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Data for the type 1 long QT syndrome family. (A) Family pedigree. (B) Electrocardiogram (ECG) of the type 1 long QT syndrome patient represents prolonged QT intervals. (C) Cartoon showing the position of exon 7-encoded pore region in the α-subunit of K V 7.1. LQTS, long QT syndrome; QTc, corrected QT interval.
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Type 1 long QT syndrome (LQT1) is a common type of cardiac channelopathy associated with loss-of-function mutations of KCNQ1. Currently there is a lack of drugs that target the defected slowly activating delayed rectifier potassium channel (IKs). With LQT1 patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CM...
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... data as well as blood and skin samples were taken following written informed consent. A family of LQT1 was identified based on the clinical symptoms and ECG ( Figure 1). The proband (the LQT1 patient) and her clinically normal father (the family control) ( Figure 1A) participated in this study. ...
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... family of LQT1 was identified based on the clinical symptoms and ECG ( Figure 1). The proband (the LQT1 patient) and her clinically normal father (the family control) ( Figure 1A) participated in this study. The ECG of the LQT1 patient ( Figure 1B) showed typical prolonga- tion of QT interval (corrected QT interval = 545 ms) ( Figure 1B). ...
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... proband (the LQT1 patient) and her clinically normal father (the family control) ( Figure 1A) participated in this study. The ECG of the LQT1 patient ( Figure 1B) showed typical prolonga- tion of QT interval (corrected QT interval = 545 ms) ( Figure 1B). The ECG recorded from the father (not shown) was normal (corrected QT interval = 398 ms). ...
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... proband (the LQT1 patient) and her clinically normal father (the family control) ( Figure 1A) participated in this study. The ECG of the LQT1 patient ( Figure 1B) showed typical prolonga- tion of QT interval (corrected QT interval = 545 ms) ( Figure 1B). The ECG recorded from the father (not shown) was normal (corrected QT interval = 398 ms). ...
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... novel KCNQ1 mutation was identified in the LQT1 family An in-frame heterozygous deletion of exon 7 (C.922 ~ 1,032 del; P.308 ~ 344 del) in the KCNQ1 gene, which was not previously reported in LQT1, was identified in the pro- band and her mother and sisters ( Figure 1A). Exon 7 en- codes a major part of the S6 transmembrane-spanning segments (the pole region) and the loop connecting S5 and S6 ( Figure 1C). ...
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... 1,032 del; P.308 ~ 344 del) in the KCNQ1 gene, which was not previously reported in LQT1, was identified in the pro- band and her mother and sisters ( Figure 1A). Exon 7 en- codes a major part of the S6 transmembrane-spanning segments (the pole region) and the loop connecting S5 and S6 ( Figure 1C). No pathogenic mutations of up to 50 other cardiac genes (including KCNE1) responsible for inherited heart diseases were identified. ...
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... patient-specific hiPSCs and hiPSC-CMs were generated LQT1 patient and control hiPSCs were derived and their pluripotency was confirmed in vitro and in vivo by the expressions of typical pluripotent stem cell markers ( Figure S1A in Additional file 1) and formation of teratoma ( Figure S1B in Additional file 1), respectively. The hiPSCs main- tained a normal karyotype ( Figure S1C in Additional file 1). ...
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... patient-specific hiPSCs and hiPSC-CMs were generated LQT1 patient and control hiPSCs were derived and their pluripotency was confirmed in vitro and in vivo by the expressions of typical pluripotent stem cell markers ( Figure S1A in Additional file 1) and formation of teratoma ( Figure S1B in Additional file 1), respectively. The hiPSCs main- tained a normal karyotype ( Figure S1C in Additional file 1). ...
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... patient-specific hiPSCs and hiPSC-CMs were generated LQT1 patient and control hiPSCs were derived and their pluripotency was confirmed in vitro and in vivo by the expressions of typical pluripotent stem cell markers ( Figure S1A in Additional file 1) and formation of teratoma ( Figure S1B in Additional file 1), respectively. The hiPSCs main- tained a normal karyotype ( Figure S1C in Additional file 1). ...
