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.

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.

Dephrin, a transmembrane ephrin with a unique structure, prevents interneuronal axons from exiting the Drosophila embryonic CNS

Development ◽  
2002 ◽  
Vol 129 (18) ◽  
pp. 4205-4218 ◽  
Author(s):  
Torsten Bossing ◽  
Andrea H. Brand
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Ectopic Expression ◽  
Axonal Pathfinding ◽  
N Terminus ◽  
Outer Border ◽  
Embryonic Cns ◽  
First Time ◽  
Neuronal Compartments

Ephrin/Eph signalling is crucial for axonal pathfinding in vertebrates and invertebrates. We identified the Drosophila ephrin orthologue, Dephrin, and describe for the first time the role of ephrin/Eph signalling in the embryonic central nervous system (CNS). Dephrin is a transmembrane ephrin with a unique N terminus and an ephrinB-like cytoplasmic tail. Dephrin binds and interacts with DEph, the Drosophila Eph-like receptor, and Dephrin and DEph are confined to different neuronal compartments. Loss of Dephrin or DEph causes the abberant exit of interneuronal axons from the CNS, whereas ectopic expression of Dephrin halts axonal growth. We propose that the longitudinal tracts in the Drosophila CNS are moulded by a repulsive outer border of Dephrin expression.

scholarly journals Deep Learning Decodes Multi-layered Roles of Polycomb Repressor Complex 2 During Mouse CNS Development

2021 ◽  
Author(s):  
Ariane Mora ◽  
Jonathan Rakar ◽  
Ignacio Monedero Cobeta ◽  
Behzad Yaghmaeian Salmani ◽  
Annika Starkenberg ◽  
...  
Keyword(s):  
Cns Development ◽  
Full Spectrum ◽  
Transcriptomic Response ◽  
Repressor Complex ◽  
Variate Analysis ◽  
Central Nervous Systems ◽  
Embryonic Cns ◽  
Spatio Temporal ◽  
Bioinformatics Workflow

A prominent aspect of most, if not all, central nervous systems (CNSs) is that anterior regions (brain) are larger than posterior ones (spinal cord). Studies in Drosophila and mouse have revealed that the Polycomb Repressor Complex 2 (PRC2) acts by several mechanisms to promote anterior CNS expansion. However, it is unclear if PRC2 acts directly and/or indirectly upon key downstream genes, what the full spectrum of PRC2 action is during embryonic CNS development and how PRC2 integrates with the epigenetic landscape. We removed PRC2 function from the developing mouse CNS, by mutating the key gene Eed, and generated spatio-temporal transcriptomic data. We developed a bioinformatics workflow that incorporates standard statistical analyses with machine learning to integrate the transcriptomic response to PRC2 inactivation with epigenetic information from ENCODE. This multi-variate analysis corroborates the central involvement of PRC2 in anterior CNS expansion, and reveals layered regulation via PRC2. These findings uncover a differential logic for the role of PRC2 upon functionally distinct gene categories that drive CNS anterior expansion. To support the analysis of emerging multi-modal datasets, we provide a novel bioinformatics package that can disentangle regulatory underpinnings of heterogeneous biological processes.

Nitric oxide and cGMP influence axonogenesis of antennal pioneer neurons

Development ◽  
2000 ◽  
Vol 127 (21) ◽  
pp. 4541-4549 ◽  
Author(s):  
C. Seidel ◽  
G. Bicker
Keyword(s):  
Nitric Oxide ◽  
Culture Medium ◽  
Schistocerca Gregaria ◽  
Soluble Guanylyl Cyclase ◽  
Cgmp Signaling ◽  
Pioneer Neurons ◽  
Abnormal Pattern ◽  
Pathway Formation ◽  
Direct Activator

The grasshopper embryo has been used as a convenient system with which to investigate mechanisms of axonal navigation and pathway formation at the level of individual nerve cells. Here, we focus on the developing antenna of the grasshopper embryo (Schistocerca gregaria) where two siblings of pioneer neurons establish the first two axonal pathways to the CNS. Using immunocytochemistry we detected nitric oxide (NO)-induced synthesis of cGMP in the pioneer neurons of the embryonic antenna. A potential source of NO are NADPH-diaphorase-stained epithelial cells close to the basal lamina. To investigate the role of the NO/cGMP signaling system during pathfinding, we examined the pattern of outgrowing pioneer neurons in embryo culture. Pharmacological inhibition of soluble guanylyl cyclase (sGC) and of NO synthase (NOS) resulted in an abnormal pattern of pathway formation in the antenna. Axonogenesis of both pairs of pioneers was inhibited when specific NOS or sGC inhibitors were added to the culture medium; the observed effects include the loss axon emergence as well as retardation of outgrowth, such that growth cones do not reach the CNS. The addition of membrane-permeant cGMP or a direct activator of the sGC enzyme to the culture medium completely rescued the phenotype resulting from the block of NO/cGMP signaling. These results indicate that NO/cGMP signaling is involved in axonal elongation of pioneer neurons in the antenna of the grasshopper.

