Bone morphogenetic proteins (BMPs) are diffusible molecules involved in a variety of cellular interactions during development. In particular, Bmp4 expression accompanies the development of the ear sensory organs during patterning and specification of sensory cell fates, and it has been shown to play a role in inner ear development and morphogenesis. However, there is no understanding of the cellular effects of BMP4 in prosensory progenitors, and about its role in the process of sensory fate specification. The present thesis project was aimed at exploring the effects of BMP-signaling on the development of hair-cells, using the chick inner ear as a model.The specific aims proposed were:1- Analyze the cellular effects caused by addition of BMP4 in a model of isolated chick otic vesicles in culture, measuring parameters of cell proliferation, cell death and sensory cell fate specification.2- Analyze the cellular effects caused by inhibition of BMP4 signaling in a model of isolated chick otic vesicles in culture, measuring parameters of cell proliferation, cell death and sensory cell fate specification.3- Analyze the expression in the innear ear of downstream targets of BMP signalling, in particular, analyse the members of Id gene family.4- Analyze the regulation of Id genes by BMP signalling in the inner ear.5- Analyze the expression of genes involved in the process of terminal differentiation, in particular, Btg1 and Btg2 genes6- Analyze the regulation of Btg1 and Btg2 gene by BMP signalling in the inner ear