Analysis of myelinated axon formation in zebrafish

Abstract

Myelin is a lipid-rich sheath formed by the spiral wrapping of specialized glial cells around axon segments. Myelinating glia allow for rapid transmission of nerve impulses and metabolic support of axons, and the absence of or disruption to myelin results in debilitating motor, cognitive, and emotional deficits in humans. Because myelin is a jawed vertebrate innovation, zebrafish are one of the simplest vertebrate model systems to study the genetics and development of myelinating glia. The morphogenetic cellular movements and genetic program that drive myelination are conserved between zebrafish and mammals, and myelin develops rapidly in zebrafish larvae, within 3–5 days post-fertilization. Myelin ultrastructure can be visualized in the zebrafish from larval to adult stages via transmission electron microscopy, and the dynamic development of myelinating glial cells may be observed in vivo via transgenic reporter lines in zebrafish larvae. Zebrafish are amenable to genetic and pharmacological screens, and screens for myelinating glial phenotypes have revealed both genes and drugs that promote myelin development, many of which are conserved in mammalian glia. Recently, zebrafish have been employed as a model to understand the complex dynamics of myelinating glia during development and regeneration. In this chapter, we describe these key methodologies and recent insights into mechanisms that regulate myelination using the zebrafish model.

Axonal regeneration in zebrafish spinal cord

“…most of human physiology and pathologies can be modeled in zebrafish (Babin, Goizet, & Raldua, ; Howe et al., ; Kabashi, Brustein, Champagne, & Drapeau, ). As some common molecular mechanisms after SCI such as microglial/macrophage response and faithful recapitulation of the myelinating program exist during regeneration and genes identified in the fish are conserved in higher vertebrates (D'Rozario, Monk, & Petersen, ), zebrafish offer a promising tool for translational research.…”

A novel myelin protein zero transgenic zebrafish designed for rapid readout of in vivo myelination

“…However, these systems lack the complexity of cell-cell interactions found in intact nervous systems and provide limited information on potential therapeutic efficacy in vivo or systemic effects of drug delivery in whole animals. A. Preston & Macklin, 2014), that fish respond to drugs in a comparable manner to other animals (MacRae & Peterson, 2015), and that detailed cellular responses to bath application of drugs are readily quantifiable for example, OPC migration, process extension, and internode growth and stability (reviewed in Buckley, Marguerie, Alderton, & Franklin, 2010;D'Rozario, Monk, & Petersen, 2017;Preston & Macklin, 2014). A large body of research shows that molecules and canonical signaling cascades driving myelination are conserved in the fish (for extensive reviews see Monk & Talbot, 2009;M.…”

“…The use of fluorescent markers for detailed quantification of oligodendrocyte behavior in response to small molecule drug exposure in real time has been well documented (see Buckley et al, 2010;D'Rozario et al, 2017;Preston & Macklin, 2014) and can be used to provide insight into potential mechanisms of drug action. The use of fluorescent markers for detailed quantification of oligodendrocyte behavior in response to small molecule drug exposure in real time has been well documented (see Buckley et al, 2010;D'Rozario et al, 2017;Preston & Macklin, 2014) and can be used to provide insight into potential mechanisms of drug action.…”

“…A large body of research shows that molecules and canonical signaling cascades driving myelination are conserved in the fish (for extensive reviews see Monk & Talbot, 2009;M. A. Preston & Macklin, 2014), that fish respond to drugs in a comparable manner to other animals (MacRae & Peterson, 2015), and that detailed cellular responses to bath application of drugs are readily quantifiable for example, OPC migration, process extension, and internode growth and stability (reviewed in Buckley, Marguerie, Alderton, & Franklin, 2010;D'Rozario, Monk, & Petersen, 2017;Preston & Macklin, 2014). Overall, these data support using zebrafish larvae as a rapid, cost-efficient model system for screening candidate small molecules in an intact animal.…”

“…Given that zebrafish embryos are transparent and develop ex utero, and that rapid myelination of the spinal cord occurs during the first week of life, the current model was designed to rapidly assay oligodendrocyte morphology and myelin membrane production in live zebrafish larvae. The use of fluorescent markers for detailed quantification of oligodendrocyte behavior in response to small molecule drug exposure in real time has been well documented (see Buckley et al, 2010;D'Rozario et al, 2017;Preston & Macklin, 2014) and can be used to provide insight into potential mechanisms of drug action.…”