Figure 7. The dominant negative allele Mitf^mi restores retinal development in the Vsx2 mutants.

(A–F) Merged images of cryosections showing DAPI staining (blue) and melanogenic pigmentation (white) in P0 orj, R200Q, and R227W mice that were Mitf wild-type (Mitf^+/+; A–C) and mi heterozygous (Mitf^mi/+; D–F). Insets show whole eyes. The retina in C was completely transformed into pigmented tissue (bounded by dashed line) and ectopic POM was partially pigmented (asterisk). Eye size and retinal histology were restored to a comparable degree in all Vsx2, mi compound mutants (D–F). Also notable in the R227W, mi compound mutant was the lack of POM in the vitreal chamber (asterisk in F). (G–L) TUBB3 staining at P0. In all cases, lamination patterns were restored in the compound mutants, indicating robust neurogenesis. Retinal tissue in I is bounded by the dashed lines. (M) The reduced eye size in the R227W mutant was partially rescued in the R227W; Mitf^mi/+ mutant at E12.5. (N) The expression of TUBB3 was detected in the R227W; Mitf^mi/+ retina at E13.5. (O) Mitf and Otx1 transcript levels were much lower in the R227W; Mitf^mi/+ retina (black bars) compared to the R227W mutant (white bars). (P) pan-Mitf transcript level in orJ; Mitf^mi/+ retina was not lower than that in orJ retina. * P≤0.05; *** P≤0.001 Scale bars: 100 µm (A–F); 1 mm (insets); 50 µm (G–L); 0.5 mm (M); 100 µm (N).