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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Research Article Genetics Nephrology

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 2

Acidic motif WNK1 mutations.

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Acidic motif WNK1 mutations. (A) Schematic representation of the WNK1 ge...
(A) Schematic representation of the WNK1 gene. The coordinates of the different exons are indicated above or below the structure with ex7 and ex25 (gray), which code for the conserved acidic and basic motifs. The proximal promoter (pP) drives the expression of the long ubiquitous kinase active isoform (L-WNK1), whereas the renal promoter (rP) drives the expression of the kinase defective kidney-specific isoform (KS-WNK1). (B) Schematic linear structure of LWNK1 and KS-WNK1. The kinase domain is represented in full black, the autoinhibitory domain (AID) is striped, coiled-coil domain 1 (CC1) and CC2 are represented in gray, and the conserved acidic motif (AM) and basic motif (BM) are represented in red. (C) Location and sequences of the mutated residues clustering in the acidic motif. The brackets indicate the number of unrelated affected subjects for each mutation. On the lower right are shown the Sanger sequencing electrophoregrams showing the various missense WNK1 mutations. (D) Conservation of the acidic motif showing residues mutated in FHHt among human WNK family members. The previously described WNK4 mutations are indicated in red; those at WNK1 and identified in this study in blue. All are located at completely conserved residues. The bottom part shows the conservation of the WNK1 acidic motif across species. The mutated residues are indicated in bold.