hERG Research Articles

Protective effect of human epicardial adipose-derived stem cells on myocardial injury driven by poly-lactic acid nanopillar array.

We investigated if poly-lactic acid (PLA) nanopillar array can trigger the differentiation of human epicardial (ADSCs) (heADSCs) into cardiomyocyte-like cells and explored the effects of these cardiomyocyte-like cells on myocardial infarction (MI) in vivo. PLA nanopillar array (200nm diameter) and plain PLA film (PLA planar) induced heADSCs were marked with carboxyfluorescein. After 7 days, the expressions of myocardiocyte-specific genes were significantly enhanced in cells seeded on PLA nanopillar array compared with that on PLA planar, especially CACNA1C, KCNH2, and MYL2 genes (p<0.05). However, the expressions of cardiac troponin T (cTNT), KCNQ1, and KCNA5 were lower than those in PLA planar-induced heADSCs (p<0.05), whereas GATA4 tended to increase with time. The cells with positively stained α-actinin and cTNT were elevated in heADSCs induced by PLA nanopillar array compared with those induced by PLA planar only (p<0.05). In vivo experiments showed that cardiac function was improved after injecting PLA-nanopillar array-induced heADSCs into the ischemic heart (p<0.05, compared with PLA planar+MI group). Furthermore, tyrosine hydroxylase density was significantly lower (p<0.05). PLA nanopillar array directly drives the differentiation of heADSCs into cardiomyocyte-like cells, and the induced heADSCs exhibit a protective effect on ischemic myocardium by improving cardiac function in MI rats.

The Action Potential Clamp Technique as a Tool for Risk Stratification of Sinus Bradycardia Due to Loss-of-Function Mutations in HCN4: An In Silico Exploration Based on In Vitro and In Vivo Data.

These days, in vitro functional analysis of gene variants is becoming increasingly important for risk stratification of cardiac ion channelopathies. So far, such risk stratification has been applied to SCN5A, KCNQ1, and KCNH2 gene variants associated with Brugada syndrome and long QT syndrome types 1 and 2, respectively, but risk stratification of HCN4 gene variants related to sick sinus syndrome has not yet been performed. HCN4 is the gene responsible for the hyperpolarization-activated 'funny' current If, which is an important modulator of the spontaneous diastolic depolarization underlying the sinus node pacemaker activity. In the present study, we carried out a risk classification assay on those loss-of-function mutations in HCN4 for which in vivo as well as in vitro data have been published. We used the in vitro data to compute the charge carried by If (Qf) during the diastolic depolarization phase of a prerecorded human sinus node action potential waveform and assessed the extent to which this Qf predicts (1) the beating rate of the comprehensive Fabbri-Severi model of a human sinus node cell with mutation-induced changes in If and (2) the heart rate observed in patients carrying the associated mutation in HCN4. The beating rate of the model cell showed a very strong correlation with Qf from the simulated action potential clamp experiments (R2 = 0.95 under vagal tone). The clinically observed minimum or resting heart rates showed a strong correlation with Qf (R2 = 0.73 and R2 = 0.71, respectively). While a translational perspective remains to be seen, we conclude that action potential clamp on transfected cells, without the need for further voltage clamp experiments and data analysis to determine individual biophysical parameters of If, is a promising tool for risk stratification of sinus bradycardia due to loss-of-function mutations in HCN4. In combination with an If blocker, this tool may also prove useful when applied to human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) obtained from mutation carriers and non-carriers.

Discovery of TBX20 as a Novel Gene Underlying Atrial Fibrillation.

