E-cadherin in the mature and developing organ of Corti of the mouse.

The reticular lamina of the mammalian cochlea is formed by the tightly joined apical surfaces of hair cells and supporting cells. This lamina creates a barrier separating endolymph and perilymph, two fluids of different composition. The preservation of this fluid barrier is a requirement of cochlear function. This study aimed to determine whether the calcium-dependent, cell adhesion molecule, E-cadherin was appropriately placed both temporally and spatially to contribute to the formation and maintenance of the reticular lamina. Cochleas aged E15 to P31 were stained immunocytochemically for E-cadherin. In the P31 organ of Corti, E-cadherin is localized to the apical intercellular junctions of supporting cells, but is absent from supporting cell-hair cell borders. During development, E-cadherin is present only on the apices and lateral edges of those cells which will eventually lie adjacent to fluid spaces--pillar, outer hair and Deiters cells. The molecule disappears from the lateral cell membranes at about the time in development that fluid spaces form. These data suggest that E-cadherin plays a role in maintaining the reticular lamina by mediating inter-supporting cell adhesion and raise the possibility that fluid space opening in the organ of Corti is facilitated by the down-regulation or redistribution of E-cadherin.