hERG Research Articles

Prostaglandin E2 suppresses KCNH1 gene expression and inhibits the proliferation of CaSki cervical cells through its four prostanoid PTGER subtypes

The main risk factor for cervical cancer is the persistent infection of high-risk HPV subtypes, notably HPV16. Another contributing factor is proinflammatory prostaglandin E2 (PGE2), a lipid abundantly found in seminal fluid. PGE2, along with its receptors (PTGER1-4), contributes to cancer development; however, its specific role in the proliferation of cervical cancer models with high HPV16 copy numbers remains unclear. In this study, we investigated the effects of PGE2 on the proliferation of CaSki cells, a cell line with a high HPV16 viral load. Surprisingly, PGE2 inhibited CaSki cell proliferation, while it increased the proliferation of SiHa, HeLa, and C-33 A cervical cancer cells. The effect of PGE2 on CaSki cell proliferation was specific, as estradiol increased cell growth. Furthermore, PGE2 suppressed expression and promoter activity of the cervical tumoral marker KCNH1. To discern the specific role of each receptor in cell proliferation, we generated stable CaSki cell lines overexpressing each receptor alongside control cells with an empty vector. Notably, PGE2 significantly inhibited cell proliferation in all stable transfected CaSki cells, suppressing oncogenic KCNH1 expression and its promoter activity. In conclusion, our findings indicate that PGE2 inhibits the proliferation of CaSki cervical cancer cells with a high HPV16 load, at least in part, by suppressing the expression of the oncogenic KCNH1 gene.

Clinical and genetic analysis of a Chinese pedigree affected with type 2 Long QT syndrome due to variant of KCNH2 gene

To explore the clinical and genetic etiology of a Chinese pedigree affected with type 2 Long QT syndrome (LQTS). A pedigree with type 2 LQTS presented at Fuwai Central China Cardiovascular Hospital on August 23, 2019 was selected as the study subject. Peripheral blood samples were collected from the proband and her parents. Following extraction of genomic DNA, whole exome sequencing (WES) was carried out for the proband, and candidate variant was screened through functional annotation and protein-protein interaction (PPI) analysis. Sanger sequencing was conducted to verify the pathogenicity of candidate variant. This study was approved by the Fuwai Central China Cardiovascular Hospital (Ethics No. 2019-15). WES revealed that the proband has harbored a missense variant of the KCNH2 gene, namely c.1478A>G (p.Tyr493Cys), which was confirmed by Sanger sequencing to have inherited from her father. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PM2_supporting+PM5+PP3+PP4). The KCNH2 gene c.1478A>G (p.Tyr493Cys) variant probably underlay the type 2 LQTS in this pedigree.

Clinical Features, Long-Term Prognosis, and Clinical Management of Genotype-Negative Long QT Syndrome Patients.

Approximately 15% to 20% of patients clinically diagnosed with long QT syndrome (LQTS) are genotype-negative (GEN-). Whether they have a different arrhythmic risk or should be managed differently remains unclear, often leading to incomplete treatment. The purpose of this study was to compare clinical aspects of GEN- and genotype-positive (GEN+) LQTS patients. We retrospectively evaluated 832 LQTS patients genetically screened in Japan (n=347) and Italy (n=485), including 698 with a disease-causing variant in the KCNQ1, KCNH2, and SCN5A genes (GEN+), and 134 without variants in these LQTS-related genes (GEN-). At diagnosis, the Japanese patients were more often probands (86% vs 60%), symptomatic (39% vs 18%), and of younger age than the Italian patients; conversely, they used less β-blockers (65% vs 95%), more rarely had a family history (FH) of LQTS (42% vs 73%), and had more cardiac events during follow-up (13% vs 4%) (P< 0.001 for all comparisons). Within the Japanese cohort, the GEN- had more cardiac arrests, used less β-blockers, and had much less FH for LQTS compared their GEN+ counterpart. The Italian cohort was more homogeneous, with just more LQTS FH among the GEN+. QTc shortening (close to 30ms in all groups) during follow-up was similar between Japanese and Italian patients, irrespective of their being GEN+ or GEN-. In both cohorts, during an average follow-up of 6 and 7 years, respectively, GEN+ and GEN- patients showed a comparable clinical outcome. Arrhythmic risk is similar between GEN+ and GEN- LQTS patients; they should be managed and treated in the same way.