Atrial fibrillation (AF), the most prevalent type of sustained cardiac dysrhythmia globally, confers strikingly enhanced risks for cognitive dysfunction, stroke, chronic cardiac failure, and sudden cardiovascular demise. Aggregating studies underscore the crucial roles of inherited determinants in the occurrence and perpetuation of AF. However, due to conspicuous genetic heterogeneity, the inherited defects accounting for AF remain largely indefinite. Here, via whole-genome genotyping with genetic markers and a linkage assay in a family suffering from AF, a new AF-causative locus was located at human chromosome 7p14.2-p14.3, a ~4.89 cM (~4.43-Mb) interval between the markers D7S526 and D7S2250. An exome-wide sequencing assay unveiled that, at the defined locus, the mutation in the TBX20 gene, NM_001077653.2: c.695A>G; p.(His232Arg), was solely co-segregated with AF in the family. Additionally, a Sanger sequencing assay of TBX20 in another family suffering from AF uncovered a novel mutation, NM_001077653.2: c.862G>C; p.(Asp288His). Neither of the two mutations were observed in 600 unrelated control individuals. Functional investigations demonstrated that the two mutations both significantly reduced the transactivation of the target gene KCNH2 (a well-established AF-causing gene) and the ability to bind the promoter of KCNH2, while they had no effect on the nuclear distribution of TBX20. Conclusively, these findings reveal a new AF-causative locus at human chromosome 7p14.2-p14.3 and strongly indicate TBX20 as a novel AF-predisposing gene, shedding light on the mechanism underlying AF and suggesting clinical significance for the allele-specific treatment of AF patients.

Identification of a novel pathogenic variant in KCNH2 in an Iranian family with long QT syndrome 2 by whole-exome sequencing.

Long QT syndrome (LQTS) is a lethal cardiac condition. However, the clinical implementation of genetic testing has now made LQTS eminently treatable. Next-generation sequencing has remarkable potential for both clinical diagnostics and research of LQTS. Here, we investigated the genetic etiology in an LQTS-suspected Iranian pedigree by whole-exome sequencing and collected all KCNH2 variants with consensus based on publications. WES was performed on the proband of this pedigree to reveal the underlying cause of sudden cardiac death (SCD). The variant found was validated and segregated by polymerase chain reaction and Sanger sequencing. Based on the literature review, KCNH2 variants were retrospectively analyzed to identify pathogenic variants, likely pathogenic variants, and variants of uncertain significance by using different prediction tools. WES identified an autosomal dominant nonsense variant, c.1425C>A: p.Tyr475Ter, in the KCNH2 gene, which appeared to be the most likely cause of LQTS in this pedigree. Moreover, our comprehensive literature review yielded 511 KCNH2 variants in association with the LQTS phenotype, with c.3002G>A (CADD Phred=49) being the most pathogenic variant. Variants in the KCNH2 gene are considered a major cause of LQTS worldwide. The detected c.1425C>A is a novel variant to be reported from Iran for the first time. This result indicates the importance of KCNH2 screening in a pedigree with SCD cases.

The effects of blood pressure and antihypertensive drugs on heart failure: A Mendelian randomization study

Background and aimsHeart failure (HF) is often triggered by hypertension and can benefit from antihypertensive treatment. We aimed to investigate whether pulse pressure (PP) could independently raise the risk of HF beyond systolic blood pressure (SBP) and diastolic blood pressure (DBP), as well as explore the potential mechanisms of antihypertensives in HF prevention. Methods and resultsWe generated genetic proxies for SBP, DBP, PP, and five drug classes based on a massive genome-wide association study. We applied two-sample Mendelian randomization (MR) using summary statistics derived from European individuals and conducted summary data-based MR (SMR) with gene expression data. In univariate analysis, PP showed an obvious association with HF risk (OR, 1.24 per 10 mm Hg increment; 95% CI, 1.16 to 1.32), which was largely attenuated in multivariable analysis when adjusted for SBP (0.89; 0.77 to 1.04). A significant decrease in HF risk was obtained with genetically proxied β-blockers (equivalent to a 10 mm Hg reduction in SBP, 0.71; 0.62 to 0.82) and calcium channel blockers (0.71; 0.65 to 0.78), but not with genetically proxied angiotensin-converting enzyme inhibitors (0.69; 0.40 to 1.19) and thiazide diuretics (0.80; 0.47 to 1.37). Additionally, the enrichment of expression for the KCNH2 gene, a target gene of β-blockers, in blood vessels and nerves was significantly associated with HF risk. ConclusionOur findings suggest that PP may not be an independent risk factor for HF. β-blockers and calcium channel blockers have a protective effect against HF, which at least partly depends on their blood pressure-lowering effect.

