Growth cone dynamics of embryonic grasshopper pioneer neurons in situ

1995 ◽  
Vol 53 ◽  
pp. 802-803
Author(s):  
Tim P. O'Connor
Keyword(s):  
Nervous System ◽  
Growth Cone ◽  
Time Lapse ◽  
Pioneer Neurons ◽  
The Central Nervous System ◽  
Neuronal Growth Cone ◽  
Time Lapse Imaging ◽  
Guidance Information ◽  
Extracellular Environment

During development of the nervous system, neurons extend axons over relatively long distances to contact their targets. A variety of molecules in the extracellular environment are instrumental in guiding a neuronal process. The motile tip of the process, the growth cone, senses and transduces this guidance information, resulting in a local reorganization and consolidation of the cytoskeleton. Although much work has been dedicated to isolating the molecules that guide a neuronal growth cone, relatively little is known about the dynamic processes that occur when a growth cone turns in response to guidance information. Recently, a number of biological systems have been developed that enable time lapse imaging of growth cones as they extend axons in situ. One of these systems is the embryonic grasshopper limb fillet.In the grasshopper embryo, a pair of sibling neurons, named the Til pioneers, are the first neurons to extend axons toward the central nervous system (CNS).

scholarly journals Accumulation of actin in subsets of pioneer growth cone filopodia in response to neural and epithelial guidance cues in situ.

1993 ◽  
Vol 123 (4) ◽  
pp. 935-948 ◽  
Author(s):  
T P O'Connor ◽  
D Bentley
Keyword(s):  
Growth Cone ◽  
Central Region ◽  
Time Lapse ◽  
Growth Cones ◽  
Target Cells ◽  
Rhodamine Phalloidin ◽  
Intermediate Target ◽  
Guidance Cues ◽  
Time Lapse Imaging

Directed outgrowth of neural processes must involve transmission of signals from the tips of filopodia to the central region of the growth cone. Here, we report on the distribution and dynamics of one possible element in this process, actin, in live growth cones which are reorienting in response to in situ guidance cues. In grasshopper embryonic limbs, pioneer growth cones respond to at least three types of guidance cues: a limb axis cue, intermediate target cells, and a circumferential band of epithelial cells. With time-lapse imaging of intracellularly injected rhodamine-phalloidin and rhodamine-actin, we monitored the distribution of actin during growth cone responses to these cues. In distal limb regions, accumulation of actin in filopodia and growth cone branches accompanies continued growth, while reduction of actin accompanies withdrawal. Where growth cones are reorienting to intermediate target cells, or along the circumferential epithelial band, actin selectively accumulates in the proximal regions of those filopodia that have contacted target cells or are extending along the band. Actin accumulations can be retrogradely transported along filopodia, and can extend into the central region of the growth cone. These results suggest that regulation and translocation of actin may be a significant element in growth cone steering.

scholarly journals The Drosophila couch potato gene: an essential gene required for normal adult behavior.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 365-375 ◽  
Author(s):  
H J Bellen ◽  
H Vaessin ◽  
E Bier ◽  
A Kolodkin ◽  
D D'Evelyn ◽  
...  
Keyword(s):  
Nervous System ◽  
Essential Gene ◽  
Flight Behavior ◽  
Regulatory Sequences ◽  
Adult Behavior ◽  
The Central Nervous System ◽  
Enhancer Detection ◽  
Dna Fragment ◽  
Mother Cells

Abstract Through enhancer detection screens we have isolated 14 insertions in an essential gene that is expressed in embryonic sensory mother cells (SMC), in most cells of the mature embryonic peripheral nervous system (PNS), and in glial cells of the PNS and the central nervous system (CNS). Embryos homozygote for amorphic alleles die, but show no obvious defects in their cuticle, PNS or CNS. The gene has been named couch potato (cpo) because several insertional alleles alter adult behavior. Homozygous hypomorphic cpo flies recover slowly from ether anaesthesia, show aberrant flight behavior, fail to move toward light and do not exhibit normal negative behavior. However, the flies are able to groom and walk, and some are able to fly when prodded, indicating that not all processes required for behavior are severely affected. A molecular analysis shows that the 14 insertions are confined to a few hundred nucleotides which probably contain key regulatory sequences of the gene. The orientation of these insertions and their position within this DNA fragment play an important role in the couch potato phenotype. In situ hybridization to whole mount embryos suggest that some insertions affect the levels of transcription of cpo in most cells in which it is expressed.

scholarly journals Individual neuronal subtypes control initial myelin sheath growth and stabilization

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Heather N. Nelson ◽  
Anthony J. Treichel ◽  
Erin N. Eggum ◽  
Madeline R. Martell ◽  
Amanda J. Kaiser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheath ◽  
Time Lapse ◽  
Marked Individual ◽  
Larval Zebrafish ◽  
Sheath Formation ◽  
Time Lapse Imaging

Abstract Background In the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors. Methods To address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes. Results In the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons. Conclusion We conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.

scholarly journals Tripartite-motif family protein 35-28 regulates microglia development by preventing necrotic death of microglial precursors in zebrafish

2020 ◽  
Vol 295 (26) ◽  
pp. 8846-8856
Author(s):  
Tao Yu ◽  
Haoyue Kuang ◽  
Jiahao Chen ◽  
Xi Lin ◽  
Yi Wu ◽  
...  
Keyword(s):  
Regulatory Protein ◽  
Neutrophil Infiltration ◽  
Time Lapse ◽  
Membrane Rupture ◽  
Family Protein ◽  
Tripartite Motif ◽  
The Central Nervous System ◽  
Time Lapse Imaging ◽  
Identification And Characterization

Microglia are tissue-resident macrophages in the central nervous system (CNS) that play essential roles in the regulation of CNS development and homeostasis. Yet, the genetic networks governing microglia development remain incompletely defined. Here, we report the identification and characterization of a microglia-defective zebrafish mutant wulonghkz12 (wulhkz12) isolated from an ethylnitrosourea (ENU)-based genetic screen. We show that wulhkz12 mutants harbors a missense point mutation in the gene region encoding the PRY/SPRY domain of the tripartite-motif family protein 35-28 (trim35-28) gene. Time-lapse imaging revealed that the loss of Trim35-28 function causes lytic necrosis of microglial precursors/peripheral macrophages, as indicated by cytoplasmic swelling and membrane rupture of these precursors and accompanied by neutrophil infiltration and systemic inflammation. Intriguingly, the lytic necrosis of microglial precursors in trim35-28–deficient mutants appeared to depend neither on the canonical pyroptotic nor necroptotic pathways, as inhibition of the key component in each pathway could not rescue the microglia phenotype in trim35-28–deficient mutants. Finally, results from tissue-specific rescue experiments suggested that Trim35-28 acts cell-autonomously in the survival of microglial precursors. Taken together, the findings of our study reveal Trim35-28 as a regulatory protein essential for microglia development.

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