EXPRESSION OF CORTICOTROPIN-RELEASING HORMONE TRANSGENES IN NEURONS OF ADULT AND DEVELOPING MICE

The DNA sequences important for cell-specific expression and developme ntal regulation of corticotropin-releasing hormone (CRH) were analyzed in transgenic mice. A construct containing 0.5 kb of CRH 5' flanking DNA linked to the chloramphenicol acetyltransferase reporter gene was expressed in many brain regions and in several ectopic peripheral site s, suggesting that this portion of the CRH gene contains basal promote r activity but lacks DNA elements necessary for appropriate tissue spe cificity. Cell specificity of transgene expression was examined with a CRH-beta-galactosidase reporter construct containing the same 0.5-kb CRH promoter fragment, but also including the CRH structural gene and 2 kb of CRH 3' flanking DNA. Transgene expression was observed in inap propriate regions of the brain, but no expression was detected in peri pheral tissues, suggesting that these additional CRH sequences suppres s inappropriately high levels of peripheral expression. Cell-specific expression improved significantly with the inclusion of 8.7 kb of CRH 5' flanking DNA. Individual transgenic lines exhibited expression in a number of the major CRH neuronal groups including the paraventricular nucleus, medial geniculate nucleus, inferior olivary nucleus, and Bar rington's nucleus. Transgene expression was properly activated in Barr ington's nucleus during development. This study demonstrates that the regulatory control of cell-specific and developmentally appropriate CR H expression is complex, utilizing multiple DNA sequence elements loca ted upstream and downstream of the CRH transcription start site. (C) 1 994 Academic Press, Inc.