Nogo-B is the major form of Nogo at the floor plate and likely mediates crossing of commissural axons in the mouse spinal cord

2017 ◽  
Vol 525 (13) ◽  
pp. 2915-2928 ◽  
Author(s):  
Liqing Wang ◽  
Chao Yu ◽  
Jun Wang ◽  
Peggy Leung ◽  
Ding Ma ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Floor Plate ◽  
Mouse Spinal Cord ◽  
Commissural Axons ◽  
Major Form

Ventral midline cells are required for the local control of commissural axon guidance in the mouse spinal cord

Development ◽  
1999 ◽  
Vol 126 (16) ◽  
pp. 3649-3659
Author(s):  
M.P. Matise ◽  
M. Lustig ◽  
T. Sakurai ◽  
M. Grumet ◽  
A.L. Joyner
Keyword(s):  
Spinal Cord ◽  
Critical Role ◽  
Floor Plate ◽  
Posterior Commissure ◽  
Ventral Midline ◽  
Mouse Spinal Cord ◽  
Commissural Axons ◽  
Midline Cells

Specialized cells at the midline of the central nervous system have been implicated in controlling axon projections in both invertebrates and vertebrates. To address the requirement for ventral midline cells in providing cues to commissural axons in mice, we have analyzed Gli2 mouse mutants, which lack specifically the floor plate and immediately adjacent interneurons. We show that a Dbx1 enhancer drives tau-lacZ expression in a subpopulation of commissural axons and, using a reporter line generated from this construct, as well as DiI tracing, we find that commissural axons projected to the ventral midline in Gli2(−/−) embryos. Netrin1 mRNA expression was detected in Gli2(−/−) embryos and, although much weaker than in wild-type embryos, was found in a dorsally decreasing gradient. This result demonstrates that while the floor plate can serve as a source of long-range cues for C-axons in vitro, it is not required in vivo for the guidance of commissural axons to the ventral midline in the mouse spinal cord. After reaching the ventral midline, most commissural axons remained clustered in Gli2(−/−) embryos, although some were able to extend longitudinally. Interestingly, some of the longitudinally projecting axons in Gli2(−/−) embryos extended caudally and others rostrally at the ventral midline, in contrast to normal embryos in which virtually all commissural axons turn rostrally after crossing the midline. This finding indicates a critical role for ventral midline cells in regulating the rostral polarity choice made by commissural axons after they cross the midline. In addition, we provide evidence that interactions between commissural axons and floor plate cells are required to modulate the localization of Nr-CAM and TAG-1 proteins on axons at the midline. Finally, we show that the floor plate is not required for the early trajectory of motoneurons or axons of the posterior commissure, whose projections are directed away from the ventral midline in both WT and Gli2(−/−) embryos, although they are less well organized in Gli2(−/−)mutants.

Complementary expression of transmembrane ephrins and their receptors in the mouse spinal cord: a possible role in constraining the orientation of longitudinally projecting axons

Development ◽  
2000 ◽  
Vol 127 (7) ◽  
pp. 1397-1410 ◽  
Author(s):  
R. Imondi ◽  
C. Wideman ◽  
Z. Kaprielian
Keyword(s):  
Spinal Cord ◽  
Floor Plate ◽  
Plate Boundaries ◽  
Eph Receptors ◽  
Axon Pathfinding ◽  
Mouse Spinal Cord ◽  
Commissural Axon ◽  
Ligand Interactions ◽  
Ventral Funiculus

In the developing spinal cord, axons project in both the transverse plane, perpendicular to the floor plate, and in the longitudinal plane, parallel to the floor plate. For many axons, the floor plate is a source of long- and short-range guidance cues that govern growth along both dimensions. We show here that B-class transmembrane ephrins and their receptors are reciprocally expressed on floor plate cells and longitudinally projecting axons in the mouse spinal cord. During the period of commissural axon pathfinding, B-class ephrin protein is expressed at the lateral floor plate boundaries, at the interface between the floor plate and the ventral funiculus. In contrast, B-class Eph receptors are expressed on decussated commissural axon segments projecting within the ventral funiculus, and on ipsilaterally projecting axons constituting the lateral funiculus. Soluble forms of all three B-class ephrins bind to, and induce the collapse of, commissural growth cones in vitro. The collapse-inducing activity associated with B-class ephrins is likely to be mediated by EphB1. Taken together, these data support a possible role for repulsive B-class Eph receptor/ligand interactions in constraining the orientation of longitudinal axon projections at the ventral midline.