In silico study of HASDI (high-affinity selective DNA intercalator) as a new agent capable of highly selective recognition of the DNA sequence

Cancer as an acquired genetic disease is based on changes both in the genome itself and in transcription processes. Accordingly, it is at the DNA level that it makes sense to search for and design agents capable of effective and selective anticancer action. In this study, we used an iterative approach based on a molecular dynamics simulation to design a highly selective DNA-intercalating agent called HASDI. To confirm its selective affinity to DNA, we conducted two simulation experiments: HASDI in a complex with a DNA fragment of the EBNA1 gene (it targets 16 nucleotide pairs of this gene) and HASDI in a complex with a random DNA fragment of the KCNH2 gene. The molecular dynamics simulation was carried out in the GROMACS 2019 package. The binding energy was calculated by gmx_MMPBSA 1.5.2. The further analysis was performed using the built-in utilities of GROMACS, gmx_MMPBSA and also XMGRACE and Pymol 1.8. As a result, we determined that the EBNA1-50nt/HASDI complex was stable throughout the whole simulation trajectory. HASDI, due to the presence of a linker modified depending on a specific pair of nitrogenous bases, formed an average of 32 hydrogen bonds with a sequence of 16 nucleotide pairs. Phenazine rings were stably intercalated every 2 base pairs. The root-mean-square deviation of HASDI in such a complex fluctuated around the value of 6.5 Å and had no tendency to increase. The calculated value of the binding free energy was − 235.3 ± 7.77 kcal/mol. The KCNH2-50nt/HASDI complex, as an example of the intercalation of the designed structure into a random part of the human genome, maintained the stability of its position at a level comparable to the EBNA1-50nt/HASDI complex. The phenazine rings were constantly intercalated in their original positions, and the root-mean-square deviation fluctuated around one value, although it had a tendency to chaotic changes. At the same time, this complex was characterized by 17–19 hydrogen bonds, on average, and the binding free energy was − 193.47 ± 14.09 kcal/mol. Moreover, the DNA duplex had local single-nucleotide melting in the region of the 4th linker. According to a significant decrease in the number of hydrogen bonds, a decrease in energy gain, as well as a decrease in the stability of the DNA duplex characteristic of the KCNH2-50nt/HASDI complex compared to the target EBNA1-50nt/HASDI complex, the molecule we designed can be considered a potentially selective DNA polyintercalating agent capable of relatively accurate recognition of 16 base pairs.

Array Comparative Genomic Hybridization Analysis of Products of Conception in Recurrent Pregnancy Loss for specific anomalies detected by USG.

To evaluate the proportion of chromosomal abnormalities in recurrent pregnancy loss (RPL) assisted by array comparative genomic hybridization (aCGH) bright out with higher detection rate, more accuracy, and less sample failure as compared with conventional cytogenetic analysis. In this study, product of conception samples with abnormal USG findings of the fetus and clinical history of RPL were first processed for karyotyping and Fluorescence In Situ Hybridization analysis. Normal results given by Karyotype and FISH samples with major anomalies detected by Ultrasound with RPL were divided into six groups and aCGH was performed to detect the gain or loss and copy number variations (CNVs) of a particular gene present in chromosomal segments. Among a total of 300 POC samples, 100 abnormal samples were identified either by karyotype (n=70) or by FISH (n=30). From the remaining 200 samples, 5 showed the presence of maternal cell contamination excluded. aCGH analysis revealed (n=195) that 74 (38%) samples with copy number variations (CNVs) and two samples with variants of unknown clinical significance (VOUS) were clinically associated with the clinical findings and 121(62%) samples showed no change in CNVs. The most frequent CNVs were loss of chromosome regions at 2q33.1, 7q11.21, 15q11.1, 16p11.2, Xp22.33, and Yp11.32. CNVs at arr[GRCh37]7p22.3,p21.2(830852-15124702)×1,7q34q36.3(141464180_158909738)×3, 14.2Mbp deletion of 7p22.3p21.2 (SUN1 gene) and 17.4Mbp duplication of 7q34q36.3 (KCNH2, CNTNAP2, and SHH genes) in one sample, CNVs at arr[GRCh37]8p22.2q22.3 (86326349_105509986)×1, 2.48Mbp deletion of 8p22.2q22.3 (GRHL1 gene) were found in another sample.

Highlights From the Circulation Family of Journals.

Highlights From the Circulation Family of Journals.

