Abstract
Ca2+ overload is one of the factors leading to Duchenne muscular dystrophy (DMD) pathogenesis. However, the molecular targets of dystrophin deficiency-dependent Ca2+ overload and the correlation between Ca2+ overload and contractile DMD phenotypes in in vitro human models remain largely elusive. In this study, we utilized DMD patient-derived induced pluripotent stem cells (iPSCs) to differentiate myotubes using doxycycline-inducible MyoD overexpression, and searched for a target molecule that mediates dystrophin deficiency-dependent Ca2+ overload using commercially available chemicals and siRNAs. We found that several store-operated Ca2+ channel (SOC) inhibitors effectively prevented Ca2+ overload and identified that STIM1–Orai1 is a molecular target of SOCs. These findings were further confirmed by demonstrating that STIM1–Orai1 inhibitors, CM4620, AnCoA4, and GSK797A, prevented Ca2+ overload in dystrophic myotubes. Finally, we evaluated CM4620, AnCoA4, and GSK7975A activities using a previously reported model recapitulating a muscle fatigue-like decline in contractile performance in DMD. All three chemicals ameliorated the decline in contractile performance, indicating that modulating STIM1–Orai1-mediated Ca2+ overload is effective in rescuing contractile phenotypes. In conclusion, SOCs are major contributors to dystrophin deficiency-dependent Ca2+ overload through STIM1–Orai1 as molecular mediators. Modulating STIM1–Orai1 activity was effective in ameliorating the decline in contractile performance in DMD.
Highlights
Duchenne muscular dystrophy (DMD) is a progressive muscular degeneration disease caused by the complete loss of dystrophin protein, eventually leading to ambulatory and respiratory deficiency, whose symptoms typically occur in early childhood [1]
We identified that storeoperated Ca2+ channel (SOC) are potent regulators of dystrophin deficiencymediated Ca2+ overload in myotubes differentiated from DMD patient-derived Induced pluripotent stem cells (iPSCs) using small-scale chemical screening. siRNA-mediated gene knockdown identified STIM1 and
Since the advantage of the standard method is that iPSCs can be differentiated into myotubes within 14 days without maturation (Figure 1A), which is beneficial for the initial study, we first confirmed whether the Ca2+ overload condition was recapitulated from dystrophic myotubes using the standard method
Summary
Duchenne muscular dystrophy (DMD) is a progressive muscular degeneration disease caused by the complete loss of dystrophin protein, eventually leading to ambulatory and respiratory deficiency, whose symptoms typically occur in early childhood [1]. DMD pathogenesis progresses with muscle contractures [8], and early DMD can be evaluated by creatine kinase (CK) leakage [9]. While a loss of dystrophin is an initial trigger of DMD, mitochondrial dysfunction contributes to DMD pathogenesis, leading to reactive oxygen species (ROS) production, ATP depletion, organelle membrane permeabilization, and the release of factors that induce necrosis and inflammation [10,11,12,13,14,15,16].
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