Fig. 2. Expression of XOtx5b and XOtx2 in retinal sections. Section in situ hybridisation of XOtx2 (A-E) and XOtx5b (F-J) in the Xenopus retina at stages 25/26 (A,F), 28 (B,G), 33 (C,H), 37 (D,I) and 41 (E,J). (A,F) XOtx2 (A) is expressed throughout the presumptive retinal pigment epithelium and retina while XOtx5b (F) expression is only in the central retina. (B,G) As retinal invagination progresses, expression of both XOtx2 (B) and XOtx5b (G) appear in the central retina. (C,H) Expression of XOtx2 (C) and XOtx5b (H) is identical. Transcripts from either of these genes are found throughout the developing retina except in the peripheral dorsal and ventral regions. (D,I) The central retinal expression of these two transcripts is reduced to particular layers. XOtx2 (D) is expressed in the outer edge of the inner nuclear layer (INL). XOtx5b (I) is also found in the outer edge of the INL and also in the outer nuclear layer (ONL). The peripheral retina still expresses these transcripts in the ganglion cell layer. (E,J) When the retina is mature, XOtx5b (J) is found in both the photoreceptor layer and the outer cells of the INL. Like XOtx2 (E), it is also found in the edge of the CMZ. XOtx2 is also expressed in cells at the outer edge of the INL. Bars: 20 µm; dashed lines indicate the extent of developing neural retina in A-D,F-I.

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