Key result
Rare missense variants in the KCNQ1 S5-Pore-S6 and CR2 regions were significantly enriched in patients with Long QT Syndrome compared to an unselected population (OR >2).
Why the study?
Rare variants in KCNQ1 occur in healthy populations far more often than LQTS1 prevalence, creating challenges in interpreting secondary findings from whole exome sequencing.
Do missense variants in specific sub-domains of the KCNQ1 gene predict Long QT Syndrome type 1 (LQTS1) pathogenicity and severity?
Observational (n=143,700)
Do missense variants in specific sub-domains of the KCNQ1 gene predict Long QT Syndrome type 1 (LQTS1) pathogenicity and severity?
Effect estimate: OR >2
Rare missense variants in the S5-Pore-S6 and CR2 regions of the KCNQ1 gene are highly predictive of Long QT Syndrome type 1 and associated with a more severe phenotype, aiding in the interpretation of secondary genetic findings.
KCNQ1 variant interpretation in secondary findings warrants caution; leaves open sub-domain-specific prediction of LQTS1 pathogenicity.
AIMS: Rare variants in the KCNQ1 gene are found in the healthy population to a much greater extent than the prevalence of Long QT Syndrome type 1 (LQTS1). This observation creates challenges in the interpretation of KCNQ1 rare variants that may be identified as secondary findings in whole exome sequencing.This study sought to identify missense variants within sub-domains of the KCNQ1-encoded Kv7.1 potassium channel that would be highly predictive of disease in the context of secondary findings. METHODS AND RESULTS: We established a set of KCNQ1 variants reported in over 3700 patients with diagnosed or suspected LQTS sent for clinical genetic testing and compared the domain-specific location of identified variants to those observed in an unselected population of 140 000 individuals. We identified three regions that showed a significant enrichment of KCNQ1 variants associated with LQTS at an odds ratio (OR) >2: the pore region, and the adjacent 5th (S5) and 6th (S6) transmembrane (TM) regions. An additional segment within the carboxyl terminus of Kv7.1, conserved region 2 (CR2), also showed an increased OR of disease association. Furthermore, the TM spanning S5-Pore-S6 region correlated with a significant increase in cardiac events. CONCLUSION: Rare missense variants with a clear phenotype of LQTS have a high likelihood to be present within the pore and adjacent TM segments (S5-Pore-S6) and a greater tendency to be present within CR2. This data will enhance interpretation of secondary findings within the KCNQ1 gene. Further, our data support a more severe phenotype in LQTS patients with variants within the S5-Pore-S6 region.
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Novelli et al. (2023) conducted an observational in Long QT Syndrome type 1 (LQTS1) (n=143,700). KCNQ1 missense variants in the S5-Pore-S6 and CR2 regions vs. Unselected population was evaluated on Association with LQTS (OR >2). Rare missense variants in the KCNQ1 S5-Pore-S6 and CR2 regions were significantly enriched in patients with Long QT Syndrome compared to an unselected population (OR >2).
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