Ion Channel Genes Research Articles

An outward-rectifying plant K+ channel SPORK2 exhibits temperature-sensitive ion-transport activity

Temperature sensing is critical for the survival of living organisms.1,2 Thermosensitive transient receptor-potential (TRP) cation channels function as thermosensors in mammals.2,3,4,5,6 In contrast to animals, landplants lack TRP genes.7,8,9 Previous patch-clamp studies in plant cells suggested the presence of ion channels whose activities are related to temperature, implying the presence of TRP-like channels.10,11,12,13,14 However, the molecular entities of such temperature-sensitive ion channels were still unknown in land plants. In this study, we observed that the unique rainfall-induced leaf-folding movement of the legumetree Samanea saman15 was temperature-sensitive by using a rainfall-mimicking assay. Chilling-induced leaf folding in S.saman was shown to be related to the swelling of the motor cells16,17 at the base of the leaflet. This swelling suggested involvement of temperature-sensitive inactivation of K+ currents, independent of fluctuations in ion channel gene expression in motor cells. These findings led us to examine the temperature sensitivity of an outward-rectifying K+ channel, SPORK2, which was reported as an ion channel responsible for the nyctinastic (circadian-rhythmic) leaf movement of S.saman.18 We alsodiscovered that SPORK2 exhibits temperature-sensitive K+ transport activity in the Xenopus oocyte expression system. Using chimeric channels, we showed that two domains of SPORK2 regulated the temperaturesensitivity. Furthermore, heterologously expressed SPORK2 in Arabidopsis guard cells induced temperature-dependent stomatal closure. Therefore, SPORK2 is an ion channel in land plantswith temperature-sensitive ion-transport activity that functions similarly to mammalian TRP channels. Our current findings advance the molecular understanding of temperature-sensing mechanisms in plants.

Impact of isorhamnetin for suppression of action potential aberrations associated with atrial fibrillation

Abstract Background Isorhamnetin, a natural flavonoid, has potent antioxidant, antifibrotic and L-type Cav1.2 channel modulation effects, but its antiarrhythmic effect has not been reported. Purpose The purpose of this study is to investigate the effect of isorhamnetin on angiotensin II (Ang II)-induced atrial fibrillation (AF) in mice. Methods Wild-type male mice (C57BL/6J, 8 weeks old) were randomly divided into the following three groups: 1) control group, 2) Ang II treated group, 3) Ang II+isorhamnetin treated group. Ang II (1000 ng/kg/min) was administered by an implantable osmotic pump for two consecutive weeks, and isorhamnetin (5 mg/kg) was administered intraperitoneally for three weeks, one week before the initiation of Ang II administration. HL-1 cells were also assigned three groups. Ang II (1 μM) was treated for one day, and isorhamnetin (10 μM) was pretreated one hour before the beginning of Ang II treatment. To evaluate the effect of isorhamnetin on AF, electrophysiologic study including AF induction and action potential duration (APD) measurement with atrial tissue and HL-1 cells was performed. The expression of ion channel genes and proteins, including Cav1.2, were also evaluated. Results AF induction rate was markedly increased by Ang II and significantly decreased by isorhamnetin. AF duration was remarkably prolonged by Ang II and significantly shortened by isorhamnetin. Atrial effective refractory period (AERP) shortened by Ang II and reversed by isorhamnetin. Ang II administration significantly prolonged APD; that was alleviated by isorhamnetin. In addition, Ang II increased the frequency of delayed afterdepolarization (DAD), whereas isorhamnetin reduced its frequency. Cav1.2 channel expression was enhanced by Ang II and normalized by isorhamnetin. On the other hand, Ang II and isorhamnetin had no effect on potassium channels. Conclusion The findings in this study suggest that isorhamnetin prevents APD prolongation via the modulation of Cav1.2 channel and reduced the frequency of DAD, which is one of the mechanisms to prevent AF vulnerability.Effect of isorhamnetin on APD

Reduction of Kcnt1 is therapeutic in mouse models of SCN1A and SCN8A epilepsy.