Citations
... Inter-and intralab AP feature heterogeneity Mean and standard deviations of action potential MDP, APD 90 and dV/dt max from 21 independent datasets. These datasets were taken from 12 different studies, where APs were recorded without the injection of hyperpolarizing current: (Clark et al., 2022;EsSalah-Lamoureux et al., 2016;Feyen et al., 2020;Garg et al., 2019;Giannetti et al., 2021;Han et al., 2014;Herron et al., 2016;Horváth et al., 2018;Lee et al., 2017;Ma et al., 2015;Ma et al., 2011;Van de Sande et al., 2021). Studies with 'N', 'A' and 'V' indicate that these cells were sorted into nodal, atrial or ventricular categories based on AP morphology. ...
Human induced pluripotent stem cell‐derived cardiomyocytes (iPSC‐CMs) offer potential as an in vitro model for studying drug cardiotoxicity and patient‐specific cardiovascular disease. The inherent electrophysiological heterogeneity of these cells limits the depth of insights that can be drawn from well‐designed experiments. In this review, we provide our perspective on some sources and the consequences of iPSC‐CM heterogeneity. We demonstrate the extent of heterogeneity in the literature and explain how such heterogeneity is exacerbated by patch‐clamp experimental artifacts in the manual and automated set‐up. Finally, we discuss how this heterogeneity, caused by both intrinsic and extrinsic factors, limits our ability to build digital twins of patient‐derived cardiomyocytes. image
... ML277 has been shown to potentiate native IKs in guinea pig and canine ventricular myocytes and human (iPSC)-derived cardiomyocytes (12,13). The ability of ML277 to abolish calcium transient and action potential alternans in rabbit atrial myocytes (14), and reverse decreased IKs to partially restore action potential duration in LQT1 patient-derived human iPSC-cardiomyocytes (15), has led others to report IKs may have therapeutic value as an antiarrhythmic target. ...
Cardiovascular disease is thought to account for nearly a third of deaths worldwide, with ischemic heart disease, including acute coronary syndromes such as myocardial infarction, accounting for 1.7 million deaths per year. There is a clear need for interventions to impart cardioprotection against ischemia. Here, we show that the slowly activating voltage-gated potassium current (IKs) potentiator ML277 imparts cardioprotection against ischemia in cellular and whole-heart models by modulating the action potential duration. In three different metabolic inhibition and reperfusion models, an increased contractile recovery and cell survival was observed with ML277, indicative of protection. Finally, ML277 reduced infarct size in an ex vivo Langendorff coronary ligation model, including if only applied on reperfusion. In conclusion, potentiation of the IKs with ML277 imparted a cardioprotection that was equivalent to the protection reported previously by ischemic preconditioning. These data suggest that IKs potentiation may be therapeutically useful in acute coronary syndromes.
... By acting on KCNQ1 and KCNQ1/KCNE1 complexes, ML277 enhances I Ks density and shortens the action potential duration in canine ventricular cardiomyocytes and human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) [12,15]. ML277 rescued I Ks dysfunction in hiPSC-CMs with a patient-specific KCNQ1 mutation as shown via elevated I Ks density and action potential shortening [16]. Similar results by ML277 were shown in patient-specific hiPSC-CM clusters based on a reduced field potential duration [17]. ...
