title: Shape Transformation of the Nuclear Envelope during Closed Mitosis.
abstract: The nuclear envelope (NE) in lower eukaryotes such as Schizosaccharomyces pombe undergoes large morphology changes during closed mitosis. However, which physical parameters are important in governing the shape evolution of the NE, and how defects in the dividing chromosomes/microtubules are reflected in those parameters, are fundamental questions that remain unresolved. In this study, we show that improper separation of chromosomes in genetically deficient cells leads to membrane tethering or asymmetric division in contrast to the formation of two equal-sized daughter nuclei in wild-type cells. We hypothesize that the poleward force is transmitted to the nuclear membrane through its physical contact with the separated sister chromatids at the two spindle poles. A theoretical model is developed to predict the morphology evolution of the NE where key factors such as the work done by the poleward force and bending and surface energies stored in the membrane have been taken into account. Interestingly, the predicted phase diagram, summarizing the dependence of nuclear shape on the size of the load transmission regions, and the pole-to-pole distance versus surface area relationship all quantitatively agree well with our experimental observations, suggesting that this model captures the essential physics involved in closed mitosis.
authors.affiliation: Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Chinese Academy of Sciences Center for Excellence in Molecular Cell Biology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zheng
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan.
authors.forename: Allen P
authors.initials: AP
authors.lastname: Liu
authors.affiliation: Department of Engineering Mechanics, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Qian
authors.affiliation: Chinese Academy of Sciences Center for Excellence in Molecular Cell Biology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China. Electronic address: chuanhai@ustc.edu.cn.
authors.forename: Chuanhai
authors.initials: C
authors.lastname: Fu
authors.affiliation: Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China. Electronic address: ylin@hku.hk.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
mesh_terms: D015825:Chromosomes, Fungal / Q000378:metabolism; D008938:Mitosis; D008954:Models, Biological; D009685:Nuclear Envelope / Q000378:metabolism*; D015530:Nuclear Matrix / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics