Fig. 7

RA signalling is required for normal levels of otic neurod1 expression in the absence of tbx1 and otx1b activity.

Embryos were treated with DMSO or DEAB from 18S to 26 hpf. (A) WT embryos treated with DMSO show normal expression of neurod1 (n = 10). (F) Treatment of WT embryos with 400 µM DEAB (n = 18) leads to a reduction in the size of the OV and a reduction neurod1 expression. (B) In otx1b^sa96-/- embryos, expression of neurod1 is shifted posteriorly (n = 4/16 embryos from a heterozygous cross). (G) In otx1b^sa96-/- embryos treated with DEAB, the OV is smaller and expression of neurod1 is reduced (n = 9/37). (C) In otx1b^sa96 sibling (sib; wild-type or heterozygote) embryos, expression of neurod1 is normal (n = 12/16 embryos from a heterozygous cross), but levels are reduced after treatment with DEAB (n = 28/37; H). (D) In tbx1^-/- (vgo) embryos, expression of otx1b is lost and expression of neurod1 is shifted posteriorly (n = 9/38). (I) tbx1^-/- embryos treated with DEAB (n = 16/62) do not express otx1b (lack of red stain); expression of neurod1 is still shifted posteriorly, but is reduced. (E) vgo sibling embryos treated with DMSO show normal expression of neurod1 (purple) and otx1b (red) (n = 29/38 embryos from a heterozygous cross). (J) Treatment of sibling embryos with DEAB (n = 46/62) leads to a reduction in neurod1 expression. All panels are lateral views with anterior to the left. Dotted outline marks position of the OV; vertical lines mark posterior extent of the neurod1-expressing domain relative to the OV. Scale bar: 50 µm.