Abstract A014: Protein-informed gene methylation signatures to predict treatment response and outcomes in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDA) is a deadly cancer with dismal outcomes. We need new biomarkers to optimize the limited treatment combinations used in current clinical practice. Many machine-learning models have been presented based on mutational or transcriptome data claiming to predict outcomes. Still, they do not provide actionable targets (genes) that could improve treatment response. Moreover, DNA-methylation changes that influence gene/protein expression have been explored for this purpose. From the literature, we curated a 122-gene panel (January 1970 to April 2024) constructed on the proteins with preclinical (on cell lines or mouse models) or clinical (tissue-based studies) evidence suggesting their individual roles in influencing response to drugs often used in managing PDA such as gemcitabine (Gem), nab-paclitaxel, oxaliplatin, 5-fluorouracil, irinotecan, and cisplatin. We hypothesized that methylation changes in these genes are surrogates for gene/protein expression and tested their clinical significance in The Cancer Genome Atlas (TCGA) PDA population (n=184). The goal was to develop methylation signatures composed of specific cytosines followed by guanine residue (CpG) sites that aid in identifying patients at high risk of treatment failure and poor outcomes. We used elastic net multivariate analysis to calculate survival and plot Kaplan Meier plots based on our gene panel. The alpha (α) used for this script was calculated based on the lowest mean error and the minimum lambda (λ) value accordingly for each iteration (100 iterations to calculate the best values for α and λ). Our analysis yielded 28 methylation signatures that could identify high-risk PDA patients with poor overall survival (OS). The number of CpG sites in these signatures ranged from 1 to 1933. The differences in OS for these signatures were better than those available in the literature. The best signature had 18 CpG sites (17 months (m) vs. not evaluable) followed by a 53-CpG site signature (16 m vs. 67m) and a 6-CpG site signature (17m vs. 67m). A signature with the highest CpG sites (1933) was not better than those with smaller ones (16m vs. 21m). Multiple signatures had &amp;gt;1 CpG sites from one gene. Early growth response 1 (EGR1) coding the KCNH2 gene has featured in most signatures. One CpG site in this gene had a clinically significant prognostic value (15m vs. 30m). Other frequently featured genes were CCDC85A, EGFR, SST, and HMGA1. The main drawbacks for this study were that Gem-related genes (&amp;gt; 60) dominated the panel, and those with Gem treatment dominated the patient population. This panel should be further refined to make it more relevant to current clinical practice. We provide preliminary evidence suggesting the clinical significance of our panel and lay the foundation for future studies that would enable us to personalize prognostication and treatment selection in PDA patients. Our work can provide novel therapeutic targets that, alone or in combination with chemotherapy, can improve the outcomes for PDA. Citation Format: Ashish Manne, Harshitha Puram, Deepak Sherpally, Sravan Jeepalyam, Upender Manne. Protein-informed gene methylation signatures to predict treatment response and outcomes in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A014.

Fentanyl and Sudden Death-A Postmortem Perspective for Diagnosing and Predicting Risk.

Sudden, unexpected deaths are extremely difficult for families, especially when the victim is a child. Most sudden deaths occur due to cardiovascular issues, and a smaller number (approximately one-quarter) are attributed to other causes, such as epilepsy. The medicinal and non-medicinal use of the synthetic opioid fentanyl, which can cause breathing problems, is frequently involved in these deaths. It is also being found more often in autopsies of sudden death cases, and the number of overdose deaths from illicit drugs containing fentanyl is increasing. There are cases in which it is mixed with other drugs. A gene known as the KCNH2 gene or human ether-a-go-go-related gene (hERG), involved in the heart's electrical activity, can be related to abnormal heart rhythms. This gene, along with others, may play a role in sudden deaths related to fentanyl use. In response, we have examined the scientific literature on genetic variations in the KCNH2 gene that can cause sudden death, the impact of fentanyl on this process, and the potential benefits of genetic testing for the victims to offer genetic counseling for their family members.

Potassium dependent structural changes in the selectivity filter of HERG potassium channels

The fine tuning of biological electrical signaling is mediated by variations in the rates of opening and closing of gates that control ion flux through different ion channels. Human ether-a-go-go related gene (HERG) potassium channels have uniquely rapid inactivation kinetics which are critical to the role they play in regulating cardiac electrical activity. Here, we exploit the K+ sensitivity of HERG inactivation to determine structures of both a conductive and non-conductive selectivity filter structure of HERG. The conductive state has a canonical cylindrical shaped selectivity filter. The non-conductive state is characterized by flipping of the selectivity filter valine backbone carbonyls to point away from the central axis. The side chain of S620 on the pore helix plays a central role in this process, by coordinating distinct sets of interactions in the conductive, non-conductive, and transition states. Our model represents a distinct mechanism by which ion channels fine tune their activity and could explain the uniquely rapid inactivation kinetics of HERG.

Clinical presentation and genetic characterization of early-onset atrial fibrillation in patients affected by long QT syndrome: A single-center experience.

