Fig. 3 . Chx10 and Mitf are necessary for their reciprocal Mitf and Chx10 mutant retinal phenotypes. (A) A Hematoxylin and Eosin-stained coronal section through a wild-type (+/+; +/+) P0 eye showing normal morphology. (B) An identical Hematoxylin and Eosin-stained section through an Mitf wild-type (+/+);Chx10^or-J/or-J (J/J) eye showing the thin, hypocellular, non-laminated NR (arrowhead). (C) The loss of one copy of Mitf (mi/+) on the Chx10 mutant background (J/J) results in a thicker, multicellular, laminated NR (arrowhead). Neuroretinal rescue in the mi/+;J/J eye (n=3/3). (D) Double Mitf;Chx10 mutants (mi/mi;J/J) have a dramatic normalization of the NR (arrowhead) when compared with the Chx10^or-J/or-J mouse (B). Neuroretinal rescue in the mi/mi;J/J eye (n=4/4). (D') An enlargement of the NR (shown in the region of the arrowhead in D) illustrating the lamination of the double mutant NR. nbl, neuroblastic layer; ipl, inner plexiform layer; gcl, ganglion cell layer. (E) Mitf^mi/mi (mi/mi) mice lacking one copy of Chx10 (J/+) express the neuroretinal marker protein Pax6 in a thickened neuroretinal-like layer (NRLL) in the dorsal part of the RPE (arrow) and in the NR (arrowhead). (F) The loss of both copies of Chx10 (J/J) in the Mitf mutant background (mi/mi) results in a normalization of the thickness of the NRLL in the dorsal RPE [highlighted by the expression of Pax6 (arrow)]. RPE rescue in mice with a background of more than 90% 129/SvJ (n=2/4). (G) In a second genetic background (see below), the Mitf mutation (mi/mi) results in a more dramatic NRLL in an animal heterozygous for the Chx10^or-J mutation (J/+). Pax6 expression is seen in both the NR (arrowhead) and NRLL (arrow). (H) Double Mitf;Chx10 mutants (mi/mi;J/J) have a normalized RPE phenotype, highlighted by the loss of ectopic Pax6-expressing tissue in the RPE (arrow). RPE rescue in a mixed 129/SvJ;B6C3He background (n=2/2). Scale bars: 80 µm in A-D; 20 µm in D'; 25 µm in E,F; 31 µm in G,H.