Expression of a lacZ transgene reveals floor plate cell morphology and macromolecular transfer to commissural axons

Development ◽  
1993 ◽  
Vol 119 (4) ◽  
pp. 1217-1228 ◽  
Author(s):  
R.M. Campbell ◽  
A.C. Peterson
Keyword(s):  
Neural Tube ◽  
Neuronal Cell ◽  
Floor Plate ◽  
Ventral Midline ◽  
Ample Evidence ◽  
Commissural Axons ◽  
Neuronal Cell Bodies ◽  
Lateral Branches ◽  
And Function ◽  
Beta Galactosidase

The floor plate is situated at the ventral midline of the neural tube and is an important intermediate target for commissural axons. During elongation, these axons converge bilaterally on the ventral midline neural tube and after crossing the floor plate make an abrupt rostral turn. Ample evidence indicates that the initial projection of commissural axons to the floor plate is guided by a chemotropic factor secreted by floor plate cells. However, the way in which the subsequent interaction of these axons with the floor plate leads them to make further trajectory changes remains undefined. In an effort to gain further understanding of the structure and function of floor plate cells, we have taken advantage of a line of transgenic mice in which these cells express beta-galactosidase and thus can be stained by histochemical means. In this line, a genomic imprinting mechanism restricts the expression of the lacZ transgene to only a proportion of the floor plate cells, allowing their morphology to be appreciated with particular clarity. Our analysis revealed that the basal processes of floor plate cells are flattened in their rostrocaudal dimension and possess fine lateral branches which are aligned with commissural axons. Unexpectedly, beta-galactosidase activity was also detected within longer transverse linear profiles traversing the floor plate whose ultrastructural appearance was not that of floor plate cells but instead corresponded to that of commissural axons. Enzyme activity was not detected in more proximal axonal segments or in the neuronal cell bodies from which these axons originated. Therefore, we propose that the transgene product, and potentially other proteins synthesized by floor plate cells, can be transferred to decussating axons.

scholarly journals Notochord grafts do not suppress formation of neural crest cells or commissural neurons

Development ◽  
1992 ◽  
Vol 116 (4) ◽  
pp. 877-886 ◽  
Author(s):  
K.B. Artinger ◽  
M. Bronner-Fraser
Keyword(s):  
Neural Crest ◽  
Dorsal Root Ganglia ◽  
Motor Neurons ◽  
Neural Tube ◽  
Dorsal Root ◽  
Neuronal Cell ◽  
Neural Crest Cells ◽  
Floor Plate ◽  
Commissural Neurons ◽  
Neuronal Cell Bodies

Grafting experiments previously have established that the notochord affects dorsoventral polarity of the neural tube by inducing the formation of ventral structures such as motor neurons and the floor plate. Here, we examine if the notochord inhibits formation of dorsal structures by grafting a notochord within or adjacent to the dorsal neural tube prior to or shortly after tube closure. In all cases, neural crest cells emigrated from the neural tube adjacent to the ectopic notochord. When analyzed at stages after ganglion formation, the dorsal root ganglia appeared reduced in size and shifted in position in embryos receiving grafts. Another dorsal cell type, commissural neurons, identified by CRABP and neurofilament immunoreactivity, differentiated in the vicinity of the ectopic notochord. Numerous neuronal cell bodies and axonal processes were observed within the induced, but not endogenous, floor plate 1 to 2 days after implantation but appeared to be cleared with time. These results suggest that dorsally implanted notochords cannot prevent the formation of neural crest cells or commissural neurons, but can alter the size and position of neural crest-derived dorsal root ganglia.

Direct action of the nodal-related signal cyclops in induction of sonic hedgehog in the ventral midline of the CNS

Development ◽  
2000 ◽  
Vol 127 (18) ◽  
pp. 3889-3897 ◽  
Author(s):  
F. Muller ◽  
S. Albert ◽  
P. Blader ◽  
N. Fischer ◽  
M. Hallonet ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Neural Tube ◽  
Direct Action ◽  
Brain Regions ◽  
Floor Plate ◽  
Ventral Midline ◽  
Signal Transducers ◽  
Step Model ◽  
Ventral Neural Tube ◽  
Differential Responsiveness

The secreted molecule Sonic hedgehog (Shh) is crucial for floor plate and ventral brain development in amniote embryos. In zebrafish, mutations in cyclops (cyc), a gene that encodes a distinct signal related to the TGF(beta) family member Nodal, result in neural tube defects similar to those of shh null mice. cyc mutant embryos display cyclopia and lack floor plate and ventral brain regions, suggesting a role for Cyc in specification of these structures. cyc mutants express shh in the notochord but lack expression of shh in the ventral brain. Here we show that Cyc signalling can act directly on shh expression in neural tissue. Modulation of the Cyc signalling pathway by constitutive activation or inhibition of Smad2 leads to altered shh expression in zebrafish embryos. Ectopic activation of the shh promoter occurs in response to expression of Cyc signal transducers in the chick neural tube. Furthermore an enhancer of the shh gene, which controls ventral neural tube expression, is responsive to Cyc signal transducers. Our data imply that the Nodal related signal Cyc induces shh expression in the ventral neural tube. Based on the differential responsiveness of shh and other neural tube specific genes to Hedgehog and Cyc signalling, a two-step model for the establishment of the ventral midline of the CNS is proposed.

scholarly journals Netrin-1 Derived from the Ventricular Zone, but not the Floor Plate, Directs Hindbrain Commissural Axons to the Ventral Midline

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Kenta Yamauchi ◽  
Maya Yamazaki ◽  
Manabu Abe ◽  
Kenji Sakimura ◽  
Heiko Lickert ◽  
...  
Keyword(s):  
Ventricular Zone ◽  
Floor Plate ◽  
Ventral Midline ◽  
Commissural Axons

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.

