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49


A homozygous SCN5A mutation associated with atrial standstill and sudden death

Tan, Reina Bianca; Gando, Ivan; Bu, Lei; Cecchin, Frank; Coetzee, William
BACKGROUND:Atrial standstill is an arrhythmogenic condition characterized by the absence of spontaneous electrical and mechanical atrial activity or in response to stimulation. There are few reported familial cases which have been associated with SCN5A mutations co-segregating with GJA5 or RYR2 however isolated SCN5A mutations are rare. OBJECTIVE:The purpose of this study was to determine the clinical and biophysical consequence of a novel SCN5A mutation identified in a family with progressive atrial standstill and sudden death. METHODS:The family of a sporadic case of congenital atrial standstill underwent genetic screening. Human Embryonic Kidney 293 cells were transfected with wild-type (WT) or mutant SCN5A cDNAs. Biophysical properties were studied using whole-cell using patch clamp methods. RESULTS:A novel homozygous SCN5A mutation, p.V1340L was identified in the proband and her sister. The proband had complete atrial standstill whereas the sister had partial atrial standstill. Heterozygous mutations were identified in the mother, father and brother. All three had normal sinus rhythm and were asymptomatic. The mutant Nav1.5(V1340L) reduced Nav1.5 current density as well as showed a depolarizing shift in the voltage-dependent steady-state activation (WT: -35.3±1.62 mV; V1340L: -22.4±2.59 mV; P = 0.001). CONCLUSIONS:A homozygous loss-of-function SCN5A mutation likely results in atrial standstill and sudden death due to suppression of initiation of action potential.
PMID: 29781517
ISSN: 1540-8159
CID: 3129702

Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes Reveal Bradycardiac Effects Caused by Co-Administration of Sofosbuvir and Amiodarone

Yu, Yankun; Liu, Feng; He, Liuming; Ramakrishna, Seeram; Zheng, Monica; Bu, Lei; Xu, Ying
Co-administration of sofosbuvir, an anti-hepatitis C virus medication, and antiarrhythmic amiodarone causes symptomatic severe bradycardia in patients and animal models. However, in a few in vitro studies, the combination of sofosbuvir and amiodarone resulted in tachycardiac effects in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This discrepancy may be attributable to the use of immature hiPSC-CMs in the in vitro studies. To address this, we evaluated the ability of our in-house hiPSC-CMs to assess the interactions between sofosbuvir and amiodarone in vitro. We performed whole-cell patch recordings on hiPSC-CMs to examine the cardiac effect of sofosbuvir and amiodarone, alone or in combination. We found that sofosbuvir and amiodarone caused bradycardiac effects (the beating rate decreased to 75% of the vehicle control, P < 0.001) on our hiPSC-CMs when applied in combination, but they had no significant effect when applied alone. Furthermore, the bradycardiac effect was membrane potential dependent: it increased with depolarization. This raised the possibility that the bradycardiac effects in vivo may originate in nodal cells, which have a more depolarized resting membrane potential compared with ventricular cells. The bradycardiac effects of sofosbuvir plus amiodarone in vitro are consistent with the clinical phenotype and suggest that our hiPSC-CMs may serve as a useful tool in assessing cardiac safety during drug discovery and development process.
PMID: 29847141
ISSN: 1557-8127
CID: 3136942

Isoproterenol-induced action potential shortening mediated by sur1-containing KATP channels in human ips-derived atrial cardiomyocytes [Meeting Abstract]

