Changing shape and shaping change: Inducing the inner ear.

The inner ear arises from non-neural ectoderm as a result of instructions sent by surrounding tissues. These interactions progressively restrict the potential of the ectoderm, resulting in the formation of the otic placode, a disk of thickened ectoderm that will give rise to all of the inner ear derivatives and its neurons. While otic placode is a surface structure, the inner ear is internalised, embedded within the cranial mesenchyme. Here, the cellular and molecular interactions that restrict the lineage of non-neural ectoderm in its transition to otic placode are reviewed, and how these interactions impinge on the coordination of otic placodal cell shape that drive the dramatic morphogenesis of the placode, as it becomes the otocyst.