Three families with autosomal dominant nephrogenic diabetes insipidus caused by aquaporin-2 mutations in the C-terminus

Am J Hum Genet. 2001 Oct;69(4):738-48. doi: 10.1086/323643. Epub 2001 Aug 30.


The vasopressin-regulated water channel aquaporin-2 (AQP2) is known to tetramerize in the apical membrane of the renal tubular cells and contributes to urine concentration. We identified three novel mutations, each in a single allele of exon 4 of the AQP2 gene, in three families showing autosomal dominant nephrogenic diabetes insipidus (NDI). These mutations were found in the C-terminus of AQP2: a deletion of G at nucleotide 721 (721 delG), a deletion of 10 nucleotides starting at nucleotide 763 (763-772del), and a deletion of 7 nucleotides starting at nucleotide 812 (812-818del). The wild-type AQP2 is predicted to be a 271-amino acid protein, whereas these mutant genes are predicted to encode proteins that are 330-333 amino acids in length, because of the frameshift mutations. Interestingly, these three mutant AQP2s shared the same C-terminal tail of 61 amino acids. In Xenopus oocytes injected with mutant AQP2 cRNAs, the osmotic water permeability (Pf) was much smaller than that of oocytes with the AQP2 wild-type (14%-17%). Immunoblot analysis of the lysates of the oocytes expressing the mutant AQP2s detected a band at 34 kD, whereas the immunoblot of the plasma-membrane fractions of the oocytes and immunocytochemistry failed to show a significant surface expression, suggesting a defect in trafficking of these mutant proteins. Furthermore, coinjection of wild-type cRNAs with mutant cRNAs markedly decreased the oocyte Pf in parallel with the surface expression of the wild-type AQP2. Immunoprecipitation with antibodies against wild-type and mutant AQP2 indicated the formation of mixed oligomers composed of wild-type and mutant AQP2 monomers. Our results suggest that the trafficking of mutant AQP2 is impaired because of elongation of the C-terminal tail, and the dominant-negative effect is attributed to oligomerization of the wild-type and mutant AQP2s. Segregation of the mutations in the C-terminus of AQP2 with dominant-type NDI underlies the importance of this domain in the intracellular trafficking of AQP2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aquaporin 2
  • Aquaporin 6
  • Aquaporins / chemistry*
  • Aquaporins / genetics*
  • Aquaporins / metabolism
  • Base Sequence
  • Blotting, Western
  • Cell Membrane / metabolism
  • Cell Membrane Permeability
  • Child, Preschool
  • DNA Mutational Analysis
  • Diabetes Insipidus, Nephrogenic / genetics*
  • Female
  • Genes, Dominant / genetics*
  • Humans
  • Infant
  • Japan
  • Male
  • Molecular Sequence Data
  • Mutation / genetics*
  • Oocytes / metabolism
  • Pedigree
  • Protein Structure, Quaternary
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Xenopus laevis


  • AQP2 protein, human
  • Aquaporin 2
  • Aquaporin 6
  • Aquaporins

Associated data

  • OMIM/107776
  • OMIM/107777
  • OMIM/125800
  • OMIM/222000
  • OMIM/304800
  • RefSeq/NM_000486