Renal tubule-specific transcription and chromosomal localization of rat thiazide-sensitive Na-Cl cotransporter gene

The molecular mechanism underlying the renal expression localization of the thiazide-sensitive Na-CI cotransporter (TSC) gene was studied, The TSC gen e was localized to chromosome 19p12-14, In cultured cells, tissue-specific transcription activity of the 5 ' -flanking region of the rat rTSC gene (5 ' FL/rTSC) was demonstrated, and the major promoter region was located betw een position -580 and -141. To further examine the tissue-specific transcri ption, transgenic rats harboring the 5 ' FL/rTSC fused upstream of the LacZ gene were generated. Immunohistochemical analysis clearly showed that LacZ gene expression was co-localized to distal convoluted tubules (DCT) with T SC, indicating that the 5 ' FL/rTSC regulates the renal tubule-specific TSC expression. Because a transcription factor, HFH-3 (hepatocyte nuclear fact or-3/folk head homologue-3), had also been localized to DCT, a possible rol e of the putative cia-acting element (HPH-3/rTSC, -400/-387 position) for H FH-3 binding in the tissue-specific transcription was examined. Deletion an d mutation analyses suggested that transcription of the HFH-3/rTSC was actu ally responsive to HFH-3, and electrophoretic mobility shift assay showed a direct binding of in vitro synthesized HFH-3 to the HFH-3/rTSC. In conclus ion, the rTSC gene is localized to rat chromosome 19p12-24. The transcripti on regulatory region of the TSC gene confers DCT-specific gene expression, DCT-specific transcription factor HFH-3 may be involved in the renal tubule -specific transcription of TSC gene.