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Fig. 6 Misexpression of ngn1 causes ectopic development of distinct types of neurons (arrowheads) in a region specific manner. (A,B) ngn1- myc-injected (A) and uninjected control (B) embryo hybridised to isl-1 probe at the 3-somite stage. Lateral views; anterior up. (C,D) ngn1-mycinjected (C) and uninjected control (D) showing isl-2 expression at the 24h stage. Ectopic isl-2 expression is detectable in the non-neural ectoderm. Optical sections through surface ectoderm at the level of the hindgut extension. Dorsal up, anterior left. (E,F) Ectopic nrd expression in ngn1-myc-injected (E) and uninjected (F) control embryo at the 3-somite stage. nrd-expressing cells are detectable in the anterior half of the yolk sac ectoderm. Lateral views, anterior up. (G-I) Ectopic nrd expression is detectable over the yolk (G) and over the surface ectoderm covering the body axis in 24h ngn1-myc-injected (I) but not in uninjected controls (H). nrd expression in the nasal placodes is expanded in ngn1-myc-injected embryos (arrow). Ventral views, anterior up (G,H). Lateral view, anterior left, dorsal up (I). (J-L) Ectopic zash1b expression is found in cells lateral to the body axis in ngn1-myc-injected (J,L) but not in uninjected controls (K). Dorsal view, anterior up (J,K). Lateral view, dorsal up, anterior left (L). (M) ngn1-myc-injected embryos express hlx-1 ectopically in cells in the endoderm. Scale bar: 50 μm (A,B,E-H,J,K), 25 μm (C,D,I,L) and 12 μm (M).