Library compounds can be administered in distinct screening paradigms to identify
compounds that affect different aspects of hair cell biology. A) Following placement in
multi-welled plates, 5-day post fertilization zebrafish larvae are exposed to library
compounds before, during, or following induced hair cell damage to identify compounds
that induce hair cell damage, protect against known ototoxins, or modulate hair cell
regeneration, respectively. Following exposure, larvae are treated with vital dyes that
selectively stain hair cells, and hair cell numbers can be assayed through basic microscopy
techniques. B) Examples of fluorescently labeled hair cells of the zebrafish lateral line. The
transgenic marker Tg(brn3c:gfp) and vital dye TO-PRO3 selectively label hair cell soma and
nuclei, respectively. Hair cell number and morphology can thus be assessed during
screening. Although different from the markers used in previous screens, these dyes
nonetheless highlight the ease at which hair cells can be visualized in vivo.