Cadherin-11 controls otolith assembly: evidence for extracellular cadherin activity.

Cadherin-11/Cdh11 is expressed through early development and strongly during inner ear development (otic placode and vesicle). Here we show that antisense knockdown of Cdh11 during early zebrafish development interferes with otolith formation. Immunofluorescence labeling showed that Cdh11 expression was concentrated on and within the otolith. Cdh11 was faintly detected at the lateral surface (sites of cell-cell contact) of otic epithelial cells and in the cytoplasm. Strongly labeled Cdh11 containing puncta were detected within the otolymph (the fluid within the otic vesicle) and associated with the otolith surface. BODIPY-ceramine-labeled vesicular structures detected in the otolymph were larger and more numerous in Cdh11 knockdown embryos. We present evidence supporting a working model that vesicular structures containing Cdh11 (perhaps containing biomineralization components) are exported from the otic epithelium into the otolymph, adhere to one another and to the surface of the growing otolith, facilitating otolith growth.