PAX6 and Anophthalmia: Homozygous mutations causing a complete loss of Pax6 expression result in anophthalmia in mice and rats.19,17Pax6 mutant mouse embryos have normal Rx expression, suggesting that Pax6 is downstream of Rx. 14 Misexpression studies with Pax6 have been carried out in Drosophila20 and Xenopus21 and have shown to induce ectopic eye tissue.