Biophysical Society Thematic Meeting

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

, Ekta Makhija

.G.V. Shivashankar

1,2,3

MechanoBiology Institute (MBI), National University of Singapore (NUS), Singapore,

Singapore,

Department of Biological Sciences, National University of Singapore (NUS),

Singapore, Singapore,

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.