Biomechanics of the Cell Nucleus: The Role of Chromatin and its Connectivity with Nuclear Proteins and the Nuclear Membrane

Yale University, New Haven CT

Investigators

Abstract

The research objective of this award is to examine how individual nuclear components contribute to the mechanical properties of the cell nucleus using a novel optical-tweezers assay in conjunction with nuclei from the genetically-facile fission yeast, S. pombe. Studies conducted under this award will test how altering the size of the nucleus, the compaction of the genome, the fluidity of the nuclear membrane, and association of chromatin with the nuclear envelope affect nuclear mechanical properties. Lamins, which are key in determining the mechanical properties of mammalian nuclei, but do not occur natively in S. pombe, will be introduced heterologously to dissect their mechanical properties from their roles in mammalian signaling and gene regulation. Fluorescence imaging of specific chromosome locations during force application to the S. pombe LINC complex, which spans the nuclear membrane, will elucidate how force is communicated into the nuclear mechanical network. If successful, these studies will elucidate how the mechanics of the nucleus emerge from its constituents, and delineate how the mechanical environment, which is essential for the differentiation programs that give rise to specific cell types, is communicated to the nucleus, where cell fate is largely determined. They will also establish S. pombe as a model system in which the mechanical role of lamins can be decoupled from their regulatory functions, thus providing a platform for future studies of lamin mutants that cause such diseases as lipodystrophy, muscular dystrophy, and progeria. Because embryonic stem (ES) cells and yeast express very low levels or no lamins, respectively, these studies will also lead to new insights into how extracellular mechanical cues drive ES cell differentiation. On the educational side, the students involved in these studies will become a new generation of teacher-scientists, who excel at quantitative approaches and possess the biological sophistication to identify and tackle cutting-edge biological problems.