KCNQ1 Research Articles

Computational Study on Effect of KCNQ1 P535T Mutation in a Cardiac Ventricular Tissue.

Heart diseases such as arrhythmia are the main causes of sudden death. Arrhythmias are typically caused by mutations in specific genes, damage in the cardiac tissue, or due to some chemical exposure. Arrhythmias caused due to mutation is called inherited arrhythmia. Induced arrhythmias are caused due to tissue damage or chemical exposure. Mutations in genes that encode ion channels of the cardiac cells usually result in (dysfunction) improper functioning of the channel. Improper functioning of the ion channel may lead to major changes in the action potential (AP) of the cardiac cells. This further leads to distorted electrical activity of the heart. Distorted electrical activity will affect the ECG that results in arrhythmia. KCNQ1 P535T mutation is one such gene mutation that encodes the potassium ion channel (KV7.1) of the cardiac ventricular tissue. Its clinical significance is not known. This study aims to perform a simulation study on P535T mutation in the KCNQ1 gene that encodes the potassium ion channel KV7.1 in the ventricular tissue grid. The effect of P535T mutation on transmural tissue grids for three genotypes (wild type, heterozygous, and homozygous) of cells are studied and the generated pseudo-ECGs are compared. Results show the delayed repolarization in the cells of ventricular tissue grid. Slower propagation of action potential in the transmural tissue grid is observed in the mutated (heterozygous and homozygous) genotypes. Longer QT interval is also observed in the pseudo-ECG of heterozygous and homozygous genotype tissue grids. From the pseudo-ECGs, it is observed that KCNQ1 P535T mutation leads to Long QT Syndrome (LQTS) which may result in life-threatening arrhythmias, such as Torsade de Pointes (TdP), Jervell and Lange-Nielsen syndrome (JLNS), and Romano-Ward syndrome (RWS).

Genetic and neural mechanisms of sleep disorders in children with autism spectrum disorder: a review.

The incidence of sleep disorders in children with autism spectrum disorder (ASD) is very high. Sleep disorders can exacerbate the development of ASD and impose a heavy burden on families and society. The pathological mechanism of sleep disorders in autism is complex, but gene mutations and neural abnormalities may be involved. In this review, we examined literature addressing the genetic and neural mechanisms of sleep disorders in children with ASD. The databases PubMed and Scopus were searched for eligible studies published between 2013 and 2023. Prolonged awakenings of children with ASD may be caused by the following processes. Mutations in the MECP2, VGAT and SLC6A1 genes can decrease GABA inhibition on neurons in the locus coeruleus, leading to hyperactivity of noradrenergic neurons and prolonged awakenings in children with ASD. Mutations in the HRH1, HRH2, and HRH3 genes heighten the expression of histamine receptors in the posterior hypothalamus, potentially intensifying histamine's ability to promote arousal. Mutations in the KCNQ3 and PCDH10 genes cause atypical modulation of amygdala impact on orexinergic neurons, potentially causing hyperexcitability of the hypothalamic orexin system. Mutations in the AHI1, ARHGEF10, UBE3A, and SLC6A3 genes affect dopamine synthesis, catabolism, and reuptake processes, which can elevate dopamine concentrations in the midbrain. Secondly, non-rapid eye movement sleep disorder is closely related to the lack of butyric acid, iron deficiency and dysfunction of the thalamic reticular nucleus induced by PTCHD1 gene alterations. Thirdly, mutations in the HTR2A, SLC6A4, MAOA, MAOB, TPH2, VMATs, SHANK3, and CADPS2 genes induce structural and functional abnormalities of the dorsal raphe nucleus (DRN) and amygdala, which may disturb REM sleep. In addition, the decrease in melatonin levels caused by ASMT, MTNR1A, and MTNR1B gene mutations, along with functional abnormalities of basal forebrain cholinergic neurons, may lead to abnormal sleep-wake rhythm transitions. Our review revealed that the functional and structural abnormalities of sleep-wake related neural circuits induced by gene mutations are strongly correlated with sleep disorders in children with ASD. Exploring the neural mechanisms of sleep disorders and the underlying genetic pathology in children with ASD is significant for further studies of therapy.

Saudi Community-Based Screening Study on Genetic Variants in β-Cell Dysfunction and Its Role in Women with Gestational Diabetes Mellitus.

