Search

Abstract Mutations in the nuclear envelope (NE) protein lamin A/C (encoded by LMNA), cause a severe form of dilated cardiomyopathy (DCM) with early-onset life-threatening arrhythmias. However, molecular mechanisms underlying increased arrhythmogenesis in LMNA-related DCM (LMNA-DCM) remain largely unknown. Here we show that a frameshift mutation in LMNA causes abnormal Ca2+ handling, arrhythmias and disformed NE in LMNA-DCM patient-specific iPSC-derived cardiomyocytes (iPSC-CMs). Mechanistically, lamin A interacts with sirtuin 1 (SIRT1) where mutant lamin A/C accelerates degradation of SIRT1, leading to mitochondrial dysfunction and oxidative stress. Elevated reactive oxygen species (ROS) then activates the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-ryanodine receptor 2 (RYR2) pathway and aggravates the accumulation of SUN1 in mutant iPSC-CMs, contributing to arrhythmias and NE deformation, respectively. Taken together, the lamin A/C deficiency-mediated ROS disorder is revealed as central to LMNA-DCM development. Manipulation of impaired SIRT1 activity and excessive oxidative stress is a potential future therapeutic strategy for LMNA-DCM.

Lamin A/C is a protein encoded by the LMNA gene and belongs to the nuclear lamina protein family. Mutations in the LMNA gene lead to several diseases: Emery-Dreifuss muscular dystrophy, familial partial lipodystrophy, limb girdle muscular dystrophy, dilated cardiomyopathy, Charcot-Marie-Tooth disease, and Hutchinson-Gilford progeria syndrome. In this study, a lamin A/C knockout human induced pluripotent stem cell line was successfully generated using the CRISPR/Cas9 genome-editing technology, which was confirmed with normal pluripotency and karyotype.

Calcium- and integrin-binding protein 1 (CIB1) has a diverse role in many different cell types and processes, including calcium signaling, migration, adhesion, proliferation, and survival. It is associated with cancer, cardiovascular disease and male infertility. Here, CRISPR/Cas9 genome-editing technology was employed to establish a CIB1 knockout human embryonic stem cell line, which exhibited normal pluripotency and karyotype.

Abstract Background Mutations in the cardiac sodium channel gene SCN5A cause Brugada syndrome (BrS), an arrhythmic disorder that is a leading cause of sudden death and lacks effective treatment. An association between SCN5A and Wnt/β-catenin signaling has been recently established. However, the role of Wnt/β-catenin signaling in BrS and underlying mechanisms remains unknown. Methods Three healthy control subjects and one BrS patient carrying a novel frameshift mutation (T1788fs) in the SCN5A gene were recruited in this study. Control and BrS patient-specific induced pluripotent stem cells (iPSCs) were generated from skin fibroblasts using nonintegrated Sendai virus. All iPSCs were differentiated into cardiomyocytes using monolayer-based differentiation protocol. Action potentials and sodium currents were recorded from control and BrS iPSC-derived cardiomyocytes (iPSC-CMs) by single-cell patch clamp. Results BrS iPSC-CMs exhibited increased burden of arrhythmias and abnormal action potential profile featured by slower depolarization, decreased action potential amplitude, and increased beating interval variation. Moreover, BrS iPSC-CMs showed cardiac sodium channel (Nav1.5) loss-of-function as compared to control iPSC-CMs. Interestingly, the electrophysiological abnormalities and Nav1.5 loss-of-function observed in BrS iPSC-CMs were accompanied by aberrant activation of Wnt/β-catenin signaling. Notably, inhibition of Wnt/β-catenin significantly rescued Nav1.5 defects and arrhythmic phenotype in BrS iPSC-CMs. Mechanistically, SCN5A-encoded Nav1.5 interacts with β-catenin, and reduced expression of Nav1.5 leads to re-localization of β-catenin in BrS iPSC-CMs, which aberrantly activates Wnt/β-catenin signaling to suppress SCN5A transcription. Conclusions Our findings suggest that aberrant activation of Wnt/β-catenin signaling contributes to the pathogenesis of SCN5A-related BrS and point to Wnt/β-catenin as a potential therapeutic target.

