Elsevier

Kidney International

Volume 97, Issue 6, June 2020, Pages 1208-1218
Kidney International

Basic Research
Collecting system–specific deletion of Kcnj10 predisposes for thiazide- and low-potassium diet–induced hypokalemia

https://doi.org/10.1016/j.kint.2019.12.016Get rights and content

The basolateral potassium channel KCNJ10 (Kir4.1), is expressed in the renal distal convoluted tubule and controls the activity of the thiazide-sensitive sodium chloride cotransporter. Loss-of-function mutations of KCNJ10 cause EAST/SeSAME syndrome with salt wasting and severe hypokalemia. KCNJ10 is also expressed in the principal cells of the collecting system. However, its pathophysiological role in this segment has not been studied in detail. To address this, we generated the mouse model AQP2cre:Kcnj10flox/flox with a deletion of Kcnj10 specifically in the collecting system (collecting system-Kcnj10-knockout). Collecting system-Kcnj10-knockout mice responded normally to standard and high potassium diet. However, this knockout exhibited a higher kaliuresis and lower plasma potassium than control mice when treated with thiazide diuretics. Likewise, collecting systemKcnj10-knockout displayed an inadequately high kaliuresis and renal sodium retention upon dietary potassium restriction. In this condition, these knockout mice became hypokalemic due to insufficient downregulation of the epithelial sodium channel (ENaC) and the renal outer medullary potassium channel (ROMK) in the collecting system. Consistently, the phenotype of collecting system-Kcnj10-knockout was fully abrogated by ENaC inhibition with amiloride and ameliorated by genetic inactivation of ROMK in the collecting system. Thus, KCNJ10 in the collecting system contributes to the renal control of potassium homeostasis by regulating ENaC and ROMK. Hence, impaired KCNJ10 function in the collecting system predisposes for thiazide and low potassium diet-induced hypokalemia and likely contributes to the pathophysiology of renal potassium loss in EAST/SeSAME syndrome.

Section snippets

CS-Kcnj10-KO mice do not exhibit any evident clinical phenotype under standard conditions

To investigate the function of Kir4.1 in the connecting tubule and collecting duct, collecting system (CS)–specific Kcnj10-knockout mice (CS-Kcnj10-KO) were generated by breeding mice with “floxed”Kcnj10 alleles (Kcnj10flox/flox) with mice expressing the Cre recombinase under the control of the aquaporin 2 (Aqp2) promoter (Aqp2cre). CS-Kcnj10-KO mice were born in a Mendelian ratio and thrived normally. Immunofluorescence staining of consecutive kidney sections with antibodies against AQP2, Kir

Discussion

EAST/SeSAME patients suffer from loss-of-function mutations of KCNJ10 in the DCT and display severe hypokalemia and a renal tubulopathy that is reminiscent of Gitelman’s syndrome.1, 2, 3 These observations led to the current concept that the renal phenotype of patients with loss-of-function mutations in KCNJ10 is mainly due to impaired DCT function.3 According to this concept, the reduced NCC activity in patients with EAST/SeSAME syndrome results in an increased NaCl delivery to the CS. The

Animals

Mice were maintained at a 12/12-hour light/dark cycle with access to standard chow (3430 Kliba-Nafag, Kaiseraugst, Switzerland) and water ad libitum. Animal experiments were conducted according to Swiss laws and approved by the veterinary administration of the Canton of Zurich, Switzerland (license numbers 213/2015 and 135/2018). For each experimental series, animals with matching weight, sex, and age were used. CS-Kcnj10-KO mice were generated by cross-breeding Kir4.1f/f (Jackson Laboratories,

Disclosure

All the authors declared no competing interests.

Acknowledgments

The authors thank Monique Carrel, Ines Tegtmeier, Pascal Peretti, and Michèle Heidemeyer for excellent technical assistance. The authors also thank the Center of Microscopy and Image Analysis (ZMB) at the University of Zurich, and particularly Dr. Joana R. Martins, for excellent support with confocal microscopy and image analysis. The authors thank Dr. Carsten Wagner (University of Zurich, Switzerland) and Dr. Markus Bleich (University of Kiel, Germany) for fruitful discussions. Part of this

References (50)

  • M.P. Méndez-González et al.

    Novel KCNJ10 gene variations compromise function of inwardly rectifying potassium channel 4.1

    J Biol Chem

    (2016)
  • D. Bockenhauer et al.

    Epilepsy, ataxia, sensorineural deafness, tubulopathy, and KCNJ10 mutations

    N Engl J Med

    (2009)
  • U.I. Scholl et al.

    Seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME syndrome) caused by mutations in KCNJ10

    Proc Natl Acad Sci U S A

    (2009)
  • M. Reichold et al.

    KCNJ10 gene mutations causing EAST syndrome (epilepsy, ataxia, sensorineural deafness, and tubulopathy) disrupt channel function

    Proc Natl Acad Sci U S A

    (2010)
  • O. Palygin et al.

    Distal tubule basolateral potassium channels: cellular and molecular mechanisms of regulation

    Curr Opin Nephrol Hypertens

    (2018)
  • C.T. Bond et al.

    Cloning and expression of a family of inward rectifier potassium channels

    Receptors Channels

    (1994)
  • U.I. Scholl et al.

    SeSAME/EAST syndrome—phenotypic variability and delayed activity of the distal convoluted tubule

    Pediatr Nephrol

    (2012)
  • D.B. Simon et al.

    Gitelman’s variant of Bartter’s syndrome, inherited hypokalaemic alkalosis, is caused by mutations in the thiazide-sensitive Na-Cl cotransporter

    Nat Genet

    (1996)
  • C. Zhang et al.

    KCNJ10 determines the expression of the apical Na-Cl cotransporter (NCC) in the early distal convoluted tubule (DCT1)

    Proc Natl Acad Sci U S A

    (2014)
  • W.-H. Wang

    Basolateral Kir4.1 activity in the distal convoluted tubule regulates K secretion by determining NaCl cotransporter activity

    Curr Opin Nephrol Hypertens

    (2016)
  • D. Penton et al.

    Extracellular K(+) rapidly controls NaCl cotransporter phosphorylation in the native distal convoluted tubule by Cl(-) -dependent and independent mechanisms

    J Physiol

    (2016)
  • C.A. Cuevas et al.

    Potassium sensing by renal distal tubules requires Kir4.1

    J Am Soc Nephrol

    (2017)
  • D. Penton et al.

    Dietary potassium and the renal control of salt balance and blood pressure

    Pflügers Arch

    (2015)
  • H.J. Gitelman et al.

    A new familial disorder characterized by hypokalemia and hypomagnesemia

    Trans Assoc Am Physicians

    (1966)
  • D.H. Ellison et al.

    Thiazide effects and adverse effects: insights from molecular genetics

    Hypertension

    (2009)
  • Cited by (14)

    View all citing articles on Scopus
    4

    RW and JL contributed equally to this study.

    View full text