Commissural axon navigation: Control of midline crossing in the vertebrate spinal cord by the semaphorin 3B signaling

Abstract

The mechanisms governing the navigation of commissural axons during embryonic development have been extensively investigated in the past years, often using the drosophila ventral nerve cord and the spinal cord as model systems. Similarities but also specificities in the general strategies, the molecular signals as well as in the regulatory pathways controlling the response of commissural axons to the guidance cues have been found between species. Whether the semaphorin signaling contributes to midline crossing in the fly nervous system remains unknown, while in contrast, it does play a prominent contribution in vertebrates. In this review we discuss the functions of the semaphorins during commissural axon guidance in the developing spinal cord, focusing on the family member semaphorin 3B (Sema3B) in the context of midline crossing in the spinal cord.

Keratan sulfate (KS)‐proteoglycans and neuronal regulation in health and disease: the importance ofKS‐glycodynamics and interactive capability with neuroregulatory ligands

“…The Robo 3 receptor is intimately associated with the development and function of the commissural axons potentiating mid‐line attractive forces through interaction with Slit proteins which guide the commissural neurons across the developing spinal cord (Friocourt and Chedotal ), a process which is also aided by the semaphorins and in particular semaphorin 3B (Pignata et al . ) and 6B (Andermatt et al . ).…”

Iterative inhibition of commissural growth cone exploration, not post-crossing barrier, ensures forward midline navigation through SlitC-PlxnA1 signaling

“…In addition, various experiments suggested that the perception of repulsive forces is set at an appropriate timing, in order to synchronize ligands activity with commissural axon progression (Neuhaus-Follini and Bashaw, 2015;Pignata et al, 2016). Experimental manipulations leading to premature sensitivity were shown to induce commissural axons to stall at the FP entry or to undergo an ipsilateral turn (Chen et al, 2008;Nawabi et al, 2010;Ducuing et al, 2019).…”

A Spatiotemporal Sequence of Sensitization to Slits and Semaphorins Orchestrates Commissural Axon Navigation

“…Unique trajectories emerge from the perception by axon tips, the growth cones, of combinations of extracellular cues exposed in choice points along their paths. A typical case is provided by commissural neurons, which must project their axons across the midline to build circuits with contralateral target cells integrating left and right neuronal activities (Evans and Bashaw, 2010;Pignata et al, 2016;Stoeckli, 2018). Midline crossing of commissural axons in the floor plate (FP) of the developing spinal cord has been extensively studied to explore axon guidance mechanisms, especially those regulating growth-cone sensitivity to guidance cues.…”