Integrated analysis of the voltage-gated potassium channel-associated gene KCNH2 across cancers

KCNH2 encodes the human ether-a-go-go-related gene (hERG) potassium channel and is an important repolarization reserve for regulating cardiac electrical activity. Increasing evidence suggests that it is involved in the development of various tumours, yet a thorough analysis of the underlying process has not been performed. Here, we have comprehensively examined the role of KCNH2 in multiple cancers by assessing KCNH2 gene expression, diagnostic and prognostic value, genetic alterations, immune infiltration correlations, RNA modifications, mutations, clinical correlations, interacting proteins, and associated signalling pathways. KCNH2 is differentially expressed in over 30 cancers and has a high diagnostic value for 10 tumours. Survival analysis showed that high expression of KCNH2 was associated with a poor prognosis in glioblastoma multiforme (GBM) and hepatocellular carcinoma (LIHC). Mutations and RNA methylation modifications (especially m6A) of KCNH2 are associated with its expression in multiple tumours. KCNH2 expression is correlated with tumour mutation burden, microsatellite instability, neoantigen load, and mutant-allele tumour heterogeneity. In addition, KCNH2 expression is associated with the tumour immune microenvironment and its immunosuppressive phenotype. KEGG signalling pathway enrichment analysis revealed that KCNH2 and its interacting molecules are involved in a variety of pathways related to carcinogenesis and signal regulation, such as the PI3K/Akt and focal adhesion pathways. Overall, we found that KCNH2 and its interaction molecular are expected to be immune-related biomarkers for cancer diagnosis and prognosis evaluation, and are potential regulatory targets of singalling pathways for tumour development due to their significant role in cancers.

A need for exhaustive and standardized characterization of ion channels activity. The case of KV11.1.

hERG, the pore-forming subunit of the rapid component of the delayed rectifier K+ current, plays a key role in ventricular repolarization. Mutations in the KCNH2 gene encoding hERG are associated with several cardiac rhythmic disorders, mainly the Long QT syndrome (LQTS) characterized by prolonged ventricular repolarization, leading to ventricular tachyarrhythmias, sometimes progressing to ventricular fibrillation and sudden death. Over the past few years, the emergence of next-generation sequencing has revealed an increasing number of genetic variants including KCNH2 variants. However, the potential pathogenicity of the majority of the variants remains unknown, thus classifying them as variants of uncertain significance or VUS. With diseases such as LQTS being associated with sudden death, identifying patients at risk by determining the variant pathogenicity, is crucial. The purpose of this review is to describe, on the basis of an exhaustive examination of the 1322 missense variants, the nature of the functional assays undertaken so far and their limitations. A detailed analysis of 38 hERG missense variants identified in Long QT French patients and studied in electrophysiology also underlies the incomplete characterization of the biophysical properties for each variant. These analyses lead to two conclusions: first, the function of many hERG variants has never been looked at and, second, the functional studies done so far are excessively heterogeneous regarding the stimulation protocols, cellular models, experimental temperatures, homozygous and/or the heterozygous condition under study, a context that may lead to conflicting conclusions. The state of the literature emphasizes how necessary and important it is to perform an exhaustive functional characterization of hERG variants and to standardize this effort for meaningful comparison among variants. The review ends with suggestions to create a unique homogeneous protocol that could be shared and adopted among scientists and that would facilitate cardiologists and geneticists in patient counseling and management.

The Phytochemical α-Mangostin Inhibits Cervical Cancer Cell Proliferation and Tumor Growth by Downregulating E6/E7-HPV Oncogenes and KCNH1 Gene Expression.

Cervical cancer is the fourth most common cancer among women worldwide. The main factor associated with the onset and progression of this neoplasia is the human papillomavirus (HPV) infection. The HPV-oncogenes E6 and E7 are critical drivers of cellular transformation, promoting the expression of oncogenes such as KCNH1. The phytochemical α-mangostin (AM) is a potent antineoplastic and antiviral compound. However, its effects on HPV oncogenes and KCNH1 gene expression remain unknown. This study evaluated the effects of AM on cell proliferation, cell cycle distribution and gene expression, including its effects on tumor growth in xenografted mice. AM inhibited cell proliferation in a concentration-dependent manner, being the most sensitive cell lines those with the highest number of HPV16 copies. In addition, AM promoted G1-cell cycle arrest in CaSki cells, while led to cell death in SiHa and HeLa cells. Of interest was the finding of an AM-dependent decreased gene expression of E6, E7 and KCNH1 both in vitro and in vivo, as well as the modulation of cytokine expression, Ki-67, and tumor growth inhibition. On these bases, we suggest that AM represents a good option as an adjuvant for the treatment and prevention of cervical cancer.

