Novel AVPR2 mutations and clinical characteristics in 28 Chinese families with congenital nephrogenic diabetes insipidus

First report on female monozygotic twins discordant for congenital nephrogenic diabetes insipidus

Ninety percent of congenital nephrogenic diabetes insipidus (NDI) are X-linked inherited and are caused by mutations in the vasopressin type 2 receptor gene (AVPR2). Most affected individuals are males. Only sporadic female cases have been reported. Here, we first reported a female monozygotic twin with discordant phenotypes for NDI carrying a missense variant c.845T>C (p.Leu282Pro) in exon 4 of AVPR2. Intracellular cAMP concentrations in COS7 cells transfected with AVPR2-L282P were significantly decreased by about 60% compared with those in wild-type AVPR2 plasmid transfected cells, suggesting this variation was pathogenic. The X-inactivation pattern was investigated in peripheral leukocytes and urine sediments in both the unaffected and affected pair. Results showed that the affected pair had a skewed X chromosome inactivation (XCI) pattern in urine sediments and a random XCI pattern in leukocytes, while the unaffected pair showed a random XCI pattern both in leukocytes and urine sediments. This was the first report of monozygotic twins who developed different phenotypes of NDI. Our study suggested that the development of NDI symptoms is more closely associated with the XCI pattern in urine sediments compared with the XCI pattern in peripheral leukocytes. Analysis of XCI in peripheral leukocytes may not be enough to explore possible mechanisms.

AVPR2 is a potential prognostic biomarker and correlated with immune infiltration in head and neck squamous cell carcinoma

PURPOSE

To explore the potential of AVPR2 in the immunotherapy of head and neck squamous cell carcinoma (HNSCC), thus providing insights into a novel antitumour strategy.

METHODS

In this study, we performed a comprehensive analysis of the AVPR2 gene in HNSCC using public datasets from The Cancer Genome Atlas and Gene Expression Omnibus. We explored the potential molecular mechanism of HNSCC in clinical prognosis and tumour immunity from the aspects of gene expression, prognosis, immune subtypes, and immune infiltration.

RESULTS

AVPR2 expression was significantly downregulated in primary HNSCC tissue compared with normal tissue. HNSCC patients with high AVPR2 expression had a better prognosis. Moreover, the results of GSEA showed that immune subtype surface AVPR2 is involved in immune modulation. Furthermore, significant strong correlations between AVPR2 expression and infiltrating immune cells existed in HNSCC, and marker genes of infiltrating immune cells were also significantly related to AVPR2 expression in HNSCC. These results suggest that AVPR2 expression can influence the infiltration of tumour immune cells. Finally, we found that only high levels of B-cell infiltration, rather than those of other immune cells, can predict a longer overall survival in patients with HNSCC. Future studies are needed to explore the role of AVPR2 and tumour-infiltrating B cells in HNSCC.

CONCLUSIONS

The AVPR2 gene may be a prognostic biomarker of HNSCC. Moreover, AVPR2 may play a role in HNSCC immune modulation, and the regulation of tumour-infiltrating B cells by AVPR2 may be a key link.

Congenital nephrogenic diabetes insipidus arginine vasopressin receptor 2 gene mutation at new site: A case report

BACKGROUND

Congenital nephrogenic diabetes insipidus (CNDI) is a rare hereditary disorder. It is associated with mutations in the arginine vasopressin receptor 2 (AVPR2) gene and aquaporin 2 (AQP2) gene, and approximately 270 different mutation sites have been reported for AVPR2. Therefore, new mutations and new manifestations are crucial to complement the clinical deficiencies in the diagnosis of this disease. We report a case of a novel AVPR2 gene mutation locus and a new clinical mani-festation.

CASE SUMMARY

We describe the case of a 48-d-old boy who presented with recurrent fever and diarrhea 5 d after birth. Laboratory tests showed electrolyte disturbances and low urine specific gravity, and imaging tests showed no abnormalities. Genetic testing revealed a novel X-linked recessive missense mutation, c.283 (exon 2) C>T (p.P95S). This mutation results in the substitution of a proline residue with a serine residue in the AVPR2 protein sequence. The diagnosis of CNDI was confirmed based on the AVPR2 gene mutation. The treatment strategy for this patient was divided into two stages, including physical cooling supplemented with appropriate amounts of water in the early stage and oral hydrochlorothia-zide (1-2 mg/kg) after a clear diagnosis. After follow-up of one and a half years, the patient gradually improved.

CONCLUSION

AVPR2 gene mutations in new loci and new clinical symptoms help clinicians understand this disease and shorten the diagnosis cycle.

Nephrogenic diabetes insipidus: a comprehensive overview

Nephrogenic diabetes insipidus (NDI) is characterized by the inability to concentrate urine that results in polyuria and polydipsia, despite having normal or elevated plasma concentrations of arginine vasopressin (AVP). In this study, we review the clinical aspects and diagnosis of NDI, the various etiologies, current treatment options and potential future developments. NDI has different clinical manifestations and approaches according to the etiology. Hereditary forms of NDI are mainly caused by mutations in the genes that encode key proteins in the AVP signaling pathway, while acquired causes are normally associated with specific drug exposure, especially lithium, and hydroelectrolytic disorders. Clinical manifestations of the disease vary according to the degree of dehydration and hyperosmolality, being worse when renal water losses cannot be properly compensated by fluid intake. Regarding the diagnosis of NDI, it is important to consider the symptoms of the patient and the diagnostic tests, including the water deprivation test and the baseline plasma copeptin measurement, a stable surrogate biomarker of AVP release. Without proper treatment, patients may developcomplications leading to high morbidity and mortality, such as severe dehydration and hypernatremia. In that sense, the treatment of NDI consists in decreasing the urine output, while allowing appropriate fluid balance, normonatremia, and ensuring an acceptable quality of life. Therefore, therapeutic options include nonpharmacological interventions, including sufficient water intake and a low-sodium diet, and pharmacological treatment. The main medications used for NDI are thiazide diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), and amiloride, used isolated or in combination.