Identification of vasopressin‐dependent early response genes in mpkCCD cells

Arginine vasopressin stimulates transcription of the aquaporin‐2 water channel (AQP2) gene, in a cAMP‐dependent manner. However, the transcriptional network involved has not been identified. To identify cAMP‐dependent early response genes that may regulate AQP2 transcription, we performed global gene‐expression analysis (Affymetrix expression arrays) on mouse mpkCCD cells treated with 0.1 nM dDAVP for 0, 1, 2, and 4 hrs and with vehicle for corresponding time periods. Analysis revealed that the majority of genes upregulated after 1 hour treatment with dDAVP were elevated only transiently, while most genes upregulated after 2 hrs remained elevated. Because cAMP mediates its effects in part via CREB phosphorylation and the cAMP response element (CRE), we identified conserved CRE sites associated with a known TATA box (CRE‐TATA) in the responding genes, upstream of the promoter. Results show that 27%, 9%, and 9% of all genes with a > 2‐fold increase in expression at 1, 2, and 4 hrs, respectively, had a CRE‐TATA within the promoter. Furthermore, a greater proportion of transcription factors were upregulated at 1 hr compared to 2 and 4 hrs. Likewise, the presence of a CRE‐TATA was positively correlated with increased gene expression. In conclusion, we identified a number of vasopressin early response genes, many of which are transcription factors that may be part of the transcriptional network that regulates AQP2 gene expression.