Structural basis of rapid inactivation of HERG potassium channels.

The exquisite fine tuning of electrical signalling in different cells types is mediated by variations in the rates that gates open and close in different ion channels. The opening and closing of the inactivation gate in Human ether-a-go-go related gene (HERG) K+ channels is uniquely rapid, which confers upon them a critical role in protecting against cardiac arrhythmias and sudden cardiac death. The molecular mechanisms that underlie the rapidity of HERG inactivation, however, remain unclear. Here, we have determined Cryo-EM structures of the conductive state as well as HERG's elusive inactivated state to 2.4 Å resolution and propose a mechanism for the fast kinetics of inactivation. The selectivity filter is pulled upward by Asn633 upon the exit of potassium ions from the upper part of the filter. This movement allows the sidechain of Ser620, located behind the selectivity filter, to alternately hydrogen bond to the upper or lower part of the selectivity filter to stabilize the conducting and inactivated states respectively. The inactivated state is also characterized by flipping of the valine carbonyls in the centre of the selectivity filter. Using molecular dynamics simulation, we have identified a transient interaction between Ser620 and Tyr616 that reduces the free energy barrier for flipping of the valine carbonyls, thereby explaining the rapidity of HERG inactivation. Our results have demonstrated the dynamic nature of potassium channels with a new model of inactivation different from the well characterized KcsA.

KCNH2 mutation c.3099_3112del causes congenital long QT syndrome type 2 with gender differences

IntroductionLong QT Syndrome (LQTS) is an inherited disease with an abnormal electrical conduction system in the heart that can cause sudden death as a result of QT prolongation. LQT2 is the second most common subtype of LQTS caused by loss of function mutations in the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene. Although more than 900 mutations are associated with the LQTS, many of these mutations are not validated or characterized. Methods and resultsSequencing analyses of genomic DNA of a family with LQT2 identified a putative mutation. i.e., KCNH2(NM_000238.3): c.3099_3112del, in KCNH2 gene which appeared to be a definite pathogenic mutation. The family pedigree information showed a gender difference in clinical features and T-wave morphology between male and female patients. The female with mutation exhibited recurring ventricular arrhythmia and syncope, while two male carriers did not show any symptoms. In addition, T-wave in females was much flatter than in males. The female proband showed a positive reaction to the lidocaine test. Lidocaine injection almost completely blocked ventricular arrhythmia and shortened the QT interval by ≥30 ms. Treatment with propranolol, mexiletine, and implantation of cardioverter-defibrillators prevented the sustained ventricular tachycardia, ventricular fibrillation, and syncope, as assessed by a 3-year follow-up evaluation. ConclusionsA putative mutation c.3099_3112del in the KCNH2 gene causes LQT2 syndrome, and the pathogenic mutation mainly causes symptoms in female progeny.

1029 genomes of self-declared healthy individuals from India reveal prevalent and clinically relevant cardiac ion channelopathy variants

BackgroundThe prevalence and genetic spectrum of cardiac channelopathies exhibit population-specific differences. We aimed to understand the spectrum of cardiac channelopathy-associated variations in India, which is characterised by a genetically diverse population and is largely understudied in the context of these disorders.ResultsWe utilised the IndiGenomes dataset comprising 1029 whole genomes from self-declared healthy individuals as a template to filter variants in 36 genes known to cause cardiac channelopathies. Our analysis revealed 186,782 variants, of which we filtered 470 variants that were identified as possibly pathogenic (440 nonsynonymous, 30 high-confidence predicted loss of function ). About 26% (124 out of 470) of these variants were unique to the Indian population as they were not reported in the global population datasets and published literature. Classification of 470 variants by ACMG/AMP guidelines unveiled 13 pathogenic/likely pathogenic (P/LP) variants mapping to 19 out of the 1029 individuals. Further query of 53 probands in an independent cohort of cardiac channelopathy, using exome sequencing, revealed the presence of 3 out of the 13 P/LP variants. The identification of p.G179Sfs*62, p.R823W and c.420 + 2 T > C variants in KCNQ1, KCNH2 and CASQ2 genes, respectively, validate the significance of the P/LP variants in the context of clinical applicability as well as for large-scale population analysis.ConclusionA compendium of ACMG/AMP classified cardiac channelopathy variants in 1029 self-declared healthy Indian population was created. A conservative genotypic prevalence was estimated to be 0.9–1.8% which poses a huge public health burden for a country with large population size like India. In the majority of cases, these disorders are manageable and the risk of sudden cardiac death can be alleviated by appropriate lifestyle modifications as well as treatment regimens/clinical interventions. Clinical utility of the obtained variants was demonstrated using a cardiac channelopathy patient cohort. Our study emphasises the need for large-scale population screening to identify at-risk individuals and take preventive measures. However, we suggest cautious clinical interpretation to be exercised by taking other cardiac channelopathy risk factors into account.

