hippocampus, and thymus presumably reflecting tissue-specific differences in promoter activity. The different promoters respond to different signals, which forms the basis for tissue-specific laterations in gene expression. Simply put, it is the process by which environmental or hormonal signals can alter GR expression in one region of the body, without affecting expression in another. Hippocampal RNA contains significant levels of the exon 17-containing GR mRNA variants expressed at undetectable levels in liver and thymus. These studies thus identify a brain-specific GR promoter, the exon 17 sequence.
