scholarly journals How Notch establishes longitudinal axon connections between successive segments of the Drosophila CNS

Development ◽  
2011 ◽  
Vol 138 (9) ◽  
pp. 1839-1849 ◽  
Author(s):  
I. Kuzina ◽  
J. K. Song ◽  
E. Giniger
Keyword(s):  
Longitudinal Axon

Targeted neuronal ablation: the role of pioneer neurons in guidance and fasciculation in the CNS of Drosophila

Development ◽  
1997 ◽  
Vol 124 (17) ◽  
pp. 3253-3262 ◽  
Author(s):  
A. Hidalgo ◽  
A.H. Brand
Keyword(s):  
Temporal Profile ◽  
Pioneer Neurons ◽  
Longitudinal Axon ◽  
Pioneer Neuron ◽  
Embryonic Cns

Although pioneer neurons are the first to delineate the axon pathways, it is uncertain whether they have unique pathfinding abilities. As a first step in defining the role of pioneer neurons in the Drosophila embryonic CNS, we describe the temporal profile and trajectory of the axons of four pioneer neurons and show that they differ from previously published reports. We show, by targeted ablation of one, two, three or four pioneer neurons at a time, that (1) no single pioneer neuron is essential for axon tract formation, (2) the interaction between two pioneers is necessary for the establishment of each fascicle and (3) pioneer neurons function synergistically to establish the longitudinal axon tracts, to guide the fasciculation of follower neurons along specific fascicles and to prevent axons from crossing the midline.

scholarly journals The Slit-binding Ig1 domain is required for multiple axon guidance activities of Drosophila Robo2

2021 ◽  
Author(s):  
LaFreda J. Howard ◽  
Marie C. Reichert ◽  
Timothy A. Evans
Keyword(s):  
Axon Guidance ◽  
Lateral Position ◽  
Commissural Axons ◽  
Lateral Zone ◽  
Guidance Receptors ◽  
Longitudinal Axon ◽  
A Cell ◽  
Pathway Formation ◽  
Embryonic Neurons

Drosophila Robo2 is a member of the evolutionarily conserved Roundabout (Robo) family of axon guidance receptors. The canonical role of Robo receptors is to signal midline repulsion in response to their cognate Slit ligands, which bind to the N-terminal Ig1 domain in most Robo family members. In the Drosophila embryonic ventral nerve cord, Robo1 and Robo2 cooperate to signal Slit-dependent midline repulsion, while Robo2 also regulates the medial-lateral position of longitudinal axon pathways and acts non-autonomously to promote midline crossing of commissural axons. Although it is clear that Robo2 signals midline repulsion in response to Slit, it is less clear whether Robo2's other activities are also Slit-dependent. To determine which of Robo2's axon guidance roles depend on its Slit-binding Ig1 domain, we have used a CRISPR/Cas9-based strategy replace the endogenous robo2 gene with a robo2 variant from which the Ig1 domain has been deleted (robo2ΔIg1). We compare the expression and localization of Robo2ΔIg1 protein with that of full-length Robo2 in embryonic neurons in vivo, and examine its ability to substitute for Robo2 to mediate midline repulsion and lateral axon pathway formation. We find that removal of the Ig1 domain from Robo2ΔIg1 disrupts both of these axon guidance activities. In addition, we find that the Ig1 domain of Robo2 is required for its proper subcellular localization in embryonic neurons, a role that is not shared by the Ig1 domain of Robo1. Finally, we report that although FasII-positive lateral axons are misguided in embryos expressing Robo2ΔIg1, the axons that normally express Robo2 are correctly guided to the lateral zone, suggesting that Robo2 may guide lateral longitudinal axons through a cell non-autonomous mechanism.

The Central Nervous System in Larval Acraniates

1959 ◽  
Vol s3-100 (52) ◽  
pp. 509-527
Author(s):  
QUENTIN BONE
Keyword(s):  
Nervous System ◽  
Dorsal Root ◽  
Giant Cells ◽  
Sensory Cells ◽  
Larval Stages ◽  
Swimming Pattern ◽  
Cell Groups ◽  
Longitudinal Axon ◽  
The Central Nervous System ◽  
The Right

This paper describes a part of the organization of the spinal cord of the larva of the Acrania, dealing chiefly with those tracts and cell groups that are probably concerned with the control of the swimming pattern. These observations serve as a basis for the comparison of the organization of the cord of the larva with that of the adult, and with that known for the larvae of the Agnatha and higher vertebrates. Other observations are concerned with the arrangement of the peripheral nervous system, which differs in some respects from that of the adult. The first section deals with the arrangement of the fibre tracts in the cord, and of the cell-bodies which give rise to these fibres. The form and connexions of the giant cells are then described; it is shown that these cells are equivalent to the Rohon-Beard sensory cells of vertebrate embryos. They send peripheral processes out through dorsal root nerves, but they differ from the vertebrate sensory neurones in their greatly enlarged dendrite field and the longitudinal axon in the cord. Thirdly, the innervation of the gill musculature is described. A ventro-lateral asymmetrical nerve is found, formed by the junction of fibres from the right anterior dorsal root nerves. Lastly, the arrangement of the whole system is discussed in relation to the systems found in the larval stages of other primitive chordates.