Diabetes (hyperglycemia) is defined as a multifactorial metabolic disorder in which insulin resistance and defects in pancreatic β-cell dysfunction are two major pathophysiologic abnormalities that underpin towards gestational diabetes mellitus (GDM). TCF7L2, KCNQ1, and KCNJ11 genes are connected to the mechanism of β-cell dysfunction. The purpose of this study was to investigate the genes associated with β-cell dysfunction and their genetic roles in the rs7903146, rs2237892, and rs5219 variants in Saudi women diagnosed with type 2 diabetes mellitus and GDM. In this case-control study, 100 women with GDM and 100 healthy volunteers (non-GDM) were recruited. Genotyping was performed using polymerase chain reaction (PCR), followed by restriction fragment length analysis. Validation was performed using Sanger sequencing. Statistical analyses were performed using multiple software packages. Clinical studies showed a β-cell dysfunction positive association in women with GDM when compared to non-GDM women (p < 0.05). Both rs7903146 (CT vs. CC: OR-2.12 [95%CI: 1.13-3.96]; p = 0.01 & T vs. C: (OR-2.03 [95%CI: 1.32-3.11]; p = 0.001) and rs5219 SNPs (AG vs. AA: OR-3.37 [95%CI: 1.63-6.95]; p = 0.0006 & G vs. A: OR-3.03 [95%CI: 1.66-5.52]; p = 0.0001) showed a positive association with genotype and allele frequencies in women with GDM. ANOVA analysis confirmed that weight (p = 0.02), BMI (p = 0.01), and PPBG (p = 0.003) were associated with rs7903146 and BMI (p = 0.03) was associated with rs2237892 SNPs. This study confirms that the SNPs rs7903146 (TCF7L2) and rs5219 (KCNJ11) are strongly associated with GDM in the Saudi population. Future studies should address the limitations of this study.

Evaluation of expression of biomarkers of PLAGL1 (ZAC1), microRNA, and their non-coding RNAs in patients with endometriosis.

Since the PLAGL1 (ZAC1) gene is expressed in the human endometrium. It may be involved in the etiology of endometrial disorders by its abnormal regulation and expression. This study aimed to investigate the Zac1 gene and related microRNA and LncRNA and its alterations in patients with endometriosis. Blood plasma, ectopic (EC) and eutopic (EU) endometrial samples were gathered from 30 patients with endometriosis and 30 healthy fertile women, and the Q-PCR technique was used to determine the expression level of Zac1 mRNA and microRNAs (miR-1271-5p, hsa-miR-490-3pin) and LncRNAs (TONSL-AS1 TONSL, KCNQ1OT1 KCNQ1). According to the results, the Zac1 gene and KCNQ1OT1 KCNQ1, TONSL-AS1 TONSL LncRNA expression were significantly decreased in the endometriosis group versus the control group (P < 0.05). MiR-1271-5p and hsa-miR-490-3pin microRNA expression were significantly raised in the endometriosis group as opposed to the control group (P < 0.05). In summary, this research for the first time revealed that identifying Zac1 expression provides us with new indicators for evaluating endometriosis.

KCNQ1 rs2237892 polymorphism modify the association between short-term ambient particulate matter exposure and fasting blood glucose: A family-based study

BackgroundThe association between particulate matter and fasting blood glucose (FBG) has shown conflicting results. Genome-wide association studies have shown that KCNQ1 rs2237892 polymorphism is associated with the risk of diabetes. Whether KCNQ1 rs2237892 polymorphism might modify the association between particulate matter and FBG is still uncertain. MethodsData collected from a family-based cohort study in Northern China, were used to perform the analysis. A generalized additive Gaussian model was used to examine the short-term effects of air pollutants on FBG. We further conducted interaction analyses by including a cross-product term of air pollutants by rs2237892 within KCNQ1 gene. ResultsA total of 4418 participants were included in the study. In the single pollutant model, the FBG level increased 0.0031 mmol/L with per 10 μg/m3 elevation in fine particular matter (PM2.5) for lag 0 day. After additional adjustments for nitrogen dioxide (NO2) and sulfur dioxide (SO2), similar results were observed for lag 0–2 days. As for particulate matter with particle size below 10 μm (PM10), the significant association between the daily average concentration of the pollutant and FBG level was observed for lag 0–3 days. Additionally, rs2237892 in KCNQ1 gene modified the association between PM and FBG level. The higher risk of FBG levels associated with elevations in PM10 and PM2.5 were more evident as the number of risk allele C increased. Individuals with a CC genotype had the highest risk of elevation in FBG levels. ConclusionShort-term exposures to PM2.5 and PM10 were associated with higher FBG levels. Additionally, rs2237892 in KCNQ1 gene might modify the association between the air pollutants and FBG levels.

