Loss of function of the nuclear envelope protein LEMD2 causes DNA damage–dependent cardiomyopathy
Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, Eric N. Olson
Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, Eric N. Olson
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Research Article Cardiology

Loss of function of the nuclear envelope protein LEMD2 causes DNA damage–dependent cardiomyopathy

Abstract

Mutations in nuclear envelope proteins (NEPs) cause devastating genetic diseases, known as envelopathies, that primarily affect the heart and skeletal muscle. A mutation in the NEP LEM domain–containing protein 2 (LEMD2) causes severe cardiomyopathy in humans. However, the roles of LEMD2 in the heart and the pathological mechanisms responsible for its association with cardiac disease are unknown. We generated knockin (KI) mice carrying the human c.T38>G Lemd2 mutation, which causes a missense amino acid exchange (p.L13>R) in the LEM domain of the protein. These mice represent a preclinical model that phenocopies the human disease, as they developed severe dilated cardiomyopathy and cardiac fibrosis leading to premature death. At the cellular level, KI/KI cardiomyocytes exhibited disorganization of the transcriptionally silent heterochromatin associated with the nuclear envelope. Moreover, mice with cardiac-specific deletion of Lemd2 also died shortly after birth due to heart abnormalities. Cardiomyocytes lacking Lemd2 displayed nuclear envelope deformations and extensive DNA damage and apoptosis linked to p53 activation. Importantly, cardiomyocyte-specific Lemd2 gene therapy via adeno-associated virus rescued cardiac function in KI/KI mice. Together, our results reveal the essentiality of LEMD2 for genome stability and cardiac function and unveil its mechanistic association with human disease.

Authors

Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, Eric N. Olson

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Figure 4

CM hypertrophy and DNA damage in KI/KI mice.

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CM hypertrophy and DNA damage in KI/KI mice. (A) Representative images o...
(A) Representative images of isolated CMs from 3-month-old WT and KI/KI mice. Scale bar: 50 μm. (B) Length of binucleated CMs isolated from 3-month-old WT and KI/KI mice. n = 3–4 mice per genotype, 100–150 total cells per genotype. ****P < 0.0001, 2-tailed, unpaired t test. (C) Width of binucleated CMs isolated from 3-month-old WT and KI/KI mice. n = 3–4 mice per genotype, 100–150 total cells per genotype. ****P < 0.0001, 2-tailed, unpaired t test. (D) Area of binucleated CMs isolated from 3-month-old WT and KI/KI mice. n = 3–4 mice per genotype, 100–150 total cells per genotype. ****P < 0.0001, 2-tailed, unpaired t test. (E) GSEA plot showing enrichment of genes related to genotoxic damage in KI/KI mice. Note that the enrichment score (green line) deviates from 0 in the right part of the plot, indicating that those genes are enriched in the KI/KI mice. n = 3 mice per genotype. (F) Percentage of nuclei positive for γ-H2AX staining in WT and KI/KI mice. n = 3–4 mice per genotype, more than 100 nuclei per mouse. *P < 0.05, 2-tailed, unpaired t test. (G) Representative photographs of γ-H2AX and cTNT staining in cardiac sections from WT and KI/KI mice. Scale bar: 20 μm. Note that the white square part of the bottom left panel has been zoomed in. Original magnification, ×160. (H–J) Cardiac mRNA expression of genes related to p53 signaling and DDR in WT and KI/KI. n = 4 mice per genotype. Myc, *P < 0.05; Gadd45g, *P < 0.05; Scd1, *P < 0.05, 2-tailed, unpaired t test.