Developmental and epileptic encephalopathies (DEEs) are severe seizure disorders with inadequate treatment options. Gain- or loss-of-function mutations of neuronal ion channel genes, including potassium channels and voltage-gated sodium channels, are common causes of DEE. We previously demonstrated that reduced expression of the sodium channel gene Scn8a is therapeutic in mouse models of sodium and potassium channel mutations. In the current study, we tested whether reducing expression of the potassium channel gene Kcnt1 would be therapeutic in mice with mutation of the sodium channel genes Scn1a or Scn8a. A Kcnt1 antisense oligonucleotide (ASO) prolonged survival of both Scn1a and Scn8a mutant mice, suggesting a modulatory effect for KCNT1 on the balance between excitation and inhibition. The cation channel blocker quinidine was not effective in prolonging survival of the Scn8a mutant. Our results implicate KCNT1 as a therapeutic target for treatment of SCN1A and SCN8A epilepsy.

Simulated Microgravity Changes the Number of Mechanically Gated and Mechanosensitive Ion Channels Genes Transcripts in Rat Ventricular Cardiomyocytes

Simulated Microgravity Changes the Number of Mechanically Gated and Mechanosensitive Ion Channels Genes Transcripts in Rat Ventricular Cardiomyocytes

Ion Channel Genes in Painful Neuropathies.

Neuropathic pain (NP) is a typical symptom of peripheral nerve disorders, including painful neuropathy. The biological mechanisms that control ion channels are important for many cell activities and are also therapeutic targets. Disruption of the cellular mechanisms that govern ion channel activity can contribute to pain pathophysiology. The voltage-gated sodium channel (VGSC) is the most researched ion channel in terms of NP; however, VGSC impairment is detected in only <20% of painful neuropathy patients. Here, we discuss the potential role of the other peripheral ion channels involved in sensory signaling (transient receptor potential cation channels), neuronal excitation regulation (potassium channels), involuntary action potential generation (hyperpolarization-activated cyclic nucleotide-gated channels), thermal pain (anoctamins), pH modulation (acid sensing ion channels), and neurotransmitter release (calcium channels) related to pain and their prospective role as therapeutic targets for painful neuropathy.

Mechanosensitive ion channel gene survey suggests potential roles in primary open angle glaucoma

Although glaucoma is a disease modulated by eye pressure, the mechanisms of pressure sensing in the eye are not well understood. Here, we investigated associations between mechanosensitive ion channel gene variants and primary open-angle glaucoma (POAG). Common (minor allele frequency > 5%) single nucleotide polymorphisms located within the genomic regions of 20 mechanosensitive ion channel genes in the K2P, TMEM63, PIEZO and TRP channel families were assessed using genotype data from the NEIGHBORHOOD consortium of 3853 cases and 33,480 controls. Rare (minor allele frequency < 1%) coding variants were assessed using exome array genotyping data for 2606 cases and 2606 controls. Association with POAG was analyzed using logistic regression adjusting for age and sex. Two rare PIEZO1 coding variants with protective effects were identified in the NEIGHBOR dataset: R1527H, (OR 0.17, P = 0.0018) and a variant that alters a canonical splice donor site, g.16-88737727-C-G Hg38 (OR 0.38, P = 0.02). Both variants showed similar effects in the UK Biobank and the R1527H also in the FinnGen database. Several common variants also reached study-specific thresholds for association in the NEIGHBORHOOD dataset. These results identify novel variants in several mechanosensitive channel genes that show associations with POAG, suggesting that these channels may be potential therapeutic targets.

Rapid changes of mRNA expressions of cardiac ion channels affected by Torsadogenic drugs influence susceptibility of rat hearts to arrhythmias induced by Beta-Adrenergic stimulation.

