Figure 8

Summary of Sox2 CKO inner ear changes.

Sox2 deletion by Isl1-cre results in profound morphological changes at E14.5: all three cristae of the semicircular canal ampullae are missing, all remaining sensory organs are smaller and have a decreased size of the sensory area. Neuronal formation is eliminated in the apex of the cochlea, whereas vestibular and basal turn neurons gradually die due to limited support by the reduced sensory epithelia. Loss of innervation toward all epithelia except for the apex of the cochlea is secondary to the lack or reduced differentiation of HCs, which is either completely absent in the apex and semicircular canal cristae, or variably disabled in the base of the cochlea, utricle, and saccule. Many HCs have an unusual neurosensory phenotype. Similarly, supporting cells (SCs) have atypical features, altered expression of markers, and abnormal distribution, forming the aberrant organ of Corti. Many ectopic HCs and SCs are also found in the cochlear base. The spatial distribution of Sox2 expression is shown in green, blue color shows neurons, and red depicts HCs. AC, anterior crista; CVG, cochleovestibular ganglion; HC, horizontal crista; HCs, hair cells; PC, posterior crista; S, saccule; SCs, supporting cells; SG, spiral ganglion; U, utricle; VG, vestibular ganglion.