Biophysical Society Thematic Meeting | Singapore

Mechanobiology of Disease

Poster Abstracts

29-POS Board 29 Cell Mechanics Regulate Nuclear and Chromatin Dynamics by Altering the Cytoskeletal and Nucleoskeletal Organization. Doorgesh S. Jokhun 1 , Ekta Makhija 1 .G.V. Shivashankar 1,2,3 , 1 MechanoBiology Institute (MBI), National University of Singapore (NUS), Singapore, Singapore, 2 Department of Biological Sciences, National University of Singapore (NUS), Singapore, Singapore, 3 FIRC Institute for Molecular Oncology (IFOM), Milan, Italy. Conditions like cancers, progeria and fibrosis are often accompanied by changes in the physical landscape of the affected tissue. At the single cell level, this alteration in physical cues modulate the cytoskeletal organization and thus the force being transmitted to the nuclear lamina and chromatin. While the role of these active forces in modulating the prestressed nuclear morphology has been well studied, their effect on nuclear and chromatin dynamics is less understood. To address this, we used distinct fibronectin micropatterns as a means of defining the mechanical landscape of single cells and seeded NIH3T3 fibroblasts transfected with H2B- GFP and TRF1-DsRed to visualize the nuclear and chromatin (telomeric) dynamics respectively. We observed that cells plated on small isotropic patterns lack apical actin stress fibers and have more plastic nuclei compared to cells on large polarized substrates. We showed that this enhanced nuclear plasticity can be attributed to active forces from short actin-myosin-formin structures and a transcriptional downregulation of laminA/C levels in the small isotropic condition. We also showed that the changes in cytoskeletal and nucleoskeletal architecture further regulate chromatin dynamics, as measured by the 3D spatiotemporal tracking of telomeres. In conditions which curb the formation of apical actin stress fibers and the expression of Lamin A/C, the telomeres explore larger volumes, move faster, more independently and more freely. Taken together, our results show that active cytoskeletal forces and rigidity from the lamin A/C nucleoskeleton, as defined by the physical state of the tissue, are important regulators of nuclear and chromatin plasticity in living cells, providing a possible mechanical route for genome regulation.

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