Journal: Advanced Science

Article Title: Temporal Stretch‐Induced Nuclear Mechanosensing Coordinates Early Chromatin Accessibility and Genome Protection

doi: 10.1002/advs.202510554

Figure Lengend Snippet: Cyclic stretch disrupts perinuclear heterochromatin and reduces nuclear stiffness. a) Schematic illustrating the DNA adenine methyltransferase identification (DamID) technique for visualizing lamina‐associated domains (LADs). The Dam‐Lamin B1 fusion protein introduces N 6 ‐methyladenine (m 6 A) marks at GATC motifs in genomic regions near the nuclear lamina. These methylation marks are specifically recognized by the m 6 A‐Tracer and could be detected by a GFP‐tagged DNA‐binding protein to visualize lamina‐associated domains. b) Representative confocal images of cells co‐transfected with m 6 A‐Tracer and Dam‐LMNB1, showing a reduction in LAD‐associated heterochromatin upon cyclic stretch. (Scale bar: 5 µm) c) Fluorescence intensity profiles of the m 6 A‐Tracer and DAPI along the nuclear axis. d) Representative transmission electron microscopy (TEM) images of nuclear periphery with (ST(+)) and without stretch (ST(−)). e) Quantification of heterochromatin area at the nuclear periphery based on TEM images, corresponding to LAD‐associated regions, with a schematic illustrating the measurement area. Heterochromatin loss was consistently observed across all analyzed cells. Quantification was performed within a 0.5 µm band from the nuclear edge, covering the entire nuclear periphery of each cell. Stretch‐induced loss of peripheral heterochromatin and increased nuclear wrinkling. (Scale bar: 2 µm; n = 15). f) Schematic depiction of the fluorescence resonance energy transfer (FRET)‐based Nesprin‐2 tension sensor (TS), a critical element of the LINC complex. g,h) FRET analysis shows increased FRET efficiency in stretched cells, indicating reduced membrane tension. Scale bar: 5 µm. ( n = 9). i,j) Atomic force microscopy (AFM) force indentation experiments reveal softening of the nucleus in the ST(+) group compared to ST(−). ( n = 7). Statistical significance is denoted as * p < 0.5 and ** p < 0.01, determined by Student's t ‐test. All experiments were conducted right after 15 min of stretching.

Article Snippet: To assess cell membrane tension, the plasmid pcDNA Nesprin tension sensor (TS, Addgene, #68127) was employed, harboring TFP, an elastin linker, and Venus.

Techniques: Methylation, Binding Assay, Transfection, Fluorescence, Transmission Assay, Electron Microscopy, Förster Resonance Energy Transfer, Membrane, Microscopy