Two Drosophila receptor-like tyrosine phosphatase genes are expressed in a subset of developing axons and pioneer neurons in the embryonic CNS

Cell ◽  
1991 ◽  
Vol 67 (4) ◽  
pp. 661-673 ◽  
Author(s):  
Xiaohang Yang ◽  
Kah Tong Seow ◽  
Sami M. Bahri ◽  
Swee Huat Oon ◽  
William Chia
Keyword(s):  
Tyrosine Phosphatase ◽  
Pioneer Neurons ◽  
Embryonic Cns

Development of a sensory afferent projection in the grasshopper embryo

Development ◽  
1981 ◽  
Vol 64 (1) ◽  
pp. 169-185
Author(s):  
Marty Shankland
Keyword(s):  
Sensory Neurons ◽  
Secondary Growth ◽  
Leading Edge ◽  
Growth Cones ◽  
Peripheral Neurons ◽  
Sensory Axons ◽  
Terminal Filament ◽  
Pioneer Neurons ◽  
Embryonic Cns ◽  
Prolonged Absence

The grasshopper's cereal nerve is established early in embryogenesis by an identified pair of peripheral neurons called the cereal pioneers. Like the peripheral pioneer neurons in other insect appendages, these two cells send their axons from the periphery to the rudimentary CNS and thus lay the foundation for a nerve that will later be followed by a large number of sensory axons. In this paper, cobalt fills of the primordial cereal nerve were used to characterize the disposition of these peripheral pioneer axons within the embryonic CNS. The pioneer axons stained by this technique terminate in ellipsoidal growth cones which have filopodia radiating from the leading edge and a single long terminal filament pointing along the path the axon is taking. The growing axons also bear filopodia along their sides, but these structures disappear as the cells mature. The pioneer axons of the cereal nerve make an abrupt turn where they first enter the ganglion rudiment and join the axons of the primary longitudinal tract. The pioneers then grow along this tract for several hundred microns without forming secondary growth cones or branches. This prolonged absence of central arborization distinguishes the peripheral pioneer axons from the axons of later-arising epidermal sensory neurons.

scholarly journals Organization of cytoskeletal elements and organelles preceding growth cone emergence from an identified neuron in situ.

1989 ◽  
Vol 108 (5) ◽  
pp. 1737-1749 ◽  
Author(s):  
F Lefcort ◽  
D Bentley
Keyword(s):  
Golgi Apparatus ◽  
Growth Cone ◽  
Actin Filaments ◽  
Limb Bud ◽  
Immunohistochemical Markers ◽  
Identified Neuron ◽  
Pioneer Neurons ◽  
Pioneer Neuron ◽  
Cytoskeletal Elements

The purpose of this study was to investigate the arrangement of cytoskeletal elements and organelles in an identified neuron in situ at the site of emergence of its growth cone just before and concurrent with the onset of axonogenesis. The Ti1 pioneer neurons are the first pair of afferent neurons to differentiate in embryonic grasshopper limbs. They arise at the distal tip of the limb bud epithelium, the daughter cells of a single precursor cell, the Pioneer Mother Cell (PMC). Using immunohistochemical markers, we characterized the organization of microtubules, centrosomes, Golgi apparatus, midbody, actin filaments, and chromatin from mitosis in the PMC through axonogenesis in the Tils. Just before and concurrent with the onset of axonogenesis, a characteristic arrangement of tubulin, actin filaments, and Golgi apparatus is localized at the proximal pole of the proximal pioneer neuron. The growth cone of the proximal cell stereotypically arises from this site. Although the distal cell's axon generally grows proximally, occasionally it arises from its distal pole; in such limbs, the axons from the sister cells extend from mirror symmetric locations on their somata. In the presence of cytochalasin D, the PMC undergoes nuclear division but not cytokinesis and although other neuronal phenotypes are expressed, axongenesis is inhibited. Our data suggest that intrinsic information determines the site of growth cone emergence of an identified neuron in situ.

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