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Myelin sheaths can remodel following damage in zebrafish demyelination models (A) Schematic of experimental timings for imaging myelin swellings in individual oligodendrocytes in the zebrafish Tg(mbp:mCherry-NTR) model. (B) Confocal images of single oligodendrocytes in the spinal cord from animals treated for 1 day with vehicle or 5 mM mtz. Yellow arrows indicate cell body location. Asterisks indicate myelin swellings. Scale bar = 10 µm. (C) Quantification of swellings/cell in dorsal and ventral spinal cord oligodendrocytes following 1-2 days treatment with vehicle/5 mM mtz. Error bars are median ± interquartile range (46 cells from 38 mtz-treated animals, 16 cells from 14 vehicle-treated animals). (D) Confocal images of myelin (Tg(mbp:EGFP-CAAX)) and the Mauthner axon (Tg(Mauthner:Gal4;UAS:mem-mScarlet)) immediately after 2 days of treatment with 5 mM mtz. Scale bar = 10 µm. (E) Confocal images of myelin (Tg(mbp:EGFP-CAAX)) and neuronal cell bodies (Tg(NBT:DsRed)) immediately post 2 days of treatment with 5 mM mtz. Asterisks indicate myelin swellings. Scale bar = 10 µm. (F) Confocal images of an individual oligodendrocyte from an animal treated for 1 day with 5 mM mtz at 4 days post-fertilisation (dpf), imaged over time 0 days (5 dpf), 2 days (6 dpf), 4 days (8 dpf) and 5 days (9 dpf) post-mtz treatment where the cell degenerates. Yellow arrows indicate cell body location. Scale bar = 10 µm. dpt = days post-treatment. (G) Confocal images of an individual oligodendrocyte from an animal treated for 1 day with 5 mM mtz at 4 dpf, imaged over time 1 day, 3 days and 4 days post-mtz treatment where the cell survives and recovers. Scale bar = 10 µm. dpt = days post-treatment. (H) Quantification of number of oligodendrocytes that degenerated or survived following treatment with 5 mM mtz (out of 39 cells from 34 animals). (I) Confocal images of individual myelin sheaths from animals treated for 1 day with 5 mM mtz, imaged over time where the swelling recovers or decreases in size. Asterisks indicate location of swellings. Scale bar = 10 µm. dpt = days post-treatment. (J) Confocal images of individual myelin sheaths from animals treated for 1 day with 5 mM mtz, imaged over time where the swelling increases in size. Asterisks indicate location of swellings. Scale bar = 10 µm. dpt = days post-treatment. (K) Quantification of number of swellings that over a 4-5 day period increased in size, remained stable or decreased in size/recovered following 1-2 days of treatment with mtz (swellings tracked in 16 cells from 14 animals). (L) Schematic of experimental timings for imaging myelin swellings in individual oligodendrocytes in the zebrafish Tg(mbp:TRPV1-tagRFPt) model. (M) Confocal images of single myelin sheaths labelled with mbp:EGFP-CAAX followed over time in the dorsal spinal cord in Tg(mbp:TRPV1-tagRFPt) animals, imaged pre-treatment, immediately post 2 hours of treatment with vehicle or 5 µM csn, and 1 day later. Scale bar = 10 µm. hpt = hours post-treatment. dpt = days post-treatment. (N) Confocal images of myelin sheaths of individually labelled Mauthner-myelinating oligodendrocytes from animals treated for 2 hours with 5 µM csn, imaged over time immediately post-treatment and 1 dpt. Asterisks indicate location of swellings. Yellow arrows indicate cell body location. Scale bars = 10 µm. hpt = hours post-treatment. dpt = days post-treatment.
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