Ventral midline cells are required for the local control of commissural axon guidance in the mouse spinal cord

Development ◽  
1999 ◽  
Vol 126 (16) ◽  
pp. 3649-3659
Author(s):  
M.P. Matise ◽  
M. Lustig ◽  
T. Sakurai ◽  
M. Grumet ◽  
A.L. Joyner
Keyword(s):  
Spinal Cord ◽  
Critical Role ◽  
Floor Plate ◽  
Posterior Commissure ◽  
Ventral Midline ◽  
Mouse Spinal Cord ◽  
Commissural Axons ◽  
Midline Cells

Specialized cells at the midline of the central nervous system have been implicated in controlling axon projections in both invertebrates and vertebrates. To address the requirement for ventral midline cells in providing cues to commissural axons in mice, we have analyzed Gli2 mouse mutants, which lack specifically the floor plate and immediately adjacent interneurons. We show that a Dbx1 enhancer drives tau-lacZ expression in a subpopulation of commissural axons and, using a reporter line generated from this construct, as well as DiI tracing, we find that commissural axons projected to the ventral midline in Gli2(−/−) embryos. Netrin1 mRNA expression was detected in Gli2(−/−) embryos and, although much weaker than in wild-type embryos, was found in a dorsally decreasing gradient. This result demonstrates that while the floor plate can serve as a source of long-range cues for C-axons in vitro, it is not required in vivo for the guidance of commissural axons to the ventral midline in the mouse spinal cord. After reaching the ventral midline, most commissural axons remained clustered in Gli2(−/−) embryos, although some were able to extend longitudinally. Interestingly, some of the longitudinally projecting axons in Gli2(−/−) embryos extended caudally and others rostrally at the ventral midline, in contrast to normal embryos in which virtually all commissural axons turn rostrally after crossing the midline. This finding indicates a critical role for ventral midline cells in regulating the rostral polarity choice made by commissural axons after they cross the midline. In addition, we provide evidence that interactions between commissural axons and floor plate cells are required to modulate the localization of Nr-CAM and TAG-1 proteins on axons at the midline. Finally, we show that the floor plate is not required for the early trajectory of motoneurons or axons of the posterior commissure, whose projections are directed away from the ventral midline in both WT and Gli2(−/−) embryos, although they are less well organized in Gli2(−/−)mutants.

Perturbation of neuronal differentiation and axon guidance in the spinal cord of mouse embryos lacking a floor plate: analysis of Danforth's short-tail mutation

Development ◽  
1991 ◽  
Vol 113 (2) ◽  
pp. 625-639 ◽  
Author(s):  
P. Bovolenta ◽  
J. Dodd
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Motor Neurons ◽  
Cell Types ◽  
Floor Plate ◽  
Ventral Midline ◽  
Cellular Targets ◽  
Commissural Axons ◽  
Short Tail ◽  
Plate Analysis

The floor plate of the vertebrate nervous system has been implicated in the guidance of commissural axons at the ventral midline. Experiments in chick have also suggested that at earlier stages of development the floor plate induces the differentiation of motor neurons and other neurons of the ventral spinal cord. Here we have examined the development of the spinal cord in a mouse mutant, Danforth's short-tail, in which the floor plate is absent from caudal regions of the neuraxis. In affected regions of the spinal cord, commissural axons exhibited aberrant projection patterns as they reached and crossed the ventral midline. In addition, motor neurons were absent or markedly reduced in number in regions of the spinal cord lacking a floor plate. Our results suggest that the floor plate is indeed an intermediate target in the projection of commissural axons and support the idea that several different mechanisms operate in concert in the guidance of axons to their cellular targets in the developing nervous system. In addition, these experiments suggest that the mechanisms that govern the differentiation of the floor plate and other ventral cell types in the neural tube are common to mammals and lower vertebrates.

scholarly journals Restraint of presynaptic protein levels by Wnd/DLK signaling mediates synaptic defects associated with the kinesin-3 motor Unc-104

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Jiaxing Li ◽  
Yao V Zhang ◽  
Elham Asghari Adib ◽  
Doychin T Stanchev ◽  
Xin Xiong ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Neuronal Cell ◽  
Synaptic Proteins ◽  
Transport Capacity ◽  
Protein Levels ◽  
Synaptic Structure ◽  
Neuronal Cell Bodies ◽  
And Function ◽  
Presynaptic Protein ◽  
Adaptive Role

