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Deleterious assembly of the lamin A/C mutant p.S143P causes ER stress in familial dilated cardiomyopathy

ABSTRACT: Mutation of the LMNA gene, encoding nuclear lamin A and lamin C (hereafter lamin A/C), is a common cause of familial dilated cardiomyopathy (DCM). Among Finnish DCM patients, the founder mutation c.427T>C (p.S143P) is the most frequently reported genetic variant. Here, we show that p.S143P lamin A/C is more nucleoplasmic and soluble than wild-type lamin A/C and accumulates into large intranuclear aggregates in a fraction of cultured patient fibroblasts as well as in cells ectopically expressing either FLAG- or GFP-tagged p.S143P lamin A. In fluorescence loss in photobleaching (FLIP) experiments, non-aggregated EGFP-tagged p.S143P lamin A is significantly more dynamic. In in vitro association studies, p.S143P lamin A failed to form appropriate filament structures but instead assembled into disorganized aggregates similar to those observed in patient cell nuclei. A whole genome expression analysis revealed an elevated unfolded protein response (UPR) in cells expressing p.S143P lamin A/C. Additional endoplasmic reticulum (ER) stress induced by tunicamycin reduced the viability of mutant lamin expressing cells further. In summary, p.S143P lamin A/C affects normal lamina structure and influences the cellular stress response, homeostasis and viability.

ORGANISM(S): Homo sapiens

PROVIDER: GSE82290 | GEO | 2016/06/10

SECONDARY ACCESSION(S): PRJNA324670

REPOSITORIES: GEO

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Project description:Background: Lamins A/C (encoded by the LMNA gene) can lead to dilated cardiomyopathy (DCM). Objectives: This study sought to undertake proteomic analysis of myocardial tissue to explore the postgenomic phenotype of end-stage lamin heart disease. Methods: Consecutive patients with end-stage lamin heart disease (LMNA-group, n=7) and ischaemic DCM (ICM-group, n=7) undergoing heart transplantation were enrolled. Samples were obtained from left atrium(LA), left ventricle(LV), right atrium(RA), right ventricle(RV) and interventricular septum(IVS). Liquid chromatography combined with mass-spectrometry was used for protein quantification. We compared protein concentrations in cardiac samples between LMNA and ICM groups. Proteins were considered differentially abundant if the quantitative difference was 1.5-fold and corrected p-value <0.05 at a false discovery rate of 0.01. Gene ontology(GO) enrichment analysis explored the related biological processes. Results: 4,247 proteins were identified in LMNA and ICM samples, of which 633 were differentially abundant in LA, 39 in LV, 181 in RA, 52 in RV, and 85 in IVS. Abundance of lamin A/C was reduced but lamin B (LMNB) increased in LMNA LA/RA tissue compared to ICM, but not in LV/RV. Transthyretin was more abundant in the LV/RV of LMNA compared to ICM while sarcomeric proteins such as titin and cardiac myosin heavy chain were generally reduced in RA/LA of LMNA. Protein expression profiling and GO enrichment analysis revealed sarcopenia, extracellular matrix(ECM) remodeling, deficient myocardial energetics, redox imbalances, and abnormal calcium handling in LMNA samples. Conclusion: Lamin heart disease is a biventricular and biatrial disease, characterized by sarcopenia, aberrant metabolism, and ECM remodeling. LMNB and transthyretin were unexpectedly abundant in the atria and ventricles respectively of patients with end-stage lamin heart disease potentially hinting to the possibility of compensatory responses.

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Deleterious assembly of the lamin A/C mutant p.S143P causes ER stress in familial dilated cardiomyopathy

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