CREB-family transcription factors and vasopressin-mediated regulation of Aqp2 gene transcription

Background

Water homeostasis is regulated by the peptide hormone arginine vasopressin (AVP), which promotes water reabsorption in the renal collecting duct. The regulation of Aqp2 gene transcription is a key mechanism through which AVP modulates water transport as disruption of this mechanism leads to water balance disorders. Therefore, an important goal is to understand the regulatory processes that control Aqp2 gene transcription. While CREB (CREB1) has been proposed as the primary transcription factor responsible for Aqp2 transcription, recent evidence challenges this view, suggesting that other CREB-like transcription factors, including ATF1 and CREM, may play a role.

Methods

We employed the CRISPR/Cas9 gene-editing system to delete Atf1 , Creb1 , and Crem in mpkCCD cells, an immortalized mouse collecting duct cell line. These cell lines were then exposed to the vasopressin analog, dDAVP, to assess the role of these transcription factors in regulating Aqp2 expression. AQP2 protein levels were measured by immunoblotting and RNA-seq was used to analyze changes in Aqp2 mRNA abundance, as well as other transcriptomic changes.

Results

Deletion of all three transcription factors (ATF1, CREB1, and CREM) led to a significant reduction in the vasopressin-induced upregulation of AQP2 protein, confirming their role in regulating Aqp2 expression. RNA-seq data showed that Aqp2 mRNA levels mirrored changes in protein abundance, supporting the idea that these transcription factors affect Aqp2 transcription. Rescue experiments in triple knockout cells showed that expressing any of the three transcription factors restored the response to vasopressin.

Conclusions

Our findings demonstrate that ATF1, CREB1, and CREM have redundant roles in regulating Aqp2 transcription. Based on these results and prior data, we propose that these CREB-family transcription factors may regulate Aqp2 gene transcription indirectly by controlling the expression of additional unidentified transcription factors.

Key Points

• CREB-family transcription factors (ATF1, CREB1, and CREM) were deleted in mpkCCD cells to assess their roles in Aqp2 gene transcription

• CRISPR/Cas9 knockout of all three transcription factors strongly reduced the ability of vasopressin to increase AQP2 mRNA and protein

• Re-expression of any of the three restored the vasopressin response indicating redundant roles of the three transcription factors