Drug-induced long QT syndrome (LQTS) and Torsades de Pointes (TdP) are serious concerns in drug development. Although rats are a useful scientific tool, their hearts, unlike larger species, usually do not respond to torsadogenic drugs. Consequently, their resistance to drug-induced arrhythmias is poorly understood. Here, we challenged rats with rapid delayed rectifier current (Ikr)-inhibiting antibiotic clarithromycin (CLA), loop diuretic furosemide (FUR) or their combination (CLA + FUR), and examined functional and molecular abnormalities after stimulation with isoproterenol. Clarithromycin and furosemide were administered orally at 12-h intervals for 7 days. To evaluate electrical instability, electrocardiography (ECG) was recorded either in vivo or ex vivo using the Langendorff-perfused heart method under basal conditions and subsequently under beta-adrenergic stimulation. Gene expression was measured using real-time quantitative PCR in left ventricular tissue. Indeed, FUR and CLA + FUR rats exhibited hypokalemia. CLA and CLA + FUR treatment resulted in drug-induced LQTS and even an episode of TdP in one CLA + FUR rat. The combined treatment dysregulated gene expression of several ion channels subunits, including KCNQ1, calcium channels and Na+/K + -ATPase subunits, while both monotherapies had no impact. The rat with recorded TdP exhibited differences in the expression of ion channel genes compared to the rest of rats within the CLA + FUR group. The ECG changes were not detected in isolated perfused hearts. Hence, we report rapid orchestration of ion channel reprogramming of hearts with QT prolongation induced by simultaneous administration of clarithromycin and furosemide in rats, which may account for their ability to avoid arrhythmias triggered by beta-adrenergic stimulation.

Hypoxia Promotes Atrial Tachyarrhythmias via Opening of ATP-Sensitive Potassium Channels.

Hypoxia-ischemia predisposes to atrial arrhythmia. Atrial ATP-sensitive potassium channel (KATP) modulation during hypoxia has not been explored. We investigated the effects of hypoxia on atrial electrophysiology in mice with global deletion of KATP pore-forming subunits. Whole heart KATP RNA expression was probed. Whole-cell KATP current and action potentials were recorded in isolated wild-type (WT), Kir6.1 global knockout (6.1-gKO), and Kir6.2 global knockout murine atrial myocytes. Langendorff-perfused hearts were assessed for atrial effective refractory period (ERP), conduction velocity, wavefront path length (WFPL), and arrhymogenicity under normoxia/hypoxia using a microelectrode array and programmed electrical stimulation. Heart histology was assessed. Expression patterns were essentially identical for all KATP subunit RNA across human heart, whereas in mouse, Kir6.1 and SUR2 (sulphonylurea receptor) were higher in ventricle than atrium, and Kir6.2 and SUR1 were higher in atrium. Compared with WT, Kir6.2 global knockout atrial myocytes had reduced tolbutamide-sensitive current and action potentials were more depolarized with slower upstroke and reduced peak amplitude. Action potential duration was prolonged in 6.1-gKO atrial myocytes, absent of changes in other ion channel gene expression or atrial myocyte hypertrophy. In Langendorff-perfused hearts, baseline atrial ERP was prolonged and conduction velocity reduced in both KATP knockout mice compared with WT, without histological fibrosis. Compared with baseline, hypoxia led to conduction velocity slowing, stable ERP, and WFPL shortening in WT and 6.1-gKO hearts, whereas WFPL was stable in Kir6.2 global knockout hearts due to ERP prolongation with conduction velocity slowing. Tolbutamide reversed hypoxia-induced WFPL shortening in WT and 6.1-gKO hearts through ERP prolongation. Atrial tachyarrhythmias inducible with programmed electrical stimulation during hypoxia in WT and 6.1-gKO mice correlated with WFPL shortening. Spontaneous arrhythmia was not seen. KATP block/absence leads to cellular and tissue level atrial electrophysiological modification. Kir6.2 global knockout prevents hypoxia-induced atrial WFPL shortening and atrial arrhythmogenicity to programmed electrical stimulation. This mechanism could be explored translationally to treat ischemically driven atrial arrhythmia.

Prophecy or Empiricy? Clinical value of predicting vs determining genetic variant functions.

The recent explosion of epilepsy genetic testing has created challenges for interpretation of gene variants. Assessments of the functional consequences of genetic variants either by predictive or experimental strategies can contribute to estimating pathogenicity, but there is no consensus on which approach is best. The Special Interest Group on Epilepsy Genetics hosted a session during the Annual American Epilepsy Society Meeting in December 2022 to discuss this topic. The session featured a debate of the relative advantages and limitations of predicting (prophecy) versus experimentally determining (empiricism) variant function using ion channel gene variants as examples. This commentary summarizes these discussions.

Novel combinations of variations in KCNQ1 were associated with patients with long QT syndrome or Jervell and Lange-Nielsen syndrome

ObjectivesLong QT syndrome (LQTS) is one of the primary causes of sudden cardiac death (SCD) in youth. Studies have identified mutations in ion channel genes as key players in the pathogenesis of LQTS. However, the specific etiology in individual families remains unknown.MethodsThree unrelated Chinese pedigrees diagnosed with LQTS or Jervell and Lange-Nielsen syndrome (JLNS) were recruited clinically. Whole exome sequencing (WES) was performed and further validated by multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing.ResultsAll of the probands in our study experienced syncope episodes and featured typically prolonged QTc-intervals. Two probands also presented with congenital hearing loss and iron-deficiency anemia and thus were diagnosed with JLNS. A total of five different variants in KCNQ1, encoding a subunit of the voltage-gated potassium channel, were identified in 3 probands. The heterozygous variants, KCNQ1 c.749T > C was responsible for LQTS in Case 1, transmitting in an autosomal dominant pattern. Two patterns of compound heterozygous variants were responsible for JLNS, including a large deletion causing loss of the exon 16 and missense variant c.1663 C > T in Case 2, and splicing variant c.605-2 A > G and frame-shift variant c.1265del in Case 3. To our knowledge, the compound heterozygous mutations containing a large deletion and missense variant were first reported in patients with JLNS.ConclusionOur study expanded the LQTS genetic spectrum, thus favoring disease screening and diagnosis, personalized treatment, and genetic consultation.

Abstract P1130: Enhanced Electrophysiological Maturation Of Human Pluripotent Stem Cell Derived Cardiomyocytes By An Optimal Combination Of Metabolic Modulators

Human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) have emerged as ideal cell source for heart regeneration. Transplantation of hPSC-CMs to the damaged heart restores contractile function via electromechanical coupling between host and graft CMs. However, a few hurdles still remain in safety for clinical application, especially a transient period of ventricular arrhythmias after transplantation into large animals. Automaticity of graft cells, related to the electrical immaturity of hPSC-CMs, most likely triggers arrhythmic events. Here, we hypothesized that modulating metabolism toward an adult-like state would control ion channel gene expression and enhance electrophysiological maturation of hPSC-CMs in vitro. We systematically optimized combination of major metabolic components, including metabolic hormones, energy source and energy sensing, to achieve ion channel gene expression and electrophysiological phenotypes that more closely resemble adult cardiomyocytes. hPSC-CMs treated with optimized media displayed slower beat rates, longer field potentials, faster conduction velocities, and improved Ca 2+ kinetics. Moreover, optimized media increased mitochondrial content, respiratory capacity and fatty acid utilization for larger energy production, induced cell cycle exit, improved global transcriptome and sarcomere structure, and increased cell size. Subsequently, the matured cells were transplanted to mouse hearts, showing the engraftment comparable to immature hPSC-CMs. These results indicate that metabolic reprogramming can enhance many elements of maturation, including electrophysiology, myofibril organization, cell cycle, and capacity for oxidative phosphorylation.

Abstract P3132: Tgfβ Signaling Triggers Nonmyocyte Gene Expression In Tbx18-induced Pacemaker Myocytes And Abbreviates Their Automaticity

Background: We have previously demonstrated reprogramming of ventricular myocytes into induced pacemaker cells (iPMs) using an embryonic transcription factor TBX18. We have also discovered that Tgfβ pathway is significantly upregulated in TBX18-iPMs, and triggers fibrosis upon gene transfer in vitro and in vivo. Here, we sought to investigate the impact of Tgfβ signaling on iPMs’ automaticity. Methods: Neonatal rat ventricular myocytes (NRVMs) were transduced with Adeno-TBX18 or control Adeno-GFP. Single cell RNAseq was performed at days 3, 6, and 14. Spontaneous field potentials from NRVM monolayers were recorded with microelectrode array. Results: TBX18 gene transfer strongly repressed working cardiomyocyte gene expression, e.g., Gja1, Scn5a, Pln throughout the 14-day period. TBX18-NRVMs progressed toward pacemaker cells, evidenced by increase in nodal pacemaker-related ion channel gene expression. TBX18 also triggered cytoskeletal remodeling, and activated nonmyocyte gene expression throughout the 2-week window. This was illustrated by ECM remodeling gene expression such as Acta2, Col1a1, and Postn. Treatment with A83-01, a small molecule inhibitor of Tgfβ receptors, mitigated the increase in nonmyocyte gene expression. TBX18-NRVMs exhibited spontaneously oscillating field potentials, reaching a peak pacing frequency of 196±36 bpm during week 1, which is comparable to the sinus rhythm of newborn rats. However, the pacing frequency gradually wavered after week 1. In contrast, A83-01-treated TBX18-iPMs showed peak pacing frequency beyond week 1, with the majority of their total beat counts near their sinus rhythm (63.3%) while only 14.9% of total beats were near the sinus rhythm in TBX18-iPMs without Tgfβ inhibition (P&lt;0.001). Interestingly, A83-01 did not impact PM-related ion channel gene expression (such as Hcn4, Gjc1) nor the percentage of TBX18-iPMs (5.1% vs. 5.4%, with or without A83-01, p=0.561), suggesting that improved automaticity may be due to its impact on nonmyocytes. Conclusion: TBX18-iPMs exhibit increased Tgfβ signaling and nonmyocyte gene expression, which negatively impacts their automaticity. Inhibition of Tgfβ signaling modulates nonmyocyte gene expression and enhances automaticity of TBX18-iPMs.

Identification of common core ion channel genes in epilepsy and Alzheimer's disease.

Although available literature indicates that the incidence of dementia in the epilepsy population and the risk of seizures in the Alzheimer's disease (AD) population are high, the specific genetic risk factors and the interaction mechanism are unclear, rendering rational genetic interpretation rather challenging. Our work aims to identify the common core ion channel genes in epilepsy and AD. In this study, we first integrated gene expression omnibus datasets (GSE48350 and GSE6834) on AD and epilepsy to identify differentially expressed genes (DEGs), performing Gene Ontology function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs. The related protein-protein interaction (PPI) network was constructed for DEGs, and the hub gene was evaluated. A total of 2800 and 35 genes were identified in GSE48350 and GSE6834, and 12 DEGs were significantly differentially expressed between the datasets. KEGG pathway analysis showed that DEGs were primarily enriched in glutamatergic synapse and dopaminergic synapse pathways. SCN2A, GRIA1, and KCNJ9 were the hub genes with high connectivity. The findings suggest that the three genes, SCN2A, GRIA1, and KCNJ9, may serve as potential targets for treating AD comorbid with epilepsy.

Altered placental ion channel gene expression in preeclamptic high-altitude pregnancies.