Early-onset atrial fibrillation (AF) has already been observed in approximately 2% of patients with genetically proven long QT syndrome (LQTS). This frequency is higher than population-based estimates of early-onset AF. However, the concomitant expression of AF in LQTS is likely underestimated. The purpose of this study was to examine the clinical presentation, genetic background, and outcomes of a cohort of patients with LQTS and early-onset AF referred to a single tertiary center. Twenty-seven patients diagnosed with congenital LQTS were included in the study based on the documentation of early-onset (age ≤50 years) clinical or subclinical AF episodes in all available medical records, including standard electrocardiograms, wearable monitor or cardiac implantable electronic devices. Seventeen patients experienced clinical AF during the follow-up period. Subclinical AF was detected in 10 patients through insertable or wearable cardiac monitors. In our series, the mean heart rate during AF episodes was found to be relatively low despite the patients' young age and the low or minimal effective doses of beta-blockers used for QTc interval control. All patients exhibiting LQTS and early-onset AF were genotype positive, carrying mutations in the KCNQ1 (66%), KCNH2, KCNE1, and SCN5A genes. Notably, most of these patients carried the same p.(R231C) mutation in the KCNQ1 gene (59%) and were from the same families, suggesting concurrent expression of familial AF and LQTS. LQTS patients are prone to developing clinical and subclinical AF, even at a younger age. The occurrence of early-onset AF in the LQTS population could be more frequent than previously assumed. AF should be considered as a potential dysrhythmia related to LQTS. Our study emphasizes the importance of carefully researching clinical and/or subclinical episodes of AF through strict heart rhythm monitoring in the LQTS population.

A method of identifying the high-risk mutations of sudden cardiac death at KCNQ1 and KCNH2 genes

Sudden Cardiac Death (SCD) often shows negative anatomy results after a systemic autopsy and the gene mutations of potassium channel play a key role in the etiology of SCD. We established a feasible system to detect SCD-related mutations and investigated the mutations at KCNQ1 and KCNH2 genes in the Chinese population. We established a mutation detection system combined with multiplex PCR, SNaPshot technique, and capillary electrophoresis. We genotyped 101 putative mutations at KCNQ1 and KCNH2 genes in 60 SCD of negative anatomy and 50 controls using the established assay and compared Odd Ratio (OR). Four coding variants were identified in the KCNQ1 gene: S546S, I145I, P448R, and G643S. The mutations of I145I and S546S did not differ significantly in the SCD compared with controls. 21 SCD individuals (35 %) and 1 control individual (2 %) showed a genotype of C/G at P448R (OR = 17.5, 95 % CI [2.40–127.82]). 24 SCD individuals (40 %) and 1 control individual (2 %) showed a genotype of C/G at G643S (OR = 20.0, 95 % CI [2.75–145.25]). We established a robust assay for rapid screening the putative SCD-related mutations in KCNQ1 and KCNH2 genes. The new assay in our study is easily amenable to the majority of laboratories without the need for new specialized equipment. Our method will meet the increasing requirement of mutation screening for SCD in regular DNA laboratories and will help screen mutations in those dead of SCD and their relatives.

The Novel Long QT Syndrome Type 2-associated F129I Mutation in the KCNH2 Gene Significantly Affects I Kr Through the hERG1 Homomeric and Heteromeric Potassium Channels

Objective: The long QT syndrome type 2 is caused by the loss-of-function mutations in the KCNH2 gene, which encodes hERG1, the voltage-gated potassium channel. The hERG1 channels conduct rapid delayed rectifier K+ currents (I Kr) in the human cardiac tissue. KCNH2 encodes 2 main isoforms—hERG1a and hERG1b, which assemble to form the homomeric or heteromeric hERG1 channels. However, the functional characteristics of the heteromeric hERG1 channels in long QT syndrome type 2 are not clear. In this study, a novel mutation in the N-terminus of hERG1a (F129I) was identified in a proband of long QT syndrome type 2. The purpose of this study was to identify the electrophysiological change of homomeric and heteromeric hERG1 channels with the F129I-hERG1a. Methods: Candidate genes were screened by direct sequencing. F129I-hERG1a was cloned in the pcDNA3.1 vector by site-directed mutagenesis. Then, the wild-type (WT) hERG1a and/or F129I-hERG1a were transiently expressed in the HEK293 cells with or without hERG1b co-expression. The expression levels of the transgenes, cellular distribution of hERG1a and hERG1b, and the electrophysiological features of the homomeric and the heteromeric hERG1 channels with the WT-hERG1a or F129I-hERG1a were analyzed using whole-cell patch-clamp electrophysiology, western blotting, and immunofluorescence techniques. Results: The proband was clinically diagnosed with long QT syndrome type 2 and carried a heterozygous mutation c.385T&gt;A (F129I) in the KCNH2 gene. Electrophysiology study proved that the F129I substitution in hERG1a significantly decreased I Kr in both the homomeric and heteromeric hERG1channels by 86% and 70%, respectively (WT-hERG1a (54.88 ± 18.74) pA/pF vs. F129I-hERG1a (7.34 ± 1.90) pA/pF, P &lt; 0.001; WT-hERG1a/hERG1b (89.92 ± 24.51) pA/pF vs. F129I-hERG1a/hERG1b (26.54 ± 9.83) pA/pF, P &lt; 0.001). The voltage dependence of IKr activation (V½ and k) was not affected by the mutation in both the homomeric and heteromeric hERG1 channels. The peak current densities and the kinetic characteristics of IKr were comparable for both WT/F129I-hERG1a and WT-hERG1a. The channel inactivation and deactivation analysis showed that F129I substitution did not affect deactivation of the homomeric hERG1a channel, but significantly accelerated the deactivation and recovery from inactivation of the heteromeric hERG1a/hERG1b channel based on the time constants of fast and slow recovery from deactivation F129I-hERG1a/hERG1b vs. WT-hERG1a/hERG1b (P &lt; 0.05). Western blotting and immunofluorescence labeling experiments showed that maturation and intracellular trafficking of the F129I-hERG1a protein was impaired and potentially increased the ratio of hERG1b to hERG1a in the F129I-hERG1a/hERG1b tetramer channel, thereby resulting in electrophysiological changes characteristic of the long QT syndrome type 2 pathology. Conclusions: I Kr was significantly reduced in the homomeric and heteromeric hERG1 channels with F129I-hERG1a. The F129I mutation significantly accelerated the deactivation and recovery from inactivation of the heteromeric F129I-hERG1a/hERG1b channel. F129I-hERG1a exhibited impaired maturation and intracellular trafficking, thereby potentially increasing the ratio of the hERG1b to hERG1a stoichiometry in the hERG1 tetrameric channel. These changes demonstrated the importance of the heteromeric hERG1 channel in long QT syndrome type 2 pathophysiology.

