Readthrough-Promoting Drugs Gentamicin and PTC124 Fail to Rescue Na _v 1.5 Function of Human-Induced Pluripotent Stem Cell–Derived Cardiomyocytes Carrying Nonsense Mutations in the Sodium Channel Gene SCN5A

Abstract

Background-Several compounds have been reported to induce translational readthrough of premature stop codons resulting in the production of full-length protein by interfering with ribosomal proofreading. Here we examined the effect of 2 of these compounds, gentamicin and PTC124, in human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes bearing nonsense mutations in the sodium channel gene SCN5A, which are associated with conduction disease and potential lethal arrhythmias. Methods and Results-We generated hiPSC from 2 patients carrying the mutations R1638X and W156X. hiPSC-derived cardiomyocytes from both patients recapitulated the expected electrophysiological phenotype, as evidenced by reduced Na + currents and action potential upstroke velocities compared with hiPSC-derived cardiomyocytes from 2 unrelated control individuals. While we were able to confirm the readthrough efficacy of the 2 drugs in Human Embryonic Kidney 293 cells, we did not observe rescue of the electrophysiological phenotype in hiPSC-derived cardiomyocytes from the patients. Conclusions-We conclude that these drugs are unlikely to present an effective treatment for patients carrying the loss-of-function SCN5A gene mutations examined in this study. (Circ Arrhythm Electrophysiol. 2016;9:e004227.

Comparative Analysis of Genetic Variations in the Nav1.5 Sodium Channel Subunits that Underlie Brugada Syndrome Using Patient-Specific iPSC-CMs

“…Compared to the use of I Na as a single parameter, action potential can re ect the impact of variants on the entire cellular electrophysiology, including the compensation of other ion channels to the sodium current impairment. Our study illuminated the abnormality in AP pro les of BrS-CMs, which is in line with previous studies (25). The BrS-CMs also presented a prolonged AP duration, which seems to be an overlapping feature of long QT type 3 and BrS (26) (27).…”

Ajmaline blocks I Na and I Kr without eliciting differences between Brugada syndrome patient and control human pluripotent stem cell-derived cardiac clusters

“…The abnormal cellular behaviour was corrected by gene editing of the mutation. In a second recent study, Kosmidis and colleagues studied two nonsense mutations in SCN5A and also found reduced sodium currents and slower AP upstroke velocity ( Kosmidis et al, 2016 ). Interestingly, readthrough therapy restored function to the channels in HEK293 cells but not hiPSC-CMs.…”

Modeling Treatment Response for Lamin A/C Related Dilated Cardiomyopathy in Human Induced Pluripotent Stem Cells

“…Nonetheless, in a recent study using hiPSC-derived cardiomyocytes from 2 patients who harbored nonsense mutations in the sodium channel gene SCN5A, R1638X and W156X, although the premature stop codon sequences in both mutations were the most optimum sequence for PTC124, UGA, PTC124 and gentamicin, another premature stop codon read-through agent, failed to restore sodium current I Na . 34 Although the sodium channel protein level was not quantified to document the restored protein translation, other downstream mechanisms such as a trafficking defect might have been responsible. This reinforces the need for precision medicine.…”