The hair bundle, an exquisitely structured organelle of filamentous actin-based protrusions, mediates the transduction of sound into electrochemical signals, thus enabling the sense of hearing. The correct assembly of the bundle during development is therefore essential to hearing. This dissertation examines the contribution of a novel mouse deafness gene, Brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 2 (Baiap2l2), to bundle maintenance and function. Altogether, this dissertation deepens the understanding of the molecular underpinnings of bundle assembly by adding BAIAP2L2 as an essential factor for bundle stability and by providing evidence for Ca2+ as a mediator of how transduction modulates bundle proteins.