Contribution of clinically relevant copy number variations in long QT syndrome: a large cohort study

Abstract Background Copy number variations (CNVs) have increasingly been recognized in the cardiovascular setting. Their role in hypertrophic cardiomyopathy or sudden cardiac death has been described, but their involvement in Long QT syndrome (LQTS) has been scarcely studied. Most of these descriptions are confined to case reports or small series. Purpose The aim of this study is to investigate the proportion of clinically relevant CNVs among a large cohort of index cases referred for genetic testing due to LQTS. Methods Retrospective study in which the presence of likely pathogenic (LP) or pathogenic (P) CNVs was evaluated in a cohort of index cases referred for genetic study with LQTS phenotype. Index cases were genotyped with customized libraries through next generation sequencing (NGS). CNVs analysis was conducted by a proprietary method by means of comparative analysis of normalized read depth data. Clinically relevant (LP or P) CNVs were then confirmed by other techniques. Results 1183 index cases were referred for genetic testing to our laboratory with long QT syndrome phenotype. Some of these index cases were referred for suspicion of Jervell-Lange-Nielsen syndrome (JNLS) or for LQTS associated with congenital deafness (n=10) or Anderson-Tawil syndrome (n=1). Around 27% (n=322) of the index cases had a positive result. CNVs analysis was run on 1071 (91%) of the index cases. Most of the CNVs were considered negative (n=994, 93%), 59 could not be analysed (6%) and in 11 patients (1%), a LP/P CNV was identified. All CNVs but three (72.72%), were confirmed by orthogonal molecular techniques (Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA)). In all, but two, the genetic study was considered positive due to the CNV findings. One of these patients carried a pathogenic lost-of-function (LOF) CNV in the LDLR gene (incidental finding) but the report was negative because he was referred for suspicion of JLNS. In another case a CNV in the DSP gene was identified in mosaicism (30-40%). However, in this case, the positive report was attributed to the presence of an additional pathogenic variant in CACNA1C. Regarding the other index cases with LP/P CNVs: 4 carried a deletion in the KCNH2 gene, 3 carried a deletion in KCNQ1 gene (one of them in homozygosis and was studied for suspicion of JLNS) and 1 carried a duplication in the KCQN1 (LOF variant). In addition, one patient carried a deletion of exon 3 in the RYR2 gene. Even if the patient was referred for suspicion of LQTS, the report was considered positive. These clinically relevant CNVs represented around 3% of the positive genetic results. Conclusions In our large cohort of patients referred for genetic testing for LQTS, around 1% of clinically relevant CNVs were identified. As such large genomic rearrangements underlie a non-neglectable portion of cases, we consider that their analysis should be performed as part of the routine genetic testing.Deletion exons 6-14 in KCNH2 gene (CNV)MLPA with deletion exons 6-14 in KCNH2

Current real-world evidence of genetic testing diagnostic yield in a large cohort of long QT syndrome

