Nanomechanical properties of enucleated cells: contribution of the nucleus to the passive cell mechanics
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Journal of Nanobiotechnology Open Access
RESEARCH
Nanomechanical properties of enucleated cells: contribution of the nucleus to the passive cell mechanics Yuri M. Efremov1* , Svetlana L. Kotova1,2, Anastasia A. Akovantseva3 and Peter S. Timashev1,2,3,4
Abstract Background: The nucleus, besides its functions in the gene maintenance and regulation, plays a significant role in the cell mechanosensitivity and mechanotransduction. It is the largest cellular organelle that is often considered as the stiffest cell part as well. Interestingly, the previous studies have revealed that the nucleus might be dispensable for some of the cell properties, like polarization and 1D and 2D migration. Here, we studied how the nanomechanical properties of cells, as measured using nanomechanical mapping by atomic force microscopy (AFM), were affected by the removal of the nucleus. Methods: The mass enucleation procedure was employed to obtain cytoplasts (enucleated cells) and nucleoplasts (nuclei surrounded by plasma membrane) of two cell lines, REF52 fibroblasts and HT1080 fibrosarcoma cells. Highresolution viscoelastic mapping by AFM was performed to compare the mechanical properties of normal cells, cytoplasts, and nucleoplast. The absence or presence of the nucleus was confirmed with fluorescence microscopy, and the actin cytoskeleton structure was assessed with confocal microscopy. Results: Surprisingly, we did not find the softening of cytoplasts relative to normal cells, and even some degree of stiffening was discovered. Nucleoplasts, as well as the nuclei isolated from cells using a detergent, were substantially softer than both the cytoplasts and normal cells. Conclusions: The cell can maintain its mechanical properties without the nucleus. Together, the obtained data indicate the dominating role of the actomyosin cytoskeleton over the nucleus in the cell mechanics at small deformations inflicted by AFM. Keywords: Nucleus, Enucleated cells, Cytoplasts, AFM, Cell mechanical properties, Viscoelasticity Introduction The nucleus is the largest cellular organelle whose main well-known functions include DNA replication and gene regulation. At the same time, the nucleus continually resists and responds to external and intercellular mechanical forces and plays a significant role in mechanosensitivity and mechanotransduction [1–4]. A proper *Correspondence: [email protected] 1 Institute for Regenerative Medicine, Sechenov University, 8 Trubetskaya St., Moscow 119991, Russia Full list of author information is available at the end of the article
genome organization and expression are dependent on the nuclear mechanics, and its alterations are associated with many human diseases, including progeria, muscular dystrophies, and cancer [5–8]. The nanomechanical properties of the nucleus were analyzed in a number of previous studies. While quite often the nucleus is considered to be the stiffest organelle in the cell [1, 9–12], other studies have shown that the nucleus is relatively soft, at least softer than the cytoskeletal stru
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