Case Report: Prenatal Whole-Exome Sequencing Identified a Novel Nonsense Mutation of the KCNH2 Gene in a Fetus With Familial 2q14.2 Duplication

Background: Pathogenic mutations in the KCNH2 gene were associated with long QT syndrome 2 (LQT2), which typically manifest in a prolonged QT interval and may lead to recurrent syncopes, seizure, or sudden death. Limited reports indicated that the KCNH2 mutations would result in LQT2 combined with tetralogy of fallot. Our goal was to present an additional case of LQT2 combined with the tetralogy of fallot in a fetus with a novel KCNH2 mutation. Case presentation: Enrolled in this study was a 23-year-old pregnant woman from Quanzhou Fujian province, China. In her pregnancy, fetal ultrasound anomalies were identified, including tetralogy of fallot, coronary sinus enlargement, and persistent left superior vena cava. No chromosomal abnormality was detected by fetal karyotype analysis. However, 238.1-kb duplication in the 2q14.2 region containing the GLI2 gene was observed in the fetus by chromosomal array analysis, which was inherited from the mother with normal clinical features and interpreted as a variant of uncertain significance (VOUS). Furthermore, whole-exome sequencing (WES) detection identified a novel nonsense c.1907C > G (p.S636*) mutation in the KCNH2 gene in the fetus, and it was classified as a likely pathogenic variant, according to the ACMG guidelines. Parental verification analysis indicated that c.1907C > G (p.S636*) mutation was inherited from the mother. Conclusion: In this study, we believe that 2q14.2 duplication may not be the reason for fetal heart defects; moreover, we described an additional case with KCNH2 gene mutation, which may lead to LQTS and be associated with congenital heart defects. In addition, our study further confirms the application value of the WES technology in prenatal genetic etiology diagnosis of fetuses with structural anomalies and unexplained structural variants.

Human induced pluripotent stem cell line ZZUNEUi027-A generated from a long QT syndrome patient with a heterozygous KCNH2 (c. 128 A > G) mutant

Long QT syndrome is one of the most common hereditary arrhythmias. Mutations in KCNH2 can cause long QT syndrome type 2 (LQT2). In this study, we generated a human induced pluripotent stem cell line ZZUNEUi027-A from a LQT2 female patient with c. 128A → G in KCNH2 gene using non-integrative Sendai viral reprogramming technology. This cell line expresses pluripotency markers, exhibits a normal female karyotype (46, XX) and could differentiate into all three germ layers in vitro. ZZUNEUi027-A can serve as a cell disease model in the understanding of LQT2 pathogenesis.

New insights of the role of the KCNH2 gene in schizophrenia: An fMRI case-control study

The KCNH2 gene, encoding for a subunit of a voltage-gated potassium channel, has been identified as a key element of neuronal excitability and a promising novel therapeutic target for schizophrenia (SZ). Nonetheless, evidence highlighting the role of KCNH2 on cognitive and brain activity phenotypes comes mainly from studies based on healthy controls (HC). Therefore, we aimed to study the role of KCNH2 on the brain functional differences between patients with SZ and HC. The fMRI sample comprised 78 HC and 79 patients with SZ (matched for age, sex and premorbid IQ). We studied the effect of the polymorphism KCNH2-rs3800779 on attention and working memory-related brain activity, evaluated through the N-back task, in regions with detected diagnostic differences (regression model, controlled for age, sex and premorbid IQ, FEAT-FSL). We report a significant diagnosis x KCNH2 interaction on brain activity (1-back vs baseline contrast) at the medial superior prefrontal cortex (Zmax=3.55, p = 0.00861). In this region, patients with SZ carrying the risk genotype (AA) show a deactivation failure, while HC depict the opposite pattern towards deactivation. The brain region with significant diagnosis x KCNH2 interaction has been previously associated with SZ. The results of this study, in which the role of KCNH2 on fMRI response is analysed for the first time in patients, suggest that KCNH2 variability contributes to inefficient brain activity modulation during the N-back task in affected subjects. These data may pave the way to further understand how KCNH2 genetic variability is related to the pathophysiological mechanisms underlying schizophrenia.

