Abstract 15961: Syncytial Model of Type 2 Long QT Syndrome Derived From Human iPS Cells Can Be Paced and Responds to Ikr Block and Activation

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Renjun Zhu ◽  
Rosy Joshi-Mukherjee ◽  
Adriana Blazeski ◽  
Kenneth R Boheler ◽  
Gordon F Tomaselli ◽  
...  
Keyword(s):  
Drug Effects ◽  
Ips Cells ◽  
Herg Channel ◽  
Long Qt ◽  
Human Ips Cells ◽  
Cycle Lengths ◽  
Channel Mutation ◽  
Diastolic Potential

Type 2 long QT (LQT2) syndrome is a cardiac disorder associated with hERG channel mutation that may lead to tachyarrhythmia and sudden death. We developed a syncytial model of cardiomyocytes (CMs) differentiated from iPS cells derived from an LQT2 patient harboring an A422T mutation. The A422T mutation has been shown to cause a marked decrease in IKr current mainly due to a trafficking defect in the hERG channel. Immunostaining of cTnI revealed that CMs were isotropically distributed with well-formed sarcomeres. Both wild type (WT) and LQT2 monolayers were stable in culture for at least 60 days with spontaneous activity, and could be paced at cycle lengths (CL) from 2000 down to 300 ms. After staining the monolayers with di-4-ANEPPS, optical mapping showed that all monolayers formed a functional syncytium that supported propagating action potentials. LQT2 monolayers had longer APD80s than WT monolayers (332±43 ms, n=6, vs. 267±46 ms, n=18, mean±SD, CL = 700 ms, p<0.005), showing the delayed repolarization expected of the LQT2 phenotype. Reentrant spiral waves were observed in LQT2 (n=2), but not WT monolayers. Application of 0.2μM E-4031 (IKr blocker) slowed repolarization and prolonged APD80 in both WT and LQT2 monolayers, and slowed conduction velocity in WT monolayers (4.7±1.0 cm/s, n=6 vs. 10.4±1.4 cm/s, n=11 control, CL = 1000 ms). The slowing effect may reflect a role of IKr in setting the maximum diastolic potential in these CMs where IK1 is weakly expressed, as has been recently suggested. Application of 10μM ML-T531 (IKr activator) shortened APD80 in LQT2 monolayers (313±36 ms vs. 162±19 ms, n=4, p<0.0001), showing successful reversal of the LQT phenotype. ML-T531 also shortened APD80 in WT monolayers (202±43 ms vs. 154±26 ms, n=4, p<0.04). These results indicate that syncytial models of heritable cardiac disease are feasible and may be useful for studying drug effects that affect electrophysiology and arrhythmogenesis.

scholarly journals Model for long QT syndrome type 2 using human iPS cells demonstrates arrhythmogenic characteristics in cell culture

2011 ◽  
Vol 5 (2) ◽  
pp. 220-230 ◽  
Author(s):  
A. L. Lahti ◽  
V. J. Kujala ◽  
H. Chapman ◽  
A.-P. Koivisto ◽  
M. Pekkanen-Mattila ◽  
...  
Keyword(s):  
Cell Culture ◽  
Long Qt Syndrome ◽  
Ips Cells ◽  
Syndrome Type ◽  
Long Qt ◽  
Human Ips Cells ◽  
Qt Syndrome

scholarly journals NAMPT/SIRT2-mediated inhibition of the p53-p21 signaling pathway is indispensable for maintenance and hematopoietic differentiation of human iPS cells

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yun Xu ◽  
Masoud Nasri ◽  
Benjamin Dannenmann ◽  
Perihan Mir ◽  
Azadeh Zahabi ◽  
...  
Keyword(s):  
Embryoid Body ◽  
P53 Protein ◽  
Ips Cells ◽  
Hematopoietic Differentiation ◽  
Cellular Functions ◽  
Nicotinamide Phosphoribosyltransferase ◽  
Signaling Axis ◽  
Human Ips Cells ◽  
Induced Pluripotent

Abstract Background Nicotinamide phosphoribosyltransferase (NAMPT) regulates cellular functions through the protein deacetylation activity of nicotinamide adenine dinucleotide (NAD+)-dependent sirtuins (SIRTs). SIRTs regulate functions of histones and none-histone proteins. The role of NAMPT/SIRT pathway in the regulation of maintenance and differentiation of human-induced pluripotent stem (iPS) cells is not fully elucidated. Methods We evaluated the effects of specific inhibitors of NAMPT or SIRT2 on the pluripotency, proliferation, survival, and hematopoietic differentiation of human iPS cells. We also studied the molecular mechanism downstream of NAMPT/SIRTs in iPS cells. Results We demonstrated that NAMPT is indispensable for the maintenance, survival, and hematopoietic differentiation of iPS cells. We found that inhibition of NAMPT or SIRT2 in iPS cells induces p53 protein by promoting its lysine acetylation. This leads to activation of the p53 target, p21, with subsequent cell cycle arrest and induction of apoptosis in iPS cells. NAMPT and SIRT2 inhibition also affect hematopoietic differentiation of iPS cells in an embryoid body (EB)-based cell culture system. Conclusions Our data demonstrate the essential role of the NAMPT/SIRT2/p53/p21 signaling axis in the maintenance and hematopoietic differentiation of iPS cells.

scholarly journals Potential role of the membrane in hERG channel functioning and drug-induced long QT syndrome

