Molecular basis of otic commitment and morphogenesis: A role for homeodomain-containing transcription factors and signaling molecules

This chapter reviews the patterning processes in the developing inner ear. Pattern formation commences in the forming otic placode and thus takes place in parallel with and is influenced by the ear induction. The commitment steps that were inferred from classical transplantation and explantation experiments are now assumed to be directly related to pattern formation and are addressed first. The next part concentrates on transcription factors, which are regionally expressed at the early stages of otic development (placode, pit, vesicle) and divides these morphologically homogeneous structures into fields or compartments committed to form individual parts of the future inner ear. Furthermore, the role of regulatory loops between signaling molecules and transcription factors during pattern formation are discussed. The last part discusses the importance of patterning genes for the morphogenetic processes that shape the inner ear. Here, data on inactivation of some of the patterning genes (Nkx5-1, Dlx5, Pax2, and others) in the mouse are reviewed. © 2003 Elsevier Inc. All rights reserved.