TISSUE-SPECIFIC EXPRESSION AND PROMOTER ANALYSES OF THE HUMAN TISSUE KALLIKREIN GENE IN TRANSGENIC MICE

The expression of the tissue kallikrein gene is tissue-specific and ex hibits a complex pattern of transcriptional and post-translational reg ulation. Information concerning the mechanism of its tissue-specific e xpression has been limited owing to the lack of suitable cell lines fo r the expression study. We approached this problem by introducing huma n tissue kallikrein gene constructs into mouse embryos, creating trans genic lines carrying its coding sequence with varying lengths of the p romoter region. One construct (PHK) contained 801 bp in the 5'-flankin g region and two deletion constructs contained either 302 bp (D300) or 202 bp (D200) of the promoter region. The expression of human tissue kallikrein in these transgenic mice was monitored by Northern blot, re verse transcriptase-PCR followed by Southern blot, and radioimmunoassa y. In all three lines, human tissue kallikrein was expressed predomina ntly in the pancreas and at lower levels in other tissues, including s alivary gland, kidney and spleen. This pattern was similar to that of tissue kallikrein expression in human tissues. The D300 line has highe r levels of transgene expression than the D200 and PHK lines. The resu lts indicate that the 202 bp segment immediately upstream of the trans lation starting site is sufficient to direct a tissue-specific express ion pattern of the human tissue kallikrein gene, and that regulatory e lements might exist between -801 and -202.