The rat corticotropin-releasing hormone gene.

In this paper we have described the isolation and characterization of the rat corticotropin releasing hormone gene. Nucleotide sequence comparisons with the human CRH gene have demonstrated several interesting regions of homology and suggest that the gene was highly conserved through evolution. Additionally we have demonstrated the tissue-specific expression of the rat CRH gene. The regional distribution of expression parallels previously documented immunocytochemical demonstrations and supports the hypothesis that CRH peptides have multiple roles in different tissues. In the peripheral tissues that express CRH mRNA it will be very interesting to document the specific cell type of synthesis by using combined immunocytochemical and in situ histochemical techniques. Additionally we have described initial studies using gene transfer techniques to examine the cAMP responsiveness of the rat CRH gene. We are presently constructing other fusion genes (CRHCAT plasmids) in order to more carefully localize the DNA sequence in the rat CRH gene which mediates this effect, and compare it to the previously reported cAMP-responsive "consensus sequence." Similarly, we also plan to utilize the CRHCAT constructs to examine regulation of the rat CRH gene by glucocorticoids and several other hormone-mediated regulatory pathways. Through these CAT fusion studies we hope to gain a better understanding of the role of certain conserved sequences in the 5' flanking DNA for transcriptional control of the rat (and human) CRH genes.