Deletion of the V2 vasopressin receptor gene in two Chinese patients with nephrogenic diabetes insipidus

Background: Congenital nephrogenic diabetes insipidus (NDI) is a rare X- linked inherited disorder characterized by the excretion of large volumes of diluted urine and caused by mutations in arginine vasopressin receptor 2 ( AVPR2) gene. To investigate the mutation of AVPR2 gene in a Chinese family with congenital NDI, we screened AVPR2 gene in two NDI patients and eight family members by PCR amplification and direct sequencing. Results: Five specific fragments, covering entire coding sequence and their flanking intronic sequences of AVPR2 gene, were not observed in both patients, while those fragments were all detected in the control subjects. Several different fragments around the AVPR2 locus were amplified step by step. It was revealed that a genomic fragment of 5,995- bp, which contained the entire AVPR2 gene and the last exon ( exon 22) of the CI gene, was deleted and a 3- bp ( GAG) was inserted. Examination of the other family members showed that the mothers and the grandmother were carriers for this deletion. Conclusion: Our findings suggest that the two patients in a Chinese family suffering from congenital NDI had a 5,995- bp deletion and 3- bp ( GAG) insertion at Xq28. The deletion contained the entire AVPR2 gene and exon 22 of the C1 gene.