Résumé
The inner ear of all jawed vertebrates arises from the epithelium of the otic vesicle and contains three semicircular canals, otoliths, and- sets of sensory neurons, all positioned precisely within the cranium to detect head orientation and movement. The
msh-C gene and two new homeobox genes,
msh-D and a gene related to
distal-less, dlx-3, are each expressed in distinct regions of the otic vesicle during its early development in zebrafish embryos. Cells in the ectoderm express
dlx-3 before induction of the otic vesicle, suggesting that
dlx-3 has an early function in this process. Later, cells aligned with the future axes of the semicircular canals specifically express either
dlx-3 or
msh-D. Even later, sensory hair cells express
msh-C and
msh-D, while other cells of the epithelium express
dlx-3. The early expression of these genes could specify the orientation and morphogenesis of the inner ear, whereas their later expression could specify the fates of particular cell types.