2004 Global Researcher Conference Proceeding
April 09 - 11, 2004
| Conference: | 2004 Global Researcher Conference |
|---|---|
| Title: | V2 vasopressin receptor-deficient mouse model: Pathophysiological changes and therapeutical implications |
| Authors: | Sangkuhl, Katrin; Schulz, Angela; Rompler, Holger; Pliquett, R.; Schellenberger, W.; Bar, J.; Yun, June; Wess, Jurgen; Schoneberg, Torsten |
| Institutions: | University of Leipzig, NIH, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, NIDDK |
About 15% out of all mutations found in patients with X chromosome-linked nephrogenic diabetes insipidus (XNDI) result in a truncation and complete loss of V2-vasopressin-receptor (AVPR2) function due to nonsense mutations. We tested the hypothesis that such mutations can be functionally rescued in vitro and in vivo by treatment with aminoglycoside antibiotics which are known for their ability to suppress premature termination codons. As a model system, we studied a mutant AVPR2 containing the inactivating E242X nonsense mutation which mimics human XNDI when introduced into mice via gene targeting techniques (1). Strikingly, treatment with the aminoglycoside geneticin increased AVP-mediated cAMP responses in cultured kidney collecting duct cells prepared from E242X mutant mice in vitro, and significantly improved the urine-concentrating ability of E242X mutant mice in vivo (2).
There is only limited knowledge about the pathophysiologically or compensatively relevant changes in renal protein expression of NDI patients. Therefore, we used the AVPR2-deficient mouse model to address this question. Messenger RNA expression levels in wild-type and hemizygous male E242X mice-pups were determined using the Affymetrix® micro-array-technology. About 60 out of 22,500 genes were significantly regulated depending on the genotype. Interestingly, several genes directly involved in AVPR2-mediated signal transduction showed no or only minor changes in their expression levels. However, several other genes (ion transporters and channels) display a strong regulation in NDI-mice. Detailed analysis of these genes may extend our current knowledge in understanding the renal pathomechanism of an AVPR2 deficiency.
- Yun et al. 2000 J. Clin. Invest.; 106:1361-1371
- Sangkuhl et al. 2004 Hum. Mol. Genet.; in press
Nearly 15% of X-NDI mutations result in V2R proteins that are missing a large part of their structure (a condition called truncation). Due to this truncation, these V2R are unable to perform their function. Sangkuhl, et al., experimented to see if the function of these mutant V2Rs could be restored by treating them, both in cell cultures as well as in living mice, with aminoglycoside antibiotics. These are known for their ability to suppress the codons in gene mutations that are responsible for signaling the protein synthesis to stop prematurely.
They found that introducing aminoglycoside to the E242X V2R mutation resulted in an increase in cAMP responses in the cell culture and an improvement in the E242X mice’s ability to concentrate their urine. The researchers are conducting further research to better understand mechanisms involved in V2R functional rescue.