Ectodermal otic placode (OP) development, which gives rise to the inner ear, is believed to be directed by signals, such as the FGFs, that emanate from the mesenchyme and neuroectoderm that lie underneath and adjacent to this tissue, respectively. However, whether FGFs signal directly to the prospective placode or are required for hindbrain-expressed OP inducers has remained unclear. Wright and Mansour now shed light on this question with their study of OP induction in Fgf3/Fgf10 double knockout mice (see ). These mice lack otic vesicles and show aberrant patterns of OP marker-gene expression,but have normal hindbrain expression patterns. The authors conclude that FGF3 and FGF10 signals from the neuroectoderm and mesenchyme, respectively, act directly on the ectoderm to bring about OP gene expression. Notably, FGF signalling was not required for ectodermal proliferation or survival.
