Figure 2.

Working model of the mechanotransduction machinery in zebrafish hair cells. A, Transmission electron micrograph of a tip link of a zebrafish hair cell (anterior macula). Note the tenting of the lower tip, suggesting that tension on the membrane was present. Also present is the upper density or plaque in the taller stereocilium. B, Schematic of the transduction components, including the presumptive orientation of the novel cadherins, Pcdh15a and Cdh23, and the position of the transduction channel at the lower link. C, Integral membrane proteins associated with Pcdh15a that are critical for mechanotransduction in zebrafish. The requirement for the Tmc proteins, which are currently the best candidates for the mechanotransduction channel in mammalian hair cells, has yet to be demonstrated in zebrafish. However, Pcdh15a physically associates with Tmc2a (see Maeda et al., 2014).