A functional scaffold of CNS neurons for the vertebrates: The developing Xenopus laevis spinal cord

Abstract

In young and developing amphibians and fish the spinal cord is functional but remarkably simple compared with the adult. Is the pattern of neurons and their connections common across at least these lower vertebrates? Does this basic pattern extend into the brainstem? Could the development of simple functioning neuronal networks depend on very basic rules of connectivity and act as pioneer networks providing a substrate for the development of more complex and subtle networks. In this review of the functional neuron classes in the Xenopus laevis tadpole spinal cord up to hatching, we will consider progress and difficulties in using anatomy, transcription factor expression, physiology, and activity to define spinal neuron types. Even here it is not straightforward and is rarely possible to bring all the different strands of evidence together. But, we think we have a rather complete picture of the hatchling tadpole spinal neuron types and can define clear roles for most of them in behavior. Our present knowledge about the hatchling Xenopus spinal cord should set up many of the problems to be unraveled in the future by more developmentally oriented research.

Mechanosensory neurons control the timing of spinal microcircuit selection during locomotion

“…Recording reliable calcium transients associated with mechanical stimulation has been possible by combining fluorescent calcium sensors in one wavelength with another fluorescent protein enabling to control for cell position (Böhm et al, 2016). Nonetheless measuring activation of RB neurons during mechanical stimulation remains challenging due to the fact that RB neurons usually fire single action potentials ( et al, 2017; Roberts et al, 2012; Winlove and Roberts, 2012) and most calcium indicator fail to report single spike without extensive averaging (see Chen et al [2013]; Tian et al [2009]). Further studies will identify the connectivity diagrams of each of these mechanosensory cell types and devise genetic strategies to silence these neurons individually to probe their contribution to speed modulation during active locomotion.…”

A Group of Segmental Premotor Interneurons Regulates the Speed of Axial Locomotion in Drosophila Larvae

“…Previous studies have identified interneurons involved in axial propagation of neural activity by electrophysiological approaches in annelids [3], crustaceans [4], fish [2,5], and amphibians [6]. More recent studies in mice and zebrafish used genetic approaches to begin to elucidate the role of specific locomotor interneurons in vivo [7][8][9][10][11][12].…”

Tissue engineering is a promising method for the repair of spinal cord injuries (Review)

“…The requirements of a scaffold for spinal cord regeneration are as follows (47,48): i) good biocompatibility, in order to avoid reactions with the immune system, ii) an ideal degradation rate and the formation of non-toxic degradation products, and iii) mechanical properties that are suitable for cell adhesion and axonal regrowth. There have been several studies that have concentrated on the microstructural design of porous scaffolds, which must be conditioned in vivo prior to implantation (49,50).…”