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.

scholarly journals Zika Virus Infection Leads to Demyelination and Axonal Injury in Mature CNS Cultures

Viruses ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 91
Author(s):  
Verena Schultz ◽  
Stephanie L. Cumberworth ◽  
Quan Gu ◽  
Natasha Johnson ◽  
Claire L. Donald ◽  
...  
Keyword(s):  
Nervous System ◽  
Neural Development ◽  
Zika Virus ◽  
Developmental Stages ◽  
Cell Types ◽  
Neural Cells ◽  
Zikv Infection ◽  
Axonal Pathology ◽  
Time Frames

Understanding how Zika virus (Flaviviridae; ZIKV) affects neural cells is paramount in comprehending pathologies associated with infection. Whilst the effects of ZIKV in neural development are well documented, impact on the adult nervous system remains obscure. Here, we investigated the effects of ZIKV infection in established mature myelinated central nervous system (CNS) cultures. Infection incurred damage to myelinated fibers, with ZIKV-positive cells appearing when myelin damage was first detected as well as axonal pathology, suggesting the latter was a consequence of oligodendroglia infection. Transcriptome analysis revealed host factors that were upregulated during ZIKV infection. One such factor, CCL5, was validated in vitro as inhibiting myelination. Transferred UV-inactivated media from infected cultures did not damage myelin and axons, suggesting that viral replication is necessary to induce the observed effects. These data show that ZIKV infection affects CNS cells even after myelination—which is critical for saltatory conduction and neuronal function—has taken place. Understanding the targets of this virus across developmental stages including the mature CNS, and the subsequent effects of infection of cell types, is necessary to understand effective time frames for therapeutic intervention.

scholarly journals Brain-Derived Neurotrophic Factor in Central Nervous System Myelination: A New Mechanism to Promote Myelin Plasticity and Repair

2018 ◽  
Vol 19 (12) ◽  
pp. 4131 ◽  
Author(s):  
Jessica Fletcher ◽  
Simon Murray ◽  
Junhua Xiao
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Neural Development ◽  
Neurotrophic Factor ◽  
Molecular Mechanisms ◽  
Demyelinating Disease ◽  
Cell Types ◽  
Brain Derived Neurotrophic Factor ◽  
Future Research ◽  
Health And Disease

Brain-derived neurotrophic factor (BDNF) plays vitally important roles in neural development and plasticity in both health and disease. Recent studies using mutant mice to selectively manipulate BDNF signalling in desired cell types, in combination with animal models of demyelinating disease, have demonstrated that BDNF not only potentiates normal central nervous system myelination in development but enhances recovery after myelin injury. However, the precise mechanisms by which BDNF enhances myelination in development and repair are unclear. Here, we review some of the recent progress made in understanding the influence BDNF exerts upon the myelinating process during development and after injury, and discuss the cellular and molecular mechanisms underlying its effects. In doing so, we raise new questions for future research.

bcl-2 protein expression is widespread in the developing nervous system and retained in the adult PNS

Development ◽  
1994 ◽  
Vol 120 (2) ◽  
pp. 301-311 ◽  
Author(s):  
D.E. Merry ◽  
D.J. Veis ◽  
W.F. Hickey ◽  
S.J. Korsmeyer
Keyword(s):  
Cell Death ◽  
Nervous System ◽  
Embryonic Development ◽  
Neural Development ◽  
Granule Cells ◽  
Cell Types ◽  
Cortical Plate ◽  
Neuronal Populations ◽  
Selective Retention ◽  
Developmental Cell Death

