Fig. 2: Mutations in genes encoding mGluR5 reduce myelin sheath length without affecting sheath number.
From: Activity-driven myelin sheath growth is mediated by mGluR5
a, HCR detection of grm5a and grm5b messenger RNA in OPCs at 5 dpf. Scale bar, 5 μm. b: HCR detection of grm5a and grm5b mRNA in OLs at 5 dpf. Scale bar, 5 μm. c,d, Schematic showing organization of human and zebrafish genes encoding mGluR5 and their CRISPR/Cas9 based editing that led to identification of mutants with premature STOP codons in exons 2 and 1 of grm5a (c) and grm5b (d), respectively. e, Images of wild-type (N = 35) and grm5a−/−grm5b−/− (N = 22) oligodendrocytes expressing mbp:eGFP–CAAX. f, Images of wild-type (N = 18) and grm5a−/−grm5b−/− (N = 12) oligodendrocytes expressing mbp:eGFP–CAAX at 4 dpf. g, Images of wild-type (N = 10) and grm5a−/−grm5b−/− (N = 14) oligodendrocytes expressing mbp:eGFP–CAAX at 7 dpf. Scale bars 15 μm (e–g). h, Mean sheath length of wild-type (N = 35, 21.11 ± 5.149) and grm5a−/−grm5b−/− (N = 22, 16.34 ± 5.38) oligodendrocytes, in 3 dpf old animals (two-sided Mann–Whitney U-test, P = 0.0035). i, Mean sheath length of wild-type (N = 18, 28.8 ± 6.5) and grm5a−/−grm5b−/− (N = 12, 19.47 ± 3.67) oligodendrocytes, in 4 dpf old animals (two-sided unpaired t-test: P = 0.0001). j, Mean sheath length of wild-type (N = 10, 31.79 ± 4.723) and grm5a−/−grm5b−/− (N = 14, 22.68 ± 4.40) oligodendrocytes, in 7 dpf old animals (two-sided unpaired t-test: P < 0.0001). k, Comparison of mean sheath length in wild-type animals between 3, 4 and 7 dpf animals (one-way ANOVA, Kruskal–Wallis test P < 0.0001; Dunn’s multiple comparisons test: wild-type 3 dpf versus 4 dpf P = 0.0002; wild-type 4 dpf to 7 dpf P = 0.7173, wild-type 3 dpf versus 7 dpf P < 0.0001). (3 dpf, 21.11 ± 5.149; 4 dpf, 28.8 ± 6.52; 7 dpf, 31.79 ± 4.72). l, Number of myelin sheath per oligodendrocyte in 3 dpf wild-type (16.2 ± 4.8) and grm5a−/−grm5b−/− (15.36 ± 3.94) (two-sided unpaired t-test; P = 0.4964). m, Number of sheaths per oligodendrocyte in 4 dpf wild-type (16.06 ± 4.03) and grm5a−/−grm5b−/− (15.92 ± 34.46) (two-sided unpaired t-test; P = 0.9301). n, Number of myelin sheath per oligodendrocyte in 7 dpf wild-type (21.2 ± 5.35) and grm5a−/−grm5b−/− (19.5 ± 8.91) (two-sided unpaired t-test; P = 0.5971). o, Comparison of the mean sheath length in grm5a−/−grm5b−/− animals between 3, 4 and 7 dpf animals (one-way ANOVA, Kruskal–Wallis test P < 0.0001; Dunn’s multiple comparisons test: grm5a−/−grm5b−/− 3 dpf versus 4 dpf P = 0.1675; grm5a−/−grm5b−/− 4 dpf to 7 dpf P = 0.2070, grm5a−/−grm5b−/− 3 dpf versus 7 dpf P < 0.0009) (3 dpf, 16.34 ± 5.38; 4 dpf, 19.47 ± 3.67; 7 dpf, 22.68 ± 4.40). Data show mean ± s.d.
