Micromechanical properties of isolated nuclei and nuclear components

Deformation of the nucleus has been suggested to be a significant step in mechanotransduction. Additionally, many established and emerging technologies exploit the ability to isolate, transfer and physically manipulate nuclei. This study focuses on providing a fundamental understanding of the mechanical properties of isolated nuclei and nuclear components. Micropipette aspiration allows for relations of stresses to strains and was used to determine mechanical properties of nuclei isolated from Xenopus laevis oocytes. Preliminary results suggest that nuclear membranes can exhibit extensional strains of up to 100%. The elastic modulus of these nuclei appear to be an order of magnitude higher than previously studied cellular membrane systems, such as erythrocytes, suggesting a rigid underlying lamin network. Micropipette aspiration combined with fluorescence labeling allows for the visualization of individual components during deformation. Fluorescent labeling of DNA within isolated nuclei suggests that the cohesive forces are stronger than the forces holding the chromatin to the nuclear membrane. The deformation of the chromatin within the nucleus does not have any significant effect on the mechanical properties of the nuclear membrane. Fluorescent antibody labeling of nuclear pores of mammalian nuclei suggests that there is significant attachment of the pores to the underlying lamina network.