On the origin of shape fluctuations of the cell nucleus
On the origin of shape fluctuations of the cell nucleus
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DOI：
10.1073/pnas.1702226114
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发表时间：
2017-09-26
影响因子：
11.1
通讯作者：
Zidovska, Alexandra
中科院分区：
文献类型：
--
作者：
Chu, Fang-Yi;Haley, Shannon C.;Zidovska, Alexandra
核膜（NE）是细胞质和核质之间的物理边界，夹在细胞内两个高度活跃的系统之间：细胞骨架和染色质。NE决定细胞核的形状和大小，细胞核在细胞周期中增加，适应染色体去浓缩，随后是基因组复制。在这项工作中，我们研究了人类细胞在短时间尺度上的核形状波动。使用旋转盘共聚焦显微镜，我们观察到NE的快速波动，通过荧光标记的层粘胶蛋白A来显示，以及NE下方的染色质球表面（CGS），通过荧光标记的组蛋白H2B来显示。我们的研究结果表明，CGS和NE的波动幅度在细胞周期中单调减小，可以作为细胞周期阶段的可靠指标。值得注意的是，我们发现，虽然CGS和NE通常在相位上波动，但它们确实表现出局部的非相位运动区域，这导致了NE和CGS的分离。为了探索这些形状波动背后的机制，我们使用了生化扰动。我们发现CGS和NE的形状波动是由热和主动驱动的，后者是由染色质和细胞骨架的力引起的。这种波动可能会影响基因调控，也会导致核转运率异常高，例如，通过NE附近的分子搅拌，或通过核孔的分子通量增加。
The nuclear envelope (NE) presents a physical boundary between the cytoplasm and the nucleoplasm, sandwiched in between two highly active systems inside the cell: cytoskeleton and chromatin. NE defines the shape and size of the cell nucleus, which increases during the cell cycle, accommodating for chromosome decondensation followed by genome duplication. In this work, we study nuclear shape fluctuations at short time scales of seconds in human cells. Using spinning disk confocal microscopy, we observe fast fluctuations of the NE, visualized by fluorescently labeled lamin A, and of the chromatin globule surface (CGS) underneath the NE, visualized by fluorescently labeled histone H2B. Our findings reveal that fluctuation amplitudes of both CGS and NE monotonously decrease during the cell cycle, serving as a reliable cell cycle stage indicator. Remarkably, we find that, while CGS and NE typically fluctuate in phase, they do exhibit localized regions of out-of-phase motion, which lead to separation of NE and CGS. To explore the mechanism behind these shape fluctuations, we use biochemical perturbations. We find the shape fluctuations of CGS and NE to be both thermally and actively driven, the latter caused by forces from chromatin and cytoskeleton. Such undulations might affect gene regulation as well as contribute to the anomalously high rates of nuclear transport by, e.g., stirring of molecules next to NE, or increasing flux of molecules through the nuclear pores.