Fig. 5. Pax6 and Foxe3 expression in Pax6^EE/EE mice. (A-C) P6 5.0-lacz reporter animals stained with X-gal. (A) At E8.75 X-gal staining appears in a teardrop-shaped region of surface ectoderm that overlies the optic vesicle (broken line) and extends temporally (arrow). (B) By E9.5 expression is most intense in a crescent-shaped region that corresponds to the nasoventral lens placode. The broken line indicates the section plane used for C-E and the arrowhead the intense X-gal staining on the nasal side of the lens placode. (C) Frozen section from an X-gal stained E9.5 P6 5.0-lacz reporter animal showing stronger staining in the nasal region (black arrowheads) of the surface ectoderm overlying the optic vesicle. (D,E) Pax6 immunofluorescence in cryosections of wild-type (D) and Pax6^EE/EE (E) eye primordia at E9.5. The broken white line indicates the border between surface ectoderm and optic vesicle (ov). This analysis indicates that the level of Pax6 immunoreactivity is greatly diminished in Pax6^EE/EE embryos in the nasal ectoderm of the lens placode (compare arrowed region in D with the equivalent region in E). The zone of diminished Pax6 immunoreactivity in Pax6^EE/EE embryos corresponds to the region where X-gal staining is strongest in the P6 5.0-lacz reporter (arrowed region in C). (F,G) Pax6 immunofluorescence in cryosections of wild-type (F) and Pax6^EE/EE (G) eyes at E13.0. Wild-type (H) and Pax6^EE/EE (I) E9.5 embryos subject to whole-mount in situ hybridization with an antisense Foxe3 probe. This indicates that in wild-type embryos, Foxe3 expression is found in the ectoderm of the lens placode as expected. In homozygous mutant embryos, Foxe3 expression is lost from the lens placode, but not from the midbrain region (red arrowheads). The optic cup that surrounds the lens pit is marked by a broken line. ov, optic vesicle; le, lens epithelium; pfc, primary fiber cells; pr, presumptive retina.

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