Abstract Background Diagnostic yield in long QT syndrome (LQTS) ranges between 30-70%, depending on the studied population. LQTS can lead to an unexpected sudden cardiac death. For this reason and due to its wider current availability, genetic testing in patients with suspicion of LQTS has spread. Purpose The aim of this study is to investigate the genetic testing yield among a large cohort of heterogeneous index cases with LQTS phenotype. Methods Diagnostic yield was restrospectively evaluated in a cohort of index cases referred to our laboratory for genetic study with LQTS phenotype. Genetic study was performed with customized libraries through next generation sequencing (NGS), which included copy number variations (CNVs) analysis. Patients with LQTS phenotype studied both with "long QT panels" and with broader cardiovascular panels were included, but those with additional cardiac phenotype (cardiomyopathies, heart defects or catecholaminergic polymorphic ventricular tachycardia) were excluded. Positive genetic reports were considered when a likely pathogenic (LP) or pathogenic (P) variant could explain patient´s phenotype. Inconclusive reports were described when a variant considered risk factor (RF) or a variant of uncertain significance variant (VUS) or a hot-VUS was identified in a clinically relevant gene. Results 1183 index cases were genotyped for LQTS phenotype. Only 164 index cases (13,8%) were studied with broader panels which included between 77 and 368 genes. The rest (n=1019) were studied with LQTS panels (either with small panels which included KCNQ1, KCNH2, KCNE1, KCNE2, SCN5A, KCNJ2, CACNA1C and with up to 36 genes-QT panels). Around 27% (n=321) of the index cases had a positive result. They carried LP/P variants in the following genes: KCNQ1 (n=166, 52%), KCNH2 (n=112), SCN5A (n=25), RYR2 (n=5), CACNA1C (n=3), HCN4 (n=4), KCNJ2 (n=2), KCNE2 (n=2) and CALM2 (n=1). 53,3% of the reports were negative. However, there were some incidental findings: 2 index cases carried P variants in LDLR, 2 carried P variants in PKP2, 2 carried a P variant in MYBPC3 and 1 index case each carried a P variant in DES, TTN and DSG2. From the 231 inconclusive reports, 37 index cases carried the RF variant in KCNE1 (p.Asp85Asn), 2 carried the RF variant in SCN5A (p.Arg1193Gln) and 50 patients carried hot-VUS in KCNQ1, KCNH2, CACNA1C, SCN5a or RYR2 gene. Conclusions In our large cohort of index cases referred for genetic testing for LQTS, diagnostic yield was around 27% when considering only LP/P variants in LQTS or arrhythmic phenotype related genes. Even by including the inconclusive but potentially relevant genetic results (RF and hot VUS), the diagnostic yield in our cohort reaches 35%. This is lower than expected for LQTS cohort. It should be taken into consideration that our cohort consists of heterogeneous patients referred for LQTS genetic testing, which would probably reflects better the real world patients seen in every day practice.

Population-specific variations in KCNH2 predispose patients to delayed ventricular repolarization upon dihydroartemisinin-piperaquine therapy.

Dihydroartemisinin-piperaquine is efficacious for the treatment of uncomplicated malaria and its use is increasing globally. Despite the positive results in fighting malaria, inhibition of the Kv11.1 channel (hERG; encoded by the KCNH2 gene) by piperaquine has raised concerns about cardiac safety. Whether genetic factors could modulate the risk of piperaquine-mediated QT prolongations remained unclear. Here, we first profiled the genetic landscape of KCNH2 variability using data from 141,614 individuals. Overall, we found 1,007 exonic variants distributed over the entire gene body, 555 of which were missense. By optimizing the gene-specific parametrization of 16 partly orthogonal computational algorithms, we developed a KCNH2-specific ensemble classifier that identified a total of 116 putatively deleterious missense variations. To evaluate the clinical relevance of KCNH2 variability, we then sequenced 293 Malian patients with uncomplicated malaria and identified 13 variations within the voltage sensing and pore domains of Kv11.1 that directly interact with channel blockers. Cross-referencing of genetic and electrocardiographic data before and after piperaquine exposure revealed that carriers of two common variants, rs1805121 and rs41314375, experienced significantly higher QT prolongations (ΔQTc of 41.8 ms and 61 ms, respectively, vs 14.4 ms in controls) with more than 50% of carriers having increases in QTc >30 ms. Furthermore, we identified three carriers of rare population-specific variations who experienced clinically relevant delayed ventricular repolarization. Combined, our results map population-scale genetic variability of KCNH2 and identify genetic biomarkers for piperaquine-induced QT prolongation that could help to flag at-risk patients and optimize efficacy and adherence to antimalarial therapy.

