Molecular anatomy of the transduction apparatus. (A) Model favored by the Holt–Géléoc–Griffith group, with TMC proteins forming the transduction channel pore. In this model, the PCDH15 end of the tip link interacts directly with TMC proteins. (B) Model consistent with the data of Kim et al. (2013), with TMC proteins coupling the tip link to the transduction channel. The interaction of PCDH15 is still with TMCs; when either tip links or TMCs are disrupted, the channel is no longer anchored at stereocilia tips and could move to a new location where reverse-polarity activation is possible.