Beta-KTx14.3, a scorpion toxin, blocks the human potassium channel KCNQ1

Potassium channels play a key role in regulating many physiological processes, thus, alterations in their proper functioning can lead to the development of several diseases. Hence, the search for compounds capable of regulating the activity of these channels constitutes an intense field of investigation. Potassium scorpion toxins are grouped into six subfamilies (α, β, γ, κ, δ, and λ). However, experimental structures and functional analyses of the long chain β-KTx subfamily are lacking. In this study, we recombinantly produced the toxins TcoKIK and beta-KTx14.3 present in the venom of Tityus costatus and Lychas mucronatus scorpions, respectively. The 3D structures of these β-KTx toxins were determined by nuclear magnetic resonance. In both toxins, the N-terminal region is unstructured, while the C-terminal possesses the classic CSα/β motif. TcoKIK did not show any clear activity against frog Shaker and human KCNQ1 potassium channels; however, beta-KTx14.3 was able to block the KCNQ1 channel. The toxin-channel interaction mode was investigated using molecular dynamics simulations. The results showed that this toxin could form a stable network of polar-to-polar and hydrophobic interactions with KCNQ1, involving key conserved residues in both molecular partners. The discovery and characterization of a toxin capable of inhibiting KCNQ1 pave the way for the future development of novel drugs for the treatment of human diseases caused by the malfunction of this potassium channel. Statement of significanceScorpion toxins have been shown to rarely block human KCNQ1 channels, which participate in the regulation of cardiac processes. In this study, we obtained recombinant beta-KTx14.3 and TcoKIK toxins and determined their 3D structures by nuclear magnetic resonance. Electrophysiological studies and molecular dynamics models were employed to examine the interactions between these two toxins and the human KCNQ1, which is the major driver channel of cardiac repolarization; beta-KTx14.3 was found to block effectively this channel. Our findings provide insights for the development of novel toxin-based drugs for the treatment of cardiac channelopathies involving KCNQ1-like channels.

Nine patients with KCNQ2-related neonatal seizures and functional studies of two missense variants

Mutations in KCNQ2 encoding for voltage-gated K channel subunits underlying the neuronal M-current have been associated with infantile-onset epileptic disorders. The clinical spectrum ranges from self-limited neonatal seizures to epileptic encephalopathy and delayed development. Mutations in KCNQ2 could be either gain- or loss-of-function which require different therapeutic approaches. To better understand genotype–phenotype correlation, more reports of patients and their mutations with elucidated molecular mechanism are needed. We studied 104 patients with infantile-onset pharmacoresistant epilepsy who underwent exome or genome sequencing. Nine patients with neonatal-onset seizures from unrelated families were found to harbor pathogenic or likely pathogenic variants in the KCNQ2 gene. The p.(N258K) was recently reported, and p. (G279D) has never been previously reported. Functional effect of p.(N258K) and p.(G279D) has never been previously studied. The cellular localization study demonstrated that the surface membrane expression of Kv7.2 carrying either variant was decreased. Whole-cell patch-clamp analyses revealed that both variants significantly impaired Kv7.2 M-current amplitude and density, conductance depolarizing shift in voltage dependence of activation, membrane resistance, and membrane time constant (Tau), indicating a loss-of-function in both the homotetrameric and heterotetrameric with Kv7.3 channels. In addition, both variants exerted dominant-negative effects in heterotetrameric with Kv7.3 channels. This study expands the mutational spectrum of KCNQ2- related epilepsy and their functional consequences provide insights into their pathomechanism.

A Role for KCNQ Channels on Cell Type-Specific Plasticity in Mouse Auditory Cortex after Peripheral Damage.

Damage to sensory organs triggers compensatory plasticity mechanisms in sensory cortices. These plasticity mechanisms result in restored cortical responses, despite reduced peripheral input, and contribute to the remarkable recovery of perceptual detection thresholds to sensory stimuli. Overall, peripheral damage is associated with a reduction of cortical GABAergic inhibition; however, less is known about changes in intrinsic properties and the underlying biophysical mechanisms. To study these mechanisms, we used a model of noise-induced peripheral damage in male and female mice. We uncovered a rapid, cell type-specific reduction in the intrinsic excitability of parvalbumin-expressing neurons (PVs) in layer (L) 2/3 of auditory cortex. No changes in the intrinsic excitability of either L2/3 somatostatin-expressing or L2/3 principal neurons (PNs) were observed. The decrease in L2/3 PV excitability was observed 1, but not 7, d after noise exposure, and was evidenced by a hyperpolarization of the resting membrane potential, depolarization of the action potential threshold, and reduction in firing frequency in response to depolarizing current. To uncover the underlying biophysical mechanisms, we recorded potassium currents. We found an increase in KCNQ potassium channel activity in L2/3 PVs of auditory cortex 1 d after noise exposure, associated with a hyperpolarizing shift in the minimal voltage activation of KCNQ channels. This increase contributes to the decreased intrinsic excitability of PVs. Our results highlight cell-type- and channel-specific mechanisms of plasticity after noise-induced hearing loss and will aid in understanding the pathologic processes involved in hearing loss and hearing loss-related disorders, such as tinnitus and hyperacusis.SIGNIFICANCE STATEMENT Noise-induced damage to the peripheral auditory system triggers central plasticity that compensates for the reduced peripheral input. The mechanisms of this plasticity are not fully understood. In the auditory cortex, this plasticity likely contributes to the recovery of sound-evoked responses and perceptual hearing thresholds. Importantly, other functional aspects of hearing do not recover, and peripheral damage may also lead to maladaptive plasticity-related disorders, such as tinnitus and hyperacusis. Here, after noise-induced peripheral damage, we highlight a rapid, transient, and cell type-specific reduction in the excitability of layer 2/3 parvalbumin-expressing neurons, which is due, at least in part, to increased KCNQ potassium channel activity. These studies may highlight novel strategies for enhancing perceptual recovery after hearing loss and mitigating hyperacusis and tinnitus.

