Fig. 6

Fate of Schwann cells after neurectomy. (A) Schematic representation of the transplantation scheme used to obtain mosaic labeling of Schwann cells. Briefly, 10 to 20 donor cells of Tg(Ubi:zebrabow:cherry) blastula stage embryos were aspirated and transplanted into Tg(8.0cldnb:lynEGFP) host embryos of the same stage. The transplanted embryos were screened for the presence of red fluorescent donor cells in the pLL at 48 hpf. (B) Distribution and morphology of transplanted Schwann cells in a mock-neurectomized larva (control). The rectangle indicates the region examined in the same fish at different timepoints. (C-E) Schwann cells were examined from 1 hpn (C) to 5 dpn (E); the cells show the same distribution and general morphology through time; however, at 5 dpn (which corresponds to 8 dpf) the cell extensions form a tubular structure typical of myelinating Schwann cells (arrow). (F) A transplanted larva that was neurectomized; the rectangle indicates the region detailed in G-I. (G-I) Organization and morphology of Schwann cells over time, from 1 hpn (G) to 5 dpn (I). At 24 hpn (H) the cells exhibited vacuoles and lost their typical bipolar morphology. After 5 dpn (8 dpf) Schwann cell numbers appear reduced and the cells show thinner processes and fail to form the extensions seen in control fish (compare E to I arrows). The rectangle in H shows the region expanded in J-L. (J-L) One day after neurectomy, Schwann cells appear to engulf debris from damaged axons (arrows in L). Scale bars: B, F: 200 µm; C-E, G-I: 25 µm; J-L: 20 µm; insets in J-L: 10 µm.