Acts as an actin bundling protein. May play a pivotal role in photoreceptor cell-specific events, such as disk morphogenesis. Important for maintaining functional hair-cell bundles in the inner ear. May stiffen the longer stereocilia of hair-cell bundles in the inner ear enabling better force transmission to tip links. Found mostly in longer hair-cell stereocilia and, in all stereocilia, present in gradient with the highest concentration at stereocilia tips. Expressed in the inner ear. Abundant in the utricle. Developmentally regulated, appearing in inner-hair cell stereocilia during final stages of elongation. Defects in Fscn2 lead to hair-cell degeneration in the inner ear and are a key contributor to the early-onset, age-related hearing loss (prebycusis) phenotype when in combination with waltzer cadherin 23 mutant. Belongs to the fascin family.