Fig. 6. Canonical Wnt signal activation inhibits epibranchial formation but does not affect OEPD formation. In all panels, embryos have been electroporated unilaterally on the right-hand side with a constitutively active (CA) β-catenin and a tracer expressing mCherry. (A) Electroporation of CA-β-catenin does not affect the size of the otic placode, as assessed by Soho1 expression. (B) The location of the mCherry tracer in the embryo shown in A indicates widespread electroporation. (C) The expression of Nkx5.1 is not altered in CA-β-catenin-expressing embryos. (D) The location of the mCherry tracer in the embryo shown in C indicates widespread electroporation. (E) Expression of Pax2 in the OEPD is initially normal at 7ss (n=3/4 show no change). (F) Section of the embryo shown in E, showing normal ectodermal Pax2 expression, although some ectopic expression is detected within the neural tube. (G) Section of the embryo shown in E, showing electroporated cells revealed by dsRed immunostaining, which cross-reacts with mCherry. (H) By 13ss, the lateral edge of the Pax2 expression domain is downregulated (n=7/9). Line depicts the level of the section taken. (I) Section of the embryo shown in H, showing reduced lateral ectodermal Pax2 expression. (J) Section of the embryo shown in H, showing electroporated cells revealed by dsRed immunostaining. (K) Foxi2 expression is reduced in response to CA-β-catenin (n=5/6). Line depicts section shown (L,M). (L) Section of the embryo shown in K, showing reduced lateral Foxi2 expression. (M) Section of the embryo in K, showing electroporated cells revealed by dsRed immunoreactivity. (N) Epibranchial neurogenesis, marked by Phox2b expression, is unaffected on the control side of electroporated embryos. (O) Phox2b expression is reduced on the electroporated side of the embryo expressing CA-β-catenin (n=10/12).