Section on Developmental Neuroscience, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35 Convent Dr., Bethesda, Maryland 20892, USA. Kelleymt@nidcd.nih.gov
The sensory epithelia of the inner ear contain mechanosensory hair cells and non-sensory supporting cells. Both classes of cell are heterogeneous, with phenotypes varying both between and within epithelia. The specification of individual cells as distinct types of hair cell or supporting cell is regulated through intra- and extracellular signalling pathways that have been poorly understood. However, new methodologies have resulted in significant steps forward in our understanding of the molecular pathways that direct cells towards these cell fates.