Deep Learning–Augmented ECG Analysis for Screening and Genotype Prediction of Congenital Long QT Syndrome

Congenital long QT syndrome (LQTS) is associated with syncope, ventricular arrhythmias, and sudden death. Half of patients with LQTS have a normal or borderline-normal QT interval despite LQTS often being detected by QT prolongation on resting electrocardiography (ECG). To develop a deep learning-based neural network for identification of LQTS and differentiation of genotypes (LQTS1 and LQTS2) using 12-lead ECG. This diagnostic accuracy study used ECGs from patients with suspected inherited arrhythmia enrolled in the Hearts in Rhythm Organization Registry (HiRO) from August 2012 to December 2021. The internal dataset was derived at 2 sites and an external validation dataset at 4 sites within the HiRO Registry; an additional cross-sectional validation dataset was from the Montreal Heart Institute. The cohort with LQTS included probands and relatives with pathogenic or likely pathogenic variants in KCNQ1 or KCNH2 genes with normal or prolonged corrected QT (QTc) intervals. Convolutional neural network (CNN) discrimination between LQTS1, LQTS2, and negative genetic test results. The main outcomes were area under the curve (AUC), F1 scores, and sensitivity for detecting LQTS and differentiating genotypes using a CNN method compared with QTc-based detection. A total of 4521 ECGs from 990 patients (mean [SD] age, 42 [18] years; 589 [59.5%] female) were analyzed. External validation within the national registry (101 patients) demonstrated the CNN's high diagnostic capacity for LQTS detection (AUC, 0.93; 95% CI, 0.89-0.96) and genotype differentiation (AUC, 0.91; 95% CI, 0.86-0.96). This surpassed expert-measured QTc intervals in detecting LQTS (F1 score, 0.84 [95% CI, 0.78-0.90] vs 0.22 [95% CI, 0.13-0.31]; sensitivity, 0.90 [95% CI, 0.86-0.94] vs 0.36 [95% CI, 0.23-0.47]), including in patients with normal or borderline QTc intervals (F1 score, 0.70 [95% CI, 0.40-1.00]; sensitivity, 0.78 [95% CI, 0.53-0.95]). In further validation in a cross-sectional cohort (406 patients) of high-risk patients and genotype-negative controls, the CNN detected LQTS with an AUC of 0.81 (95% CI, 0.80-0.85), which was better than QTc interval-based detection (AUC, 0.74; 95% CI, 0.69-0.78). The deep learning model improved detection of congenital LQTS from resting ECGs and allowed for differentiation between the 2 most common genetic subtypes. Broader validation over an unselected general population may support application of this model to patients with suspected LQTS.

Novel Gain-of-Function Mutation in the Kv11.1 Channel Found in the Patient with Brugada Syndrome and Mild QTc Shortening.

Brugada syndrome (BrS) is an inherited disease characterized by right precordial ST-segment elevation in the right precordial leads on electrocardiograms (ECG), and high risk of life-threatening ventricular arrhythmia and sudden cardiac death (SCD). Mutations in the responsible genes have not been fully characterized in the BrS patients, except for the SCN5A gene. We identified a new genetic variant, c.1189C>T (p.R397C), in the KCNH2 gene in the asymptomatic male proband diagnosed with BrS and mild QTc shortening. We hypothesize that this variant could alter IKr-current and may be causative for the rare non-SCN5A-related form of BrS. To assess its pathogenicity, we performed patch-clamp analysis on IKr reconstituted with this KCNH2 mutation in the Chinese hamster ovary cells and compared the phenotype with the wild type. It appeared that the R397C mutation does not affect the IKr density, but facilitates activation, hampers inactivation of the hERG channels, and increases magnitude of the window current suggesting that the p.R397C is a gain-of-function mutation. In silico modeling demonstrated that this missense mutation potentially leads to the shortening of action potential in the heart.

Establishment and characterization of ZJUCHi003: an induced pluripotent stem cell line from a patient with Temple-Baraitser/Zimmermann-Laband syndrome carrying KCNH1 c.1070G > A (p.R357Q) variant.

Pathogenic variants of the KCNH1 gene can cause dominant-inherited Temple-Baraitser/Zimmermann-Laband syndrome with severe mental retardation, seizure, gingival hyperplasia and nail hypoplasia. This study established an induced pluripotent stem cell (iPSC) line using urinary cells from a girl with KCNH1 recurrent/hotspot pathogenic variant c.1070G > A (p.R357Q). The cell identity, pluripotency, karyotypic integrity, absence of reprogramming virus and mycoplasma contamination, and differential potential to three germ layers of the iPSC line, named as ZJUCHi003, were characterized and confirmed. Furthermore, ZJUCHi003-derived neurons manifested slower action potential repolarization process and wider action potential half-width than the normal neurons. This cell line will be useful for investigating the pathogenic mechanisms of KCNH1 variants-associated symptoms, as well as for evaluating novel therapeutic approaches.

