Mechanotransduction in hair bundles is required for spontaneous activity at the presynapse. (A) Diagram illustrating the hair cells with the hair bundles highlighted by a dashed box where we measure their spontaneous calcium activity. The structure of the hair bundle from a single hair cell at is illustrated on top. The mechanotransduction (MET) channels are gated by tip links made up of Pcdh15a Cdh23. Pharmacological application of BAPTA, an extracellular calcium chelator, breaks tip links and acutely disrupts MET function. (B–D) Representative GCaMP6s temporal traces show that disruption of tip links using pcdh15a mutants (B,C) or by pharmacologically disrupting tip links using BAPTA (D) disrupts spontaneous activity in hair bundles. (E) Diagram illustrating the hair cells with the hair cell presynaptic area highlighted by a dashed box at the base of the hair cells where we measure the spontaneous presynaptic calcium activity. (E–H) Representative GCaMP6s temporal traces show that disruption of tip links using pcdh15a mutants (F–G) or by pharmacologically disrupting tip links using BAPTA (H) also disrupts spontaneous calcium activity at the presynapse. All measurements were performed in immature hair cells at day 3.
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