Fig. 1. Localization of chick Sfrp1 transcripts during eye development. Embryos of indicated developmental stages were hybridised (A-E) in toto or (F-H,K,L) in frontal cryostat tissue sections. Embryos are viewed (A) dorsally or (C) laterally. Images in (B,D,E) represent (B) transversal and (D,E) frontal paraffin sections of whole mount processed embryos. Image in (I,J,K) are high magnification views of (E,F) and of the boxed area in (H), respectively. Note the early expression of Sfrp1 in the prospective neural retina, (arrow in B) lens placode ectoderm and (A-D) lens vesicle. cSfrp1 transcripts are first localized to (arrows in E,I) the centro-dorsal retina, expand later to (F,G,J) the periphery and become restricted to (H,K,L) the inl following neurogenesis gradients. inl, inner nuclear layer; lv, lens vesicle; pnr, presumptive neural retina; ppe, presumptive pigment epithelium. Bar: (A,F,G) 400 µm; (B) 94 µm; (C) 500 µm; (D,E,G) 50 µm; (K,L) 40 µm; (H) 625 µm.