MUTATIONS AFFECTING DEVELOPMENT OF THE ZEBRAFISH EAR

In a large scale screen for genetic defects in zebrafish embryogenesis we identified mutations affecting several aspects of ear development, including: specification of the otic placode, growth of the otic vesi cle (otocyst), otolith formation, morphogenesis of the semicircular ca nals and differentiation of the otic capsule, Here we report initial p henotypic and genetic characterization of 20 of these mutations defini ng 13 independent loci. Embryos mutant at the quadro locus display abn ormal specification of the otic placode, As revealed by dlx-3 expressi on, the otic field in the mutant embryos is smaller or split into two fields, At later stages of development the ear of quadro mutants is fr equently divided into two smaller, incomplete units, Four loci affect ear shape shortly after formation of the otic vesicle, All of them als o display abnormal brain morphology, Mutations in five loci result in the absence of otolith formation; two of these also produce changes of ear morphology, Two loci, little richard and golas, affect morphology of the otic vesicle shortly before formation of the semicircular cana ls, In both cases the morphogenesis of the semicircular canals is disr upted, Finally, the antytalent locus is involved in late expansion of the ear structure, Analysis of mutations presented here vuill strength en our understanding of vertebrate ear morphogenesis and provide novel entry points to its genetic analysis.