Computer-aided drug design of molecules that potentially bind to the cardiac KCNQ1 potassium channel.

Each year, approximately 5000 Albertans die of a heart-related disorder, making it one of the leading causes of death in the province. The activity of the heart is controlled by electrical processes which are mediated primarily by ion channels. The KCNQ1 potassium channel regulates the delayed-rectifier IKs current of the cardiac action potential. Loss of function or aberrant gain of function in this channel causes several different arrhythmias, which include long QT syndrome (LQTS), a heart disorder that causes ventricular fibrillation and sudden cardiac death in children and young adults. In this study, computational tools were used aiming to design new potent modulators for this channel. A virtual screening was carried out; several properties including bioavailability and binding free energies were estimated. This study identifies regions for ligand binding optimization and further experimental validation.

Clinical and functional characterisation of a recurrent KCNQ1 variant in the Belgian population

BackgroundThe c.1124_1127delTTCA p.(Ile375Argfs*43) pathogenic variant is the most frequently identified molecular defect in the KCNQ1 gene in the cardiogenetics clinic of the Antwerp University Hospital. This variant was observed in nine families presenting with either Jervell-Lange-Nielsen syndrome or long QT syndrome (LQTS). Here, we report on the molecular, clinical and functional characterization of the KCNQ1 c.1124_1127delTTCA variant.ResultsForty-one heterozygous variant harboring individuals demonstrated a predominantly mild clinical and electrophysiological phenotype, compared to individuals harboring other KCNQ1 pathogenic variants (5% symptomatic before 40 years of age, compared to 24% and 29% in p.(Tyr111Cys) and p.(Ala341Val) variant carriers, respectively, 33% with QTc ≤ 440 ms compared to 10% in p.(Tyr111Cys) and p.(Ala341Val) variant carriers). The LQTS phenotype was most comparable to that observed for the Swedish p.(Arg518*) founder mutation (7% symptomatic at any age, compared to 17% in p.(Arg518*) variant carriers, 33% with QTc ≤ 440 ms compared to 16% in p.(Arg518*) variant carriers). Surprisingly, short tandem repeat analysis did not reveal a common haplotype for all families. One KCNQ1 c.1124_1127delTTCA harboring patient was diagnosed with Brugada syndrome (BrS). The hypothesis of a LQTS/BrS overlap syndrome was supported by electrophysiological evidence for both loss-of-function and gain-of-function (acceleration of channel kinetics) in a heterologous expression system. However, BrS phenotypes were not identified in other affected individuals and allelic KCNQ1 expression testing in patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) showed nonsense mediated decay of the c.1124_1127delTTCA allele.ConclusionsThe c.1124_1127delTTCA frameshift variant shows a high prevalence in our region, despite not being confirmed as a founder mutation. This variant leads to a mild LQTS phenotype in the heterozygous state. Despite initial evidence for a gain-of-function effect based on in vitro electrophysiological assessment in CHO cells and expression of the KCNQ1 c.1124_1127delTTCA allele in patient blood cells, additional testing in iPSC-CMs showed lack of expression of the mutant allele. This suggests haploinsufficiency as the pathogenic mechanism. Nonetheless, as inter-individual differences in allele expression in (iPSC-) cardiomyocytes have not been assessed, a modifying effect on the BrS phenotype through potassium current modulation cannot be excluded.