Cell death is a common feature of neural development in all vertebrates. The bcl-2 proto-oncogene has been shown to protect a variety of cell types from programmed cell death. We have examined the distribution of bcl-2 protein in the developing and adult nervous systems. bcl-2 protein is widespread during embryonic development. Proliferating neuroepithelial cells of ventricular zones as well as the postmitotic cells of the cortical plate, cerebellum, hippocampus and spinal cord express bcl-2. Postnatally, bcl-2 is principally retained in the granule cells of the cerebellum and dentate gyrus of the hippocampus. bcl-2 expression in the CNS declines with aging. In the peripheral nervous system, neurons and supporting cells of sympathetic and sensory ganglia retain substantial bcl-2 protein throughout life. The widespread expression of bcl-2 in CNS and PNS neurons during embryonic development and its selective retention in the adult PNS is consistent with a role for bcl-2 in regulating neuronal survival. In addition, the expression of bcl-2 in some neuronal populations beyond the recognized period of cell death is suggestive of a role for bcl-2 beyond simply protecting neurons from developmental cell death.

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.

Cadherins in Brain Morphogenesis and Wiring

2012 ◽  
Vol 92 (2) ◽  
pp. 597-634 ◽  
Author(s):  
Shinji Hirano ◽  
Masatoshi Takeichi
Keyword(s):  
Nervous System ◽  
Cell Adhesion ◽  
Cell Polarity ◽  
Neural Development ◽  
Planar Cell Polarity ◽  
The Past ◽  
Vertebrate Brain ◽  
Dependent Cell ◽  
And Function ◽  
Neural Disorders

Cadherins are Ca2+-dependent cell-cell adhesion molecules that play critical roles in animal morphogenesis. Various cadherin-related molecules have also been identified, which show diverse functions, not only for the regulation of cell adhesion but also for that of cell proliferation and planar cell polarity. During the past decade, understanding of the roles of these molecules in the nervous system has significantly progressed. They are important not only for the development of the nervous system but also for its functions and, in turn, for neural disorders. In this review, we discuss the roles of cadherins and related molecules in neural development and function in the vertebrate brain.

scholarly journals The Morphogenic Mapping of the Brain and the Design of the Nervous System

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Peter Sheesley ◽  
Mark McMenamin ◽  
Janusz Kusyk ◽  
Stuart Pivar
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Neural Development ◽  
Vertebral Column ◽  
Simple Algorithm ◽  
Hypothetical Model ◽  
Spinal Nerves ◽  
Vertebrate Brain ◽  
The Brain ◽  
Inside Out

This paper reports the discovery of a geometrical algorithm that provides a coherent step by step mechanical account of the structure of the nervous system, including the vertebrate brain, the spinal cord, the vertebral column, and the spinal nerves. The morphology of these organs and the observed steps of neural development are well described, consequent of centuries of study. But morphogenesis, the origin and cause of these forms, has not been studied since the last half of the nineteenth century. Neurology does not teach how the brain gained its shape, nor have any causative theories of brain formation been published in recent times. This paper proposes a hypothetical construction based on the discovery of a simple algorithm which generates topologically the form of the brain, the spinal cord, and the vertebral column by the deformation of a gridded segmented sphere by the inversion of its surface. The hypothetical model is in close analogy with nature: the blastula is a segmented gridded sphere which results from the subdivision of the egg. The first step of embryogenesis is gastrulation, where blastula is pressed to enter its own interior, pulling the surface inside out, forming the embryo.

LIGHT AND ELECTRON MICROSCOPICAL STUDY OF THE EFFECT OF OESTROGEN ON THE CHICKEN OVIDUCT

1967 ◽  
Vol 56 (3) ◽  
pp. 391-402 ◽  
Author(s):  
H. I. Ljungkvist
Keyword(s):  
Secretory Granules ◽  
Apical Cell ◽  
Cell Types ◽  
Microscopical Study ◽  
List Type ◽  
New Production ◽  
General Increase ◽  
Chicken Oviduct ◽  
Electron Microscopical ◽  
Aortic Perfusion