2010 ◽  
Vol 1798 (9) ◽  
pp. 1651-1662 ◽  
Author(s):  
Étienne Chartrand ◽  
Alexandre A. Arnold ◽  
Andrée Gravel ◽  
Sarah Jenna ◽  
Isabelle Marcotte
Keyword(s):  
Long Qt Syndrome ◽  
Potential Role ◽  
Herg Channel ◽  
Long Qt ◽  
Drug Induced ◽  
Qt Syndrome

scholarly journals Alternating Cycle Lengths Increases Dispersion of Action Potential Durations (APD) in Transgenic Rabbit Model of Long QT Syndrome Type 2

2012 ◽  
Vol 102 (3) ◽  
pp. 539a-540a
Author(s):  
Tae Yun Kim ◽  
Paul Jeng ◽  
Chantel Taylor ◽  
JungMin Hwang ◽  
Xuwen Peng ◽  
...  
Keyword(s):  
Action Potential ◽  
Long Qt Syndrome ◽  
Rabbit Model ◽  
Syndrome Type ◽  
Long Qt ◽  
Transgenic Rabbit ◽  
Cycle Lengths ◽  
Qt Syndrome

scholarly journals Short-Long Heart Rate Variation Increases Dispersion of Action Potential Duration in Long QT Type 2 Transgenic Rabbit Model

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Tae Yun Kim ◽  
Paul Jeng ◽  
JungMin Hwang ◽  
Zachary Pfeiffer ◽  
Divyang Patel ◽  
...  
Keyword(s):  
Short Term Memory ◽  
Rabbit Model ◽  
Polymorphic Ventricular Tachycardia ◽  
Rate Variation ◽  
Short Term ◽  
Long Qt ◽  
Term Memory ◽  
Transgenic Rabbit ◽  
Cycle Lengths

Abstract The initiation of polymorphic ventricular tachycardia in long QT syndrome type 2 (LQT2) has been associated with a characteristic ECG pattern of short-long RR intervals. We hypothesize that this characteristic pattern increases APD dispersion in LQT2, thereby promoting arrhythmia. We investigated APD dispersion and its dependence on two previous cycle lengths (CLs) in transgenic rabbit models of LQT2, LQT1, and their littermate controls (LMC) using random stimulation protocols. The results show that the short-long RR pattern was associated with a larger APD dispersion in LQT2 but not in LQT1 rabbits. The multivariate analyses of APD as a function of two previous CLs (APDn = C + α1CLn−1 + α2CLn−2) showed that α1 (APD restitution slope) is largest and heterogeneous in LQT2 but uniform in LQT1, enhancing APD dispersion under long CLn−1 in LQT2. The α2 (short-term memory) was negative in LQT2 while positive in LQT1, and the spatial pattern of α1 was inversely correlated to α2 in LQT2, which explains why a short-long combination causes a larger APD dispersion in LQT2 but not in LQT1 rabbits. In conclusion, short-long RR pattern increased APD dispersion only in LQT2 rabbits through heterogeneous APD restitution and the short-term memory, underscoring the genotype-specific triggering of arrhythmias in LQT syndrome.

The role of in vitro phenotypes for clinical risk stratification of sudden death in Long QT Syndrome Type 2

2015 ◽  
Vol 24 ◽  
pp. S232-S233
Author(s):  
K. Phan ◽  
C. Ng ◽  
S. McNitt ◽  
A. Moss ◽  
W. Zareba ◽  
...  
Keyword(s):  
Sudden Death ◽  
Risk Stratification ◽  
Long Qt Syndrome ◽  
Syndrome Type ◽  
Long Qt ◽  
Clinical Risk ◽  
Qt Syndrome

scholarly journals NAMPT/SIRT2–mediated inhibition of the p53-p21 signaling pathway is indispensable for maintenance and hematopoietic differentiation of human iPS cells

2020 ◽  
Author(s):  
Julia Skokowa ◽  
Yun Xu ◽  
Masoud Nasri ◽  
Benjamin Dannenmann ◽  
Perihan Mir ◽  
...  
Keyword(s):  
Embryoid Body ◽  
P53 Protein ◽  
Ips Cells ◽  
Hematopoietic Differentiation ◽  
Cellular Functions ◽  
Nicotinamide Phosphoribosyltransferase ◽  
Signaling Axis ◽  
Human Ips Cells ◽  
Induced Pluripotent

Abstract Background: Nicotinamide phosphoribosyltransferase (NAMPT) regulates cellular functions through the protein deacetylation activity of nicotinamide adenine dinucleotide (NAD+)-dependent sirtuins (SIRTs). SIRTs regulate functions of histones and none-histone proteins. The role of NAMPT/SIRTs pathway in the regulation of maintenance and differentiation of human induced pluripotent stem (iPS) cells is not fully elucidated. Methods: We evaluated the effects of specific inhibitors of NAMPT-, or SIRT2 on the pluripotency, proliferation, survival and hematopoietic differentiation of human iPS cells. We also studied the molecular mechanism downstream of NAMPT/SIRTs in iPS cells. Results: We demonstrated that NAMPT is indispensable for the maintenance, survival and hematopoietic differentiation of induced pluripotent stem (iPS) cells. We found that inhibition of NAMPT or SIRT2 in iPS cells induces p53 protein by promoting its lysine acetylation. This leads to activation of the p53 target, p21, with subsequent cell cycle arrest and induction of apoptosis in iPS cells. NAMPT and SIRT2 inhibition also affects hematopoietic differentiation of iPS cells in an embryoid body (EB)-based cell culture system. Conclusions: Our data demonstrate the essential role of the NAMPT/SIRT2/p53/p21 signaling axis in the maintenance and hematopoietic differentiation of iPS cells.

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