A novel stop-gain pathogenic variant in the KCNQ1 gene causing long QT syndrome 1

BackgroundInherited primary arrhythmias, such as long QT (LQT) syndromes, are electrical abnormalities of the heart mainly due to variants in 3 genes. We herein describe a novel stop-gain pathogenic variant in the KCNQ1 gene in an Iranian child with LQT syndrome 1.MethodsThe patient and his family underwent clinical evaluation, electrocardiographic Holter monitoring, and whole-exome sequencing. Sanger sequencing and segregation analysis were used to confirm the variant in the patient and his family, respectively. The pathogenicity of the variant was checked via an in silico analysis.ResultsThe proband suffered from bradycardia and had experienced syncope without stress. The corrected QT interval was 470 ms (the Schwartz score ≥ 3.5), and the Holter monitoring showed sinus rhythm, infrequent premature atrial contractions, and a prolonged QT interval in some leads. Whole-exome and Sanger sequencing showed c.968G > A in 3 affected family members. According to the American College of Medical Genetics and Genomics criteria, c.968G > A was classified as a pathogenic variant.ConclusionsThe KCNQ1 gene is the main cause of LQT syndromes in our population. The common genes of LQT syndromes should be studied in our country’s different ethnicities to determine the exact role of these genes in these subpopulations.

Functional Characterization of a Spectrum of Novel Romano-Ward Syndrome KCNQ1 Variants.

The KCNQ1 gene encodes the α-subunit of the cardiac voltage-gated potassium (Kv) channel KCNQ1, also denoted as Kv7.1 or KvLQT1. The channel assembles with the ß-subunit KCNE1, also known as minK, to generate the slowly activating cardiac delayed rectifier current IKs, a key regulator of the heart rate dependent adaptation of the cardiac action potential duration (APD). Loss-of-function variants in KCNQ1 cause the congenital Long QT1 (LQT1) syndrome, characterized by delayed cardiac repolarization and a QT interval prolongation in the surface electrocardiogram (ECG). Autosomal dominant loss-of-function variants in KCNQ1 result in the LQT syndrome called Romano-Ward syndrome (RWS), while autosomal recessive variants affecting function, lead to Jervell and Lange-Nielsen syndrome (JLNS), associated with deafness. The aim of this study was the characterization of novel KCNQ1 variants identified in patients with RWS to widen the spectrum of known LQT1 variants, and improve the interpretation of the clinical relevance of variants in the KCNQ1 gene. We functionally characterized nine human KCNQ1 variants using the voltage-clamp technique in Xenopus laevis oocytes, from which we report seven novel variants. The functional data was taken as input to model surface ECGs, to subsequently compare the functional changes with the clinically observed QTc times, allowing a further interpretation of the severity of the different LQTS variants. We found that the electrophysiological properties of the variants correlate with the severity of the clinically diagnosed phenotype in most cases, however, not in all. Electrophysiological studies combined with in silico modelling approaches are valuable components for the interpretation of the pathogenicity of KCNQ1 variants, but assessing the clinical severity demands the consideration of other factors that are included, for example in the Schwartz score.

JS-NG-8: CASE REPORT: POSSIBLE NEW CHANNELOPATHY ASSOCIATED WITH ELEVATED ALDOSTERONE LEVELS

Background: Potassium channelopathies are associated with prolonged QT cardiac syndrome. New potassium channelopathies in somatic cells, including KCNJ5 mutations, also underlie some forms of primary hyperaldosteronism. We present a first-in-human report of an association between a KCNQ1 loss of function mutation manifesting with life threatening-ventricular tachycardia (VT), severe hypokalemia and presumed hyperaldosteronism. Case Presentation: The patient is a 51-year-old Asian woman known for obesity, Wolff-Parkinson-White post ablation, and recurrent syncopal episodes with polymorphic VT due to prolonged QTc, requiring an implantable cardioverter defibrillator. On initial presentation for syncope, spontaneous hypokalemia was discovered at 3.1 mmol/L. She had multiple hospitalizations for torsade storms and persistent hypokalemia resistant to aggressive potassium supplementation until addition of spironolactone. Investigations revealed a suppressed plasma renin activity &lt; 0.05 ng/L/s, serum aldosterone concentration at 302 pmol/L, and an aldosterone to renin ratio (ARR) &gt; 6040. Repeated ARR was &gt; 10980. Confirmatory saline suppression testing or adrenal vein sampling were not performed due to risk of recurrent VT associated with spironolactone cessation. A comprehensive evaluation for the etiology of this patient's clinical presentation revealed a mutation in the KCNQ1 gene type 1. Literature review: The voltage-dependent K(+) channel responsible for activating delayed K(+) current is composed of pore-forming KCNQ1 and regulatory KCNE1/3 subunits which loss of function predispose to sustained torsade de pointes. Animal models demonstrate that KCNQ1 and KCNE1 mRNAs are expressed in the zona glomerulosa of adrenal glands where potassium channels directly participate in the control of aldosterone production. Although KCNE3 is not expressed in mouse adrenals, its deletion is thought to cause activation of lymphocytes targeting adrenal glands, leading to hyperaldosteronism. Furthermore, administration of spironolactone to KCNE3 knockout mice ameliorates their QT prolongation and predisposition to VT. There have been no case reports of an association between KCNQ1/E1/E3 loss of function and hyperaldosteronism in humans. Conclusion: This raises the question if this mechanism can also be a component of human KCNQ1 and KCNE1/3-linked arrhythmogenesis and hyperaldosteronism. Alternatively, we can further speculate that patients with hyperaldosteronism who develop malignant arrhythmias during hypokalemia are subjects with impaired repolarization reserve as a consequence of variants in genes known to cause long QT syndrome. The variants, leading to subclinical ion channel dysfunction, are typically silent until unmasked by electrolytes abnormalities such as hypokalemia. To our knowledge, this case is a first report of a potentially novel channelopathy associated with hyperaldosteronism in humans. These findings are hypothesis generating and require further investigations.

