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Nuclear envelope rupture causes RNA polymerase loss in LMNA cardiomyopathy

ABSTRACT: Localized rupture of the nuclear envelope has been reported in various pathologies, including cancer, neurodegenerative disease, myocardial infarction, as well as dilated cardiomyopathy caused by Lamin A/C gene mutations (LMNA-DCM). Whether and how nuclear rupture contributes to disease remains unclear. Here, we report that nuclear rupture causes global transcriptional deficiency in a mouse model of LMNA-DCM. We observed that ruptured nuclei lost chromatin-bound RNA polymerase II, leading to downregulation of numerous genes essential for cardiomyocyte structure and function. Notably, over one third of ruptured nuclei resealed and regained transcription. Resealing involved the ESCRT-III membrane remodeling complex and was cardioprotective, as its blockade increased rupture frequency and accelerated cardiomyopathy. However, resealing was ineffective: resealed nuclei re-ruptured at twice the resealing rate and ten-fold faster than the de novo rupture rate. A mathematical model predicted a steady accumulation of ruptured nuclei despite ongoing resealing. Consistently, a human LMNA-mutant heart contained numerous ruptured nuclei at the time of disease presentation. These findings link nuclear rupture to organ deterioration through global transcriptional deficiency and suggested rupture repair as a critical modifier of nuclear rupture-associated conditions.

ORGANISM(S): Mus musculus

PROVIDER: GSE325163 | GEO | 2026/04/03

REPOSITORIES: GEO

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Project description:Lamin A/C proteins, encoded by the LMNA gene, are intermediate filament proteins of the nuclear lamina, and predominantly expressed in differentiated cells including cardiomyocytes. Mutations in LMNA are associated with laminopathies, congenital diseases affecting muscle and homeostasis. One of the laminopathies associated with a missense mutation (N195K) in the A-type lamins results in dilated cardiomyopathy (DCM) with arrhythmias and sudden death. However it is unknown how the mutation in this LMNA gene contributes to the mechanism of arrhythmia and sudden death. To investigate this a mouse line expressing the Lmna-N195K (LmnaN195K/N195K) was used. Mutant mice demonstrated reduced fractional shortening, LV mass, wall thickness and dilated cardiomyopathy by echocardiography at 6 weeks consistent with human DCM, and died at an early age (6-7 weeks). Comparative cDNA microarray analysis from LmnaN195K/N195K and the wild type (WT) control ventricles at 6 weeks age revealed significant alterations in the expression of ion channels, transporter proteins, caveolins and associated proteins such as MAP kinases. Transmission electron microscopy analysis showed structural alterations of the ventricular myocytes with increase in number of caveolae. Quantitative Western blot analysis confirmed reduced expression for Cavβ (2 fold) subunits of the L-type Ca2+ channel. In contrast the expression levels of Cav3 (2.5 fold) was significantly increased. To investigate the functional impact of Lmna N195K on the ICa,L, we transiently expressed either the WT LMNA+GFP, Lmna N195K+GFP or GFP (control) in isolated neonatal mouse ventricular myocytes and performed whole cell patch clamp analysis. Transient expression of Lmna N195K significantly reduced (58 %) peak ICa,L (-6.0 ± 2 pA/pF, n=9) compared to GFP control (-14 ± 2 pA/pF, n=8). Expression of WT LMNA did not affect the ICa,L (-14.2 ± 2.5 pA/pF, n=8) compared to control. Conclusion: We conclude that Lmna N195K mutation results in reduced expression of ion channels and scaffolding proteins in the left ventricle with a significant reduction in peak ICa,L in ventricular myocytes and these may contribute to the mechanism of arrhythmia and dilated cardiomyopathy. 6 samples

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Nuclear envelope rupture causes RNA polymerase loss in LMNA cardiomyopathy

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