mapping the spread of clones derived from single labelled cells within the neural tube of the chick embryo. A single cell in the ventrolateral neural tube of the trunk was marked in situ with the fluorescent tracer lysinated rhodamine dextran (LRD) and its descendants located after two days of further incubation. We find that clones derived from cells labelled before overt segmentation of the adjacent mesoderm do not respect any boundaries within the neural tube. Those derived from cells marked after mesodermal segmentation, however, never cross an invisible boundary aligned with the middle of each somite, and tend to be elongated along the mediolateral axis of the neural tube. When the somite pattern is surgically disturbed, neighbouring clones derived from neuroectodermal cells labelled after somite formation behave like clones derived from younger cells: they no longer respect any boundaries, and are not elongated mediolaterally. These results indicate that periodic lineage restrictions do exist in the developing spinal cord of the chick embryo, but their maintenance requires the presence of the adjacent somite mesoderm.

Regional differences in retinoid release from embryonic neural tissue detected by an in vitro reporter assay

Development ◽  
1992 ◽  
Vol 116 (1) ◽  
pp. 55-66 ◽  
Author(s):  
M. Wagner ◽  
B. Han ◽  
T.M. Jessell
Keyword(s):  
Spinal Cord ◽  
Retinoic Acid ◽  
Neural Tube ◽  
Neural Tissue ◽  
Floor Plate ◽  
Luciferase Reporter ◽  
Reporter Assay ◽  
Embryonic Tissues ◽  
Low Concentrations

Retinoic acid and related retinoids have been suggested to contribute to the pattern of cell differentiation during vertebrate embryonic development. To identify cell groups that release morphogenetically active retinoids, we have developed a reporter assay that makes use of a retinoic acid inducible response element (RARE) to drive lacZ or luciferase reporter genes in stably transfected cell lines. This reporter gene assay allows detection of retinoids released from embryonic tissues over a range equivalent to that induced by femtomole amounts of retinoic acid. We have used this assay first to determine whether the floor plate, a cell group that has polarizing properties in neural tube and limb bud differentiation, is a local source of retinoids within the spinal cord. We have also examined whether the effects of exogenously administered retinoic acid on anteroposterior patterning of cells in the developing central nervous system correlate with differences in retinoid release from anterior and posterior neural tissue. We find that the release of morphogenetically active retinoids from the floor plate is only about 1.5-fold that of the dorsal spinal cord, which does not have neural tube or limb polarizing activity. These results suggest that the spatial distribution of retinoid release from spinal cord tissues differs from that of the neural and limb polarizing activity. This assay has also shown that retinoids are released from the embryonic spinal cord at much greater levels than from the forebrain. This result, together with previous observations that the development of forebrain structures is suppressed by low concentrations of retinoic acid, suggest that the normal development of forebrain structures is dependent on the maintenance of low concentrations of retinoids in anterior regions of the embryonic axis. This assay has also provided initial evidence that other embryonic tissues with polarizing properties in vivo release retinoids in vitro.

Anti-apoptotic role of Sonic hedgehog protein at the early stages of nervous system organogenesis

Development ◽  
2001 ◽  
Vol 128 (20) ◽  
pp. 4011-4020 ◽  
Author(s):  
Jean-Baptiste Charrier ◽  
Françoise Lapointe ◽  
Nicole M. Le Douarin ◽  
Marie-Aimée Teillet
Keyword(s):  
Cell Death ◽  
Nervous System ◽  
Chick Embryo ◽  
Sonic Hedgehog ◽  
Neural Tube ◽  
Primitive Streak ◽  
Embryo Cell ◽  
Floor Plate ◽  
Cell Death Program ◽  
Midline Cells

In vertebrates the neural tube, like most of the embryonic organs, shows discreet areas of programmed cell death at several stages during development. In the chick embryo, cell death is dramatically increased in the developing nervous system and other tissues when the midline cells, notochord and floor plate, are prevented from forming by excision of the axial-paraxial hinge (APH), i.e. caudal Hensen’s node and rostral primitive streak, at the 6-somite stage (Charrier, J. B., Teillet, M.-A., Lapointe, F. and Le Douarin, N. M. (1999). Development126, 4771-4783). In this paper we demonstrate that one day after APH excision, when dramatic apoptosis is already present in the neural tube, the latter can be rescued from death by grafting a notochord or a floor plate fragment in its vicinity. The neural tube can also be recovered by transplanting it into a stage-matched chick embryo having one of these structures. In addition, cells engineered to produce Sonic hedgehog protein (SHH) can mimic the effect of the notochord and floor plate cells in in situ grafts and transplantation experiments. SHH can thus counteract a built-in cell death program and thereby contribute to organ morphogenesis, in particular in the central nervous system.

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