Long QT syndrome type 1 with affected IKs is associated with a high risk for developing Torsade de Pointes (TdP) arrhythmias and eventually sudden cardiac death. Therefore, it is of high interest to explore drugs that target IKs as antiarrhythmics. We examined the antiarrhythmic effect of IKs channel activator ML277 in the chronic atrioventricular block (CAVB) dog model. TdP arrhythmia sensitivity was tested in anesthetized mongrel dogs (n = 7) with CAVB in series: (1) induction experiment at 4 ± 2 weeks CAVB: TdP arrhythmias were induced with our standardized protocol using dofetilide (0.025 mg/kg), and (2) prevention experiment at 10 ± 2 weeks CAVB: the antiarrhythmic effect of ML277 (0.6–1.0 mg/kg) was tested by infusion for 5 min preceding dofetilide. ML277: (1) temporarily prevented repolarization prolongation induced by dofetilide (QTc: 538 ± 65 ms at induction vs. 393 ± 18 ms at prevention, p < 0.05), (2) delayed the occurrence of the first arrhythmic event upon dofetilide (from 129 ± 28 s to 180 ± 51 s, p < 0.05), and (3) decreased the arrhythmic outcome with a significant reduction in the number of TdP arrhythmias, TdP score, arrhythmia score and total arrhythmic events (from 669 ± 132 to 401 ± 228, p < 0.05). IKs channel activation by ML277 temporarily suppressed QT interval prolongation, delayed the occurrence of the first arrhythmic event and reduced the arrhythmic outcome in the CAVB dog model.
... As for the ion channel conductances, this parameter was varied to introduce heterogeneity in this key element of intracellular calcium handling. [12], 3 [13], 4 [14], 5 [15], 6 [16] 7 [17], 8 [18], 9 [19], 10 [20], 11 [21], 12 [22], 13 [23], 14 [24], 15 [25], 16 [26], 17 [27], 18 [28], 19 [29], 20 [30], 21 [31], 22 [32] Fig. 4.2: A. The resultant log-normal distributions for the Ks scaling factor, along with histograms resulting from 100 samples, are shown for the representative parametric variation in adult CM and the hiPSC-CM inputs for the models. B. The scaling factors that were sampled in order to create the PoM are shown for two cardiomyocyte models. ...
Inter-cellular heterogeneity is central to the dynamic range and robustness of function in many tissues, particularly electrically excitable tissues. In pancreatic islet 훽-cells, inter-cellular heterogeneity underlies the range of insulin response to glucose. In human-induced-pluripotent stem cell-derived cardiomyocytes (hiPSCCMs), inter-cellular heterogeneity presents a key challenge for drug screening applications. In this study, we assess the ability to reconstruct inter-cellular heterogeneity in silico by applying a “population of models” (PoMs) framework, i.e. collections of computational cells created via Monte Carlo variation of model parameters. We define parameter variation based on experimentally observed heterogeneity in properties such as ion current conductances and enzymatic affinities. We then assess the accuracy of those reconstructions, based on the degree to which variation in PoM outputs (e.g. action potential duration) matches experimentally observed variation. We report that this “ground-up” approach underestimates functional heterogeneity in the hiPSC-CM population, but overestimates it in adult human cardiomyocytes. In contrast, the 훽-cell PoM captures three distinct and physiologically relevant subclasses of 훽-cell function. In the future, we expect PoM approaches like these willpermit incorporation of realistic cellular heterogeneity in detailed models of intact tissues, and thereby aid development of sophisticated tissue-engineered platforms for therapeutics.
... However, the lack of structural mechanism for any of these activators that bind and modulate KCNQ1 largely impedes the development of new therapeutics. Among these activators, a small-molecule ML277 exhibits several unique properties: 1) it effectively activates the KCNQ1 channel with an EC 50 of 260 nM (30,36), more potent than other known KCNQ1/I Ks activators; 2) it exclusively activates the KCNQ1 channel without altering other key cardiac ion channels (such as hERG, Ca V 1.2, and Na V 1.5) or neuronal KCNQ (KCNQ2-KCNQ5) channels (30,36); 3) it shortens the action potential duration in human-induced pluripotent stem cellderived cardiomyocytes (including LQT1 conditions) and guinea pig cardiomyocytes (36)(37)(38)(39); and 4) we recently found that ML277 can specifically activate the AO state current by enhancing the VSD-PD coupling (6,13). All these properties enable ML277 as a promising candidate for treating cardiac arrythmia. ...