Guidance of commissural growth cones at the floor plate in embryonic rat spinal cord

Development ◽  
1990 ◽  
Vol 109 (2) ◽  
pp. 435-447 ◽  
Author(s):  
P. Bovolenta ◽  
J. Dodd
Keyword(s):  
Spinal Cord ◽  
Axon Guidance ◽  
Plate Boundary ◽  
Growth Cones ◽  
Floor Plate ◽  
Morphological Properties ◽  
Rat Spinal Cord ◽  
Commissural Axons ◽  
Carbocyanine Dye

The floor plate of the embryonic rat spinal cord has been proposed to act as an intermediate target that plays a role in the pattern of extension of commissural axons. To begin to examine the role of the floor plate in axon guidance at the midline, we have studied the precision of the commissural axon projection to and across the floor plate during development. To delineate the pathway, the fluorescent carbocyanine dye, Di-I, has been used as a probe. We show that commissural axons traverse the floor plate and turn rostrally at its contralateral border with remarkable precision. Axons were not observed to turn ipsilaterally and turned only upon reaching the contralateral edge of the floor plate. Virtually all commissural axons follow this route. The morphology of commissural growth cones was also examined. As they encountered the floor plate, commissural growth cones became larger and increased in complexity. The reorientation of axons in register with the floor plate boundary and the change in the morphological properties of commissural growth cones as they traverse the midline suggest that the floor plate may act as a guidepost with functions similar to cells that have been implicated in axon guidance in invertebrates.

Orientation of commissural axons in vitro in response to a floor plate-derived chemoattractant

Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 19-30 ◽  
Author(s):  
M. Placzek ◽  
M. Tessier-Lavigne ◽  
T. Jessell ◽  
J. Dodd
Keyword(s):  
Spinal Cord ◽  
Collagen Gel ◽  
Axon Growth ◽  
Local Environment ◽  
Floor Plate ◽  
Target Cells ◽  
Commissural Axon ◽  
Commissural Axons ◽  
Commissural Neurons

Developing axons are guided to their targets by molecular cues in their local environment. Some cues are short-range, deriving from cells along axonal pathways. There is also increasing evidence for longer-range guidance cues, in the form of gradients of diffusible chemoattractant molecules, which originate from restricted populations of target cells. The guidance of developing commissural axons within the spinal cord depends on one of their intermediate cellular targets, the floor plate. We have shown previously that floor plate cells secrete a diffusible factor(s) that can alter the direction of commissural axon growth in vitro. Here we show that the factor is an effective chemoattractant for commissural axons. It can diffuse considerable distances through a collagen gel matrix and through dorsal and ventral neural epithelium in vitro to reorient the growth of virtually all commissural axons. The orientation of axons occurs in the absence of detectable effects on the survival of commissural neurons or on the rate of commissural axon extension. The regionally restricted expression of the factor suggests that it is present in the embryonic spinal cord in a gradient with its high point at the floor plate. These observations support the idea that the guidance of commissural axons to the ventral midline of the spinal cord results in part from the secretion of a chemoattractant by the floor plate.

scholarly journals Floor plate-derived neuropilin-2 functions as a secreted semaphorin sink to facilitate commissural axon midline crossing

2015 ◽  
Vol 29 (24) ◽  
pp. 2617-2632
Author(s):  
Berenice Hernandez-Enriquez ◽  
Zhuhao Wu ◽  
Edward Martinez ◽  
Olav Olsen ◽  
Zaven Kaprielian ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Floor Plate ◽  
Axon Pathfinding ◽  
Developmentally Regulated ◽  
Commissural Axon ◽  
Commissural Axons ◽  
Receptor Complexes ◽  
Midline Crossing

Commissural axon guidance depends on a myriad of cues expressed by intermediate targets. Secreted semaphorins signal through neuropilin-2/plexin-A1 receptor complexes on post-crossing commissural axons to mediate floor plate repulsion in the mouse spinal cord. Here, we show that neuropilin-2/plexin-A1 are also coexpressed on commissural axons prior to midline crossing and can mediate precrossing semaphorin-induced repulsion in vitro. How premature semaphorin-induced repulsion of precrossing axons is suppressed in vivo is not known. We discovered that a novel source of floor plate-derived, but not axon-derived, neuropilin-2 is required for precrossing axon pathfinding. Floor plate-specific deletion of neuropilin-2 significantly reduces the presence of precrossing axons in the ventral spinal cord, which can be rescued by inhibiting plexin-A1 signaling in vivo. Our results show that floor plate-derived neuropilin-2 is developmentally regulated, functioning as a molecular sink to sequester semaphorins, preventing premature repulsion of precrossing axons prior to subsequent down-regulation, and allowing for semaphorin-mediated repulsion of post-crossing axons.

