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Published on: March 3, 2021
Functional defects in hiPSCs-derived cardiomyocytes from patients with a PLEKHM2-mutation associated with dilated
Nataly Korover1, Sharon Etzion2, Alexander Cherniak3
1Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel. natalyk@post.bgu.ac.il.
Insights
Mutations in the PLEKHM2 gene impair autophagy and cardiac function in dilated cardiomyopathy (DCM) patients. Patient-derived cardiomyocytes show defective contraction and calcium handling, contributing to heart failure.
Area of Science:
- Cardiovascular Biology
- Cellular and Molecular Medicine
- Genetics and Genomics
Background:
- Dilated cardiomyopathy (DCM) is a heart muscle disease leading to heart failure and sudden cardiac death, with poorly understood causes.
- A previous study linked recessive mutations in the autophagy regulator PLEKHM2 gene to DCM and left ventricular non-compaction (LVNC).
Purpose of the Study:
- To investigate the impact of mutated PLEKHM2 on cardiac tissue using patient-derived induced pluripotent stem cells.
- To understand how PLEKHM2 mutations affect cardiomyocyte function, gene expression, and autophagy.
Main Methods:
- Generated and characterized induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from DCM patients with PLEKHM2 mutations and healthy controls.
- Assessed gene expression of contractile and structural proteins, sarcomere organization, intracellular calcium handling, and autophagy flux in iPSC-CMs.
Main Results:
- Patient iPSC-CMs exhibited reduced expression of key contractile and calcium-handling proteins (e.g., myosin heavy chains, troponins, SERCA2, CASQ2).
- Sarcomeres were less aligned, and cells showed slower beating, lower calcium amplitude, and abnormal calcium transient kinetics.
- Autophagy flux was impaired in patient iPSC-CMs, evidenced by reduced autophagosome accumulation upon treatment.
Conclusions:
- Mutated PLEKHM2 impairs cardiomyocyte function by affecting gene expression related to contraction and calcium signaling.
- Defective autophagy and impaired cardiac contraction in patient iPSC-CMs may contribute to the pathophysiology of DCM.
- These findings highlight the role of PLEKHM2 in cardiac health and suggest potential therapeutic targets for DCM.
Abstract:
Dilated cardiomyopathy (DCM) is a primary myocardial disease, leading to heart failure and excessive risk of sudden cardiac death with rather poorly understood pathophysiology. In 2015, Parvari's group identified a recessive mutation in the autophagy regulator, PLEKHM2 gene, in a family with severe recessive DCM and left ventricular non-compaction (LVNC). Fibroblasts isolated from these patients exhibited abnormal subcellular distribution of endosomes, Golgi apparatus, lysosomes and had impaired autophagy flux. To better understand the effect of mutated PLEKHM2 on cardiac tissue, we generated and characterized induced pluripotent stem cells-derived cardiomyocytes (iPSC-CMs) from two patients and a healthy control from the same family. The patient iPSC-CMs showed low expression levels of genes encoding for contractile functional proteins (α and β-myosin heavy chains and 2v and 2a-myosin light chains), structural proteins integral to heart contraction (Troponin C, T and I) and proteins participating in Ca2+ pumping action (SERCA2 and Calsequestrin 2) compared to their levels in control iPSC-derived CMs. Furthermore, the sarcomeres of the patient iPSC-CMs were less oriented and aligned compared to control cells and generated slowly beating foci with lower intracellular calcium amplitude and abnormal calcium transient kinetics, measured by IonOptix system and MuscleMotion software. Autophagy in patient's iPSC-CMs was impaired as determined from a decrease in the accumulation of autophagosomes in response to chloroquine and rapamycin treatment, compared to control iPSC-CMs. Impairment in autophagy together with the deficiency in the expression of NKX2.5, MHC, MLC, Troponins and CASQ2 genes, which are related to contraction-relaxation coupling and intracellular Ca2+ signaling, may contribute to the defective function of the patient CMs and possibly affect cell maturation and cardiac failure with time.
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