Cells (Sep 2022)

<i>ACTN2</i> Mutant Causes Proteopathy in Human iPSC-Derived Cardiomyocytes

  • Antonia T. L. Zech,
  • Maksymilian Prondzynski,
  • Sonia R. Singh,
  • Niels Pietsch,
  • Ellen Orthey,
  • Erda Alizoti,
  • Josefine Busch,
  • Alexandra Madsen,
  • Charlotta S. Behrens,
  • Moritz Meyer-Jens,
  • Giulia Mearini,
  • Marc D. Lemoine,
  • Elisabeth Krämer,
  • Diogo Mosqueira,
  • Sanamjeet Virdi,
  • Daniela Indenbirken,
  • Maren Depke,
  • Manuela Gesell Salazar,
  • Uwe Völker,
  • Ingke Braren,
  • William T. Pu,
  • Thomas Eschenhagen,
  • Elke Hammer,
  • Saskia Schlossarek,
  • Lucie Carrier

DOI
https://doi.org/10.3390/cells11172745
Journal volume & issue
Vol. 11, no. 17
p. 2745

Abstract

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Genetic variants in α-actinin-2 (ACTN2) are associated with several forms of (cardio)myopathy. We previously reported a heterozygous missense (c.740C>T) ACTN2 gene variant, associated with hypertrophic cardiomyopathy, and characterized by an electro-mechanical phenotype in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Here, we created with CRISPR/Cas9 genetic tools two heterozygous functional knock-out hiPSC lines with a second wild-type (ACTN2wt) and missense ACTN2 (ACTN2mut) allele, respectively. We evaluated their impact on cardiomyocyte structure and function, using a combination of different technologies, including immunofluorescence and live cell imaging, RNA-seq, and mass spectrometry. This study showed that ACTN2mut presents a higher percentage of multinucleation, protein aggregation, hypertrophy, myofibrillar disarray, and activation of both the ubiquitin-proteasome system and the autophagy-lysosomal pathway as compared to ACTN2wt in 2D-cultured hiPSC-CMs. Furthermore, the expression of ACTN2mut was associated with a marked reduction of sarcomere-associated protein levels in 2D-cultured hiPSC-CMs and force impairment in engineered heart tissues. In conclusion, our study highlights the activation of proteolytic systems in ACTN2mut hiPSC-CMs likely to cope with ACTN2 aggregation and therefore directs towards proteopathy as an additional cellular pathology caused by this ACTN2 variant, which may contribute to human ACTN2-associated cardiomyopathies.

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