RESEARCH OF THE ROLE OF ID PROTEIN(THE INHIBITOR OF DIFFERENTIATION) IN DEVELOPMENT OF RAT COCHLEA

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Cochlear progenitor hair cell line are useful for studies of cellular specification, gene expression features, and signal transduction involved in development of hair cells. To obtain embryonic and postnatal cochlear progenitor hair cell lines, we immortalized primary cultures of sensorineural epitherial cells from otocysts on embryonic day 12(E12) and explants of organ of Corti tissues on postnatal day 5(P5). Primary cultures and explants were then tranduced by thr E6/E7 genes of human papilloma virus type 16, and were passed for > 50 passages and partial clonal cells were isolated by limiting dilution. The expression of neuronal, neural, epithelial, hair cell markers and important transcription factors were examined in these cell lines. These cell lines may represent progeniotor hair cells at the different stages of cochlear development.Another result is as described below.Inhibitor of differentiation (Id3) is an important transcription factor expressed in the cochlear tissue and progenitor hair cells. It is likely to be involved in cell-cycle progression and the proliferation of cochlear progenitor hair cells during the embryonic stage. To characterize the expression of Id3 in the developing cochlear tissue and explore its role in the growth and proliferation of progenitor hair cells, the expression of Id3 gene in the developing cochlear tissue was examined by means of molecular biological methods and progenitor hair cell line were studied using specific antisense oligonucleotides. The Id3 gene was expressed in the rapidly growing otocyst on embryonic day 12 and specifically in the fundamental structures of the cochlea, e.g. the organ of Corti, spiral ganglions and steria vasclaris, on postnatal day 1. Inhibition of Id3 gene expression with antisense oligonucleotides in cultured otocyst epithelial cells and OT 12p reduced DNA synthesis and cell-cycle progression, suggesting that Id3 participates in the proliferation of cochlear progenitor hair cells.