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Clin Endocrinol (Oxf). 2016 Dec;85(6):845-851. doi: 10.1111/cen.13132. Epub 2016 Jul 12.

Functional characterization of two novel germline mutations of the KCNJ5 gene in hypertensive patients without primary aldosteronism but with ACTH-dependent aldosterone hypersecretion.

Author information

1
Division of Endocrinology, Metabolism and Diabetes, First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, 'Aghia Sophia' Children's Hospital, Athens, Greece.
2
Department of Endocrinology and Diabetes Center, 'G. Gennimatas' General Hospital, Athens, Greece.
3
Bioinformatics & Medical Informatics Team, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
4
Molecular Neurophysiology and Biophysics Section, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
5
Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
6
Department of Pathophysiology, National and Kapodistrian University of Athens Medical School, 'Laikon' Hospital, Athens, Greece.

Abstract

BACKGROUND:

Germline mutations of the KCNJ5 gene encoding Kir3·4, a member of the inwardly rectifying K+ channel, have been identified in 'normal' adrenal glands, patients with familial hyperaldosteronism (FH) type III, aldosterone-producing adenomas (APAs) and sporadic cases of primary aldosteronism (PA).

OBJECTIVE:

To present two novel KCNJ5 gene mutations in hypertensive patients without PA, but with Adrenocorticotropic hormone (ACTH)-dependent aldosterone hypersecretion.

DESIGN AND PATIENTS:

Two hypertensive patients without PA, who exhibited enhanced ACTH-dependent response of aldosterone secretion, underwent genetic testing for the presence of the CYP11B1/CYP11B2 chimeric gene and KCNJ5 gene mutations. Genomic DNA was isolated from peripheral white blood cells, and the exons of the entire coding regions of the above genes were amplified and sequenced. Electrophysiological studies were performed to determine the effect of identified mutation(s) on the membrane reversal potentials. Structural biology studies were also carried out.

RESULTS:

Two novel germline heterozygous KCNJ5 mutations, p.V259M and p.Y348N, were detected in the two subjects. Electrophysiological studies showed that the Y348N mutation resulted in significantly less negative reversal potentials, suggesting loss of ion selectivity, while the V259M mutation did not affect the Kir3.4 current. In the mutated structural biology model, the N348 mutant resulted in significant loss of the ability for hydrogen bonding, while the M259 mutant was capable of establishing weaker interactions. The CYP11B1/CYP11B2 chimeric gene was not detected.

CONCLUSIONS:

These findings expand on the clinical spectrum of phenotypes associated with KCNJ5 mutations and implicate these mutations in the pathogenesis of hypertension associated with increased aldosterone response to ACTH stimulation.

PMID:
27293068
PMCID:
PMC5118167
DOI:
10.1111/cen.13132
[Indexed for MEDLINE]
Free PMC Article

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