Paclitaxel Inhibits KCNQ Channels in Primary Sensory Neurons to Initiate the Development of Painful Peripheral Neuropathy.

Cancer patients undergoing paclitaxel infusion usually experience peripheral nerve degeneration and serious neuropathic pain termed paclitaxel-induced peripheral neuropathy (PIPN). However, alterations in the dose or treatment schedule for paclitaxel do not eliminate PIPN, and no therapies are available for PIPN, despite numerous studies to uncover the mechanisms underlying the development/maintenance of this condition. Therefore, we aimed to uncover a novel mechanism underlying the pathogenesis of PIPN. Clinical studies suggest that acute over excitation of primary sensory neurons is linked to the pathogenesis of PIPN. We found that paclitaxel-induced acute hyperexcitability of primary sensory neurons results from the paclitaxel-induced inhibition of KCNQ potassium channels (mainly KCNQ2), found abundantly in sensory neurons and axons. We found that repeated application of XE-991, a specific KCNQ channel blocker, induced PIPN-like alterations in rats, including mechanical hypersensitivity and degeneration of peripheral nerves, as detected by both morphological and behavioral assays. In contrast, genetic deletion of KCNQ2 from peripheral sensory neurons in mice significantly attenuated the development of paclitaxel-induced peripheral sensory fiber degeneration and chronic pain. These findings may lead to a better understanding of the causes of PIPN and provide an impetus for developing new classes of KCNQ activators for its therapeutic treatment.

1064 LONG QTC IN HCM: A CONSEQUENCE OF MYOCARDIAL HYPERTROPHY OR A DISTINCT GENETIC DISEASE?

Abstract Hypertrophic cardiomyopathy (HCM) is an autosomal dominant condition, characterized by the presence of unexplained left ventricular hypertrophy. This condition is usually associated with electrocardiographic abnormalities including QTc prolongation reported in the 13% of HCM patients. The main explanation for QTc prolongation in HCM is myocardial hypertrophy and the related structural damage. However, mechanisms other than myocardial hypertrophy, including long QT syndrome (LQTS) gene mutations, may also be involved. The addictive effect of 2 disease-causing mutations has been already reported in other pathological conditions. In the present study we investigated the possible co-inheritance of pathogenic variants associated with both LQTS and HCM, exploring the hypothesis of a distinct genetic basis underlying QTc prolongation in HCM. For this purpose, we considered a cohort of 150 HCM patients carrying pathogenic variants in sarcomeric genes. Out of them we selected 25 patients carrying a QTc prolongation not explained by any other cause (drugs, etc). The QTc was considered prolonged if greater than 450 ms in males and greater than 470 ms in females. NGS analysis was performed with Illumina TrueSight Cardio panel genes on Illumina MiniSeq platform to evaluate the presence of pathogenetic variants in LQTS related genes. We identified pathogenic/likely pathogenic variants in LQTS related gene KCNQ1 (c.1781G&amp;gt;A, p. Arg594Gln; c.532G&amp;gt;A, p. Ala178Thr) in two patients (8%) and uncertain significant variants in SCN5A, KCNJ5, AKAP9 and ANK2 in four patients (16%). Although the results of our study are limited by the small number of patients included in the analysis, they highlight a minor contribution of LQTS genes in HCM patients with a QTc prolongation. The screening for ion channel gene mutations should be considered in HCM patients with QTc prolongation, not explained by any other cause. This strategy may be important for risk stratification and treatment planning.

