Figure 2.
Formation of an ectopic organ of Corti in the Lmo4-null cochlea. A–H, Ectopic hair cells are observed in Lmo4-null cochlea. Cross-sections through the indicated turns of the cochlea duct were immunolabeled with anti-MYO6 (green) and nuclear counterstained with propidium iodide (red). Brackets indicate the native OC, which contains one row of inner hair cells and three rows of outer hair cells. Asterisks indicate the ectopic hair cells. I–J′, Ectopic hair cells and pillar cells are formed in the Lmo4-null cochlea. Whole-mount immunocytochemistry using anti-P75 (red) and FITC-conjugated phalloidin (green) reveals the formation of eOC in the Lmo4-null cochlea. I′and J′are higher-magnification images of I and J, respectively. Arrow and arrowhead in J indicates pillar cells in the native OC and eOC. Arrowheads in I′ indicate outer hair cells in control cochlea. Arrowheads in J′ indicate ectopic inner hair cells in the eOC. K, L, SEM image shows that planar cell polarity of hair cells is affected in Lmo4-null cochlea. Arrowheads show that the orientation of hair cell stereocilia in the region of ectopic hair cell formation is disrupted in Lmo4-null cochlea. M–P″, The Lmo4-null cochlea contains an ectopic and reverse orientated OC. Compared with the control (M, O), immunolabeling of the Lmo4-null cochlea (N, P) with anti-MYO6 (green) and anti-PROX1 or anti-JAG1 (red) at E17.5 shows the formation of an eOC completed with hair cells and supporting cells. Arrowheads indicate the inner hair cells. Q, R, Cross-sections through the control (Q) and Lmo4-null (R) cochlea at E18.5 stained for MYO6 (red), S100A1 (green), and DAPI (blue) confirms that the ectopic region is oriented as a mirror image to the native organ. Arrowheads indicate the inner hair cells in the eOC and arrows show inner hair cells in the native OC. Scale bars: A-H, I′, J′, M, N, 50 μm; I, J, 200 μm; M′, N′, N″, O′, P′, P″, Q, R, 20 μm.