- Recent genetic studies in zebrafish have led to significant advances in several areas of inner ear development. Progress has been particularly rapid in elucidating mechanisms of preotic development-processes acting prior to and during induction of the otic placode. Functions required for early patterning of the otic placode and vesicle are in many cases similar in zebrafish and mouse, but there are also some important differences that probably underlie the structural differences between the inner ear in fish vs mammals. Finally, ongoing mutagenesis screens are identifying genes required for auditory and vestibular sensory functions and hair cell differentiation and survival. Analysis of such genes could provide an experimentally amenable model for some kinds of human deafness. 2003 Elsevier Inc. All rights reserved.