Identification of two novel aquaporin-2 mutations in a Thai girl with congenital nephrogenic diabetes insipidus.
OBJECTIVE
To describe a Thai girl with congenital nephrogenic diabetes insipidus (NDI) and perform mutation analysis of the AQP2 gene.


METHODS
Case report.


METHODS
A 6-year old girl with a history of failure to thrive, polydipsia and polyuria was studied. Polyuria and polydipsia were observed within the first few months of life. Despite normal serum osmolality and electrolyte, the result of water deprivation test was compatible with a diagnosis of NDI.


METHODS
The entire coding regions of the AQP2 gene were assessed by polymerase chain reaction and sequencing analysis. The presence of mutations was also confirmed by restriction enzyme digestion analysis.


RESULTS
Two heterozygous novel missense mutations were identified. Both were located in exon 1; a guanine-to-thymine substitution at nucleotide position 3 (c.3G-->T) inherited from her mother and a guanine-to-adenine at position 85 (c.85G-->A) inherited from her father, resulting in a methionine to isoleucine at codon 1 (p.M1I) and glycine to serine at codon 29 (p.G29S), respectively. These mutations have never been previously described and were not detected in 100 ethnic-matched unaffected control chromosomes.


CONCLUSIONS
We report two novel mutations of the AQP2 gene, p.M1I and p.G29S, associated with autosomal recessive congenital NDI. This study expands the genotypic spectrum of AQP2 mutations and emphasizes an important role of genetic testing for definite diagnosis and genetic counseling.
Sahakitrungruang
Taninee
T
Division of Pediatric Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
Wacharasindhu
Suttipong
S
Sinthuwiwat
Thivaratana
T
Supornsilchai
Vichit
V
Suphapeetiporn
Kanya
K
Shotelersuk
Vorasuk
V
D000595:Amino Acid Sequence; D051399:Aquaporin 2 / Q000235:genetics*; D002648:Child; D004247:DNA / Q000235:genetics; D004252:DNA Mutational Analysis; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D018500:Diabetes Insipidus, Nephrogenic / Q000151:congenital / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014868:Water Deprivation / Q000502:physiology
D051399:Aquaporin 2; D007004:Hypoglycemic Agents; D004247:DNA; D003894:Deamino Arginine Vasopressin