Fig. 1. (A-L) Xbh1 expression during retinal development. In situ hybridization with either a Xbh1 (A-H) or a Xath5 (H-L) probe on Xenopus embryos at stage 28 (A,E,I), 33 (B,F,J), 38 (C,G,K) and 42 (D,H,L), respectively. (A-D) Lateral views of embryos after whole-mount in situ hybridization (anterior is on the left). (E-L) In situ hybridization on transversal retinal sections. The red hatch (G) delimitates the ciliary marginal zone (CMZ) and the three main retinal layers (ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer). (H) Cross section of a retina from a stage 42 embryo analyzed by double in situ hybridization, showing Xbh1 (purple) and Xath5 (red) expression. (L) The same section as in H showing Xath5 expression alone. The yellow bracket indicates the region where Xath5 and Xbh1 expression overlaps in the CMZ; the yellow arrow indicates co-expression of Xbh1 and Xath5 in INL cells. (M-O) High magnification of CMZ following double in situ hybridization shows expression of Xbh1 (M), Xath5 (N), or both (O). (P,Q) Combined BrdU staining (green) and in situ hybridization (blue) performed on adjacent sections of a stage 42 retina with a Xbh1 (P) or a Xath5 probe (Q). Arrowheads show two identical nuclei stained on adjacent sections.