Actin-bundling protein. In the inner ear, it is required for stereocilia formation. Mediates liquid packing of actin filaments that is necessary for stereocilia to grow to their proper dimensions (PubMed:27811163). Monomer. In the inner ear, it is expressed in the organ of Corti (PubMed:25124451). Abundant in the utricle (at protein level) (PubMed:27811163). Phosphorylated. Knockout animals have a progressive form of hearing loss at all frequencies. Hearing loss is moderate in young adult mice, progresses to severe deafness with age, and is associated with defects in stereocilia morphology. Stereocilia are shorter and narrower than those of wild-type mice.