Transcriptional regulation by Barhl1 and Brn-3c in organ-of-Corti-derived cell lines.
Barhl1 and Brn-3c have been identified as transcription factors that are essential for survival and maintenance of hair cells of the inner ear. Little is known about the mechanism of how Brn-3c or Barhl1 may regulate transcription in the inner ear. In this study, the transcriptional function of both Brn-3c and Barhl1 was investigated in the organ-of-Corti-derived cell lines, OC-1 and OC-2. We examined regulatory domains in these transcription factors by linking regions of Barhl1 and Brn-3c to the DNA binding domain of the heterologous transcription factor GAL4 and assayed their effect on a heterologous promoter containing GAL4 DNA binding sites by co-transfection into OC-1 and OC-2 cell lines. Brn-3c was found to contain an independent N-terminal activation domain that is sufficient to activate gene transcription in the organ of corti derived cell lines. Barhl1 on the other hand was found to act as a transcriptional repressor with repressive activity not restricted to a particular domain of Barhl1. In addition, we analyzed the effect of Barhl1 on the promoters of the neurotrophin genes NT-3 and BDNF in OC-1 and OC-2 cell lines. However, Barhl1 was not found to directly regulate neurotrophin promoter constructs in these cells.