IPSC-derived cardiomyocytes from patients with myotonic dystrophy type 1 have abnormal ion channel functions and slower conduction velocities

Hugo Poulin,Aurélie Mercier,Isabelle Deschenes,Jack Puymirat,Mohamed Chahine,Mohammed Djemai,Valérie Pouliot,Mohamed Boutjdir

doi:10.1038/s41598-021-82007-8

Abstract

Cardiac complications such as electrical abnormalities including conduction delays and arrhythmias are the main cause of death in individuals with Myotonic Dystrophy type 1 (DM1). We developed a disease model using iPSC-derived cardiomyocytes (iPSC-CMs) from a healthy individual and two DM1 patients with different CTG repeats lengths and clinical history (DM1-1300 and DM1-300). We confirmed the presence of toxic RNA foci and mis-spliced MBNL1/2 transcripts in DM1 iPSC-CMs. In DM1-1300, we identified a switch in the cardiac sodium channel SCN5A from the adult to the neonatal isoform. The down-regulation of adult SCN5A isoforms is consistent with a shift in the sodium current activation to depolarized potentials observed in DM1-1300. L-type calcium current density was higher in iPSC-CMs from DM1-1300, which is correlated with the overexpression of the CaV1.2 transcript and proteins. Importantly, INa and ICaL dysfunctions resulted in prolonged action potentials duration, slower velocities, and decreased overshoots. Optical mapping analysis revealed a slower conduction velocity in DM1-1300 iPSC-CM monolayers. In conclusion, our data revealed two distinct ions channels perturbations in DM1 iPSC-CM from the patient with cardiac dysfunction, one affecting Na+ channels and one affecting Ca2+ channels. Both have an impact on cardiac APs and ultimately on heart conduction.

Highlights

Cardiac complications such as electrical abnormalities including conduction delays and arrhythmias are the main cause of death in individuals with Myotonic Dystrophy type 1 (DM1)
The MBNL2 transcript containing exon 7 is overexpressed in a DM1 mouse model, while the transcript containing exon 5 is overexpressed in iPSC-CMs from other DM1 p atients[29,32]
We found remarkable mis-splicing events in RNAs that code proteins directly implicated in cardiac electrical function such as: ANK3 coding for ankyrin-3 protein which interacts with NaV1.5 channels to regulate its membrane localization, CAC‐ NA1D coding for the L-type calcium channel CaV1.3 involved in automaticity of cardiomyocytes, or KCNJ16 coding for the potassium inwardly-rectifying channel Kir5.1 involved in homeostasis of membrane potential

Summary

Introduction

Cardiac complications such as electrical abnormalities including conduction delays and arrhythmias are the main cause of death in individuals with Myotonic Dystrophy type 1 (DM1). Our data revealed two distinct ions channels perturbations in DM1 iPSC-CM from the patient with cardiac dysfunction, one affecting Na+ channels and one affecting Ca2+ channels. Both have an impact on cardiac APs and on heart conduction. The pathogenic mechanism involves an RNA gain-of-function in which DMPK repeat-containing transcripts accumulate in nuclei to form nuclear foci (ribonuclear inclusion) This process results in the sequestration and alteration in the functions of RNA-binding proteins involved in regulating RNA s plicing[3]. No data are available regarding the potential role of N a+ and C a2+ channels in the electrical abnormalities seen in DM1 patients using human cardiomyocytes relevant to a specific pathology such as DM1

Methods

Results

Conclusion