Inherited long QT syndrome (LQTS) is an autosomal dominant cardiac disorder that can lead to arrhythmias and sudden cardiac death. It is associated with mutations in several genes, including KCNH2, which encodes the K_V11.1 potassium channel crucial for cardiac repolarization.

Diagnosing LQTS is challenging due to its highly variable presentation, incomplete penetrance, and dynamic changes in the QT interval. Additionally, most missense variants identified in genetic testing are classified as variants of uncertain significance (VUS) due to insufficient evidence. Understanding the functional impact of these VUS is critical for improving diagnosis and treatment.

Previous studies have shown that high-throughput functional assays, such as automated patch-clamp (APC) assays, can enhance the interpretation of these variants by providing evidence of their pathogenicity.

A recent study aimed to validate the pathogenicity of two missense KCNH2 variants found in families diagnosed with LQTS using such a calibrated APC assay on the high-throughput SyncroPatch 384 system.

The specific variants investigated were p.(Ile607Phe) and p.(Tyr611Cys). Researchers utilized HEK293 cell lines to express these variants and measure ion channel function. The APC assay was designed to determine the Z-scores for these variants, providing a quantitative measure of their functional impact.

The APC assay revealed significant loss-of-function in both variants, with Z-scores indicating severe impairment. The homozygous p.(Ile607Phe) variant exhibited a Z-score of –5.16, while the heterozygous form showed a Z-score of –3.97. The p.(Tyr611Cys) variant had a Z-score of –6.63. These results suggest a strong pathogenic effect, consistent with clinical observations of severe LQTS symptoms in affected individuals. The functional data supported reclassifying these variants from VUS to likely pathogenic (p.(Ile607Phe)) and pathogenic (p.(Tyr611Cys)).

Overall, this study shows that incorporating functional assessment into the diagnostic process for LQTS significantly enhances the accuracy of variant classification. The validated APC assay provides robust evidence for the pathogenicity of KCNH2 variants, enabling better clinical management and personalized treatment strategies. Future research should focus on expanding this approach to other genetic variants associated with LQTS and similar conditions.

—
Find the full article here: https://www.sciencedirect.com/science/article/pii/S2949774424010148

Learn more about our automated patch clamp solutions: https://www.nanion.de/product-categories/automated-patch-clamp/