Abstract Background Although human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are a promising cell resource for cardiovascular research, these cells exhibit an immature phenotype that hampers their potential applications. The inwardly rectifying potassium channel Kir2.1, encoded by the KCNJ2 gene, has been thought as an important target for promoting electrical maturation of iPSC-CMs. However, a comprehensive characterization of morphological and functional changes in iPSC-CMs overexpressing KCNJ2 (KCNJ2 OE) is still lacking. Methods iPSC-CMs were generated using a 2D in vitro monolayer differentiation protocol. Human KCNJ2 construct with green fluorescent protein (GFP) tag was created and overexpressed in iPSC-CMs via lentiviral transduction. The mixture of iPSC-CMs and mesenchymal cells was cocultured with decellularized natural heart matrix for generation of 3D human engineered heart tissues (EHTs). Results We showed that mRNA expression level of KCNJ2 in iPSC-CMs was dramatically lower than that in human left ventricular tissues. KCNJ2 OE iPSC-CMs yielded significantly increased protein expression of Kir2.1 and current density of Kir2.1-encoded IK1. The larger IK1 linked to a quiescent phenotype that required pacing to elicit action potentials in KCNJ2 OE iPSC-CMs, which can be reversed by IK1 blocker BaCl2. KCNJ2 OE also led to significantly hyperpolarized maximal diastolic potential (MDP), shortened action potential duration (APD) and increased maximal upstroke velocity. The enhanced electrophysiological maturation in KCNJ2 OE iPSC-CMs was accompanied by improvements in Ca2+ signaling, mitochondrial energy metabolism and transcriptomic profile. Notably, KCNJ2 OE iPSC-CMs exhibited enlarged cell size and more elongated and stretched shape, indicating a morphological phenotype toward structural maturation. Drug testing using hERG blocker E-4031 revealed that a more stable MDP in KCNJ2 OE iPSC-CMs allowed for obtaining significant drug response of APD prolongation in a concentration-dependent manner. Moreover, KCNJ2 OE iPSC-CMs formed more mature human EHTs with better tissue structure and cell junction. Conclusions Overexpression of KCNJ2 can robustly enhance maturation of iPSC-CMs in electrophysiology, Ca2+ signaling, metabolism, transcriptomic profile, cardiomyocyte structure and tissue engineering, thus providing more accurate cellular model for elucidating cellular and molecular mechanisms of cardiovascular diseases, screening drug-induced cardiotoxicity, and developing personalized and precision cardiovascular medicine.

The transient receptor potential vanilloid subfamily 1 (TRPV1) is a polymodal nociceptor that is highly expressed in sensory nerves. Activation of TRPV1 receptors excites primary afferent nociceptors by opening cation channels, allowing the influx of Na+ and Ca2+ ions into the cytoplasm. Here, a TRPV1 knockout human embryonic stem cell line was generated using the CRISPR/Cas9 genome-editing technology to further study the function of TRPV1. The cell line confirmed with normal pluripotency and karyotype.