PO-714-04 HIGH PREVALENCE OF NEURODEVELOPMENTAL DISORDERS IN PEDIATRIC LONG QT SYNDROME PATIENTS

Long QT Syndrome (LQTS) is a familial ion channelopathy associated with a structurally normal heart and risk of sudden cardiac death. Most cases are associated with variants in KCNQ1 and KCNH2 genes. Ion channel variants have been implicated in neurodevelopmental disorders (NDDs), yet the link between LQTS and NDDs in children has not been well characterized.

PO-646-07 KCNH2 VARIANTS IDENTIFIED AS PATHOGENIC, DAMAGING, AND DYSFUNCTIONAL DO NOT RELIABLY IDENTIFY LONG QT SYNDROME IN LARGE PATIENT BIOBANK

Long QT syndrome (LQTS) type 2 (LQT2) is caused by loss of function mutations in the KCNH2 gene that encodes the Kv11.1 K+ channel. Classification rubrics assist in delineating candidate LQT2-causing KCNH2 missense variants based on allele frequency, in silico prediction programs, and functional data.

EN-580-03 SUPPRESSION AND REPLACEMENT GENE THERAPY FOR KCNH2-MEDIATED ARRHYTHMIAS

KCNH2-mediated arrhythmias are caused by either loss-of-function (type 2 long QT syndrome, LQT2) or gain-of-function (type 1 short QT syndrome, SQT1) pathogenic variants in the KCNH2-encoded Kv11.1 potassium channel which is essential for the rapid delayed rectifier current (IKr) that contributes to the cardiac action potential (AP). No current therapies target the molecular cause of either LQT2 or SQT1. To rescue the pathologic phenotype in cell models of LQT2 and SQT1 using our novel gene therapy. A dual-component “suppression-and-replacement” (SupRep) KCNH2 gene therapy was created by cloning into a single construct a custom-designed KCNH2 shRNA that produces ∼80% knockdown (suppression) and a “shRNA-immune” (shIMM) KCNH2 cDNA (replacement). Patient-derived induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and their CRISPR-Cas9 variant-corrected isogenic control (IC) iPSC-CMs were made for 3 LQT2- (G604S, G628S, N633S) and 1 SQT1- (N588K) causative variants. All 4 variant lines were treated with KCNH2-SupRep or non-targeting control shRNA (sham). FluoVolt voltage dye was used to measure the APD at 90% repolarization (APD90). KCNH2-SupRep achieved mutation-independent rescue of the pathologic phenotype in both LQT2 and SQT1. For LQT2-causative variants, treatment with KCNH2-SupRep resulted in shortening of the pathologically prolonged APD90 to near curative (IC-like) APD90 levels (G604S IC, 471±25ms; G628S IC, 429±16ms; N633S IC, 405±55ms) compared to treatment with sham (G604S: SupRep-treated, 452±76ms vs. sham-treated, 550±41ms, p<0.0001; G628S: SupRep-treated, 491±38ms vs. sham-treated, 674±20ms, p<0.0001; N633S: SupRep-treated, 399±105ms vs. sham-treated, 577±39ms, p<0.0001). Conversely, for the SQT1-causative N588K, treatment with KCNH2-SupRep resulted in therapeutic prolongation of the pathologically shortened APD90 (IC: 429±16ms; SupRep-treated: 396±61ms; sham-treated: 274±12ms). We provide the first proof-of-principle gene therapy for correction of both LQT2 and SQT1. Akin to our sentinel discovery of SupRep gene therapy for LQT1, KCNH2-SupRep gene therapy successfully corrected/normalized the pathologic APD90, thereby eliminating the pathognomonic feature of both LQT2 and SQT1.