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KCNJ1
potassium inwardly rectifying channel subfamily J member 1
The KCNJ1 gene provides instructions for making a protein that forms a potassium channel, crucial for ion transport in the kidneys and maintaining fluid balance. KCNJ1 is a gene that encodes the ROMK protein, an inwardly rectifying potassium channel.
KCNJ1 is located on the long (q) arm of chromosome 11, at band 11q24.3. Arm ratio per GRCh38 - banding schematic.
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Overview
The KCNJ1 gene provides the blueprint for a protein called ROMK, which functions as a potassium channel. These channels are essential for controlling the flow of positively charged potassium ions across cell membranes. In the human body, channels formed by the KCNJ1 protein are predominantly found in the kidneys, where they are critical for maintaining the balance of ions and fluids.
What the gene does
The ROMK protein, encoded by the KCNJ1 gene, is part of a larger family of proteins that create potassium channels. These channels facilitate the movement of potassium ions into and out of cells, which is fundamental for generating and transmitting electrical signals. In the kidneys, ROMK channels work alongside other ion transporters, such as NKCC2 (produced from the SLC12A1 gene), to regulate ion movement. Specifically, the transport of potassium ions by ROMK is necessary for NKCC2 to effectively reabsorb salt (sodium chloride) from urine back into the bloodstream. This salt retention mechanism is important for managing the body's fluid levels and helping to regulate blood pressure.
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Chromosome location
The KCNJ1 gene is situated on chromosome 11 at position 11q24.3. This location specifies where the gene can be found within the human genome.
Protein structure
The KCNJ1 protein consists of 391 amino acids and contains several key functional regions. A critical component is the Selectivity filter, located between amino acids 141-146, which dictates which ions can pass through the channel. Additionally, a Polyphosphoinositide (PIP2)-binding region, spanning amino acids 180-207, allows the protein to interact with specific lipid molecules, influencing its activity and regulation.
Key variants
Genetic variations within the KCNJ1 gene can influence its function. These changes might include single nucleotide alterations or larger structural modifications, potentially impacting the protein's ability to form functional potassium channels. The specific effects of these variants can range from mild alterations in protein activity to severe disruptions, leading to various health implications.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.163G>T | p.Asp55Tyr | Pathogenic | ★★☆☆ | KCNJ1-related disorders |
c.240G>A | p.Trp80Ter | Pathogenic/Likely pathogenic | ★★☆☆ | KCNJ1-related disorders |
c.251C>T | p.Ala84Val | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter syndrome |
c.272C>T | p.Pro91Leu | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter disease type 2 |
c.416_417del | p.Phe139fs | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter disease type 2 |
c.472G>A | p.Ala158Thr | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter syndrome |
c.504dup | p.Arg169fs | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter disease type 2 |
c.874C>T | p.Arg292Trp | Pathogenic | ★★☆☆ | Bartter syndrome |
c.875G>A | p.Arg292Gln | Pathogenic/Likely pathogenic | ★★☆☆ | Bartter disease type 2 |
c.887T>G | p.Val296Gly | Pathogenic/Likely pathogenic | ★★☆☆ | KCNJ1-related disorders |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in the KCNJ1 gene are known to cause Bartter syndrome, particularly type II. This inherited condition can lead to severe health challenges that often become apparent either before or shortly after birth. Additionally, common genetic variations (polymorphisms) in KCNJ1 have been studied for their potential influence on blood pressure levels, with some rare variants suggested to offer protection against high blood pressure.
Inheritance pattern
Conditions caused by pathogenic KCNJ1 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
The KCNJ1 gene is included in several NHS Genomic Medicine Service national test directories. It is listed as green on panels for Foetal anomalies (R21), Nephrocalcinosis or nephrolithiasis (R256), and Renal tubulopathies (R198), indicating its established role in these conditions within a clinical diagnostic setting.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the function of the KCNJ1 gene?
The KCNJ1 gene provides instructions for the ROMK protein, which forms a potassium channel. This channel is crucial for moving potassium ions across cell membranes, especially in the kidneys, where it helps regulate fluid balance and blood pressure.
What health conditions are associated with the KCNJ1 gene?
Variants in the KCNJ1 gene are primarily associated with Bartter syndrome type II, a severe inherited disorder affecting kidney function. Some research also suggests that variations in KCNJ1 may play a role in influencing blood pressure levels.
How is the KCNJ1 gene relevant to kidney health?
In the kidneys, the KCNJ1 gene's protein, ROMK, is essential for the reabsorption of salt from urine back into the bloodstream. This process is vital for maintaining proper fluid levels in the body and contributing to blood pressure regulation.
References
- Welling PA, Ho K. A comprehensive guide to the ROMK potassium channel: form and function in health and disease. American journal of physiology. Renal physiology. 2009. PMID: 19458126
- Ji W, Foo JN, O'Roak BJ. Rare independent mutations in renal salt handling genes contribute to blood pressure variation. Nature genetics. 2008. PMID: 18391953
- Tobin MD, Tomaszewski M, Braund PS. Common variants in genes underlying monogenic hypertension and hypotension and blood pressure in the general population. Hypertension (Dallas, Tex. : 1979). 2008. PMID: 18443236
- Peters M, Ermert S, Jeck N. Classification and rescue of ROMK mutations underlying hyperprostaglandin E syndrome/antenatal Bartter syndrome. Kidney international. 2003. PMID: 12911542
- Jeck N, Derst C, Wischmeyer E. Functional heterogeneity of ROMK mutations linked to hyperprostaglandin E syndrome. Kidney international. 2001. PMID: 11318951
- Derst C, Konrad M, Köckerling A. Mutations in the ROMK gene in antenatal Bartter syndrome are associated with impaired K+ channel function. Biochemical and biophysical research communications. 1997. PMID: 9015377
- Simon DB, Karet FE, Rodriguez-Soriano J. Genetic heterogeneity of Bartter's syndrome revealed by mutations in the K+ channel, ROMK. Nature genetics. 1996. PMID: 8841184