Whole genome bisulfite sequencing of sperm reveals differentially methylated regions in male partners of idiopathic recurrent pregnancy loss cases

To study the genome wide alterations in sperm DNA methylation in male partners of idiopathic recurrent pregnancy loss cases and note regions as potential diagnostic markers DESIGN: Case-Control study and methylome analysis of human sperm SUBJECTS: Control group consists of apparently healthy fertile men having fathered a child within the last 2 years (n = 39); and Case group consists of male partners of idiopathic recurrent pregnancy loss cases having two or more consecutive 1st trimester pregnancy losses (n = 47). None MAIN OUTCOME MEASURES: Sperm DNA samples of controls and cases were selected for Whole Genome Bisulfite Sequencing analysis based on the previously set thresholds of global methylation levels and methylation levels of imprinted genes (KvDMR and ZAC). Whole Genome Bisulfite Sequencing of selected sperm genomic DNA was performed to identify differentially methylated CpG sites of idiopathic recurrent pregnancy loss cases compared to fertile controls. Pathway analysis of all the differentially methylated genes was done by DAVID functional annotation tool and Kyoto Encyclopedia of Genes and Genomes tool. Differentially methylated CpGs within genes relevant to embryo and placenta development were selected to further validate their methylation levels in study population by pyrosequencing. A total of 9497 differentially methylated CpGs with highest enrichment in intronic regions were obtained. 5352 differentially methylated regions and 2087 differentially methylated genes were noted. Signaling pathways involved in development were enriched upon pathway analysis. Select CpGs within genes PPARG, KCNQ1, SETD2 and MAP3K4 showed distinct hypomethylated sub-populations within idiopathic recurrent pregnancy loss study population. Our study highlights the altered methylation landscape of idiopathic recurrent pregnancy loss sperm and their possible implications in pathways of embryo and placental development. The CpG sites that are hypomethylated specifically in sperm of idiopathic recurrent pregnancy loss sub-population can be further assessed as predictive biomarkers.

Continuous Bayesian variant interpretation accounts for incomplete penetrance among Mendelian cardiac channelopathies

PurposeThe congenital Long QT Syndrome (LQTS) and Brugada Syndrome (BrS) are Mendelian autosomal dominant diseases that frequently precipitate fatal cardiac arrhythmias. Incomplete penetrance is a barrier to clinical management of heterozygotes harboring variants in the major implicated disease genes KCNQ1, KCNH2, and SCN5A. We apply and evaluate a Bayesian penetrance estimation strategy that accounts for this phenomenon. MethodsWe generated Bayesian penetrance models for KCNQ1-LQT1 and SCN5A-LQT3 using variant-specific features and clinical data from the literature, international arrhythmia genetic centers, and population controls. We analyzed the distribution of posterior penetrance estimates across 4 genotype-phenotype relationships and compared continuous estimates with ClinVar annotations. Posterior estimates were mapped onto protein structure. ResultsBayesian penetrance estimates of KCNQ1-LQT1 and SCN5A-LQT3 are empirically equivalent to 10 and 5 clinically phenotype heterozygotes, respectively. Posterior penetrance estimates were bimodal for KCNQ1-LQT1 and KCNH2-LQT2, with a higher fraction of missense variants with high penetrance among KCNQ1 variants. There was a wide distribution of variant penetrance estimates among identical ClinVar categories. Structural mapping revealed heterogeneity among “hot spot” regions and featured high penetrance estimates for KCNQ1 variants in contact with calmodulin and the S6 domain. ConclusionsBayesian penetrance estimates provide a continuous framework for variant interpretation.

Influence of KCNQ1 and TCF7L2 genes associated with the role of type 2 diabetes

T2DM is a long-term metabolic disorder characterized by either the pancreas' inability to produce enough insulin or the body's inability to properly utilize the insulin it produces. The β-cell function and blood glucose homeostasis are two areas where TCF7L2 (Transcription factor 7 like 2) appears to be a significant candidate gene. KCNQ1 (potassium voltage-gated channel subfamily, member 1 has been discovered as a T2DM susceptibility gene in Asian populations by genome-wide association studies with rs2237892 polymorphism and an increased risk of developing T2DM. The aim of this study was to investigate the association between rs7903146 and rs2237892 SNP studies in T2DM patients. In this study, 60 T2DM cases and 60 controls were selected. Genotyping was performed for rs7903146 and rs2237892 SNPs using specific primers and restriction enzymes, then all PCR products were loaded on an agarose gel stained with ethidium bromide. The current study results confirmed rs7903146 SNP was strongly associated with genotype (OR-4.14; 95%CI:1.07-15.98; p=0.02) and allele frequencies (OR-4.60; 95%CI:1.66-12.70; p=0.001) whereas in rs2237892 SNP was not associated with any of the genotypes (OR-4.29; 95%CI:0.46-39.58; p=0.16; OR-3.21) or allele frequencies (OR-6.26; 95%CI:0.74-52.83; p=0.055). The current study results were found to be associated with global studies carried out in rs7903146 and rs2237892 SNP. The strength of this current study was to involve Saudi nationalities and we have screened rs7903146 and rs2237892 SNPs which plays a major role in T2DM. Involving 60 T2DM cases/60 controls was the major limitation of this study. Missing validation through Sanger sequencing analysis was one of the limitations of this study. In conclusion, the current study results confirmed rs7903146 SNP was strongly associated with T2DM and rs2237892 SNP was not associated with T2DM patients.