ABSTRACT Oviducts from 20 one-day old chickens were used. Ten chickens were injected subcutaneously with 0.2 mg oestradiol for 5 days, the remaining ones serving as controls. The chickens were fixed by an aortic perfusion with 2.5% glutaraldehyde in phosphate buffer, pH 7.2. The treatment with oestrogen resulted in the following changes: general increase in oviduct length and thickness, differentiation of the epithelial membrane into three cell types: basal, apical and gland cells, increase in the number of cilia in the apical cell, probably due to a new production of cilia, formation of secretory granules in the vaginal epithelium as seen by light microscopy, formation of proteinlike secretory granules in the apical cell as seen by electron microscopy, increase in protein synthesis, observed as an augmentation of the endoplasmic reticulum.

scholarly journals The role of CPEB family proteins in the nervous system function in the norm and pathology

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eugene Kozlov ◽  
Yulii V. Shidlovskii ◽  
Rudolf Gilmutdinov ◽  
Paul Schedl ◽  
Mariya Zhukova
Keyword(s):  
Nervous System ◽  
Gene Regulation ◽  
Neural Development ◽  
Fragile X ◽  
Autism Spectrum ◽  
Mrna Transport ◽  
Ribonucleoprotein Complexes ◽  
Posttranscriptional Gene Regulation ◽  
Nervous System Function ◽  
Functional Features

AbstractPosttranscriptional gene regulation includes mRNA transport, localization, translation, and regulation of mRNA stability. CPEB (cytoplasmic polyadenylation element binding) family proteins bind to specific sites within the 3′-untranslated region and mediate poly- and deadenylation of transcripts, activating or repressing protein synthesis. As part of ribonucleoprotein complexes, the CPEB proteins participate in mRNA transport and localization to different sub-cellular compartments. The CPEB proteins are evolutionarily conserved and have similar functions in vertebrates and invertebrates. In the nervous system, the CPEB proteins are involved in cell division, neural development, learning, and memory. Here we consider the functional features of these proteins in the nervous system of phylogenetically distant organisms: Drosophila, a well-studied model, and mammals. Disruption of the CPEB proteins functioning is associated with various pathologies, such as autism spectrum disorder and brain cancer. At the same time, CPEB gene regulation can provide for a recovery of the brain function in patients with fragile X syndrome and Huntington's disease, making the CPEB genes promising targets for gene therapy.

scholarly journals Rgs4 is a regulator of mTOR activity required for motoneuron axon outgrowth and neuronal development in zebrafish

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aya Mikdache ◽  
Marie-José Boueid ◽  
Lorijn van der Spek ◽  
Emilie Lesport ◽  
Brigitte Delespierre ◽  
...  
Keyword(s):  
Nervous System ◽  
G Protein ◽  
Neural Development ◽  
Neuronal Development ◽  
Axon Outgrowth ◽  
Rgs Proteins ◽  
Protein Signaling ◽  
Loss Of Function ◽  
G Protein Coupled

AbstractThe Regulator of G protein signaling 4 (Rgs4) is a member of the RGS proteins superfamily that modulates the activity of G-protein coupled receptors. It is mainly expressed in the nervous system and is linked to several neuronal signaling pathways; however, its role in neural development in vivo remains inconclusive. Here, we generated and characterized a rgs4 loss of function model (MZrgs4) in zebrafish. MZrgs4 embryos showed motility defects and presented reduced head and eye sizes, reflecting defective motoneurons axon outgrowth and a significant decrease in the number of neurons in the central and peripheral nervous system. Forcing the expression of Rgs4 specifically within motoneurons rescued their early defective outgrowth in MZrgs4 embryos, indicating an autonomous role for Rgs4 in motoneurons. We also analyzed the role of Akt, Erk and mechanistic target of rapamycin (mTOR) signaling cascades and showed a requirement for these pathways in motoneurons axon outgrowth and neuronal development. Drawing on pharmacological and rescue experiments in MZrgs4, we provide evidence that Rgs4 facilitates signaling mediated by Akt, Erk and mTOR in order to drive axon outgrowth in motoneurons and regulate neuronal numbers.

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