Poster abstracts
Poster number 2 submitted by Oluwafolajimi Adesanya
Myotonic Dystrophy type I (DM1) Impairs Cardiac Bioenergetics and Disrupts Cardiac Mitochondrial Fusion-Fission Dynamics
Oluwafolajimi Adesanya (Department of Biochemistry, University of Illinois Urbana-Champaign), Pouya Nabie (Department of Biochemistry, University of Illinois Urbana-Champaign), Subhashis Natua (Department of Biochemistry, University of Illinois Urbana-Champaign), Auinash Kalsotra (Department of Biochemistry, University of Illinois Urbana-Champaign)
Abstract:
Background: DM1 is the commonest cause of adult-onset muscular dystrophy, affecting 1-in-2100 people in the U.S. DM1 is a (CTG)n trinucleotide repeat expansion disease in the 3’UTR of the DMPK gene. Once expressed, the repeat RNA form toxic hairpins, which sequester the muscle blind-like (MBNL) family of splicing factors. This inducing tissue-wide disruption of alternative splicing events, resulting in DM1 symptoms, including muscle weakness, neurological defects, and cardiomyopathy. Here, we explored the effect of DM1 on cardiac mitochondria function.
Methods: Using an inducible, cardiomyocyte-specific DM1 mouse model, we performed extracellular flux analysis on mitochondrial fractions obtained from heart tissue of control and DM1 mice. This was accompanied by quantification of ATP production, to determine OXPHOS efficiency. Further, we performed TOM20 immunofluorescence (IF) microscopy to assess the integrity of mitochondrial morphology, and gene expression studies to identify mis-splicing events involving mitochondria-related genes in heart tissues obtained from the DM1 mice and deceased human DM1 subjects.
Results: DM1 induced a multi-state increase in cardiac oxygen consumption rate (OCR) which was however accompanied by decreased ATP levels (2.83µM v. 2.45µM, p=0.0079) indicating decreased efficiency of cardiac OXPHOS. DM1 also induced a disruption in mitochondria network, with increased mitochondria fragmentation on IF microscopy. These findings correlated with an increased exclusion of Mitochondria Fission Factor (Mff) exon 6 in DM1 mice (ΔΨ: -16.8%, p=0.0069) and human heart samples (ΔΨ: -19%, p<0.01). Interestingly, this resulted in an increased expression of a shortened 29kDa MFF protein isoform in DM1 mice (Δ%29kDa: 47%, p=0.0003) and human (Δ29kDa: 21.1%, p<0.0001) heart samples.
Conclusion: DM1 impairs cardiac bioenergetic function potentially through the mis-splicing of critical genes regulating mitochondrial fusion-fission dynamics.
References:
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3. Jiang, H., Mankodi, A., Swanson, M. S., Moxley, R. T. & Thornton, C. A. Myotonic dystrophy type 1 is associated with nuclear foci of mutant RNA, sequestration of muscleblind proteins and deregulated alternative splicing in neurons. Hum. Mol. Genet. 13, 3079–3088 (2004).
4. Miller, J. W. et al. Recruitment of human muscleblind proteins to (CUG)(n) expansions associated with myotonic dystrophy. EMBO J. 19, 4439–4448 (2000).
Keywords: Myotonic Dystrophy, Mitochondria, Bioenergetics