Figure 3.

Lens induction and specification are defective in the severely affected Six3^f/Δ;Le-Cre-mutant lens. Cre activity was restricted to the PLE in E9.5 (A) and E10.5 (A′) Six3^f/Δ;Le-Cre-mutant embryos. (B′) Six3 expression was deleted from the mutant PLE (arrow) but was unaffected in the developing optic vesicle (arrowhead). (C′) Pax6 expression in the PLE was drastically reduced (arrow), and that of Sox2 was absent (arrow in D′); however, Pax6 and Sox2 expression in the optic vesicle remained normal (arrowheads in C′, D′). (E′–K′) Lens induction and specification was arrested, as indicated by the lack of thickening or invagination of the PLE and the absence of Sox2 expression. In E10.5 Six3^f/Δ;Le-Cre mutant embryos, Six3 expression in the PLE was deleted (arrows in E′) but not that in the neural retina lineage. In this embryo, the optic vesicle appeared to be duplicated. (F′) Pax6 expression was downregulated in the PLE (area between arrowheads), and that of Sox2 (G′, region between the two arrows) was absent. Expression of lens differentiation markers Prox1 (H′), sFrp2 (I′), and FoxE3 (J′) was not detected in the mutant tissue, where the lens pit should have formed. (K′) Expression of Meis1 remained unchanged.