The cardiac KCNQ1 potassium channel carries the important I Ks current and controls the heart rhythm. Hundreds of mutations in KCNQ1 can cause life-threatening cardiac arrhythmia. Although KCNQ1 structures have been recently resolved, the structural basis for the dynamic electro-mechanical coupling, also known as the voltage sensor domain–pore domain (VSD-PD) coupling, remains largely unknown. In this study, utilizing two VSD-PD coupling enhancers, namely, the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP 2 ) and a small-molecule ML277, we determined 2.5–3.5 Å resolution cryo-electron microscopy structures of full-length human KCNQ1-calmodulin (CaM) complex in the apo closed, ML277-bound open, and ML277-PIP 2 -bound open states. ML277 binds at the “elbow” pocket above the S4-S5 linker and directly induces an upward movement of the S4-S5 linker and the opening of the activation gate without affecting the C-terminal domain (CTD) of KCNQ1. PIP 2 binds at the cleft between the VSD and the PD and brings a large structural rearrangement of the CTD together with the CaM to activate the PD. These findings not only elucidate the structural basis for the dynamic VSD-PD coupling process during KCNQ1 gating but also pave the way to develop new therapeutics for anti-arrhythmia.
... For example, Wuriyanghai et al. (2018) reported expression of a novel LQT-1 mutation, KCNQ1-A344D, expressed in human induced pluripotent stem cell cardiac myocytes (hiPSC-CMs and found that ML277 exposure resulted in a significant reduction in action potential duration not only in hiPSC-CMs expressing the A344D mutation, but also in control, wild type cells. These results are like those reported by Ma et al. (2015) in which the effects of ML277 were reported to reduce action potential duration not only in cells expressing a novel KCNQ1 C-terminal deletion mutation but also in control cells that were mutation-free. Further work by Kuusela et al. (2016) indicated that ML277 shortened action potentials in iPSC-myocytes expressing the G589D C-terminal KCNQ1 mutation, the founder LQT-1 mutation of the Finnish population. ...
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.
... KCNQ1 is most expressed in cardiac and cochlear tissue [14,22]. Specifically, cardiac KCNQ1 LOF mutations are associated with type 1 long-QT syndrome [22][23][24][25][26][27][28][29][30]. Cochlear KCNQ1 pathology involves the autosomal recessive long-QT syndrome (Jervell Lange-Nielsen syndrome), which is associated with potassium channelopathy leading to bilateral sensorineural hearing loss as well as the cardiac arrhythmia [26][27][28][29]. ...
The broad distribution of voltage-gated potassium channels (VGKCs) in the human body makes them a critical component for the study of physiological and pathological function. Within the KCNQ family of VGKCs, these aqueous conduits serve an array of critical roles in homeostasis, especially in neural tissue. Moreover, the greater emphasis on genomic identification in the past century has led to a growth in literature on the role of the ion channels in pathological disease as well. Despite this, there is a need to consolidate the updated findings regarding both the pharmacotherapeutic and pathological roles of KCNQ channels, especially regarding neural plasticity and motor disorders which have the largest body of literature on this channel. Specifically, KCNQ channels serve a remarkable role in modulating the synaptic efficiency required to create appropriate plasticity in the brain. This role can serve as a foundation for clinical approaches to chronic pain. Additionally, KCNQ channels in motor disorders have been utilized as a direction for contemporary pharmacotherapeutic developments due to the muscarinic properties of this channel. The aim of this study is to provide a contemporary review of the behavior of these channels in neural plasticity and motor disorders. Upon review, the behavior of these channels is largely dependent on the physiological role that KCNQ modulatory factors (i.e., pharmacotherapeutic options) serve in pathological diseases.
