Laboratory for Molecular Diagnostics
Center for Nephrology and Metabolic Disorders

Renal outer-medullary potassium channel

The KCNJ1 gene encoding an important renal potassium channel causes, when mutated, autosomal recessive antenatal Bartter syndrome type 2.

Epidemiology

Although exact data are not available, mutation in this gene are thought to occur 1 in 50,000-100,000 newborn.

Expression

The gene is expressed in epithelial cells of the thick ascending limb of the loop of Henle. The mature protein, a potassium channel, resides in the apical membrane.

Phenotype

As the potassium channel (ROMK) and the sodium-potassium-chloride cotransporter (NKCC2) form a functional unit, dysfuntion of either component causes the same clinical picture of autosomal recessive antenatal Bartter syndrome.

Gene Regulation

This inwardly rectifying potassium channel forms a functional unit with the sodium-potassium-chloride cotransporter. The cotransporter moves sodium and potassium, one of each ion, and two chloride from lumen into cell. The excess of sodium and chroride is removed basolateral transpoters, the sodium-potassium ATPase and a chloride channel. The excess potassium however is recycled back into the lumen by an inwardly rectifying potassium channel. Hence this channel keeps the system of net sodium chlorid reabsorption running.

WNK1 and WNK2, the genes involved in pseudohypoaldosteronism type 2, interact with intersectin-1 (ITSN1), an endocytic scaffold protein, thereby stimulating the potassium channel (ROMK) endocytosis. Hence, These genes play an important role in regulating channel function.[Error: Macro 'ref' doesn't exist]

Genetests:

Clinic Method Carrier testing
Turnaround 5 days
Specimen type genomic DNA
Clinic Method Multiplex Ligation-Dependent Probe Amplification
Turnaround 20 days
Specimen type genomic DNA
Clinic Method Genomic sequencing of the entire coding region
Turnaround 10 days
Specimen type genomic DNA
Clinic Method Massive parallel sequencing
Turnaround 25 days
Specimen type genomic DNA

Related Diseases:

Antenatal Bartter syndrome type 2
KCNJ1

References:

1.

He G et al. (2007) Intersectin links WNK kinases to endocytosis of ROMK1.

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2.

Simon DB et al. (1996) Genetic heterogeneity of Bartter's syndrome revealed by mutations in the K+ channel, ROMK.

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3.

et al. (1997) Mutations in the gene encoding the inwardly-rectifying renal potassium channel, ROMK, cause the antenatal variant of Bartter syndrome: evidence for genetic heterogeneity. International Collaborative Study Group for Bartter-like Syndromes.

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4.

Schwalbe RA et al. (1998) Functional consequences of ROMK mutants linked to antenatal Bartter's syndrome and implications for treatment.

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Update: Sept. 26, 2018