(A–C) Expression of brn3c:gfp in hs:atoh1a/+ transgenic embryos (A, C) and a hs:atoh1a/+;hs:sox2/+ double transgenic embryo (B) heat shocked at 24 hpf and photographed at 34 hpf. The specimen in (C) was also injected with sox2-MO. The inset in (A) shows a heat-shocked brn3c:gfp/+ control embryo at 34 hpf. (D–L) sox2 expression in a control embryo (D), atoh1a/b morphants (E, F), wild-type embryos exposed to SU5402 (G), DAPT (H), or both DAPT and SU5402 (I) beginning at 26 hpf, a hs:atoh1a/+ embryo heat shocked at 24 hpf (J), a hs:gal4/+;UAS-NICD/+ embryo heat shocked at 24 hpf (K), and a hs:fgf8/+ embryo heat shocked at 30 hpf (L). sox2 expression is shown at 30 hpf, except (D, E, 18 hpf) and (L, 36 hpf). Expression in control embryos does not change appreciably between 30 and 36 hpf. All images show lateral views with anterior to the left and dorsal to the top.