Specification of a subset of DRG neurons fails in sox10 mutants. (A-C) Whole mount in situ hybridisation of 36 hpf wild-type (A) and sox10 mutant (B) embryos for ngn1. Quantitation (mean+s.d., C) showed highly significant reduction in mutants (*** P<0.0001; Student's t-test; n=15 for both data sets). (D-F) Injection of sox10 morpholino (MO; E), but not 3 bp-mismatch morpholino (MM; D), into ngn1:gfp transgenic fish results in reduction of both melanophores (left panels) and DRG sensory neuron precursors (arrowheads, right panels) at 48 hpf. Mismatch morpholino-injected embryos are indistinguishable from uninjected embryos. Quantification (mean+s.d., F) showed highly significant effect in sox10 morphants (*** P<0.0001; ANOVA with Tukey's Post Test; n=22 for sox10 MO, n=20 for both sox10 MM and uninjected data sets). Numbers of GFP+ cells (F) are slightly greater than numbers of ngn1+ cells (C) consistent with the later stage examined and perdurance of GFP in cells in which the promoter is no longer active. (G-I) Ngn1 knock down using a previously characterised morpholino in sox10 mutant embryos results in near-complete loss of escaper DRG sensory neurons, even in the trunk (H), compared with uninjected sox10 mutants (G). This reduction was highly significant (I) (*** P<0.0001; Student's t-test) (n=16 for each data set). Scale bars: 20 μm in A,B; 50 μm in G,H; 100 μm in D,E.
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