Fig. 2. Sustained FGF overexpression stimulates OEPD fate but inhibits otic differentiation. (A) Schematic showing the strategy for electroporation into the anterior primitive streak of HH4 ex ovo cultured chicken embryos. Cathode and anode are shown, dorsal (d) is down and ventral (v) up. (B,C) Unilateral electroporation targets the paraxial mesoderm and the overlying neural ectoderm on one side of the embryo (B). Section shows unilateral electroporation of the mCherry tracer construct revealed by a dsRed antibody (C). (D) Control embryos, electroporated with empty vector show normal Pax2 expression. Line marks the axial level of the section. (E) pEF-Fgf3 extends the Pax2 expression domain (n=10/22). (F)pEF-Fgf19 extends the Pax2 expression domain (n=15/28). (G) Both pEF-Fgf3 and pEF-Fgf19 extend the Pax2 OEPD expression domain (n=15/22). Line marks the axial level of the section. (H) Section taken through the control embryo in D, showing normal Pax2 expression. (I) Section taken through the trigeminal region of the pEF-Fgf embryo in G, showing the unilateral extended Pax2 expression domain. (J) Control embryos, electroporated with empty vector, show normal bilateral Soho1 expression. Line marks the axial level of the section. (K) pEF-Fgf3 reduces the Soho1 domain (n=7/10). (L) pEF-Fgf19 reduces Soho1 expression (n=9/13). (M) Both pEF-Fgf3 and pEF-Fgf19 reduce Soho1 expression (n=8/11). Line marks the axial level of the section. (N) Section taken through the control embryo in J, showing normal bilateral Soho1 expression. (O) Section of the pEF-Fgf electroporated embryo in M, showing unilateral reduction of Soho1 expression. (P) Control embryos, electroporated with empty vector, show normal bilateral Nkx5.1 expression. (Q) pEF-Fgf3 reduces the Nkx5.1 domain (n=1/2). (R)pEF-Fgf19 reduces Nkx5.1 expression (n=5/11). (S) Electroporation of both pEF-Fgf3 and pEF-Fgf19 reduces Nkx5.1 expression (n=5/5). In all cases, the electroporated side is on the right.