Cardiomyocytes generated from CPVTD307H patients are arrhythmogenic in response to β-adrenergic stimulation.
Bottom Line: Our study focuses on the autosomal recessive form of the disease caused by the missense mutation D307H in the cardiac calsequestrin gene, CASQ2.Next, iPSCs were differentiated to cardiomyocytes (iPSCs-CMs), which expressed the mutant CASQ2 protein.Electron microscopy analysis revealed that compared with control iPSCs-CMs, CPVT iPSCs-CMs displayed a more immature phenotype with less organized myofibrils, enlarged sarcoplasmic reticulum cisternae and reduced number of caveolae.
Affiliation: The Sohnis Family Stem Cells Center, Haifa, Israel.Show MeSH
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Mentions: The adrenergically mediated arrhythmogenic features of CPVT iPSCs-CMs were demonstrated by exposing cardiomyocytes to isoproterenol. As depicted in Figure 6A–C, while in control cardiomyocytes isoproterenol increased contraction amplitude (see details below) but was not arrhythmogenic, in CPVT cardiomyocytes isoproterenol caused the generation of after-contractions (which are the mechanical equivalent of DADs) and triggered activity. These arrhythmias were associated with elevation in the resting tension level (marked by the double-headed arrows in Fig. 6B and C), probably resulting from a prominent diastolic [Ca2+]i rise as demonstrated in Figure 6F. Because in some of the CPVT preparations, pacing alone caused marked elevation in diastolic [Ca2+]i followed by after-contractions and cessation of contractions, the response to isoproterenol was not tested in these experiments. Overall we performed 11 control experiments in none of which after-contractions or diastolic [Ca2+]i rise were generated by isoproterenol. In the CPVT series we performed 15 experiments in two CPVT iPSCs clones. In five experiments (33%) pacing alone caused after-contractions in the absence of isoproterenol, in seven experiments (47%) isoproterenol generated after-contractions and triggered contractions, and in three experiments (20%) after-contractions were not generated either by pacing or isoproterenol.
Affiliation: The Sohnis Family Stem Cells Center, Haifa, Israel.