title: Characterization of two novel missense mutations in the AQP2 gene causing nephrogenic diabetes insipidus.
abstract: Here, we report the aquaporin 2 (AQP2) mutational analysis of a patient with nephrogenic diabetes insipidus heterozygote due to two novel missense mutations. Direct sequencing of DNA in the male patient revealed that he was compound heterozygote for two mutations in the AQP2 gene: a thymine-to-adenine transversion at position 450 (c.450T>A) in exon 2 and a guanine-to-thymine at nucleotide position 643 (c.643G>T) in exon 4. The double heterozygous 450T>A and 643G>T transversion causes the amino acid substitution D150E and G215C. Direct sequencing of exons 2 and 4 of the AQP2 gene from each of the parents revealed that the c.450T>A mutation was inherited from the father while the c.643G>T mutation was inherited from the mother. Analysis of AQP2 excretion demonstrated that no AQP2 was detectable in the urine of the proband, whereas normal AQP2 levels were measured in both parents. When expressed in renal cells, both proteins were retarded in the endoplasmic reticulum and no redistribution was observed after forskolin stimulation. Of note, homology modeling revealed that the two mutations involve two highly conserved residues providing important clues about the role of the wt residues in AQP2 stability and function.
authors.affiliation: Department of Biochemistry and Biomedical Technologies, University Federico II--CEINGE, Naples, Italy.
authors.forename: Achille
authors.initials: A
authors.lastname: Iolascon
authors.forename: Veruska
authors.initials: V
authors.lastname: Aglio
authors.forename: Grazia
authors.initials: G
authors.lastname: Tamma
authors.forename: Maria
authors.initials: M
authors.lastname: D'Apolito
authors.forename: Francesco
authors.initials: F
authors.lastname: Addabbo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Procino
authors.forename: Maria Carmela
authors.initials: MC
authors.lastname: Simonetti
authors.forename: Giovanni
authors.initials: G
authors.lastname: Montini
authors.forename: Loreto
authors.initials: L
authors.lastname: Gesualdo
authors.forename: Erik W
authors.initials: EW
authors.lastname: Debler
authors.forename: Maria
authors.initials: M
authors.lastname: Svelto
authors.forename: Giovanna
authors.initials: G
authors.lastname: Valenti
mesh_terms: D000818:Animals; D051399:Aquaporin 2 / Q000235:genetics*; D001483:Base Sequence; D018500:Diabetes Insipidus, Nephrogenic / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D007223:Infant; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2