Expression of Numb and Numb-like in the development of mammalian auditory sensory epithelium.

The Numb and Numb-like are evolutionarily conserved cell fate-determining factors in mammals. For the first time, we investigate the involvement of the Numb and Numb-like in the developing auditory sensory epithelium. We show that both of them are expressed in the rat auditory sensory epithelium, and the four isoforms of the Numb have dynamic expression patterns during cochlear development. At the early stage of the auditory epithelium development, they occur in all progenitor cells. At the late stage of cell differentiation, they are expressed mainly in the cytoplasm of apical cells and their locations are different. Furthermore, we find overexpression of the Numb or Numb-like, in cochlear whole mount cultures, can upregulate mRNA level of Rath1, which is important in the hair-cell development.