Lader, J M; Lin, B; Yang, H; Coetzee, W A; Bu, L; Gelb, B D; Fishman, G I
Background: KAT P channels couple cellular metabolism and electrophysiology. Their molecular composition varies in different tissues and species. Rodent atrial KAT P channels have the SUR1 regulatory subunit, are activated by diazoxide and have been implicated in arrhythmogenesis in hypertension and excess beta-adrenergic tone. In contrast, human atrial KATP channels are insensitive to diazoxide and modulate APD only during extreme metabolic stress, where the SUR2A regulatory subunit is thought to be predominant. Objective: We hypothesized that changes in the human atrial action potential associated with beta-agonism are mediated by recruitment of SUR1-containing KATP channels. Methods: We used human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes where expression of a fuorescent reporter is driven by the atrial-specifc gene sarcolipin. Atrial specifcation was induced with retinoic acid. Di-4-ANBDQBS was used to perform optical action potential measurements on days 65-80 of differentiation. Excised patch clamping was used to evaluate KAT P channel density. Heterozygous ABCC8 (SUR1+/-) cells were generated using CRISPR/CAS9. Results: Optical mapping data are for APD90 with stimulation at 1.25 Hz The combination of isoproterenol (ISO, 10mu M) and rolipram (ROL, 10mu M) abbreviated APD compared to control (247.4+/-12.5ms, n=16 vs 344.2+/-22.9ms, n=22; p=0.002). This was ameliorated by 10mu M glibenclamide (312.0+/-18.9ms, n=23 vs 247.4+/-12.5ms, n=16; p=0.01). More patches from cells exposed to ISO and ROL had functional KATP channels (4/22 vs 0/24, p=0.045). Diazoxide shortened APD (267.3+/-21.7ms, n=20 vs 344.2+/-22.9ms, n=22; p=0.02). This was potentiated by prior beta-agonism (179.7+/-14.3ms, n=18 vs 267.3+/-21.7ms, n=20; p=0.002). Deletion of one ABCC8 allele ameliorated APD shortening with exposure to ISO, ROL, and diazoxide (240.9+/-18.2ms, n=14 vs 179.7+/-14.3ms, n=18; p=0.012). Functional KATP channel density after exposure to beta-agonists was reduced in SUR1+/-cells (1/40 vs 4/22, p=0.049). Conclusion: SUR1-containing KATP channels partially mediate beta-adrenergic APD shortening in human atrial cells and may represent a therapeutic target for atrial arrhythmia prevention
EMBASE:622469922
ISSN: 1556-3871
CID: 3151332

Cardiac stem cells for myocardial regeneration: promising but not ready for prime time

Lader, Joshua; Stachel, Maxine; Bu, Lei
Remarkable strides have been made in the treatment of ischemic heart disease in decades. As the initial loss of cardiomyocytes associated with myocardial infarction serves as an impetus for myocardial remodeling, the ability to replace these cells with healthy counterparts would represent an effective treatment for many forms of cardiovascular disease. The discovery of cardiac stem cells (that can differentiate into multiple lineages) highlighted the possibility for development of cell-based therapeutics to achieve this ultimate goal. Recent research features cardiac stem cell maintenance, proliferation, and differentiation, as well as direct reprogramming of various somatic cells into cardiomyocytes, all within the context of the holy grail of regeneration of the injured heart. Much work remains to be done, but the future looks bright!
PMID: 28591641
ISSN: 1879-0429
CID: 2619722

One-Step Biallelic and Scarless Correction of a beta-Thalassemia Mutation in Patient-Specific iPSCs without Drug Selection

Liu, Yali; Yang, Yi; Kang, Xiangjin; Lin, Bin; Yu, Qian; Song, Bing; Gao, Ge; Chen, Yaoyong; Sun, Xiaofang; Li, Xiaoping; Bu, Lei; Fan, Yong
Monogenic disorders (MGDs), which are caused by single gene mutations, have a serious effect on human health. Among these, beta-thalassemia (beta-thal) represents one of the most common hereditary hematological diseases caused by mutations in the human hemoglobin beta (HBB) gene. The technologies of induced pluripotent stem cells (iPSCs) and genetic correction provide insights into the treatments for MGDs, including beta-thal. However, traditional approaches for correcting mutations have a low efficiency and leave a residual footprint, which leads to some safety concerns in clinical applications. As a proof of concept, we utilized single-strand oligodeoxynucleotides (ssODNs), high-fidelity CRISPR/Cas9 nuclease, and small molecules to achieve a seamless correction of the beta-41/42 (TCTT) deletion mutation in beta thalassemia patient-specific iPSCs with remarkable efficiency. Additionally, off-target analysis and whole-exome sequencing results revealed that corrected cells exhibited a minimal mutational load and no off-target mutagenesis. When differentiated into hematopoietic progenitor cells (HPCs) and then further to erythroblasts, the genetically corrected cells expressed normal beta-globin transcripts. Our studies provide the most efficient and safe approach for the genetic correction of the beta-41/42 (TCTT) deletion in iPSCs for further potential cell therapy of beta-thal, which represents a potential therapeutic avenue for the gene correction of MGD-associated mutants in patient-specific iPSCs.
PMCID:5363452
PMID: 28325300
ISSN: 2162-2531
CID: 2494512

