Abstract
ABSTRACTDemyelinating diseases consist of a variety of autoimmune conditions in which the myelin sheath is damaged due to genetic and/or environmental factors. During clinical treatment, some patients undergo partial remyelination, especially during the early disease stages. However, the mechanisms that regulate demyelination remain unclear. The myelin structure, myelin formation and myelin-related gene expression are highly conserved between mammals and zebrafish. Therefore, the zebrafish is an ideal model organism to study myelination. In this study, we generated a transgenic zebrafish Tg(mbp:nfsB-egfp) expressing a fusion protein composed of enhanced green fluorescent protein (EGFP) and NTR from the myelin basic protein (mbp) promoter. Tg(mbp:nfsB-egfp) expressed NTR-EGFP reproducibly and hereditarily in oligodendrocytes along the spinal cord. Treatment of zebrafish larvae Tg(mbp:nfsB-egfp) with metronidazole (Mtz) resulted in the selective ablation of oligodendrocytes and led to demyelination, accompanied by behavioral changes, including decreased total movement distance, velocity, total movement time and fast movement time. After withdrawal of Mtz for a seven day recovery period, the expression of EGFP and MBP protein was observed again which indicates remyelination. Additionally, locomotor capacity was restored. Collectively, Tg(mbp:nfsB-egfp), a heritable and stable transgenic line, provides a novel, powerful tool to study the mechanisms of demyelination and remyelination.
Highlights
The myelin sheath is the membrane structure protecting, supporting and nourishing axons
To verify whether Tg(mbp:nfsB-egfp)nk002 was still active in adults, we examined the expression of GFP by immunohistochemistry on sections of the transverse spinal cord at 3 mpf
Remyelination occurs and locomotor capacity recovers in Tg(mbp:nfsB-egfp)nk002 larvae To investigate the potential for regeneration following demyelination induced by Mtz, larvae were collected randomly from the 10 dpf Mtz treatment group and routinely cultured in E3 medium until 17 dpf, which was defined as the recovery group
Summary
The myelin sheath is the membrane structure protecting, supporting and nourishing axons. After exposing 5 dpf Tg(mbp:nfsB-egfp)nk larvae to 5 mM Mtz for 5 days, the treatment group had reduced fluorescence signal in the spinal cord (Fig. 2D) compared with steady EGFP expression in the control group (Fig. 2C). Remyelination occurs and locomotor capacity recovers in Tg(mbp:nfsB-egfp)nk larvae To investigate the potential for regeneration following demyelination induced by Mtz, larvae were collected randomly from the 10 dpf Mtz treatment group and routinely cultured in E3 medium until 17 dpf, which was defined as the recovery group. The turn angle and angular velocity in larvae from the recovery group were very similar to larvae from the control group (Fig. 4G,H, t-test, P.0.05) These data indicate that the larvae recovered from the Mtz treatment after 7 days of regular husbandry, and regeneration of the myelin sheath occurred.
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