High-altitude (>2,500 m) residence increases the risk of pregnancy vascular disorders such as fetal growth restriction and preeclampsia, each characterized by impaired placental function. Genetic attributes of highland ancestry confer relative protection against vascular disorders of pregnancy at high altitudes. Although ion channels have been implicated in placental function regulation, neither their expression in high-altitude placentas nor their relationship to high-altitude preeclampsia has been determined. Here, we measured the expression of 26 ion-channel genes in placentas from preeclampsia cases and normotensive controls in La Paz, Bolivia (3,850 m). In addition, we correlated gene transcription to maternal and infant ancestry proportions. Gene expression was assessed by PCR, genetic ancestry evaluated by ADMIXTURE, and ion channel proteins localized by immunofluorescence. In preeclamptic placentas, 11 genes were downregulated (ABCC9, ATP2A2, CACNA1C, KCNE1, KCNJ8, KCNK3, KCNMA1, KCNQ1, KCNQ4, PKD2, and TRPV6) and two were upregulated (KCNQ3 and SCNN1G). KCNE1 expression was positively correlated with high-altitude Amerindian ancestry and negatively correlated with non-high altitude. SCNN1G was negatively correlated with African ancestry, despite minimal African admixture. Most ion channels were localized in syncytiotrophoblasts (Cav1.2, TRPP2, TRPV6, and Kv7.1), whereas expression of Kv7.4 was primarily in microvillous membranes, Kir6.1 in chorionic plate and fetal vessels, and MinK in stromal cells. Our findings suggest a role for differential placental ion channel expression in the development of preeclampsia. Functional studies are needed to determine processes affected by these ion channels in the placenta and whether therapies directed at modulating their activity could influence the onset or severity of preeclampsia.

Mutational analysis of mechanosensitive ion channels in the carnivorous Venus flytrap plant

How the Venus flytrap (Dionaea muscipula) evolved the remarkable ability to sense, capture, and digest animal prey for nutrients has long puzzled the scientific community.1 Recent genome and transcriptome sequencing studies have provided clues to the genes thought to play a role in these tasks.2,3,4,5 However, proving a causal link between these and any aspect of the plant's hunting behavior has been challenging due to the genetic intractability of this non-model organism. Here, we use CRISPR-Cas9 methods to generate targeted modifications in the Venus flytrap genome. The plant detects prey using touch-sensitive trigger hairs located on its bilobed leaves.6 Upon bending, these hairs convert mechanical touch signals into changes in the membrane potential of sensory cells, leading to rapid closure of the leaf lobes to ensnare the animal.7 Here, we generate mutations in trigger-hair-expressed MscS-like (MSL)-family mechanosensitive ion channel genes FLYCATCHER1 (FLYC1) and FLYCATCHER2 (FLYC2)5 and find that double-mutant plants have a reduced leaf-closing response to mechanical ultrasound stimulation. While we cannot exclude off-target effects of the CRISPR-Cas9 system, our genetic analysis is consistent with these and other functionally redundant mechanosensitive ion channels acting together to generate the sensory system necessary for prey detection.

Nerve Injury-Induced γH2AX Reduction in Primary Sensory Neurons Is Involved in Neuropathic Pain Processing.

Phosphorylation of the serine 139 of the histone variant H2AX (γH2AX) is a DNA damage marker that regulates DNA damage response and various diseases. However, whether γH2AX is involved in neuropathic pain is still unclear. We found the expression of γH2AX and H2AX decreased in mice dorsal root ganglion (DRG) after spared nerve injury (SNI). Ataxia telangiectasia mutated (ATM), which promotes γH2AX, was also down-regulated in DRG after peripheral nerve injury. ATM inhibitor KU55933 decreased the level of γH2AX in ND7/23 cells. The intrathecal injection of KU55933 down-regulated DRG γH2AX expression and significantly induced mechanical allodynia and thermal hyperalgesia in a dose-dependent manner. The inhibition of ATM by siRNA could also decrease the pain threshold. The inhibition of dephosphorylation of γH2AX by protein phosphatase 2A (PP2A) siRNA partially suppressed the down-regulation of γH2AX after SNI and relieved pain behavior. Further exploration of the mechanism revealed that inhibiting ATM by KU55933 up-regulated extracellular-signal regulated kinase (ERK) phosphorylation and down-regulated potassium ion channel genes, such as potassium voltage-gated channel subfamily Q member 2 (Kcnq2) and potassium voltage-gated channel subfamily D member 2 (Kcnd2) in vivo, and KU559333 enhanced sensory neuron excitability in vitro. These preliminary findings imply that the down-regulation of γH2AX may contribute to neuropathic pain.

