Mutation affecting the conserved acidic WNK1 motif causes inherited hyperkalemic hyperchloremic acidosis
Hélène Louis-Dit-Picard, … , Juliette Hadchouel, Xavier Jeunemaitre
Hélène Louis-Dit-Picard, … , Juliette Hadchouel, Xavier Jeunemaitre
Published August 13, 2020
Citation Information: J Clin Invest. 2020;130(12):6379-6394. https://doi.org/10.1172/JCI94171.
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Mutation affecting the conserved acidic WNK1 motif causes inherited hyperkalemic hyperchloremic acidosis

Abstract

Gain-of-function mutations in with no lysine (K) 1 (WNK1) and WNK4 genes are responsible for familial hyperkalemic hypertension (FHHt), a rare, inherited disorder characterized by arterial hypertension and hyperkalemia with metabolic acidosis. More recently, FHHt-causing mutations in the Kelch-like 3–Cullin 3 (KLHL3-CUL3) E3 ubiquitin ligase complex have shed light on the importance of WNK’s cellular degradation on renal ion transport. Using full exome sequencing for a 4-generation family and then targeted sequencing in other suspected cases, we have identified new missense variants in the WNK1 gene clustering in the short conserved acidic motif known to interact with the KLHL3-CUL3 ubiquitin complex. Affected subjects had an early onset of a hyperkalemic hyperchloremic phenotype, but normal blood pressure values”Functional experiments in Xenopus laevis oocytes and HEK293T cells demonstrated that these mutations strongly decrease the ubiquitination of the kidney-specific isoform KS-WNK1 by the KLHL3-CUL3 complex rather than the long ubiquitous catalytically active L-WNK1 isoform. A corresponding CRISPR/Cas9 engineered mouse model recapitulated both the clinical and biological phenotypes. Renal investigations showed increased activation of the Ste20 proline alanine–rich kinase–Na+-Cl– cotransporter (SPAK-NCC) phosphorylation cascade, associated with impaired ROMK apical expression in the distal part of the renal tubule. Together, these new WNK1 genetic variants highlight the importance of the KS-WNK1 isoform abundance on potassium homeostasis.

Authors

Hélène Louis-Dit-Picard, Ilektra Kouranti, Chloé Rafael, Irmine Loisel-Ferreira, Maria Chavez-Canales, Waed Abdel-Khalek, Eduardo R. Argaiz, Stéphanie Baron, Sarah Vacle, Tiffany Migeon, Richard Coleman, Marcio Do Cruzeiro, Marguerite Hureaux, Nirubiah Thurairajasingam, Stéphane Decramer, Xavier Girerd, Kevin O’Shaugnessy, Paolo Mulatero, Gwenaëlle Roussey, Ivan Tack, Robert Unwin, Rosa Vargas-Poussou, Olivier Staub, Richard Grimm, Paul A. Welling, Gerardo Gamba, Eric Clauser, Juliette Hadchouel, Xavier Jeunemaitre

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Figure 5

Normal BP on both normal and high-salt diet in Wnk1+/delE631 mice.

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Normal BP on both normal and high-salt diet in Wnk1+/delE631 mice. (A–C)...
(A–C) SBP and DBP profiles over 24 hours of SBP and DBP under a12-hour day/12-hour night schedule in Wnk1+/+ (n = 6) and Wnk1+/delE631 (n = 7) mice examined with a telemetric system under basal conditions (A). Night SBP and DBP of the same mice before (6 nights = basal) or during (7 nights) oral administration of HCTZ (240 mg/kg/d) (B). Night SBP and DBP of another group of mice (n = 4 Wnk1+/+, n = 4 Wnk1+/delE631) before (6 nights = basal) or during (6 nights) the administration of high (3%) Na+ diet (C). (D–F) Biological characteristics. In the mutant mice, significant hyperkalemia (5.1 ± 0.5 vs. 4.3 ± 0.2 mmol/L, P < 0.0001; n = 20) (D); hyperchloremia (114 ± 2 vs. 110 ± 3 mmol/L, P < 0.0001; n = 20) (E); and metabolic acidosis (HCO3–, 22.8 ± 2.1 vs. 24.6 ± 2.5 mmol/L, P < 0.05; n = 20) (F) were observed together with normal creatinine values (not shown). Data are represented as mean ± SEM. Statistical comparisons were made using unpaired Student’s t test. (G and H) Renin expression. Levels of renin mRNA were measured by RT-qPCR in the kidney cortex of Wnk1+/+ (n = 7) and Wnk1+/delE631 (n = 7) mice in baseline conditions (G) or of Wnk1+/+ (n = 6) and Wnk1+/delE631 (n = 6) mice fed a low (0%) K+ diet (H). Results (mean ± SEM) are expressed in arbitrary units relative to the expression of ubc. The expression level in Wnk1+/+ mice under basal conditions was arbitrarily set to 1. *P< 0.05; **P < 0.01; ****P < 0.0001, unpaired Student’s t test.