scholarly journals Tbx20 controls the expression of the KCNH2 gene and of hERG channels

2017 ◽  
Vol 114 (3) ◽  
pp. E416-E425 ◽  
Author(s):  
Ricardo Caballero ◽  
Raquel G. Utrilla ◽  
Irene Amorós ◽  
Marcos Matamoros ◽  
Marta Pérez-Hernández ◽  
...  
Keyword(s):  
Cho Cells ◽  
African Ancestry ◽  
Chinese Hamster ◽  
Induced Pluripotent Stem Cell ◽  
Delayed Rectifier ◽  
Heterozygous Mutation ◽  
Delayed Rectifier Current ◽  
Induced Pluripotent ◽  
Herg Channels ◽  
Generation Sequencing

Long QT syndrome (LQTS) exhibits great phenotype variability among family members carrying the same mutation, which can be partially attributed to genetic factors. We functionally analyzed the KCNH2 (encoding for Kv11.1 or hERG channels) and TBX20 (encoding for the transcription factor Tbx20) variants found by next-generation sequencing in two siblings with LQTS in a Spanish family of African ancestry. Affected relatives harbor a heterozygous mutation in KCNH2 that encodes for p.T152HfsX180 Kv11.1 (hERG). This peptide, by itself, failed to generate any current when transfected into Chinese hamster ovary (CHO) cells but, surprisingly, exerted “chaperone-like” effects over native hERG channels in both CHO cells and mouse atrial-derived HL-1 cells. Therefore, heterozygous transfection of native (WT) and p.T152HfsX180 hERG channels generated a current that was indistinguishable from that generated by WT channels alone. Some affected relatives also harbor the p.R311C mutation in Tbx20. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), Tbx20 enhanced human KCNH2 gene expression and hERG currents (IhERG) and shortened action-potential duration (APD). However, Tbx20 did not modify the expression or activity of any other channel involved in ventricular repolarization. Conversely, p.R311C Tbx20 did not increase KCNH2 expression in hiPSC-CMs, which led to decreased IhERG and increased APD. Our results suggest that Tbx20 controls the expression of hERG channels responsible for the rapid component of the delayed rectifier current. On the contrary, p.R311C Tbx20 specifically disables the Tbx20 protranscriptional activity over KCNH2. Therefore, TBX20 can be considered a KCNH2-modifying gene.

scholarly journals Co-expression of calcium channels and delayed rectifier potassium channels protects the heart from proarrhythmic events

2019 ◽  
Author(s):  
Sara Ballouz ◽  
Melissa M Mangala ◽  
Matthew D Perry ◽  
Stewart Heitmann ◽  
Jesse A Gillis ◽  
...  
Keyword(s):  
Ion Channel ◽  
Cardiac Electrophysiology ◽  
Meta Analysis ◽  
Surrogate Marker ◽  
Induced Pluripotent Stem Cell ◽  
Delayed Rectifier ◽  
Cardiac Electrical Activity ◽  
Channel Expression ◽  
Induced Pluripotent ◽  
Electrical Signaling

AbstractCardiac electrical activity is controlled by the carefully orchestrated activity of more than a dozen different ion conductances. Yet, there is considerable variability in cardiac ion channel expression levels both within and between subjects. In this study we tested the hypothesis that variations in ion channel expression between individuals are not random but rather there are modules of co-expressed genes and that these modules make electrical signaling in the heart more robust.Meta-analysis of 3653 public RNA-Seq datasets identified a strong correlation between expression of CACNA1C (L-type calcium current, ICaL) and KCNH2 (rapid delayed rectifier K+ current, IKr), which was verified in mRNA extracted from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). In silico modeling, validated with functional measurements in hiPSC-CM, indicates that the co-expression of CACNA1C and KCNH2 limits the variability in action potential duration and reduces susceptibility to early afterdepolarizations, a surrogate marker for pro-arrhythmia.Impact StatementCoexpressed levels of potassium and calcium ion channel genes in the heart encode more robust cardiac electrophysiology and provide insights into genetic basis of arrhythmic risk

Abstract 96: A Unique Jervell Lange-Nielsen Syndrome Mutation Modeled in Induced Pluripotent Stem Cell Derived Cardiomyocytes

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Kevin Bersell ◽  
Tao Yang ◽  
Dan Roden
Keyword(s):  
Stem Cell ◽  
Next Generation Sequencing ◽  
Pluripotent Stem Cell ◽  
Induced Pluripotent Stem Cell ◽  
Reference Sequence ◽  
Next Generation ◽  
Long Qt ◽  
Short Reads ◽  
Induced Pluripotent ◽  
Generation Sequencing

Introduction: Current screening for mutations in human disease is turning increasingly to next-generation methods that map short reads to a reference sequence. We report here an unusual variant that was undetected by next generation sequencing in a patient diagnosed with Jervell Lange-Nielsen syndrome (JLNS) and initial results in an induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model. Methods and Results: A diagnosis of JLNS was made in a middle-aged woman with congenital deafness and QT intervals as long as 800 msec. However, next-generation sequencing found only a heterozygous KCNQ1 mutation, R518X. Convinced by the clinical phenotype that a second causative variant was highly likely, we used Sanger sequencing of PCR KCNQ1 amplicons to identify a 36-basepair poly-adenine tract, encoding 12 lysines, inserted within the coding sequence at the 5’ end of exon 15. Electrophysiological studies in patient-specific IPSC-CMs revealed marked prolongation of ventricular-like action potentials (Figure). Conclusion: Long inserts of the type we identified here have not been previously reported in the long QT syndromes. We speculate that next generation-based short reads containing this variant could not be mapped to a reference sequence and thus this type of variant will be missed by next-generation analysis unless bioinformatics filters are specifically modified to include this possibility. Validation of this long QT syndrome iPSC-CM model provides a human cell based platform for drug discovery and mechanistic studies to further our understanding of disease pathogenesis.

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