Fig. 7.

Model of the role of bone morphogenetic proteins (Bmps) in organ of Corti formation. In wild-type cochlea, Bmp4 and Bmp7 secreted from the abneural region regulate hair cell formation. The levels of Bmps are modulated by the antagonist, Noggin. In the absence of Noggin, the net level of Bmp4 and may be the level of Bmp7 as well across the prosensory domain are increased leading to extra hair cell formation in the organ of Corti.