Xenopus laevis as a Model Organism for the Study of Spinal Cord Formation, Development, Function and Regeneration

Abstract

The spinal cord is the first central nervous system structure to develop during vertebrate embryogenesis, underscoring its importance to the organism. Because of its early formation, accessibility to the developing spinal cord in amniotes is challenging, often invasive and the experimental approaches amenable to model systems like mammals are limited. In contrast, amphibians, in general and the African-clawed frog Xenopus laevis, in particular, offer model systems in which the formation of the spinal cord, the differentiation of spinal neurons and glia and the establishment of spinal neuron and neuromuscular synapses can be easily investigated with minimal perturbations to the whole organism. The significant advances on gene editing and microscopy along with the recent completion of the Xenopus laevis genome sequencing have reinvigorated the use of this classic model species to elucidate the mechanisms of spinal cord formation, development, function and regeneration.

A Label-free Multicolor Optical Surface Tomography (ALMOST) imaging method for nontransparent 3D samples

“…These NTDs include spina bifida and anencephaly [20]. Xenopus is a good model system for spinal cord formation [21, 22], as the vertebrate-specific program of neurulation can be observed easily outside the uterus. While zebrafish would potentially be an alternative and inherently transparent model system that can be imaged with the available techniques (light sheet microscopy), the process of neurulation differs, and the zebrafish undergoes so-called secondary neurulation [23], which is different from the more human-relevant primary neurulation.…”

Calcium Signaling in Vertebrate Development and Its Role in Disease

“…Pharmacologically disrupting calcium transients by blocking IP3R and other membrane-localized Ca 2+ channels, using 2ABP and nifedipine, abolished both apical constriction and movements of the neural plate towards closing. Also, this disruption reduced the width of the neural gene Sox2 expression zone and ultimately resulted in neural tube closure defects; these defects included impaired forebrain, hindbrain and midbrain in Xenopus and Ciona [ 4 , 66 , 68 , 69 , 70 , 71 ]. These results suggest that dysregulation of calcium during convergent extension and neural tube closure results in severe central nervous system defects.…”

Could electrical coupling contribute to the formation of cell assemblies?

“…Consequently, the intrinsic properties and pairwise interactions of their constituent neurons can be characterized, including analyses of their communication via gap junctions, action potential-gated synapses or graded synapses. An extensive and elegant literature exists on CPGs, such as those in the stomatogastric ganglion of crustaceans (Daur et al, 2016), in locomotor networks of lamprey (Grillner and Wallén, 2002), amphibians (Wolf et al, 2009;Borodinsky, 2017), zebrafish (Saint-Amant and Drapeau, 2000;Warp et al, 2012;Berg et al, 2018), and mice (Hanson and Landmesser, 2003;Lu et al, 2015), in the brainstem respiratory CPG of rodents (Rekling et al, 2000), and in others (Rybak et al, 2006;Grillner and Jessell, 2009;Garcia-Campmany et al, 2010). The CPG field is one area of study that sets the standard on how basic cellular neurophysiology determines biological function.…”