Tseng Yiider, Lee Jerry S H, Kole Thomas P, Jiang Ingjye, Wirtz Denis
Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, 3400 N. Charles Street, MD 21218, USA.
J Cell Sci. 2004 Apr 15;117(Pt 10):2159-67. doi: 10.1242/jcs.01073.
The microstructure of the nucleus, one of the most studied but least understood cellular organelles, is the subject of much debate. Through the use of particle nanotracking, we detect and quantify the micro-organization as well as the viscoelastic properties of the intranuclear region in single, live, interphase somatic cells. We find that the intranuclear region is much stiffer than the cytoplasm; it is also more elastic than viscous, which reveals that the intranuclear region displays an unexpectedly strong solid-like behavior. The mean shear viscosity and elasticity of the intranuclear region of Swiss 3T3 fibroblasts are 520 Poise (P) and 180 dyn/cm(2), respectively. These measurements determine a lower bound of the propulsive forces (3-15 picoNewton) required for nuclear organelles such as promyelocytic-leukemia bodies to undergo processive transport within the nucleus by overcoming friction forces set by the intranuclear viscosity. Dynamic analysis of the spontaneous movements of nanospheres embedded in the nucleus reveals the presence of putative transient nuclear microdomains of mean size 290+/-50 nm, which are mostly absent in the cytoplasm. The strong elastic character and micro-organization of the intranuclear region revealed by particle nanotracking analysis may help the nucleus to preserve its structural coherence. These studies also highlight the difference between the low interstitial nucleoplasmic viscosity, which controls the transport of nuclear proteins and molecules, and the much higher mesoscale viscosity, which affects the diffusion and directed transport of nuclear organelles and re-organization of interphase chromosomes.
细胞核是研究最多但了解最少的细胞器之一，其微观结构一直是众多争论的焦点。通过粒子纳米追踪技术，我们检测并量化了单个活体细胞间期核内区域的微观组织以及粘弹性特性。我们发现，核内区域比细胞质硬得多；它的弹性也大于粘性，这表明核内区域呈现出出人意料的强固体状行为。瑞士3T3成纤维细胞核内区域的平均剪切粘度和弹性分别为520泊（P）和180达因/平方厘米。这些测量确定了核细胞器（如早幼粒细胞白血病小体）在核内进行定向运输时克服核内粘度所产生的摩擦力所需的推进力下限（3 - 15皮牛顿）。对嵌入细胞核的纳米球自发运动的动态分析揭示了平均大小为290±50纳米的假定瞬时核微区的存在，而这些微区在细胞质中大多不存在。粒子纳米追踪分析揭示的核内区域的强弹性特征和微观组织可能有助于细胞核保持其结构连贯性。这些研究还突出了控制核蛋白和分子运输的低间隙核质粘度与影响核细胞器扩散和定向运输以及间期染色体重组的高得多的中尺度粘度之间的差异。
