Using Xenopus laevis retinal and spinal neurons to study mechanisms of axon guidance in vivo and in vitro

Abstract

The intricate and precise establishment of neuronal connections in the developing nervous system relies on accurate navigation of growing axons. Since Ramón y Cajal's discovery of the growth cone, the phenomenon of axon guidance has been revealed as a coordinated operation of guidance molecules, receptors, secondary messengers, and responses driven by the dynamic cytoskeleton within the growth cone. With the advent of new and accelerating techniques, Xenopus laevis emerged as a robust model to investigate neuronal circuit formation during development. We present here the advantages of the Xenopus nervous system to our growing understanding of axon guidance.

Xenopus laevis as a model system to study cytoskeletal dynamics during axon pathfinding

“…The genomes of both have been recently sequenced and have displayed high gene collinearity with the human genome (Hellsten et al, 2010;Session et al, 2016). X. laevis, in particular, has been well-utilized to study axon guidance and development, because of their significantly larger growth cone size (Erdogan et al, 2016).…”

“…Many model systems have been widely used to study axon guidance and development, including hippocampal neurons from rat and mouse embryos (Andersen & Bi, ), bag cell neurons from adult Aplysia californica (Lee, Decourt, & Suter, ; Suter & Miller, ), dorsal root ganglia neurons from chicken embryos (Dontchev & Letourneau, ; Fantetti & Fekete, ), and retinal ganglia cells and spinal cord neurons from X. laevis embryos (Chien & Harris, ; Erdogan, Ebbert, & Lowery, ; Santiago‐Medina, Myers, & Gomez, ). While all systems have specific advantages and disadvantages, it is clear that X. laevis provides an ideal system for studying the role of the cytoskeleton, because it has neuronal growth cones that are easy to obtain, manipulate, culture, and image at a low cost (Figure ).…”

Characterization of Xenopus laevis guanine deaminase reveals new insights for its expression and function in the embryonic kidney

“…Multiple +TIPs have been described and characterized using Xenopus laevis (Lee et al, 2004;Lowery et al, 2013;Marx et al, 2013;Nwagbara et al, 2014;Lucaj et al, 2015;Rutherford et al, 2016;Erdogan et al, 2017). Xenopus embryos can be easily manipulated, and their primary embryonic neural cells are facile to obtain, culture, and image, as they display large growth cones (10 microns or more), which are useful for imaging cytoskeletal dynamics (Erdogan et al, 2016;Slater et al, 2017). Live cell imaging is particularly important, as some +TIPs only bind to growing MTs and, thus, their localization dynamics cannot be visualized using immunohistochemistry of fixed cells (Nwagbara et al, 2014).…”

Real time large scale in vivo observations reveal intrinsic synchrony, plasticity and growth cone dynamics of midline crossing axons at the ventral floor plate of the zebrafish spinal cord

“…In the spinal cord, individual sensory Rohon-Beard axonal growth has been followed live in vivo by widefield and confocal microscopy in the zebrafish (Andersen and Halloran, 2012;Lee et al, 2017;Liu and Halloran, 2005), and individual motoneurons by confocal microscopy in the zebrafish and Xenopus (Bremer and Granato, 2016;Plazas et al, 2013) and widefield in Drosophila (Murray and Whitington, 1999). Though there are compelling reasons to study axon guidance with the Xenopus model (reviewed by (Erdogan et al, 2016)), a live imaging study of Xenopus spinal cord floor plate commissurals was based mostly on fixed samples (Moon and Gomez, 2005) because the closely apposed notochord obscured live imaging, just as mouse commissural axon studies also rely on fixed samples (e.g. studies by Brose et al (1999); Comer et al (2015); Jaworski et al (2015)).…”