Expression of pluripotency-inducing factors in the developing chick eye. (A) RT-PCR analysis of pluripotency-inducing factors at Stage 8 to 9 and ciliary margin (CM) and retinal pigmented epithelium (RPE) at Stage 24 (E4). Expression of the housekeeping gene gapdh was used as an internal control. rdh10 and mitf are specifically expressed in the CM and RPE respectively and were used as controls for the specificity of the tissues. Immunohistochemical staining using antibodies against (B) Sox2, (C) Klf4, (D) c-Myc and (E) Lin-28 in the anterior region of E4 eyes (in green). In the posterior region, (F) Sox2, (G) Klf4, (H) c-Myc and (I) Lin-28 were tested along with Mitf (microphthalmia-associated transcriptional factor; in red). The scale bar in panel E represents 100 μm and also applies to panels B, C and D. Scale bar in panel I represents 50 μm and applies to panels F, G and H. CM, ciliary margin; L: lens; NE: neuroepithelium; RPE, retinal pigmented epithelium.