OTX2 and coloboma: In this study we have demonstrated that in zebrafish, Otx (Otx1a and Otx2, with some contribution from Otx1b) but not Mitf (Mitfa and Mitfb) transcription factors are required for normal RPE development, and that their absence causes a delay in gene expression and pigmentation culminating, in the most severe cases, in significant coloboma.