Early in its development, the vertebrate inner ear acquires axial identities from the tissues surrounding it. These subsequently influence the development of all the inner ear components. On p. , Bok and co-workers report that the hindbrain determines dorsoventral (DV) but not anteroposterior (AP) axial specification in the chick inner ear. By rotating the hindbrain around its AP axis, the researchers show that the induction of the otic placode - which gives rise to the inner ear - precedes axial specification and that reversing the AP orientation of the hindbrain before axial specification does not affect inner ear development. By contrast,reversing the DV axis of the hindbrain changes the DV axial identity of the inner ear. Additional experiments identify Sonic Hedgehog as one of the hindbrain signals that patterns the ventral axis of the inner ear; the signals and tissues that confer AP axial identity remain unknown.