Multilevel analyses of SCN5A mutations in arrhythmogenic right ventricular dysplasia/cardiomyopathy suggest non-canonical mechanisms for disease pathogenesis

Te Riele, Anneline S J M; Agullo-Pascual, Esperanza; James, Cynthia A; Leo-Macias, Alejandra; Cerrone, Marina; Zhang, Mingliang; Lin, Xianming; Lin, Bin; Sobreira, Nara L; Amat-Alarcon, Nuria; Marsman, Roos F; Murray, Brittney; Tichnell, Crystal; van der Heijden, Jeroen F; Dooijes, Dennis; van Veen, Toon A B; Tandri, Harikrishna; Fowler, Steven J; Hauer, Richard N W; Tomaselli, Gordon; van den Berg, Maarten P; Taylor, Matthew R G; Brun, Francesca; Sinagra, Gianfranco; Wilde, Arthur A M; Mestroni, Luisa; Bezzina, Connie R; Calkins, Hugh; Peter van Tintelen, J; Bu, Lei; Delmar, Mario; Judge, Daniel P
AIMS: Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C) is often associated with desmosomal mutations. Recent studies suggest an interaction between the desmosome and sodium channel protein Nav1.5. We aimed to determine the prevalence and biophysical properties of mutations in SCN5A (the gene encoding Nav1.5) in ARVD/C. METHODS AND RESULTS: We performed whole-exome sequencing in six ARVD/C patients (33% male, 38.2 +/- 12.1 years) without a desmosomal mutation. We found a rare missense variant (p.Arg1898His; R1898H) in SCN5A in one patient. We generated induced pluripotent stem cell-derived cardiomyocytes (hIPSC-CMs) from the patient's peripheral blood mononuclear cells. The variant was then corrected (R1898R) using Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 technology, allowing us to study the impact of the R1898H substitution in the same cellular background. Whole-cell patch clamping revealed a 36% reduction in peak sodium current (P = 0.002); super-resolution fluorescence microscopy showed reduced abundance of NaV1.5 (P = 0.005) and N-Cadherin (P = 0.026) clusters at the intercalated disc. Subsequently, we sequenced SCN5A in an additional 281 ARVD/C patients (60% male, 34.8 +/- 13.7 years, 52% desmosomal mutation-carriers). Five (1.8%) subjects harboured a putatively pathogenic SCN5A variant (p.Tyr416Cys, p.Leu729del, p.Arg1623Ter, p.Ser1787Asn, and p.Val2016Met). SCN5A variants were associated with prolonged QRS duration (119 +/- 15 vs. 94 +/- 14 ms, P < 0.01) and all SCN5A variant carriers had major structural abnormalities on cardiac imaging. CONCLUSIONS: Almost 2% of ARVD/C patients harbour rare SCN5A variants. For one of these variants, we demonstrated reduced sodium current, Nav1.5 and N-Cadherin clusters at junctional sites. This suggests that Nav1.5 is in a functional complex with adhesion molecules, and reveals potential non-canonical mechanisms by which Nav1.5 dysfunction causes cardiomyopathy.
PMCID:5220677
PMID: 28069705
ISSN: 1755-3245
CID: 2400672

Culture in Glucose-Depleted Medium Supplemented with Fatty Acid and 3,3',5-Triiodo-l-Thyronine Facilitates Purification and Maturation of Human Pluripotent Stem Cell-Derived Cardiomyocytes

Lin, Bin; Lin, Xianming; Stachel, Maxine; Wang, Elisha; Luo, Yumei; Lader, Joshua; Sun, Xiaofang; Delmar, Mario; Bu, Lei
With recent advances in stem cell technology, it is becoming efficient to differentiate human pluripotent stem cells (hPSCs) into cardiomyocytes, which can subsequently be used for myriad purposes, ranging from interrogating mechanisms of cardiovascular disease, developing novel cellular therapeutic approaches, as well as assessing the cardiac safety profile of compounds. However, the relative inability to acquire abundant pure and mature cardiomyocytes still hinders these applications. Recently, it was reported that glucose-depleted culture medium supplemented with lactate can facilitate purification of hPSC-derived cardiomyocytes. Here, we report that fatty acid as a lactate replacement has not only a similar purification effect but also improves the electrophysiological characteristics of hPSC-derived cardiomyocytes. Glucose-depleted culture medium supplemented with fatty acid and 3,3',5-Triiodo-l-thyronine (T3) was used during enrichment of hPSC-derived cardiomyocytes. Compared to untreated control cells, the treated cardiomyocytes exhibited enhanced action potential (AP) maximum upstroke velocity (as shown by a significant increase in dV/dtmax), action potential amplitude, as well as AP duration at 50% (APD50) and 90% (APD90) of repolarization. The treated cardiomyocytes displayed higher sensitivity to isoproterenol, more organized sarcomeric structures, and lower proliferative activity. Expression profiling showed that various ion channel and cardiac-specific genes were elevated as well. Our results suggest that the use of fatty acid and T3 can facilitate purification and maturation of hPSC-derived cardiomyocytes.
PMCID:5641374
PMID: 29067001
ISSN: 1664-2392
CID: 2756622

