Fig. 6. Aberrant Otx2 expression in Gbx2 mutants. Otx2 (A,C,E,G) and Lfng (B,D,F,H) expression patterns in heterozygous (A-D) and homozygous (E-H) Gbx2 inner ears. (A,B and E,F) Comparable pairs of 12 µm adjacent sections dorsal to the pairs shown in C,D and G,H respectively. Otx2 and Lfng expression domains are complementary in heterozygous, but overlap with each other in homozygous Gbx2 otocysts (brackets). (I) The Otx2 expression domain expands medially in the growing cochlear duct of Gbx2^-/- ears at 12 dpc (double arrows). (J-L) Comparable cochlear sections at 15.5 dpc. (J) Otx2 expression in the Reissner's membrane of a +/– cochlear duct (bracket). (K,L) Adjacent cochlear sections of Gbx2^-/- mutants probed for Otx2 (K) and Lfng (L) transcripts. A bracket in K marks the normal Otx2 expression domain and arrows indicate ectopic Otx2 expression in the medial region. Arrows in L indicate a Lfng-positive sensory region in the cochlea, and arrowheads indicate the sensory region in the posterior crista. (M,N) Adjacent +/– inner ear sections at 10.5 dpc probed for Gbx2 (M) and Otx2 (N) transcripts. Arrows indicate the borders of expression domain for each gene, and double arrows indicate the lateral restriction of Otx2 expression domain. Schematics on the right indicate the levels of sections. Scale bars: in B, 100 µm for A-H; in L, 100 µm for L,K; in N, 50 µm for M,N.