... The membrane expression of KCNQ1/KCNE1 channels in rat ventricular cardiomyocytes is decreased through the actions of PKCβII, a cPKC isozyme, after GqPCR activation (93). A decrease in I Ks is known to be a contributor to long QT syndrome (LQTS) (94). Several mutations in KCNQ1 channels have been linked to LQTS, some of which are close to or directly involved in channel-PIP 2 interactions (95). ...
Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2 or PIP2). The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various protein kinase C (PKC) isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage-dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on PIP2 as a mechanistic endpoint to control channel gating.
... The reduced severity of this particular mutation is further supported by the electrophysiological characterization of the R243C, W248R, and E261K mutations in KCNQ1 in Xenopus oocytes by Franqueza et al. [22], who observed that the W248R and E261K mutations in the S4-S5 linker of KCNQ1 reduced the generated current by 80% to 100% compared to wild-type KCNQ1 current, while the R243C mutated KCNQ1 only reduced this current by 60% [22]. Furthermore, hiPSC-CMs of both lines do not display a long APD compared to hiPSC-CMs of previously published LQT1 lines with different mutations [20,35,36]. The absence of an extremely long APD in the present study may be obscured due to the huge APD variability between hiPSC-CMs lines [37], but it could also be mutation-dependent [38] and a further indication of the reduced severity of this particular R243C mutation. ...
Long-QT syndrome type 1 (LQT1) is caused by mutations in KCNQ1. Patients heterozygous for such a mutation co-assemble both mutant and wild-type KCNQ1-encoded subunits into tetrameric Kv7.1 potassium channels. Here, we investigated whether allele-specific inhibition of mutant KCNQ1 by targeting a common variant can shift the balance towards increased incorporation of the wild-type allele to alleviate the disease in human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs). We identified the single nucleotide polymorphisms (SNP) rs1057128 (G/A) in KCNQ1, with a heterozygosity of 27% in the European population. Next, we determined allele-specificity of short-hairpin RNAs (shRNAs) targeting either allele of this SNP in hiPSC-CMs that carry an LQT1 mutation. Our shRNAs downregulated 60% of the A allele and 40% of the G allele without affecting the non-targeted allele. Suppression of the mutant KCNQ1 allele by 60% decreased the occurrence of arrhythmic events in hiPSC-CMs measured by a voltage-sensitive reporter, while suppression of the wild-type allele increased the occurrence of arrhythmic events. Furthermore, computer simulations based on another LQT1 mutation revealed that 60% suppression of the mutant KCNQ1 allele shortens the prolonged action potential in an adult cardiomyocyte model. We conclude that allele-specific inhibition of a mutant KCNQ1 allele by targeting a common variant may alleviate the disease. This novel approach avoids the need to design shRNAs to target every single mutation and opens up the exciting possibility of treating multiple LQT1-causing mutations with only two shRNAs.
... Dermal fibroblasts from two people in a family with LQTS-1 and two healthy people were infected with retroviral vectors encoding the human transcription factors OCT3/4, SOX2, KLF4, and c-MYC and converted into hPSCs in another study [139]. Another research examined the therapeutic potential of new IKs activators in LQTS using dermal fibroblasts differentiated into hPSCs [140]. ...
The occurrence of heart electrophysiology dysfunction or/and muscle damage is referred to as cardiotoxicity. The heart weakens and becomes less efficient at pumping and hence circulating blood. Cardiomyopathy can be caused by a variety of factors, including viral infections, diseases such as diabetes, ischemia, hyperten-sion, obesity, radiation therapy, antipsychotic drugs, cytotoxic drugs, most notably chemotherapeutic agents; antitumor antibiotics, monoclonal antibodies, tyrosine kinase inhibitors, platinum-based compounds, microtubule inhibitors, vinca alka-loids, antimetabolites, proteasome inhibitors, topoisomerase inhibitors, alkylating agents, corticosteroids. This chapter focuses on the mechanisms of cardiotoxicity, animal models and transgenic methods used in studies, and the effects of therapeutic agents on cardiotoxicity.