Transcriptional regulation of E-cadherin by small activating RNA: A new double-stranded RNA

Wu, Zhiming; Li, Yan; Li, Zhiyong; Liu, Zhuowei; Qin, Zike; Li, Xiangdong; Ye, Yunlin; Bu, Lei; Lin, Bin; Wang, Zhanyu; Jia, Guojin; Chen, Gang
Recent studies have reported that chemically synthesized small activating RNA (saRNA) targeting the promoter regions of a gene can activate its expression in different cell lines. This technique can be a powerful therapeutic method for diseases caused by complete inactivation or reduced expression of specific genes. E-cadherin is a typical tumor suppressor gene. Loss of E-cadherin mediates the transition from benign lesions to invasive, metastatic cancer. In this study, several 21-nt small double-stranded RNAs (dsRNAs) targeting the promoter regions of human E-cadherin were designed and synthesized and the features of their function were investigated to study the regulatory role of dsRNA on E-cadherin expression. A new saRNA (dsEcad661) that can enhance E-cadherin expression by targeting non-coding regulatory regions in gene promoters was identified. Using dsRNA with modified base quantity and cholesterol-conjugated dsRNA, we found the antisense strand may be the guide strand of saRNA in the upregulation of E-cadherin. These findings provide several important pieces of evidence that may improve understanding of the function of saRNA and may promote its development for clinical application.
PMID: 27498620
ISSN: 1791-2423
CID: 2213512

Genetically humanized pigs exclusively expressing human insulin are generated through custom endonuclease-mediated seamless engineering [Letter]

Yang, Yi; Wang, Kepin; Wu, Han; Jin, Qin; Ruan, Degong; Ouyang, Zhen; Zhao, Bentian; Liu, Zhaoming; Zhao, Yu; Zhang, Quanjun; Fan, Nana; Liu, Qishuai; Guo, Shimei; Bu, Lei; Fan, Yong; Sun, Xiaofang; Li, Xiaoping; Lai, Liangxue
PMID: 26993040
ISSN: 1759-4685
CID: 2032242

Endothelin-1 supports clonal derivation and expansion of cardiovascular progenitors derived from human embryonic stem cells

Soh, Boon-Seng; Ng, Shi-Yan; Wu, Hao; Buac, Kristina; Park, Joo-Hye C; Lian, Xiaojun; Xu, Jiejia; Foo, Kylie S; Felldin, Ulrika; He, Xiaobing; Nichane, Massimo; Yang, Henry; Bu, Lei; Li, Ronald A; Lim, Bing; Chien, Kenneth R
Coronary arteriogenesis is a central step in cardiogenesis, requiring coordinated generation and integration of endothelial cell and vascular smooth muscle cells. At present, it is unclear whether the cell fate programme of cardiac progenitors to generate complex muscular or vascular structures is entirely cell autonomous. Here we demonstrate the intrinsic ability of vascular progenitors to develop and self-organize into cardiac tissues by clonally isolating and expanding second heart field cardiovascular progenitors using WNT3A and endothelin-1 (EDN1) human recombinant proteins. Progenitor clones undergo long-term expansion and differentiate primarily into endothelial and smooth muscle cell lineages in vitro, and contribute extensively to coronary-like vessels in vivo, forming a functional human-mouse chimeric circulatory system. Our study identifies EDN1 as a key factor towards the generation and clonal derivation of ISL1(+) vascular intermediates, and demonstrates the intrinsic cell-autonomous nature of these progenitors to differentiate and self-organize into functional vasculatures in vivo.
PMCID:4786749
PMID: 26952167
ISSN: 2041-1723
CID: 2046552