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Published on: September 15, 2017
Identification of a novel WNK4 mutation in Chinese patients with pseudohypoaldosteronism type II
Chong Zhang1, Zhaohui Wang, Jingyuan Xie
1Department of Nephrology, School of Medicine, Shanghai Jiao Tong University, China.
Background:
It has been reported that mutations in WNK1 and WNK4 cause pseudohypoaldosteronism type II (PHA2), an autosomal dominant renal disease. WNK kinase proteins are expressed in the kidney and regulate ion transport including the thiazide-sensitive sodium chloride cotransporter (NCC). In this report, we screened 4 Chinese PHA2 pedigrees for WNK4 mutations, identified a novel mutation, and studied its effects on NCC protein trafficking in vitro.
Methods:
The patients' genomic DNA was extracted from peripheral leukocytes. Sequence analysis was performed by PCR amplification of the 19 exons of WNK4. The wild-type or mutant WNK4 was coexpressed with NCC in HEK293 cells. We measured the effect of wild-type WNK4 compared to the mutant WNK4 on NCC protein surface expression.
Results:
A novel missense mutation in WNK4, K1169E, was identified in 1 of the 4 pedigrees. Analysis of confocal images showed that K1169E lost its inhibitory effect on NCC surface expression compared to wild-type WNK4 when expressed in HEK293 cells, while it did not change NCC total protein expression.
Conclusions:
We identified an unreported disease-causing WNK4 missense mutation, K1169E, in 1 Chinese PHA2 pedigree. This mutation appears to be a 'loss of function' of NCC inhibition and suggests that some important functional roles lie in the 2nd coiled-coil domain of WNK4.
Insights
Researchers identified a new WNK4 mutation, K1169E, in Chinese patients with pseudohypoaldosteronism type II (PHA2). This mutation disrupts the inhibition of the sodium chloride cotransporter (NCC), indicating a loss of function in WNK4.
Area of Science:
- Genetics
- Molecular Biology
- Nephrology
Background:
- Pseudohypoaldosteronism type II (PHA2) is an autosomal dominant renal disease linked to mutations in WNK1 and WNK4.
- WNK kinases are crucial for kidney ion transport, including the thiazide-sensitive sodium chloride cotransporter (NCC).
Purpose of the Study:
- To screen Chinese PHA2 pedigrees for WNK4 mutations.
- To investigate the functional impact of a novel WNK4 mutation on NCC protein trafficking and surface expression.
Main Methods:
- Genomic DNA extraction from patient leukocytes.
- PCR amplification and sequence analysis of WNK4 exons.
- Coexpression of wild-type or mutant WNK4 with NCC in HEK293 cells.
- Confocal microscopy to assess NCC surface expression.
Main Results:
- A novel WNK4 missense mutation, K1169E, was identified in one Chinese PHA2 pedigree.
- The K1169E mutation abolished the inhibitory effect of WNK4 on NCC surface expression.
- Total NCC protein expression remained unchanged by the K1169E mutation.
Conclusions:
- The K1169E mutation is a novel, disease-causing mutation in WNK4 for PHA2.
- This mutation represents a loss-of-function, impairing WNK4's inhibition of NCC.
- Functional significance of WNK4's 2nd coiled-coil domain in NCC regulation is suggested.
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