scholarly journals Evidence for a Role of srGAP3 in the Positioning of Commissural Axons within the Ventrolateral Funiculus of the Mouse Spinal Cord

PLoS ONE ◽  
2011 ◽  
Vol 6 (5) ◽  
pp. e19887 ◽  
Author(s):  
Claire Bacon ◽  
Volker Endris ◽  
Irwin Andermatt ◽  
Vera Niederkofler ◽  
Robert Waltereit ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Mouse Spinal Cord ◽  
Commissural Axons ◽  
Ventrolateral Funiculus

Perturbation of neuronal differentiation and axon guidance in the spinal cord of mouse embryos lacking a floor plate: analysis of Danforth's short-tail mutation

Development ◽  
1991 ◽  
Vol 113 (2) ◽  
pp. 625-639 ◽  
Author(s):  
P. Bovolenta ◽  
J. Dodd
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Motor Neurons ◽  
Cell Types ◽  
Floor Plate ◽  
Ventral Midline ◽  
Cellular Targets ◽  
Commissural Axons ◽  
Short Tail ◽  
Plate Analysis

The floor plate of the vertebrate nervous system has been implicated in the guidance of commissural axons at the ventral midline. Experiments in chick have also suggested that at earlier stages of development the floor plate induces the differentiation of motor neurons and other neurons of the ventral spinal cord. Here we have examined the development of the spinal cord in a mouse mutant, Danforth's short-tail, in which the floor plate is absent from caudal regions of the neuraxis. In affected regions of the spinal cord, commissural axons exhibited aberrant projection patterns as they reached and crossed the ventral midline. In addition, motor neurons were absent or markedly reduced in number in regions of the spinal cord lacking a floor plate. Our results suggest that the floor plate is indeed an intermediate target in the projection of commissural axons and support the idea that several different mechanisms operate in concert in the guidance of axons to their cellular targets in the developing nervous system. In addition, these experiments suggest that the mechanisms that govern the differentiation of the floor plate and other ventral cell types in the neural tube are common to mammals and lower vertebrates.

scholarly journals The role of floor plate contact in the elaboration of contralateral commissural projections within the embryonic mouse spinal cord

2006 ◽  
Vol 296 (2) ◽  
pp. 499-513 ◽  
Author(s):  
Stephanie R. Kadison ◽  
Fujio Murakami ◽  
Michael P. Matise ◽  
Zaven Kaprielian
Keyword(s):  
Spinal Cord ◽  
Floor Plate ◽  
Embryonic Mouse ◽  
Mouse Spinal Cord

Commissural axon pathfinding on the contralateral side of the floor plate: a role for B-class ephrins in specifying the dorsoventral position of longitudinally projecting commissural axons

Development ◽  
2001 ◽  
Vol 128 (23) ◽  
pp. 4859-4871 ◽  
Author(s):  
Ralph Imondi ◽  
Zaven Kaprielian
Keyword(s):  
Spinal Cord ◽  
Late Phase ◽  
Longitudinal Axis ◽  
Contralateral Side ◽  
Floor Plate ◽  
Axon Pathfinding ◽  
Lower Vertebrate ◽  
Commissural Axon ◽  
Commissural Axons

In both invertebrate and lower vertebrate species, decussated commissural axons travel away from the midline and assume positions within distinct longitudinal tracts. We demonstrate that in the developing chick and mouse spinal cord, most dorsally situated commissural neuron populations extend axons across the ventral midline and through the ventral white matter along an arcuate trajectory on the contralateral side of the floor plate. Within the dorsal (chick) and intermediate (mouse) marginal zone, commissural axons turn at a conserved boundary of transmembrane ephrin expression, adjacent to which they form a discrete ascending fiber tract. In vitro perturbation of endogenous EphB-ephrinB interactions results in the failure of commissural axons to turn at the appropriate dorsoventral position on the contralateral side of the spinal cord; consequently, axons inappropriately invade more dorsal regions of B-class ephrin expression in the dorsal spinal cord. Taken together, these observations suggest that B-class ephrins act locally during a late phase of commissural axon pathfinding to specify the dorsoventral position at which decussated commissural axons turn into the longitudinal axis.

Sign in / Sign up

Export Citation Format

Share Document