# Disruption of Nuclear‐Cytoskeletal Linkage by Coil‐1a LMNA Mutations in Emery–Dreifuss Muscular Dystrophy

## TL;DR

This study shows that mutations in the LMNA gene cause nuclear shape and positioning issues in a muscular dystrophy, and that targeted treatments can reverse these effects.

## Contribution

The study identifies how Coil-1a LMNA mutations disrupt nuclear-cytoskeletal linkage and demonstrates that mutation-specific ASOs can correct these defects.

## Key findings

- EDMD-related LMNA mutations caused multilobular nuclear morphology and reduced nuclear contour ratio.
- Patient-derived MSCs showed abnormal nuclear shape and increased nuclear fragility under stress.
- Mutation-specific ASO treatment restored nuclear shape and reduced nuclear fragility and mechanosensing.

## Abstract

Emery–Dreifuss muscular dystrophy (EDMD) is a progressive genetic myopathy that mainly affects the muscles used for movement (skeletal muscles) and the heart (cardiac muscles). The disease is frequently associated with mutations in genes encoding nuclear envelope proteins, most notably LMNA, which encodes lamin A—a critical structural component of the nuclear lamina. Lamin A plays a pivotal role in maintaining nuclear architecture and mechanotransduction. In contrast to most other cell types, nuclei in healthy skeletal muscle fibres are typically localized at the periphery of the myofiber. However, muscle biopsies from EDMD patients often reveal aberrant nuclear morphology and ectopic nuclear positioning, with nuclei clustered or mislocalized toward the centre of the myofiber. Despite these characteristic nuclear abnormalities, the molecular mechanisms underlying nuclear mispositioning in EDMD remain incompletely understood. In particular, the interaction networks between EDMD‐related mutant lamin A and other nuclear and cytoskeletal components that govern nuclear positioning are poorly characterized in the current literature.

EDMD‐related lamin A variants (L35V, L38F or Y45C), which are located within the Coil‐1a domain, were overexpressed in RD cells. Mesenchymal stem cells (MSCs) were generated by redifferentiating induced pluripotent stem cells (iPSCs), which were derived from fibroblasts of an EDMD (L35P) patient. To investigate morphological and molecular abnormalities caused by mutations, immunofluorescence imaging, immunoblotting and subcellular fractionation were performed. Functional consequences of these morphological alterations were evaluated by assessing mechanotransduction signalling and cell viability.

EDMD‐related LMNA mutations (L35V, L38F, Y45C) in the Coil‐1a domain induced multilobular nuclear morphology, accompanied by a decrease in nuclear contour ratio (1.9–3.0‐fold vs. WT, p < 0.0001). Similarly, patient‐derived MSCs (L35P‐MSCs) exhibited a ~2.28‐fold decrease in contour ratio relative to healthy subject‐derived MSCs. Abnormal nuclear shape was associated with structural alterations in nuclear‐cytoskeletal proteins and nuclear positioning regulators. Mechanosensing activity, assessed by YAP1 nuclear translocation, was increased (~1.72‐fold vs. Nor‐CTRL, p < 0.01), and nuclear fragility under physical stress was elevated by ~20% (vs. Nor‐CTRL, p < 0.0001). Treatment with mutation‐specific ASOs in patient‐derived MSCs restored the contour ratio (~1.97‐fold vs. NC‐CTRL, p < 0.01), normalized nuclear‐cytoskeletal organization, reduced mechanosensing response (~1.65‐fold vs. NC‐CTRL, p < 0.01) and decreased nuclear fragility by ~11% (vs. NC‐CTRL, p < 0.0001).

Our findings indicate that nuclear morphological alterations contribute to the impaired nuclear‐cytoskeletal integrity and nuclear positioning, which are closely linked to cellular mechanics and function. Mutation‐specific ASO treatment alleviated these nuclear defects, suggesting that ASO‐based therapeutic strategies may provide a mutation‐targeted approach to correcting nuclear abnormalities in EDMD.