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Distinct pathological signatures in human cellular models of myotonic dystrophy subtypes
Ellis Y. Kim, … , Hao F. Zhang, Elizabeth M. McNally
Ellis Y. Kim, … , Hao F. Zhang, Elizabeth M. McNally
Published February 7, 2019
Citation Information: JCI Insight. 2019;4(6):e122686. https://doi.org/10.1172/jci.insight.122686.
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Research Article Cardiology Stem cells

Distinct pathological signatures in human cellular models of myotonic dystrophy subtypes

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Abstract

Myotonic dystrophy (DM) is the most common autosomal dominant muscular dystrophy and encompasses both skeletal muscle and cardiac complications. DM is nucleotide repeat expansion disorder in which type 1 (DM1) is due to a trinucleotide repeat expansion on chromosome 19 and type 2 (DM2) arises from a tetranucleotide repeat expansion on chromosome 3. Developing representative models of DM in animals has been challenging due to instability of nucleotide repeat expansions, especially for DM2, which is characterized by nucleotide repeat expansions often greater than 5,000 copies. To investigate mechanisms of human DM, we generated cellular models of DM1 and DM2. We used regulated MyoD expression to reprogram urine-derived cells into myotubes. In this myogenic cell model, we found impaired dystrophin expression, in the presence of muscleblind-like 1 (MBNL1) foci, and aberrant splicing in DM1 but not in DM2 cells. We generated induced pluripotent stem cells (iPSC) from healthy controls and DM1 and DM2 subjects, and we differentiated these into cardiomyocytes. DM1 and DM2 cells displayed an increase in RNA foci concomitant with cellular differentiation. iPSC-derived cardiomyocytes from DM1 but not DM2 had aberrant splicing of known target genes and MBNL sequestration. High-resolution imaging revealed tight association between MBNL clusters and RNA foci in DM1. Ca2+ transients differed between DM1- and DM2 iPSC–derived cardiomyocytes, and each differed from healthy control cells. RNA-sequencing from DM1- and DM2 iPSC–derived cardiomyocytes revealed distinct misregulation of gene expression, as well as differential aberrant splicing patterns. Together, these data support that DM1 and DM2, despite some shared clinical and molecular features, have distinct pathological signatures.

Authors

Ellis Y. Kim, David Y. Barefield, Andy H. Vo, Anthony M. Gacita, Emma J. Schuster, Eugene J. Wyatt, Janel L. Davis, Biqin Dong, Cheng Sun, Patrick Page, Lisa Dellefave-Castillo, Alexis Demonbreun, Hao F. Zhang, Elizabeth M. McNally

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Figure 10

Aberrant but distinct calcium transient patterns in DM1- and DM2 iPSC–derived cardiomyocytes.

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Aberrant but distinct calcium transient patterns in DM1- and DM2 iPSC–de...
iPSC-derived cardiomyocytes were labeled with Indo-1 and paced to monitor Ca2+ shifts within the cells. (A) Representative Ca2+ transient profiles from cardiomyocytes paced at 0.25 Hz derived from healthy control, DM1, and DM2 cardiomyocytes. (B) Average Ca2+ transients (paced at 0.25 Hz) from healthy control, DM1, and DM2 cardiomyocyte cell lines. (C) Diastolic Ca2+ was reduced in DM2 cardiomyocytes. (D) Peak Ca2+ transient amplitude, measured by the difference in peak and diastolic Ca2+, was not different across groups. (E and F) The peak rate of Ca2+ release (E) and the peak rate of Ca2+ reuptake (F) were significantly different in DM2 cardiomyocytes, consistent with altered release and reuptake kinetics compared with healthy control cardiomyocytes. (G–I) Times to peak Ca2+ (G), 50% Ca2+ release (H), and 50% Ca2+ reuptake (I) differed between DM subtypes and healthy control cardiomyocyte cells. Control, 2 cell lines, 33 cell patches; DM1, 2 cell lines, 40 cell patches; DM2, 4 cell lines, 78 cell patches. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, 1-way ANOVA tested at each frequency.

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