Figure 6.

Six3 expression in the PLE precedes that of Pax6 and is initially unaffected in small eye-mutant embryos. (A) Six3 is expressed in the PLE (arrowhead) of a wild-type 5-somite-stage embryo. (A′) Pax6 expression is not yet detected in that region. At later stages, Six3 (B–D) and Pax6 (B′–D′) are detected in the PLE (arrowheads) and optic vesicles. Six3 expression in the PLE was examined in small eye (Pax6^{Sey-1Neu/Sey-1Neu})-mutant embryos. Pax6 was not required for the initial expression of Six3 in the PLE (arrowheads in E′, F′) but was required for its maintenance in the PLE at later stages (arrowheads in G′, H′).