In situ hybridization on 12μm transverse sections through the otocyst of E12.5 (A-F, A’-F’) and E13.5 (G-L, G’-L’) mouse embryos using probes for Pax2 (A, A’, G, G’), Zic1 (B, B’, H, H’), Zic2 (C, C’, I, I’), Zic3 (D, D’, J, J’), Zic4 (E, E’, K, K’), and Zic5 (F, F’, L, L’). Note that Pax2 is expressed in the otic epithelium, while Zic gene expression is restricted to the surrounding mesenchyme. Abbreviations: oe, otic epithelium; ed, endolymphatic duct; co, cochlea; scc, semicircular canals; nt, neural tube; gl, ganglion; hv, head vein; d, dorsal; m, medial. Blue dashed line defines border between the otic epithelium and the mesenchyme (A, A’, B, B’, G, G’, H, H’). Scale bar in A, 200μm (applies to A-L); scale bar in A’, 50μm (applies to A’-L’).