New genetic link in pulmonary arterial hypertension holds therapeutic promise

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1. A new link has been found between KCNK3 gene mutations and pulmonary arterial hypertension.

2. The mutations identified affect the ability of the KCNK3 ion channel to conduct current. 

3. A drug known to stimulate KCNK3 channels can restore conductivity of some of the mutant channels in vitro. 

Study Rundown: Pulmonary hypertension refers to the pathologic state of having elevated blood pressures in the pulmonary arteries. This is most commonly a product of heart or lung disease. Pulmonary arterial hypertension (PAH) is characterized by pulmonary hypertension that is inherited or spontaneously-arising and not due to one of the more common causes.

The genetic basis of PAH is not fully understood. Some genes are known to be involved, but more remain to be found. One family with PAH but no known PAH mutations formed the basis for this study. The authors used genetic sequencing to search for mutations shared by affected members of the family. They ultimately identified a mutation in the gene KCNK3 as the most likely causal mutation.

The authors provide solid supporting evidence for the role of KCNK3 in PAH. Importantly, they show that the mutations they identified in PAH patients affect the normal current-conducting ability of the KCNK3 potassium channel. In a promising finding, a drug known to activate the KCNK3 channel, ONO-RS-082, was shown to restore function to some (but not all) of the mutant proteins.

Click to read the study in NEJM

Relevant Reading: Molecular pathogenesis of pulmonary arterial hypertension

In-Depth [functional genetics study]: After analyzing whole-exome sequencing data from Family 1, a KCNK3 missense mutation emerged as the most likely causal mutation. KCNK3 is known to play a role in pulmonary vascular tone, and the mutant allele segregated with PAH. The authors found five additional KCNK3 mutations among patients and families with previously idiopathic PAH.

The functional effect of these mutations was evaluated by expressing the mutant proteins in cultured cells. Patch-clamp techniques were used to measure the flow of current across the membranes of transfected cells. Cells expressing the mutant proteins could not conduct as much current as cells expressing the wild-type protein.

The phospholipase A2 inhibitor ONO-RS-082 is known to activate the wild-type KCNK3 channel. The authors found that ONO-RS-082 has a similar activating effect on two of the mutant KCNK3 channels. This helps to correct the conductance of the mutant channels back towards normal. However, the drug did not activate a third mutant allele that was tested.

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