The kinesin-3 family member Unc-104/KIF1A is required for axonal transport of many presynaptic components to synapses, and mutation of this gene results in synaptic dysfunction in mice, flies and worms. Our studies at the Drosophila neuromuscular junction indicate that many synaptic defects in unc-104-null mutants are mediated independently of Unc-104’s transport function, via the Wallenda (Wnd)/DLK MAP kinase axonal damage signaling pathway. Wnd signaling becomes activated when Unc-104’s function is disrupted, and leads to impairment of synaptic structure and function by restraining the expression level of active zone (AZ) and synaptic vesicle (SV) components. This action concomitantly suppresses the buildup of synaptic proteins in neuronal cell bodies, hence may play an adaptive role to stresses that impair axonal transport. Wnd signaling also becomes activated when pre-synaptic proteins are over-expressed, suggesting the existence of a feedback circuit to match synaptic protein levels to the transport capacity of the axon.

scholarly journals Neurotensin Attenuates Nociception by Facilitating Inhibitory Synaptic Transmission in the Mouse Spinal Cord

2021 ◽  
Vol 15 ◽  
Author(s):  
Ming-Ming Zhang ◽  
Yu-Peng Feng ◽  
Xin-Tong Qiu ◽  
Tao Chen ◽  
Yang Bai ◽  
...  
Keyword(s):  
Synaptic Transmission ◽  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Intrathecal Injection ◽  
Neuronal Cell ◽  
Histochemical Staining ◽  
Inhibitory Synaptic Transmission ◽  
Spinal Dorsal ◽  
Neuronal Cell Bodies ◽  
And Function

Neurotensin (NT) is an endogenous tridecapeptide in the central nervous system. NT-containing neurons and NT receptors are widely distributed in the spinal dorsal horn (SDH), indicating their possible modulatory roles in nociception processing. However, the exact distribution and function of NT, as well as NT receptors (NTRs) expression in the SDH, have not been well documented. Among the four NTR subtypes, NTR2 is predominantly involved in central analgesia according to previous reports. However, the expression and function of NTR2 in the SDH has not yet been directly elucidated. Specifically, it remains unclear how NT-NTR2 interactions contribute to NT-mediated analgesia. In the present study, by using immunofluorescent histochemical staining and immunohistochemical staining with in situ hybridization histochemical staining, we found that dense NT- immunoreactivity (NT-ir) and moderate NTR2-ir neuronal cell bodies and fibers were localized throughout the superficial laminae (laminae I-II) of the SDH at the light microscopic level. In addition, γ-aminobutyric acid (GABA) and NTR2 mRNA were colocalized in some neuronal cell bodies, predominantly in lamina II. Using confocal and electron microscopy, we also observed that NT-ir terminals made both close contacts and asymmetrical synapses with the local GABA-ir neurons. Second, electrophysiological recordings showed that NT facilitated inhibitory synaptic transmission but not glutamatergic excitatory synaptic transmission. Inactivation of NTR2 abolished the NT actions on both GABAergic and glycinergic synaptic release. Moreover, a behavioral study revealed that intrathecal injection of NT attenuated thermal pain, mechanical pain, and formalin induced acute inflammatory pain primarily by activating NTR2. Taken together, the present results provide direct evidence that NT-containing terminals and fibers, as well as NTR2-expressing neurons are widely distributed in the spinal dorsal horn, GABA-containing neurons express NTR2 mainly in lamina II, GABA coexists with NTR2 mainly in lamina II, and NT may directly increase the activity of local inhibitory neurons through NTR2 and induce analgesic effects.

The Red Neuronal Pigment in the Nervous System of the Mussel, Mytilus Edulis: Localization and Its Effect on Lateral Ciliary Activity with Spectral and Analytical Changes

1981 ◽  
Vol 39 ◽  
pp. 494-495
Author(s):  
Anthony A. Paparo ◽  
Judith A. Murphy
Keyword(s):  
Nervous System ◽  
Mytilus Edulis ◽  
Neuronal Cell ◽  
Ciliary Activity ◽  
Neuronal Cell Bodies ◽  
The Central Nervous System ◽  
Intracellular Organelles ◽  
The Common ◽  
The Individual ◽  
Cryostat Sections

The purpose of this study was to localize the red neuronal pigment in Mytilus edulis and examine its role in the control of lateral ciliary activity in the gill. The visceral ganglia (Vg) in the central nervous system show an over al red pigmentation. Most red pigments examined in squash preps and cryostat sec tions were localized in the neuronal cell bodies and proximal axon regions. Unstained cryostat sections showed highly localized patches of this pigment scattered throughout the cells in the form of dense granular masses about 5-7 um in diameter, with the individual granules ranging from 0.6-1.3 um in diame ter. Tissue stained with Gomori's method for Fe showed bright blue granular masses of about the same size and structure as previously seen in unstained cryostat sections.Thick section microanalysis (Fig.l) confirmed both the localization and presence of Fe in the nerve cell. These nerve cells of the Vg share with other pigmented photosensitive cells the common cytostructural feature of localization of absorbing molecules in intracellular organelles where they are tightly ordered in fine substructures.

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