Requirements of DFR1/Heartless, a mesoderm-specific Drosophila FGF-receptor, for the formation of heart, visceral and somatic muscles, and ensheathing of longitudinal axon tracts in CNS

Development ◽  
1997 ◽  
Vol 124 (11) ◽  
pp. 2119-2128 ◽  
Author(s):  
E. Shishido ◽  
N. Ono ◽  
T. Kojima ◽  
K. Saigo
Keyword(s):  
Growth Factor Receptor ◽  
Fgf Receptor ◽  
Longitudinal Axon ◽  
The Central Nervous System ◽  
Targeted Expression ◽  
Map Kinase Pathway ◽  
Mutant Phenotypes ◽  
To Receive ◽  
Kinase Pathway ◽  
Somatic Muscles

DFR1 encodes a mesoderm-specific fibroblast growth factor receptor in Drosophila. Here, we identified and characterized a protein-null mutant of DFR1 and examined DFR1 expression in embryos using anti-DFR1 antibody. Mutant phenotypes were completely rescued by a genomic fragment from the DFR1 locus. After invagination, mesodermal cells expressing DFR1 undergo proliferation and spread out dorsally to form a monolayer beneath the ectoderm. In mutant embryos, however, the mesoderm is not capable of extending to the normal dorsal limit and consequently mesodermal cells fail to receive ectodermal signals and thus rendered incapable of differentiating into primordia for the heart, visceral and somatic muscles. DFR1 is also required for normal development of the central nervous system. The absence of DFR1 resulted in the failure of longitudinal glia to enwrap longitudinal axon tracts. DFR1 mutant phenotypes were partially mimicked by the targeted expression of activated Yan, thus demonstrating the MAP kinase pathway to be involved in differentiation of mesoderm.

Glia maintain follower neuron survival during Drosophila CNS development

Development ◽  
2000 ◽  
Vol 127 (2) ◽  
pp. 237-244 ◽  
Author(s):  
G.E. Booth ◽  
E.F. Kinrade ◽  
A. Hidalgo
Keyword(s):  
Axon Guidance ◽  
Neuronal Survival ◽  
Cell Number ◽  
Cns Development ◽  
Neuronal Fate ◽  
Missing Gene ◽  
Pioneer Neurons ◽  
Longitudinal Axon ◽  
Glial Function ◽  
Embryonic Cns

While survival of CNS neurons appears to depend on multiple neuronal and non-neuronal factors, it remains largely unknown how neuronal survival is controlled during development. Here we show that glia regulate neuronal survival during formation of the Drosophila embryonic CNS. When glial function is impaired either by mutation of the glial cells missing gene, which transforms glia toward a neuronal fate, or by targeted genetic glial ablation, neuronal death is induced non-autonomously. Pioneer neurons, which establish the first longitudinal axon fascicles, are insensitive to glial depletion whereas the later extending follower neurons die. This differential requirement of neurons for glia is instructive in patterning and links control of cell number with axon guidance during CNS development.

Longitudinal axon guidance

2006 ◽  
Vol 16 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Esther T Stoeckli
Keyword(s):  
Axon Guidance ◽  
Longitudinal Axon

scholarly journals From embryonic fascicles to adult tracts: organization of neuropile from a developmental perspective

1984 ◽  
Vol 112 (1) ◽  
pp. 45-64
Author(s):  
M. Bastiani ◽  
K. G. Pearson ◽  
C. S. Goodman
Keyword(s):  
Nervous System ◽  
Embryonic Development ◽  
Growth Cone ◽  
Morphological Differentiation ◽  
Growth Cones ◽  
The Other ◽  
Developmental Perspective ◽  
Longitudinal Axon ◽  
Repeated Pattern ◽  
Thoracic And Abdominal

We discuss ideas emerging from our studies on selective axonal fasciculation in the grasshopper embryo that have implications for the organization of the adult neuropile in insects and perhaps other animals. While one of our laboratories has been studying the embryonic development of the G neurone (in the mesothoracic segment) and its lineal homologues (in other segments), the other has been studying the morphology and physiology of this same neurone and its segmental homologues in the adult nervous system. Our embryonic studies show that the growth cone of the G neurone selectively fasciculates with the A/P fascicle in preference to all other longitudinal axon fascicles at it turns anteriorly. The homologues of G in other thoracic and abdominal segments fasciculate in this same bundle. However, early in their morphological differentiation, they reveal interesting segmental differences. Our studies on the adult nervous system show that the segmental homologues of the G neurone share many properties in common (e.g. axons in the LDT: lateral dorsal tract) while other features are quite different. The notion emerging from these studies is that a basic segmentally-repeated pattern arises during embryogenesis: a stereotyped axonal scaffold upon which growth cones faithfully fasciculate. Evolutionary plasticity allows the specialization of lineally equivalent neurones in different segments within the context of the neuropilar neighbourhood that they find themselves in as a consequence of their selective fasciculation.

Targeted ablation of glia disrupts axon tract formation in the Drosophila CNS

Development ◽  
1995 ◽  
Vol 121 (11) ◽  
pp. 3703-3712 ◽  
Author(s):  
A. Hidalgo ◽  
J. Urban ◽  
A.H. Brand
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Growth Cone ◽  
Growth Cones ◽  
Complete Loss ◽  
Drosophila Embryo ◽  
Novel Technique ◽  
Cell Ablation ◽  
Longitudinal Axon ◽  
Growth Cone Guidance

Glial cells are thought to play a role in growth cone guidance, both in insects and in vertebrates. In the developing central nervous system of the Drosophila embryo, the interface glia form a scaffold prior to the extension of the first pioneer growth cones. Growing axons appear to contact the glial scaffold as the axon tracts are established. We have used a novel technique for targeted cell ablation to kill the interface glia and thus to test their role in establishment of the embryonic axon tracts. We show that ablation of the interface glia early in development leads to a complete loss of the longitudinal axon tracts. Ablation of the glia later in embryonic development results in defects comprising weakening and loss of axon fascicles within the connectives. We conclude that the interface glia are required first for growth cone guidance in the formation of the longitudinal axon tracts in the Drosophila embryo and then either to direct the follower growth cones, or to maintain the longitudinal axon tracts.

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