Browse
Submit Data
Databases
API
Help

Dataset Information

13 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Evidence for a role of srGAP3 in the positioning of commissural axons within the ventrolateral funiculus of the mouse spinal cord.

ABSTRACT: Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3) in commissural axon guidance using a knockout (KO) mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptors Robo1 and Robo2 and immunohistochemistry studies showed that srGAP3 co-localises with Robo1 in the ventral and lateral funiculus and with Robo2 in the lateral funiculus. Stalling axons have been reported in the floor-plate of Slit and Robo mutant spinal cords but our axon tracing experiments revealed no dorsal commissural axon stalling in the floor plate of the srGAP3 KO mouse. Interestingly we observed a significant thickening of the ventral funiculus and a thinning of the lateral funiculus in the srGAP3 KO spinal cord, which has also recently been reported in the Robo2 KO. However, axons in the enlarged ventral funiculus of the srGAP3 KO are Robo1 positive but do not express Robo2, indicating that the thickening of the ventral funiculus in the srGAP3 KO is not a Robo2 mediated effect. We suggest a role for srGAP3 in the lateral positioning of post crossing axons within the ventrolateral funiculus.

SUBMITTER: Bacon C

PROVIDER: S-EPMC3104994 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Ndfip Proteins Target Robo Receptors for Degradation and Allow Commissural Axons to Cross the Midline in the Developing Spinal Cord.

Project description:Commissural axons initially respond to attractive signals at the midline, but once they cross, they become sensitive to repulsive cues. This switch prevents axons from re-entering the midline. In insects and mammals, negative regulation of Roundabout (Robo) receptors prevents premature response to the midline repellant Slit. In Drosophila, the endosomal protein Commissureless (Comm) prevents Robo1 surface expression before midline crossing by diverting Robo1 into late endosomes. Notably, Comm is not conserved in vertebrates. We identified two Nedd-4-interacting proteins, Ndfip1 and Ndfip2, that act analogously to Comm to localize Robo1 to endosomes. Ndfip proteins recruit Nedd4 E3 ubiquitin ligases to promote Robo1 ubiquitylation and degradation. Ndfip proteins are expressed in commissural axons in the developing spinal cord and removal of Ndfip proteins results in increased Robo1 expression and reduced midline crossing. Our results define a conserved Robo1 intracellular sorting mechanism between flies and mammals to avoid premature responsiveness to Slit.

| S-EPMC6913780 | biostudies-literature

Mis-expression of L1 on pre-crossing spinal commissural axons disrupts pathfinding at the ventral midline.

Project description:In vertebrates, spinal commissural axons project along a transverse path toward and across the floor plate (FP). Post-crossing commissural axons alter their responsiveness to FP-associated guidance cues and turn to project longitudinally in a fasciculated manner prior to extending away from the midline. The upregulation of the neural cell adhesion molecule L1 on crossed commissural axon segments has been proposed to facilitate pathfinding on the contralateral side of the FP. To explore this possibility in vivo, we used Math1 regulatory sequences to target L1 to commissural axons before they cross the ventral midline. L1 mis-expression did not alter the distribution of commissural axon-associated markers or the ventral extension of commissural axons toward the midline. However, commissural axons often stalled or inappropriately projected into the longitudinal plane at the ipsilateral FP margin. These observations suggest that L1-mediated pathfinding decisions are normally delayed until axons have crossed the ventral midline (VM).

| S-EPMC2111042 | biostudies-literature

SlitC-PlexinA1 mediates iterative inhibition for orderly passage of spinal commissural axons through the floor plate.

Project description:Spinal commissural axon navigation across the midline in the floor plate requires repulsive forces from local Slit repellents. The long-held view is that Slits push growth cones forward and prevent them from turning back once they became sensitized to these cues after midline crossing. We analyzed with fluorescent reporters Slits distribution and FP glia morphology. We observed clusters of Slit-N and Slit-C fragments decorating a complex architecture of glial basal process ramifications. We found that PC2 proprotein convertase activity contributes to this pattern of ligands. Next, we studied Slit-C acting via PlexinA1 receptor shared with another FP repellent, the Semaphorin3B, through generation of a mouse model baring PlexinA1Y1815F mutation abrogating SlitC but not Sema3B responsiveness, manipulations in the chicken embryo, and ex vivo live imaging. This revealed a guidance mechanism by which SlitC constantly limits growth cone exploration, imposing ordered and forward-directed progression through aligned corridors formed by FP basal ramifications.

| S-EPMC7775108 | biostudies-literature

Mammalian BarH1 confers commissural neuron identity on dorsal cells in the spinal cord.

