AE4 is an anion exchanger almost exclusively expressed in the collecting ducts of the kidney. This very restricted expression prompted us to analyze its transcription in more detail. 5' RACE yielded alternative transcriptional start sites that are predicted to code for N-terminal protein variants. Comparison of the 5' genomic sequence between species identified a transcriptionally active region with three conserved spans. In transgenic mice beta-galactosidase expression driven by this fragment resembled endogenous AE4 expression and was predominantly restricted to type B intercalated cells. Hence this promoter could prove useful to target type B intercalated cells by genetic approaches.
