Biology subjects

Syunyaev, R.

Publications and source records attributed to Syunyaev, R..

3 recordsLinked to original sources

bioRxiv2023

Human sodium current voltage-dependence at physiological temperature measured by coupling patch-clamp experiment to a mathematical model.

Voltage-gated sodium channels are crucial to action potential propagation in excitable tissues. Voltage-clamp measurements of sodium current are very challenging and are usually performed at room temperature due to the high amplitude and fast activation of the current. In this study, we measured sodium currents voltage dependence in stem-cell-derived cardiomyocytes at physiological temperature. Although apparent activation and inactivation curves measured as the sodium current amplitude dependence on voltage step is within the range reported in previous studies, we demonstrate a systematic error in our measurements that is due to deviation of membrane potential from the command potential of the amplifier. We show how this artifact can be accounted for by the computer simulation of the patch-clamp experiment. This patch-clamp model optimization technique yields a surprising result: -11.5 mV half-activation and -87 mV half-inactivation of the sodium current. Although the half-activation is strikingly different from what was previously believed to be typical for the cardiac sodium current, we show that this estimate explains conduction velocity dependence on extracellular potassium in hyperkalemic conditions. Key pointsO_LIVoltage gated sodium currents play a crucial role in excitable tissues including neurons, cardiac and skeletal muscles. C_LIO_LIMeasurement of sodium current is challenging because of its high amplitude and rapid kinetics, especially at physiological temperature. C_LIO_LIWe have used the patch-clamp technique to measure human sodium current voltage-dependence in human induced pluripotent stem cell-derived cardiomyocytes. C_LIO_LIThe patch-clamp data was processed by optimization of the model accounting for voltage-clamp experiment artifacts, revealing a large difference between apparent parameters of sodium current and the results of the optimization. C_LIO_LIWe conclude that actual sodium current activation is extremely depolarized in comparison to previous studies. C_LIO_LIThe new sodium current model provides a better understanding of action potential propagation, we demonstrate that it explains propagation in hyperkalemic conditions. C_LI

biophysics↗

bioRxiv2021

Open-Source Low-Cost Cardiac Optical Mapping System

Fluorescent imaging with voltage- or calcium-sensitive dyes, i.e. optical mapping, is one of the indispensable modern techniques to study cardiac electrophysiology, unsurpassed by temporal and spatial resolution. High-speed CMOS cameras capable of optical registration of action potential propagation are in general very costly. We present a complete solution priced below US$ 1,000 (including camera and lens) at the moment of publication with an open-source image acquisition and processing software. We demonstrate that the iDS UI-3130CP rev.2 camera we used in this study is capable of 200x200 977 frames per second (FPS) action potential recordings from rodent hearts. The signal-to-noise-ratio of a conditioned signal was 16 {+/-} 10 for rodent hearts. A comparison with a specialized MiCAM Ultimate-L camera has shown that signal-to-noise ratio (SNR) is sufficient for accurate measurements of AP waveform, conduction velocity ({+/-} 0.04 m/s) and action potential duration ({+/-} 7ms) in mouse and rat hearts. We measured the action potential prolongation during 4-aminopyridine administration in mouse heart, showing that proposed system signal quality is adequate for drug studies.

bioengineering↗

bioRxiv2020

Human library of cardiac promoters and enhancers

Genome regulatory elements play a critical role during cardiac development and maintenance of normal physiological homeostasis, and genome-wide association studies identified a large number of SNPs associated with cardiovascular diseases localized in intergenic zones. We used cap analysis of gene expression (CAGE) to identify transcription start sites (TSS) with one nucleotide resolution that effectively maps genome regulatory elements in a representative collection of human heart tissues. Here we present a comprehensive and fully annotated CAGE atlas of human promoters and enhancers from four chambers of the non-diseased human donor hearts, including both atria and ventricles. We have identified 10,528 novel regulatory elements, where 2,750 are classified as TSS and 4,258 novel enhancers, which were validated with ChIP-seq libraries and motif enrichment analysis. We found that heart-region specific expression patterns are primarily based on the alternative promoter and specific enhancer activity. Our study significantly increased evidence of the association of regulatory elements-located variants with heart morphology and pathologies. The precise location of cardiac disease-related SNPs within the regulatory regions and their correlation with a specific cell type offers a new understanding of genetic heart diseases.

genomics↗