Project description:Commissural neurons in the spinal cord project their axons through the floor plate using a number of molecular interactions, such as netrins and their receptor DCC (deleted in colorectal cancer). However, the molecular cascades that control differentiation of commissural neurons are less characterized. A homeobox gene, MBH1 (mammalian BarH1) was expressed specifically in a subset of dorsal cells in the developing spinal cord. Transgenic mice that carried lacZ and MBH1-flanking genome sequences demonstrated that MBH1 was expressed by commissural neurons. To analyze the function of MBH1, we established an in vivo electroporation method for the transfer of DNA into the mouse spinal cord. Ectopic expression of MBH1 drove dorsal cells into the fate of commissural neurons with concomitant expression of TAG-1 (transiently expressed axonal surface glycoprotein 1) and DCC. Cells ectopically expressing MBH1 migrated to the deep dorsal horn, in which endogenous MBH1-positive cells accumulated. These results suggest that MBH1 functions upstream of TAG-1 and DCC and is involved in the fate determination of commissural neurons in the spinal cord.

| S-EPMC6742033 | biostudies-literature

Spinal Cord Injury regulates circular mRNA expression in axons

Project description:Injured axons in the CNS do not spontaneously regenerate leading to paralysis. Neurons can transport RNA and ribosomes to the site of injury where de novo translation has been known to occur, facilitating repair. Yet the tools available for studying axonal specific RNA are limited. We came up with a simple modification using Cold Active Proteases that enabled us to enrich for axonal RNA from rats with spinal cord injury (SCI) compared to non-injured. Our enriched axonal prep was then analyzed by bulk RNA-seq, where we looked at total RNA and we found differentially expressed genes (DEGs). Analyzing our bulk RNA-seq by Gene Ontology, we found the second most significant pathway for all DEGs was for axonogenesis, with markedly low glial cell contamination. From our DEGs we detected Rims2, which is reported to be predominately a circular RNA (circRNA) in the rodent CNS. Upon further annotation, we found over 200 putative circRNAs. circRNAs are abundant and well conserved in the brain, they are thought to be transcriptional regulators by functioning as microRNA (miR) sponges or binding to RNA-binding proteins (RBPs). By computational analysis using Circular RNA Interactome, we are able to predict which miRs or RBPs could bind to circRims2.

2023-07-25 | GSE230066 | GEO

Topographically specific regeneration of sensory axons in the spinal cord.

Project description:Artemin, a member of the glial-derived neurotrophic factor family, promotes robust regeneration of sensory axons after dorsal root crush. We report here that several classes of sensory axons regenerate to topographically appropriate regions of the dorsal horn with artemin treatment. Projections of regenerated muscle and cutaneous myelinated sensory afferents are restricted to the correct spinal segments and to appropriate regions within spinal gray matter. Regenerated unmyelinated axons expressing calcitonin gene-related peptide project only to superficial laminae of the dorsal horn, where uninjured nociceptive afferents project normally. In contrast, intraventricular infusion of a soluble form of the Nogo receptor that blocks the action of several myelin-associated inhibitory proteins promotes relatively unrestricted regeneration of sensory axons throughout the dorsal white and gray matter of the spinal cord. These results demonstrate that cues capable of guiding regenerating axons to appropriate spinal targets persist in the adult mammalian cord, but only some methods of stimulating regeneration allow the use of these cues by growing axons.

| S-EPMC2895079 | biostudies-other

Manipulating Robo expression in vivo perturbs commissural axon pathfinding in the chick spinal cord.

Project description:In vertebrate embryos, most spinal commissural axons cross the ventral midline (VM) and project either alongside or significant distances away from the floor plate (FP). The upregulation of repulsive Robo1/2 receptors on postcrossing commissural axons, in mammals, presumably allows these axons to respond to the midline-associated repellents, Slit1-3, facilitating their expulsion from, and prohibiting their reentry into, the FP. Compelling data suggest that Robo3 represses Robo1/2 function on precrossing axons and that Robo1/2 inhibit attractive guidance receptors on postcrossing axons, thereby ensuring that decussated axons are selectively responsive to midline Slits. However, whether Robo1/2 expel decussated commissural axons from the VM and/or prevent their reentry into the FP has not been explicitly established in vivo. Furthermore, some commissural axons do not require Robo1/2 to elaborate appropriate contralateral projections in the mouse spinal cord. Here, we use unilateral in ovo electroporation together with Atoh1 and Neurog1 enhancer elements to visualize, and assess the consequences of manipulating Robo expression on, dl1 and dl2 chick commissural axons. In response to misexpressing a cytoplasmic truncation of Robo1 and/or Robo2, which should block all Robo-ligand interactions, postcrossing commissural axons extend alongside, but do not project away from or reenter the FP. In contrast, misexpression of full-length Robo2 prevents many commissural axons from crossing the VM. Together, these findings support key and selective in vivo roles for Robo receptors in presumably altering the responsiveness of decussated commissural axons and facilitating their expulsion from the VM within the chick spinal cord.

| S-EPMC2886497 | biostudies-literature

Pioneer axons employ Cajal's battering ram to enter the spinal cord.

