# Temporal Stretch‐Induced Nuclear Mechanosensing Coordinates Early Chromatin Accessibility and Genome Protection

## TL;DR

This study shows how mechanical stretching of cells leads to changes in the nucleus that affect chromatin and protect the genome.

## Contribution

The study reveals a coordinated nuclear mechanosensing cascade linking cytoskeletal remodeling to chromatin accessibility and genome protection.

## Key findings

- Cyclic stretching causes rapid chromatin decondensation and nuclear softening with reduced H3K9me3 levels.
- Perinuclear actin assembly and emerin translocation correlate with chromatin accessibility and DNA repair gene activation.
- Failure to coordinate these events leads to DNA damage, highlighting a biophysical mechanism for genomic integrity.

## Abstract

Cells respond to mechanical stimuli by transmitting forces to the nucleus, activating mechanosensitive molecules that alter chromatin organization and gene expression. While force‐induced changes in cell fate are recognized, the spatiotemporal dynamics of nuclear mechanosensing remain unclear. Here, nuclear responses are investigated to temporal cyclic stretching in human dermal fibroblasts, uncovering a cascade of mechanosensitive events linking cytoskeletal remodeling, chromatin accessibility, and gene expression. Brief cyclic stretch induces rapid chromatin decondensation and nuclear softening, marked by reduced H3K9me3 levels. The stretch reinforces perinuclear actin assembly from globular actins, activated by Ca2+ release from the nucleus/endoplasmic reticulum. Notably, perinuclear actin remodeling correlated with decreased H3K9me3 coordinates through emerin translocation at the nuclear envelope. Genome‐wide profiling reveals increased accessibility of loci associated with mechanotransduction and DNA damage repair. Failure to coordinate these events results in DNA damage due to impaired chromatin decondensation, demonstrating a biophysical mechanism protecting genomic integrity. These nuclear events are further evidenced in vivo using a skin tissue model, where spatial transcriptomics confirm mechanosensitive chromatin reorganization through actin‐dependent pathways in dermal fibroblasts. This study illuminates mechanisms by which temporally regulated mechanical forces elicit nuclear mechanosensing responses, linking perinuclear mechanosensitive molecules to epigenetic remodeling and downstream regulation of cell fate.

Cyclic stretching of fibroblasts triggers coordinated nuclear mechanosensing events, including calcium ion release, perinuclear actin assembly, emerin translocation, and H3K9me3 loss, increasing chromatin accessibility for specific genes related to mechanotransduction and repair.