A screen for genetic defects of the zebrafish ear.

To advance the understanding of genetic mechanisms involved in the patterning and the differentiation of the vertebrate auditory system, we screened for mutations affecting ear development in the zebrafish larva. Fifteen recessive mutant alleles have been isolated and analyzed. The phenotypes of these mutants involve abnormalities in ear morphology, otolith formation, or both processes in parallel. Among morphological defects, we found mutations affecting early patterning of the otic vesicle, the morphogenesis of semicircular canals, and the expansion of the ear lumen. The two most severe mutant phenotypes involve the absence of anterior and posterior cristae, as well as a severely misshapen morphology of the ear. In the category of otolith mutants, we found defects in otolith formation, growth, and shape. As it proved to be the case in past screening efforts of this type, these mutant lines represent an asset in the studies of molecular mechanisms that regulate vertebrate ear development.