Resistance to thyroid hormone induced tachycardia in RTHα syndrome

Mutations in thyroid hormone receptor α1 (TRα1) cause Resistance to Thyroid Hormone α (RTHα), a disorder characterized by hypothyroidism in TRα1-expressing tissues including the heart. Surprisingly, we report that treatment of RTHα patients with thyroxine to overcome tissue hormone resistance does not elevate their heart rate. Cardiac telemetry in male, TRα1 mutant, mice indicates that such persistent bradycardia is caused by an intrinsic cardiac defect and not due to altered autonomic control. Transcriptomic analyses show preserved, thyroid hormone (T3)-dependent upregulation of pacemaker channels (Hcn2, Hcn4), but irreversibly reduced expression of several ion channel genes controlling heart rate. Exposure of TRα1 mutant male mice to higher maternal T3 concentrations in utero, restores altered expression and DNA methylation of ion channels, including Ryr2. Our findings indicate that target genes other than Hcn2 and Hcn4 mediate T3-induced tachycardia and suggest that treatment of RTHα patients with thyroxine in high dosage without concomitant tachycardia, is possible.

Diagnostic yield and predictive value on left ventricular remodelling of genetic testing in dilated cardiomyopathy.

We assessed the diagnostic yield of genetic testing and the relationship of left ventricular (LV) reverse remodelling (LVRR) with the presence of DNA pathogenic (P) or likely pathogenic (LP) variants in patients with dilated cardiomyopathy (DCM). From 680 outpatients followed at the Heart Failure Outpatient Clinic of our institution, we selected subjects with a diagnosis of DCM as defined by LV ejection fraction (LVEF) ≤40% and LV dilatation not explained by coronary artery disease or other causes. All patients were offered genetic investigation of 42 disease-associated DCM genes with next-generation sequencing. Seventy patients fulfilled the definition of DCM and 66 underwent genetic investigation. We identified 18 P/LP variants in 16 patients, with a diagnostic yield of 24%. The most common variants were truncating TTN variants (n=7), followed by LMNA (n=3), cytoskeleton Z-disc (n=3), ion channel (n=2), motor sarcomeric (n=2), and desmosomal (n=1) genes. After a median follow-up of 53months (inter-quartile range 20-111), patients without P/LP variants exhibited higher systolic and diastolic blood pressure, lower plasma brain natriuretic peptide levels, and a larger extent of LVRR, as reflected by the increase in LVEF (+14% vs. +1%, P=0.0008) and decrease in indexed LV end-diastolic diameter (-6.5 vs. -2mm/m2 , P=0.03) compared with patients with P/LP variants. Our results confirm the high diagnostic yield of genetic testing in selected DCM patients and suggest that identification of P/LP variants in DCM portends poorer LVRR in response to guideline-directed medical therapy.

Genome-wide identification and expression analysis of the cyclic nucleotide-gated ion channel (CNGC) gene family in Saccharum spontaneum

BackgroundCyclic nucleotide-gated ion channels (CNGCs) are nonselective cation channels that are ubiquitous in eukaryotic organisms. As Ca2+ channels, some CNGCs have also proven to be K+-permeable and involved in plant development and responses to environmental stimuli. Sugarcane is an important sugar and energy crop worldwide. However, reports on CNGC genes in sugarcane are limited.ResultsIn this study, 16 CNGC genes and their alleles were identified from Saccharum spontaneum and classified into 5 groups based on phylogenetic analysis. Investigation of gene duplication and syntenic relationships between S. spontaneum and both rice and Arabidopsis demonstrated that the CNGC gene family in S. spontaneum expanded primarily by segmental duplication events. Many SsCNGCs showed variable expression during growth and development as well as in tissues, suggesting functional divergence. Light-responsive cis-acting elements were discovered in the promoters of all the identified SsCNGCs, and the expression of most of the SsCNGCs showed a diurnal rhythm. In sugarcane, the expression of some SsCNGCs was regulated by low-K+ treatment. Notably, SsCNGC13 may be involved in both sugarcane development and its response to environmental stimuli, including response to low-K+ stress.ConclusionThis study identified the CNGC genes in S. spontaneum and provided insights into the transcriptional regulation of these SsCNGCs during development, circadian rhythm and under low-K+ stress. These findings lay a theoretical foundation for future investigations of the CNGC gene family in sugarcane.

