Fig. 1

iGluSnFR expression under the GFAP promoter reduces significantly the myelinating oligodendrocyte number in zebrafish. The number of ClaudinK⁽⁺⁾ OLs was reduced in iGluSnFR-expressing zebrafish larvae at 5 dpf. (a) Z-projections of proximal spinal cord regions in lateral view obtained by two-photon in vivo microscopy. The top row shows double transgenic fish expressing GFAP:iGluSnFR and ClaudinK:TdTomato. In the second row, iGluSnFR⁽⁻⁾ littermate controls are shown. The third row shows images of double transgenic fish expressing GFAP:GFAP-GFP and ClaudinK:TdTomato. Red and green channels are presented in the first and second image of each row, respectively. The third right image is a merge of both channels. Fish that express iGluSnFR appear to have reduced numbers of red-labeled OLs. Scale bar: 50 μm. (b–d) Quantification of cell numbers of total (b), dorsal (c), and ventral (d) OLs. The number of OLs was quantified by counting TdTomato⁽⁺⁾ cells per Z-stack. Each Z-stack had the same dimensions in x, y, and z and was obtained from approximately the same region within the fish. The total number of OLs was significantly reduced in iGluSnFR-expressing fish (red dots) (b). Both regions (dorsal and ventral) show significant OL loss (c, d). However, the percentage decrease in dorsal OL numbers was higher (c). The iGluSnFR⁽⁻⁾ (blue squares) and GFAP-Ctrl (green triangles) larvae do not show any significant difference between each other. Data were analyzed by one-way ANOVA followed by Bonferroni's multiple comparisons. *** indicates a p-value < 0.001; (b) F = 91.47; df = 80; (c) F = 80.49; df = 80; (d) F = 49.28; df = 80. Dot plots show arithmetic mean ± standard deviation. N = 3, n in iGluSnFR⁽⁺⁾ = 34; n in iGluSnFR⁽⁻⁾ = 32 and n in GFAP-Ctrl = 15