Modeling mutation-specific arrhythmogenic phenotypes in isogenic human iPSC-derived cardiac tissues

Disease modeling using human induced pluripotent stem cells (hiPSCs) from patients with genetic disease is a powerful approach for dissecting pathophysiology and drug discovery. Nevertheless, isogenic controls are required to precisely compare phenotypic outcomes from presumed causative mutations rather than differences in genetic backgrounds. Moreover, 2D cellular models often fail to exhibit authentic disease phenotypes resulting in poor validation in vitro. Here we show that a combination of precision gene editing and bioengineered 3D tissue models can establish advanced isogenic hiPSC-derived cardiac disease models, overcoming these drawbacks. To model inherited cardiac arrhythmias we selected representative N588D and N588K missense mutations affecting the same codon in the hERG potassium channel gene KCNH2, which are reported to cause long (LQTS) and short (SQTS) QT syndromes, respectively. We generated compound heterozygous variants in normal hiPSCs, and differentiated cardiomyocytes (CMs) and mesenchymal cells (MCs) to form 3D cardiac tissue sheets (CTSs). In hiPSC-derived CM monolayers and 3D CTSs, electrophysiological analysis with multielectrode arrays showed prolonged and shortened repolarization, respectively, compared to the isogenic controls. When pharmacologically inhibiting the hERG channels, mutant 3D CTSs were differentially susceptible to arrhythmic events than the isogenic controls. Thus, this strategy offers advanced disease models that can reproduce clinically relevant phenotypes and provide solid validation of gene mutations in vitro.

Exploring the impact of a KCNH2 missense variant on Long QT syndrome: insights into a novel gender-selective, incomplete penetrance inheritance mode.

Long QT syndrome (LQTS) is an inherited malignant arrhythmia syndrome that poses a risk of sudden death. Variants in the Potassium Voltage-Gated Channel Subfamily H Member 2 (KCNH2) gene are known to cause Long QT syndrome through an autosomal dominant inheritance pattern. However, as of now, there have been no reports of any KCNH2 variant leading to Long QT syndrome exhibiting incomplete penetrance that is influenced by gender. Whole-exome sequencing (WES) was conducted on the proband to identify pathogenic variants. Subsequently, Sanger sequencing was employed to validate the identified likely pathogenic variants in all family members. We analyzed a pedigree spanning three-generations afflicted by Long QT syndrome. WES revealed a novel KCNH2 missense variant (p.Val630Gly, c.1889T>G) as the causative factor for the family's phenotype. Within this family, all three male carriers of the KCNH2 variant carriers exhibited the Long QT syndrome phenotype: one experienced sudden death during sleep, another received an implantable cardioverter defibrillator (ICD), and a younger man displayed a prolonged QTc interval without any instances of syncope or malignant arrhythmia to date. Interestingly, the middle-aged female carrier showed no Long QT Syndrome phenotype. However, her offspring, diagnosed with Turner syndrome (45, X) and also a carrier of this variant, experienced frequent syncope starting at 12 years old and was diagnosed with Long QT syndrome, leading to an ICD implantation when she was 15 years old. These observations suggest that the manifestation of Long QT syndrome associated with this KCNH2 variant exhibits incomplete penetrance influenced by gender within this family, indicating potential protective mechanisms against the syndrome in females affected by this variant. Our investigation has led to the identification of a novel pathogenic KCNH2 variant responsible for Long QT syndrome within a familial context characterized by gender-selective, incomplete penetrance. This discovery highlights a unique pathogenic inheritance pattern for the KCNH2 gene associated with Long QT syndrome, and could potentially shed light on the distinct penetrance behaviors and patterns of the KCNH2 gene. This discovery broadens our exploration of the KCNH2 gene in cardiac arrhythmias, highlighting the intricate genetic dynamics behind Long QT syndrome.

Escitalopram-induced QTc prolongation and its relationship with KCNQ1, KCNE1, and KCNH2 gene polymorphisms

BackgroundEscitalopram can cause prolongation of the QT interval on the electrocardiogram (ECG). However, only some patients get pathological QTc prolongation in clinic. We investigated the influence of KCNQ1, KCNE1, and KCNH2 gene polymorphisms along with clinical factors on escitalopram-induced QTc prolongation. MethodsA total of 713 patients prescribed escitalopram were identified and had at least one ECG recording in this retrospective study. 472 patients with two or more ECG data were divided into QTc prolongation (n = 119) and non-prolongation (n = 353) groups depending on the threshold change in QTc of 30 ms above baseline value (∆QTc ≥ 30 ms). 45 patients in the QTc prolongation group and 90 patients in the QTc non-prolongation group were genotyped for 43 single nucleotide polymorphisms (SNPs) of KCNQ1, KCNE1, and KCNH2 genes. ResultsPatients with QTc prolongation (∆QTc ≥ 30 ms) got higher escitalopram dose (10.3 mg) than patients without QTc prolongation (9.4 mg), although no significant relationship was found between QTc interval and escitalopram dose in the linear mixed model. Patients who were older/coronary disease/hypertension or carried with KCNE1 rs1805127 C allele, KCNE1 rs4817668 C allele, KCNH2 rs3807372 AG/GG genotype were significantly at risk for QTc prolongation (∆QTc ≥ 30 ms). Concomitant antipsychotic treatment was associated with a longer QTc interval. LimitationsA relatively small sample size and lack of the blood concentration of escitalopram restricted the accurate relationship between escitalopram dose and QTc interval. ConclusionOur study revealed that KCNQ1, KCNE1, and KCNH2 gene polymorphisms along with clinical factors provide a complementary effect in escitalopram-induced QTc prolongation.

