Repressive regulation of the aquaporin-2 gene.
Furuno, Masahiro, Shinichi Uchida, Fumiaki Marumo, and Sei Sasaki.
Second Department of Internal Medicine, Tokyo Medical and Dental
University, School of Medicine, Tokyo 113, Japan, Pharmaceutical
Basic Research Laboratories, Central Pharmaceutical Research
Institute, Yokohama 236, Japan
APStracts 3:0130F, 1996.
Expression of aquaporin-2 (AQP2) is exclusively limited to kidney
collecting duct cells, and this strictly limited expression could be
mediated by transcription of the gene. We first examined AQP2 mRNA
expression in many cultured epithelial cells derived from kidney.
Northern blot using OK, LLC-PK1, MDCK, OMCD, and primary culture of
IMCD cells did not reveal any significant signal. A more sensitive
method, RNase protection assay, could detect a faint signal in OMCD
cells when they were bathed in a hypertonic medium. Reverse
transcribed PCR applied to primary culture of IMCD cells showed a
rapid dissipation of AQP2 mRNA within 4 days after culture. A
reporter gene assay performed in the first day of primary culture of
IMCD cells showed that the 5' region up to -2.9 kb worked as a
promoter. Deletion experiments showed that at least 2 regions, from
-434 to -364 and -153 to -84, contain negatively acting cis-elements.
When connected to a heterologous promoter, these regions repressed
the activity in an orientation-dependent manner. These results
suggest that transcription of AQP2 gene is strictly regulated and its
ability is rapidly depressed in culture condition. This cell
differentiation specific expression of the gene may be, at least in
part, mediated by the repressors present in its 5' flanking region.
Received 13 November 1995; accepted in final form 28 June 1996.
APS Manuscript Number F384-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996