Summary: Background: Brugada syndrome (BrS) is a cardiac channelopathy that can result in sudden cardiac death (SCD). SCN5A is the most frequent gene linked to BrS, but the genotype–phenotype correlations are not completely matched. Clinical phenotypes of a particular SCN5A variant may range from asymptomatic to SCD. Here, we used comparison of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) derived from a SCN5A mutation-positive (D356Y) BrS family with severely affected proband, asymptomatic mutation carriers (AMCs) and healthy controls to investigate this variation. Methods: 26 iPSC lines were generated from skin fibroblasts using nonintegrated Sendai virus. The generated iPSCs were differentiated into cardiomyocytes using a monolayer-based differentiation protocol. Findings: D356Y iPSC-CMs exhibited increased beat interval variability, slower depolarization, cardiac arrhythmias, defects of Na+ channel function and irregular Ca2+ signaling, when compared to controls. Importantly, the phenotype severity observed in AMC iPSC-CMs was milder than that of proband iPSC-CMs, an observation exacerbated by flecainide. Interestingly, the iPSC-CMs of the proband exhibited markedly decreased Ca2+ currents in comparison with control and AMC iPSC-CMs. CRISPR/Cas9-mediated genome editing to correct D356Y in proband iPSC-CMs effectively rescued the arrhythmic phenotype and restored Na+ and Ca2+ currents. Moreover, drug screening using established BrS iPSC-CM models demonstrated that quinidine and sotalol possessed antiarrhythmic effects in an individual-dependent manner. Clinically, venous and oral administration of calcium partially reduced the malignant arrhythmic events of the proband in mid-term follow-up. Interpretation: Patient-specific and genome-edited iPSC-CMs can recapitulate the varying phenotypic severity of BrS. Our findings suggest that preservation of the Ca2+ currents might be a compensatory mechanism to resist arrhythmogenesis in BrS AMCs. Funding: National Key R&D Program of China (2017YFA0103700), National Natural Science Foundation of China (81922006, 81870175), Natural Science Foundation of Zhejiang Province (LD21H020001, LR15H020001), National Natural Science Foundation of China (81970269), Key Research and Development Program of Zhejiang Province (2019C03022) and Natural Science Foundation of Zhejiang Province (LY16H020002).

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant inherited cardiovascular disease characterized by left ventricular hypertrophy and cardiomyocyte disarray. In this study, a skin biopsy was obtained from a HCM patient, who carried a missense mutation (c.4384G > A; p.E1462K) in the myosin heavy chain 7 (MYH7) gene. The skin fibroblasts were subsequently reprogrammed with a non-integrated Sendai viral method to generate a patient-specific induced pluripotent stem cell (iPSC) line. The generated iPSC line showed typical morphology and normal karyotype, expressed pluripotency markers, and was capable to differentiate into three germ layers.

Hypertrophic cardiomyopathy (HCM) is an inherited cardiovascular disease characterized by left ventricular hypertrophy and a high risk of sudden death. In this study, a skin biopsy was obtained from a HCM patient harboring a heterozygous missense mutation (c.3764C>A; p.A1225D) in the myosin binding protein C3 (MYBPC3) gene. The isolated fibroblasts were reprogrammed using non-integrated Sendai viral method to establish the patient-specific induced pluripotent stem cell (iPSC) line. The established iPSC line displayed normal morphology and karyotype, expressed pluripotency markers, and can differentiate into three germ layers in vivo.

Long QT syndrome (LQT) is an inherited primary arrhythmic disorder characterized by prolonged QT interval on the surface electrocardiogram and life-threatening arrhythmia. In this study, a skin biopsy was obtained from an LQT type 2 (LQT2) patient, who carried a nonsense mutation (c.1956C > A; p.Y652X) in the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene. The skin fibroblasts were reprogrammed by non-integrated Sendai viral method to generate a patient-specific induced pluripotent stem cell (iPSC) line. The generated iPSC line showed typical embryonic stem cell-like morphology, exhibited normal karyotype, expressed pluripotency markers, and was capable to differentiate into three germ layers.

Due to events such as natural disasters and navigation equipment failures, enormous calamity may be caused by the interruption of the navigation network which is a guarantee for the flight safety of civil aviation aircraft. The navigation network consists of the navigation stations as nodes and the routes between them as edges. Different nodes have different effects on the vulnerability of the network due to their different abilities to maintain the stability of the network topology and the normal function of the network. To quantify this difference and identify key nodes that have a greater impact on the vulnerability of the navigation network, an indicator to assess the importance of a navigation station is proposed which combines the structural importance reflected by node topology centrality and functional importance reflected by node weight. The structural importance of a node corresponds to its topology features including local dominance of the node and its global influence, and the important contribution to both adjacent and nonadjacent nodes from this node, while the functional importance is indicated by the flight flow serviced by the node during a fixed period of time. Vulnerability evaluation shows that the navigation network is more vulnerable when subject to the intentional attack of nodes with higher comprehensive node importance than an intentional attack of nodes with a larger value of indicators used in previous literature. Finally, the vulnerability of the navigation network is improved through changing the topology of the most critical node and balancing the node importance of the whole network.