Project description:Sensory axons must traverse a spinal cord glia limitans to connect the brain with the periphery. The fundamental mechanism of how these axons enter the spinal cord is still debatable; both Ramon y Cajal's battering ram hypothesis and a boundary cap model have been proposed. To distinguish between these hypotheses, we visualized the entry of pioneer axons into the dorsal root entry zone (DREZ) with time-lapse imaging in zebrafish. Here, we identify that DRG pioneer axons enter the DREZ before the arrival of neural crest cells at the DREZ. Instead, actin-rich invadopodia in the pioneer axon are necessary and sufficient for DREZ entry. Using photoactivable Rac1, we demonstrate cell-autonomous functioning of invasive structures in pioneer axon spinal entry. Together these data support the model that actin-rich invasion structures dynamically drive pioneer axon entry into the spinal cord, indicating that distinct pioneer and secondary events occur at the DREZ.

| S-EPMC6362287 | biostudies-literature

Glutamate receptors on myelinated spinal cord axons: I. GluR6 kainate receptors.

Project description:The deleterious effects of glutamate excitotoxicity are well described for central nervous system gray matter. Although overactivation of glutamate receptors also contributes to axonal injury, the mechanisms are poorly understood. Our goal was to elucidate the mechanisms of kainate receptor-dependent axonal Ca(2+) deregulation.Dorsal column axons were loaded with a Ca(2+) indicator and imaged in vitro using confocal laser-scanning microscopy.Activation of glutamate receptor 6 (GluR6) kainate receptors promoted a substantial increase in axonal [Ca(2+)]. This Ca(2+) accumulation was due not only to influx from the extracellular space, but a significant component originated from ryanodine-dependent intracellular stores, which, in turn, depended on activation of L-type Ca(2+) channels: ryanodine, nimodipine, or nifedipine blocked the agonist-induced Ca(2+) increase. Also, GluR6 stimulation induced intraaxonal production of nitric oxide (NO), which greatly enhanced the Ca(2+) response: quenching of NO with intraaxonal (but not extracellular) scavengers, or inhibition of neuronal NO synthase with intraaxonal Nomega-nitro-L-arginine methyl ester, blocked the Ca(2+) increase. Loading axons with a peptide that mimics the C-terminal PDZ binding sequence of GluR6, thus interfering with the coupling of GluR6 to downstream effectors, greatly reduced the agonist-induced axonal Ca(2+) increase. Immunohistochemistry showed GluR6/7 clusters on the axolemma colocalized with neuronal NO synthase and Ca(v)1.2.Myelinated spinal axons express functional GluR6-containing kainate receptors, forming part of novel signaling complexes reminiscent of postsynaptic membranes of glutamatergic synapses. The ability of such axonal "nanocomplexes" to release toxic amounts of Ca(2+) may represent a key mechanism of axonal degeneration in disorders such as multiple sclerosis where abnormal accumulation of glutamate and NO are known to occur.

| S-EPMC2902553 | biostudies-literature

Activation of Rho in the injured axons following spinal cord injury.

Project description:Axons of the adult central nervous system have very limited ability to regenerate after injury. This inability may be, at least partly, attributable to myelin-derived proteins, such as myelin-associated glycoprotein, Nogo and oligodendrocyte myelin glycoprotein. Recent evidence suggests that these proteins inhibit neurite outgrowth by activation of Rho through the neurotrophin receptor p75(NTR)/Nogo receptor complex. Despite rapidly growing knowledge on these signals at the molecular level, it remained to be determined whether Rho is activated after injury to the central nervous system. To assess this question, we establish a new method to visualize endogenous Rho activity in situ. After treatment of cerebellar granular neurons with the Nogo peptide in vitro, Rho is spatially activated and colocalizes with p75(NTR). Following spinal cord injury in vivo, massive activation of Rho is observed in the injured neurites. Spatial regulation of Rho activity may be necessary for axonal regulation by the inhibitory cues.

| S-EPMC1299028 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data