Genome-wide distribution of histone trimethylation reveals a global impact of bisphenol A on telomeric binding proteins and histone acetyltransferase factors: a pilot study with human and in vitro data

ObjectiveTo assess the genetic and epigenetic effects promoted by Bisphenol A (BPA) exposure in adolescent males from the Spanish INMA-Granada birth cohort, and in human cells.MethodsDNA methylation was analysed using MEDIP. Repeat number variation in genomic DNA was evaluated, along with the analysis of H3K4me3 by using chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq). Analyses were performed with material extracted from whole blood of the adolescents, complemented by in vitro assessments of human (HeLa) cells exposed to 10 nM BPA, specifically, immunofluorescence evaluation of protein levels, gene expression analysis and ChIP‒qPCR analysis.ResultsAdolescents in the high urinary BPA levels group presented a higher level of Satellite A (SATA) repetitive region copy numbers compared to those in the low BPA group and a tendency towards increase in telomere length. We also observed decreased DNA methylation at the promoters of the imprinted genes H19, KCNQ1, and IGF2; at LINE1 retroelements; and at the ARID2, EGFR and ESRRA and TERT genes. Genome-wide sequencing revealed increased H3K4me3 occupancy at the promoters of genes encoding histone acetyltransferases, telomeric DNA binding factors and DNA repair genes. Results were supported in HeLa cells exposed to 10 nM BPA in vitro. In accordance with the data obtained in blood samples, we observed higher H3K4me3 occupancy and lower DNA methylation at some specific targets in HeLa cells. In exposed cells, changes in the expression of genes encoding DNA repair factors (ATM, ARID2, TRP53) were observed, and increased expression of several genes encoding telomeric DNA binding factors (SMG7, TERT, TEN1, UPF1, ZBTB48) were also found. Furthermore, an increase in ESR1/ERa was observed in the nuclei of HeLa cells along with increased binding of ESR1 to KAT5, KMT2E and TERF2IP promoters and decreased ESR1 binding at the RARA promoter. The DNA damage marker p53/TP53 was also increased.ConclusionIn this pilot study, genome-wide analysis of histone trimethylation in adolescent males exposed to BPA revealed a global impact on the expression of genes encoding telomeric binding proteins and histone acetyltransferase factors with similar results in HeLa cells. Nevertheless, larger studies should confirm our findings.

Pharmacological rescue of specific long QT variants of KCNQ1/KCNE1 channels.

The congenital Long QT Syndrome (LQTS) is an inherited disorder in which cardiac ventricular repolarization is delayed and predisposes patients to cardiac arrhythmias and sudden cardiac death. LQT1 and LQT5 are LQTS variants caused by mutations in KCNQ1 or KCNE1 genes respectively. KCNQ1 and KCNE1 co-assemble to form critical IKS potassium channels. Beta-blockers are the standard of care for the treatment of LQT1, however, doing so based on mechanisms other than correcting the loss-of-function of K+ channels. ML277 and R-L3 are compounds that enhance IKS channels and slow channel deactivation in a manner that is dependent on the stoichiometry of KCNE1 subunits in the assembled channels. In this paper, we used expression of IKS channels in Chinese hamster ovary (CHO) cells and Xenopus oocytes to study the potential of these two drugs (ML277 and R-L3) for the rescue of LQT1 and LQT5 mutant channels. We focused on the LQT1 mutation KCNQ1-S546L, and two LQT5 mutations, KCNE1-L51H and KCNE1-G52R. We found ML277 and R-L3 potentiated homozygote LQTS mutations in the IKS complexes-KCNE1-G52R and KCNE1-L51H and in heterogeneous IKS channel complexes which mimic heterogeneous expression of mutations in patients. ML277 and R-L3 increased the mutant IKS current amplitude and slowed current deactivation, but not in wild type (WT) IKS. We obtained similar results in the LQT1 mutant (KCNQ1 S546L/KCNE1) with ML277 and R-L3. ML277 and R-L3 had a similar effect on the LQT1 and LQT5 mutants, however, ML277 was more effective than R-L3 in this modulation. Importantly we found that not all LQT5 mutants expressed with KCNQ1 resulted in channels that are potentiated by these drugs as the KCNE1 mutant D76N inhibited drug action when expressed with KCNQ1. Thus, our work shows that by directly studying the treatment of LQT1 and LQT5 mutations with ML277 and R-L3, we will understand the potential utility of these activators as options in specific LQTS therapeutics.