Role of SoxE genes in the development of the auditory portion of the inner ear

The transcription factors of the soxE family, including sox8, sox9 and sox10 play important roles in diverse developmental processes. However little is known about their function during inner ear development. In the developing inner ear we detected sox9 and sox10 in the sensory epithelia since the formation of the otic placode. As the organ of Corti begins to differentiate, sox9 and sox10 expression are progressively restricted to supporting cells. To elucidate the role of sox10, we first analysed sox10 knockout mice. Using sox2 as a molecular marker of the prosensory domain, we showed that sox 10 is not required for its formation but is necessary for its maintenance. Indeed, we observed a significant shortening of the cochlear duct. Interestingly, expression of the notch ligand Jagged 1, which plays a crucial role during cochlear development, is decreased in the prosensory area of sox10-deficient mice. In parallel, using both gain- and loss-of function approaches, we showed that sox9 is required for cell patterning in the organ of Corti. Taken together, these results demonstrate diverse roles of soxE genes during the inner ear development, specification and maintenance of differentiated cells within the cochlea.