TRANSCRIPTIONAL REGULATORY REGION OF BRN-2 REQUIRED FOR ITS EXPRESSION IN DEVELOPING OLFACTORY EPITHELIAL-CELLS

Brain-2 is a class III POU transcription factor expressed in developin g nervous system. In this study, we have examined the transcriptional regulatory region of Brn-2. Expression of Brn-2 is activated when P19 embryonal carcinoma cells are induced to differentiate into neural cel ls with retinoic acid (RA). In P19 cells, the 0.5 kb upstream region o f Brn-2 was sufficient for the transcriptional activation during RA-in duced differentiation. Deletion analysis of the 0.5 kb region located a proximal enhancer (between -422 and -379 with respect to the transla tional initiation codon), which was essential for the activation. By g el shift assay and methylation interference assay, a specific binding factor was detected that recognized a core sequence GAGCCAAT found wit hin the proximal enhancer. To examine whether the 0.5 kb upstream regi on can function in embryos, transgenic mice were generated that contai ned LacZ gene driven by the 0.5 kb upstream region. In these transgeni c mice, LacZ was expressed in developing olfactory epithelial cells be tween embryonic day 12.5 and 14.5. Immunostaining with an anti-Brain-2 antibody demonstrated the expression of Brain-2 in the olfactory epit helium (most likely olfactory receptor neurons) at similar development al stages. These results suggest that the 0.5 kb upstream region of Br n-2 is sufficient for the expression in the developing olfactory cells and that the DNA binding factor recognizing the proximal enhancer may be involved in the olfactory cell specific expression. (C) 1998 Elsev ier Science B.V. All rights reserved.