High-resolution live imaging reveals axon-glia interactions during peripheral nerve injury and repair in zebrafish

Abstract

Neural damage is a devastating outcome of physical trauma. The glia are one of the main effectors of neuronal repair in the nervous system, but the dynamic interactions between peripheral neurons and Schwann cells during injury and regeneration remain incompletely characterized. Here, we combine laser microsurgery, genetic analysis, high-resolution intravital imaging and lattice light-sheet microscopy to study the interaction between Schwann cells and sensory neurons in a zebrafish model of neurotrauma. We found that chronic denervation by neuronal ablation leads to Schwann-cell death, whereas acute denervation by axonal severing does not affect the overall complexity and architecture of the glia. Neuronal-circuit regeneration begins when Schwann cells extend bridging processes to close the injury gap. Regenerating axons grow faster and directionally after the physiological clearing of distal debris by the Schwann cells. This might facilitate circuit repair by ensuring that axons are guided through unoccupied spaces within bands of Büngner towards their original peripheral target. Accordingly, in the absence of Schwann cells, regenerating axons are misrouted, impairing the re-innervation of sensory organs. Our results indicate that regenerating axons use haptotaxis as a directional cue during the reconstitution of a neural circuit. These findings have implications for therapies aimed at neurorepair, which will benefit from preserving the architecture of the peripheral glia during periods of denervation.

Transposons As Tools for Functional Genomics in Vertebrate Models

“…7). Since the body of a zebrafish larva is transparent through all developmental stages, such transgenic fish have been used to visualize the vascular system [108], the central and peripheral nervous systems [109, 110], the regenerating processes of the sensory system and fin [111, 112], the cellular process of muscle wound repair [113], and proteolytic cleavage of the extracellular domain of a membrane protein (Neuregulin) in the motor neurons [114], among others. Also, the transgenic fish were applied to image the activity of specific neuronal populations or endothelial cells by targeted expression of a calcium indicator GCaMP [115, 116].…”

“…( C ) Central and enteric nervous system in SAGFF234A at 5 dpf [110]. ( D ) Lateral line glial cells in gSAGFF202A at 5 dpf [111]. ( E ) Caudal trunk (and the wound epidermis) in HGn21A embryo at 1 dpf [112].…”

Analysis of myelinated axon formation in zebrafish

“…This repair and regenerative program is orchestrated by bursts of injury-specific genes such as c-Jun, a transcription factor normally downregulated during myelinating SC development (Arthur-Farraj et al, 2012). The role of SCs in peripheral nerve repair has been studied in the PLLn (Graciarena, Dambly-Chaudière, & Ghysen, 2014; Xiao et al, 2015), motor nerves (Rosenberg, Isaacman-Beck, Franzini-Armstrong, & Granato, 2014), and the adult zebrafish maxillary barbels (ZMB) (LeClair & Topczewski, 2010; Moore, Mark, Hogan, Topczewski, & LeClair, 2012). In the larval PLLn, following laser-mediated axonal transection, adjacent SCs extend bridging processes toward the site of injury and begin clearance of axonal debris (Xiao et al, 2015).…”

Seeing is believing: multi-scale spatio-temporal imaging towards in vivo cell biology

“…Owing to the superior temporal and spatial resolution that can be achieved (below the diffraction limit and with a time interval of <1 s), the authors provided new insights into the growth mechanisms of microtubules. In addition, by imaging living zebrafish embryos with LSFM, the interaction between Schwann cells and axons during neuron damage repair was observed in vivo (Xiao et al, 2015). More recently, two-photon Bessel beam light-sheet microscopy was optimized to study how cells maintained in a 3D culture mechanically react to changes in their microenvironment, at a subcellular level and without spatial constraint (Welf et al, 2016).…”