RPE phenotypes in Vax1/Vax2/Mitf mutants.

*In all mutants that are Vax1−/−, the prospective ventral RPE domain is present in the early optic vesicle/optic cup stage, but gradually displaced by the overgrowing presumptive ventral optic stalk domain that also abnormally contains VSX2-expressing cells, resulting in ventral coloboma after E14;**Interestingly, about 50% of the Vax1−/−;Mitf −/− embryonic eye sections showed only mild dorsal RPE phenotypes (see Figure 2F). It is possible that loss of VAX1 functions increases the local dosages of antiretinogenic factors such as VAX2, JAGGED1, or TFEC [19] but such changes may be too subtle to be detected by immunostaining or in situ hybridization.***Although the Vax1+/−;Vax2−/−;Mitf +/− embryos appeared to have largely normal RPE pigmentation (Figure 3C), on sections there were some patches of thickened dorsal-proximal RPE subdomains that express VSX2 at very low levels.