DOI: 10.5061/dryad.612jm640k
title: Co-expression of calcium and hERG potassium channels reduces the incidence of proarrhythmic events

description: Abstract Aims Cardiac electrical activity is extraordinarily robust.
 However, when it goes wrong it can have fatal consequences. Electrical
 activity in the heart is controlled by the carefully orchestrated activity
 of more than a dozen different ion conductances. Whilst there is
 considerable variability in cardiac ion channel expression levels between
 individuals, studies in rodents have indicated that there are modules of
 ion channels whose expression co-vary. The aim of this study was to
 investigate whether meta-analytic co-expression analysis of large-scale
 gene expression data sets could identify modules of co-expressed cardiac
 ion channel genes in human hearts that are of functional importance.
 Methods and Results Meta-analysis of 3653 public human 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 also observed in human adult heart tissue samples. In
 silico modeling suggested that co-expression of CACNA1C and KCNH2 would
 limit the variability in action potential duration seen with variations in
 expression of ion channel genes and reduce susceptibility to early
 afterdepolarizations, a surrogate marker for pro-arrhythmia. We also found
 that levels of KCNH2 and CACNA1C expression are correlated in human
 induced pluripotent stem cell derived cardiac myocytes and the levels of
 CACNA1C and KCNH2 expression were inversely correlated with the magnitude
 of changes in repolarization duration following inhibition of IKr.
 Conclusions Meta-analytic approaches of multiple independent human gene
 expression datasets can be used to identify gene modules that are
 important for regulating heart function. Specifically, we have verified
 that there is co-expression of CACNA1C and KCNH2 ion channel genes in
 human heart tissue, and in silico analyses suggest that CACNA1C-KCNH2
 co-expression increases the robustness of cardiac electrical activity.
 Translational Perspective Here, we show, using meta-analysis of multiple
 independent human gene expression datasets, that there is co-expression of
 KCNH2-CACNA1C in human heart tissue which was then confirmed in human
 cardiac myocytes derived from induced pluripotent stem cells. Both in
 silico and functional studies show that the co-expression of CACNA1C and
 KCNH2 increases the robustness of cardiac electrical signalling. Our data
 also suggest that those patients who express higher levels of CACNA1C and
 KCNH2 are likely to be more susceptible to arrhythmias when exposed to
 drugs that block IKr, the major cause of drug-induced cardiac arrhythmias.
description: Extracellular field potentials were
 recorded from hiPSC-CM monolayers using a Maestro-APEX multi-electrode
 array (MEA) system (Axion Biosystems, Atlanta, GA, USA). Briefly, cell
 monolayers were maintained for 20-30 days in STEMDiff cardiomyocte
 maintenance media (STEM CELL Technologies), on EStim classic 48 well MEA
 plates (Axion Biosystems, Atlanta, USA), prior to recording. Monolayers,
 maintained at 37°C, were paced at 1 Hz and signals digitized at 12.5 kHz
 using AxIS v2.5.1.10 software (Axion Biosystems, Atlanta, GA, USA). Field
 potential durations were measured from the peak depolarization spike to
 the peak of the repolarization wave. After 30 minutes of pacing
 equilibration, Electrograms were recorded for 5 minutes in control
 conditions, 5 minutes in the presence of cisapride (200nM), and for 5
 minutes in the presence of cisparide + nifedipine (50 nM) and measurements
 averaged over the last 10 beats of each recording period. This allowed for
 the possibility that if there was any beat to beat variation this could be
 averaged out over the ten beats. Twelve wells were plated for each line
 and all wells from which signals were recorded (n=7-12) were included in
 the analysis.
description: MEA guide.txt (description of contents of raw data files and how
 to extract the data) The data set contains 6 raw dat
 files (matlab files):            Plate1_baseline.mat            Plate1_cis.mat            Plate1_nif.mat            Plate2_baseline.mat            Plate2_cis.mat            Plate2_nif.mat