KCNH2A561V Heterozygous Mutation Inhibits KCNH2 Protein Expression via The Activation of UPR Mediated by ATF6.

The potassium channel protein KCNH2 is encoded by KCNH2 gene, and there are more than 300 mutations of KCNH2. Unfolded protein response (UPR) is typically initiated in response to an accumulation of unfolded and/or misfolded proteins in the endoplasmic reticulum (ER). The present study aimed to explore the UPR process and the role of activating transcription factor 6 (ATF6) in the abnormal expression of potassium voltage-gated channel subfamily H member 2 (KCNH2)A561V. The wild-type (wt) KCNH2 and A561V mutant KCNH2 was constructed with his-tag. The 293 cells were used and divided into KCNH2wt+KCNH2A561V, KCNH2wt and KCNH2A561V groups. The expression levels of ATF6 and KCNH2 in different groups were detected by Western blotting, reverse transcription-quantitative PCR, immunofluorescence and immuno-coprecipitation assays. The protein types and abundance of immuno-coprecipitation samples were analyzed by mass spectrometry. The proteomic analysis of the mass spectrometry results was carried out by using the reactome database and GO (Gene Ontology) tool. The mRNA expression levels of KCNH2 and ATF6 in the KCNH2wt+KCNH2A561V group were higher compared with the KCNH2A561V group. However, the full-length protein expression of ATF6 was inhibited, indicating that ATF6 was highly activated and a substantial number of ATF6 was sheared in KCNH2wt+KCNH2A561V group compared with control group. Furthermore, A561V-KCNH2 mutation leading to the accumulation of the immature form of KCNH2 (135 kDa bands) in ER, resulting in the reduction of the ratio of 155 kDa/135 kDa. In addition, the abundance of UPR-related proteins in the KCNH2A561V group was higher compared with the KCNH2wt+KCNH2A561V group. The 'cysteine biosynthetic activity' of GO:0019344 process and the 'positive regulation of cytoplasmic translation activity' of GO:2000767 process in the KCNH2A561V group were higher compared with the KCNH2wt+KCNH2A561V group. Hence, co-expression of wild-type and A561V mutant KCNH2 in 293 cells activated the UPR process, which led to the inhibition of protein translation and synthesis, in turn inhibiting the expression of KCNH2. These results provided a theoretical basis for clinical treatment of Long QT syndrome.

Unexpectedly high prevalence of structural genomic variations in the Long QT Syndrome: evidence for broader clinical uptake

Abstract Background Long QT syndrome (LQTS) is an inherited channelopathy predisposing young and otherwise healthy individuals to ventricular arrhythmias causing syncope or sudden cardiac death. Point mutations in the KCNQ1, KCNH2, and SCN5A genes are the most common causes of LQTS, and up to 75% of patients can be genotyped by standard DNA sequencing. However, standard genetic testing fails to detect structural genomic rearrangements - including large deletions or duplications of DNA segments - known as copy number variants (CNVs). While previous studies suggested that CNVs account for less than 5% of genotype-negative cases(1-2), no recent data have been reported. Purpose The study aimed to determine the prevalence and spectrum of CNVs in LQTS susceptibility genes in unrelated patients who tested negative for point mutations in a panel of 16 genes associated with LQTS. Methods Next-generation sequencing (NGS) was used to screen CNVs in unrelated, clinically diagnosed LQTS patients without point mutations in 16 genes associated with LQTS. Loss of heterozygosity in LQTS-associated genes was used to assess the presence of CNVs using standard commercial software. The multiplex ligation-dependent probe amplification (MLPA) assay was used to confirm the CNVs identified by NGS. Results The cohort included 48 patients (63% women; mean age 31±19 years, range 3 years to 68 years) with definitive clinical diagnosis of LQTS (mean QTc 490±33 ms) according to the 2022 ESC guidelines(3). Overall, 7/48 patients (15%, 95% CI 6-28%) had CNVs. Six of the seven CNVs involved KCNQ1 in the heterozygous state, including three large deletions (exons 3-6, exons 12-15, and exon 16) and three duplications (exon 2, exons 3-6, and exons 3-15), whereas the remaining patient had a complete KCNH2 deletion. MLPA confirmed all CNVs identified by NGS. Of note, no CNVs were identified in LQTS-related genes whose pathogenicity has been questioned. Conclusions Our study highlights the unexpectedly high prevalence of structural genomic rearrangements in the KCNQ1 and KCNH2 genes in LQTS patients. Routine screening for copy number variants in LQTS patients is critical for accurate diagnosis, risk stratification, and personalized treatment strategies.Figure 1