β3-integrin is required for differentiation in OC-2 cells derived from mammalian embryonic inner ear

We have identified 4 integrin subunits which are expressed in OC-2 cells: α6, αv, β1 and β3. Among these, the relative level of expression of the αv, β1 and β3 subunits increased in a time dependent manner when the cells were exposed to the differentiating temperature of 39°C, most notably so for β3 which was not detectable at 33°C. Treatment of fully differentiated OC-2 cells with siRNA against the four integrin subunits reduced the expression of not only the respective integrin proteins but also of the hair cell marker Myosin VIIa. Conversely over-expression of β3 was sufficient to induce the expression of Myosin VIIa at 33°C.Our data demonstrate that modulation of integrin expression is associated with the differentiation process of the OC-2 cells. This suggests that the maturation of the organ of Corti, from where OC-2 cells are derived, may also depend on changes of gene expression associated with integrin expression.Sound travels as waves of compressed air into the outer ear; it is amplified by the movement of ossicles in the middle ear; and finally is converted into a neuronal signal in the inner ear. In the organ of Corti, sound stimulation of the sensory "hair" cells leads to release of glutamate to initiate neuronal signals which are carried to and processed in the brain. The organ of Corti is a specialised epithelial tissue containing three rows of outer hair cells, one row of inner hair cells and a variety of supporting cells. Each hair cell is surrounded by and separated from its neighbours by intervening supporting cells. The bodies of the supporting cells also intervene between the base of the hair cells and the basilar membrane, the extracellular matrix that underlies the organ of Corti, such that supporting cells, but not hair cells are attached to the basilar membrane. The base of each hair cell is in contact with a nerve terminal where the mechanical sound signal is converted into an electrical nerve signal.The cellular composition and architectur