Recurrent hydatidiform mole (RHM) is characterized by the occurrence of at least twice hydatidiform mole. Unlike sporadic complete hydatidiform moles (CHMs), which are androgenetic with 2 paternal chromosomes, CHMs associated with familial recurrence are genetically biparental with a maternal and a paternal chromosome. NLRP7 mutations have been reported in 55% of RHM cases. Here, we generated induced pluripotent stem cells (iPSCs) from a patent with NLRP7 gene mutation c.1261C > T by reprogramming peripheral blood mononuclear cells by non-integrated method. The resulting iPSCs carrying NLRP7 mutation, had normal karyotype, expressed pluripotency markers, and could differentiate into three germ layers in vivo.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited disease in which the right ventricular myocardium is replaced by progressive fibrous adipose tissue. ARVC is clinically characterized by right ventricular enlargement, ventricular arrhythmia, and sudden cardiac death. It eventually leads to heart failure, and thus has a significant impact on the patient's health. In this study, human dermal fibroblasts were obtained from a patient with ARVC, which were subsequently reprogrammed with a non-integrated Sendai virus to generate a patient-specific induced pluripotent stem cell (iPSC) line. The iPSC line exhibited normal karyotype and morphology, expressed pluripotency markers, and was capable of differentiating into three germ layers.

Wilson’s disease (WD) is an inherited autosomal recessive disease, which is caused by the mutation of ATP7B gene encoding copper-transporting ATPase protein. The WD patients always suffer from the excessive copper deposition in the liver and other tissues because of the dysfunction of the copper-transporting ATPase protein. In this study, we generated a patient-specific induced pluripotent stem cell (iPSC) line (ZJUi003-A), which showed normal karyotype, expressed pluripotency markers and was capable to differentiate into three germ layers.

5-Aminolevulinic acid (ALA) is a common precursor of tetrapyrroles as well as a crucial growth regulator in higher plants. ALA has been proven to be effective in improving photosynthesis and alleviating the adverse effects of various abiotic stresses in higher plants. However, little is known about the mechanism of ALA in ameliorating the photosynthesis of plant under abiotic stress. In this paper, we studied the effects of exogenous ALA on salinity-induced damages of photosynthesis in cucumber (Cucumis sativus L.) seedlings. We found that the morphology (plant height, leave area), light utilization capacity of PS II [qL, Y(II)] and gas exchange capacity (Pn, gs, Ci, and Tr) were significantly retarded under NaCl stress, but these parameters were all recovered by the foliar application of 25 mg L-1 ALA. Besides, salinity caused heme accumulation and up-regulation of gene expression of ferrochelatase (HEMH) with suppression of other genes involved in chlorophyll synthesis pathway. Exogenously application of ALA under salinity down-regulated the heme content and HEMH expression, but increased the gene expression levels of glutamyl-tRNA reductase (HEMA1), Mg-chelatase (CHLH), and protochlorophyllide oxidoreductase (POR). Moreover, the contents of intermediates involved in chlorophyll branch were increased by ALA, including protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-Proto IX, protochlorophyllide (Pchlide), and chlorophyll (Chl a and Chl b) under salt stress. Ultrastructural observation of mesophyll cell showed that the damages of photosynthetic apparatus under salinity were fixed by ALA. Collectively, the chlorophyll biosynthesis pathway was enhanced by exogenous ALA to improve the tolerance of cucumber under salinity.