Association between clinical phenotypes of hypertrophic cardiomyopathy and Ca2+ gene variation gene variation

Objective: To observe the association between clinical phenotypes of hypertrophic cardiomyopathy (HCM) patients and a rare calcium channel and regulatory gene variation (Ca2+ gene variation) and to compare clinical phenotypes of HCM patients with Ca2+ gene variation, a single sarcomere gene variation and without gene variation and to explore the influence of rare Ca2+ gene variation on the clinical phenotypes of HCM. Methods: Eight hundred forty-two non-related adult HCM patients diagnosed for the first time in Xijing Hospital from 2013 to 2019 were enrolled in this study. All patients underwent exon analyses of 96 hereditary cardiac disease-related genes. Patients with diabetes mellitus, coronary artery disease, post alcohol septal ablation or septal myectomy, and patients who carried sarcomere gene variation of uncertain significance or carried>1 sarcomere gene variation or carried>1 Ca2+ gene variation, with HCM pseudophenotype or carrier of ion channel gene variations other than Ca2+ based on the genetic test results were excluded. Patients were divided into gene negative group (no sarcomere or Ca2+ gene variants), sarcomere gene variation group (only 1 sarcomere gene variant) and Ca2+ gene variant group (only 1 Ca2+ gene variant). Baseline data, echocardiography and electrocardiogram data were collected for analysis. Results: A total of 346 patients were enrolled, including 170 patients without gene variation (gene negative group), 154 patients with a single sarcomere gene variation (sarcomere gene variation group) and 22 patients with a single rare Ca2+ gene variation (Ca2+ gene variation group). Compared with gene negative group, patients in Ca2+ gene variation group had higher blood pressure and higher percentage of family history of HCM and sudden cardiac death (P<0.05); echocardiographic results showed that patients in Ca2+ gene variation group had thicker ventricular septum ((23.5±5.8) mm vs. (22.3±5.7) mm, P<0.05); electrocardiographic results showed that patients in Ca2+ gene variation group had prolonged QT interval ((416.6±23.1) ms vs. (400.6±47.2) ms, P<0.05) and higher RV5+SV1 ((4.51±2.26) mv vs. (3.50±1.65) mv, P<0.05). Compared with sarcomere gene variation group, patients in Ca2+ gene variation group had later onset age and higher blood pressure (P<0.05); echocardiographic results showed that there was no significant difference in ventricular septal thickness between two groups; patients in Ca2+ gene variation group had lower percentage of left ventricular outflow tract pressure gradient>30 mmHg (1 mmHg=0.133 kPa, 22.8% vs. 48.1%, P<0.05) and the lower early diastolic peak velocity of the mitral valve inflow/early diastolic peak velocity of the mitral valve annulus (E/e') ratio ((13.0±2.5) vs. (15.9±4.2), P<0.05); patients in Ca2+ gene variation group had prolonged QT interval ((416.6±23.1) ms vs. (399.0±43.0) ms, P<0.05) and lower percentage of ST segment depression (9.1% vs. 40.3%, P<0.05). Conclusion: Compared with gene negative group, the clinical phenotype of HCM is more severe in patients with rare Ca2+ gene variation; compared with patients with sarcomere gene variation, the clinical phenotype of HCM is milder in patients with rare Ca2+ gene variation.