Chromatin Hydrodynamics
Chromatin Hydrodynamics
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DOI：
10.1016/j.bpj.2014.03.038
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发表时间：
2014-05-06
影响因子：
3.4
通讯作者：
Zidovska, Alexandra
中科院分区：
文献类型：
--
作者：
Bruinsma, Robijn;Grosberg, Alexander Y.;Zidovska, Alexandra
根据最近观察到的染色质在活体分化细胞细胞核内的大规模相关运动，我们提出了一个流体理论--双流体模型，在该理论中，核的内容被描述为染色质溶液，核质起到溶剂的作用，染色质纤维起到溶质的作用。这个系统既受被动热涨落的影响，又受与自由能量消耗有关的主动标量和矢量事件的影响，如ATP水解。标量事件驱动纵向粘弹性模式(其中染色质纤维相对于溶剂移动)，而矢量事件产生横向模式(其中染色质纤维与溶剂一起移动)。利用线性响应方法，我们得到了将染色质密度和速度关联函数与有源源的关联函数和染色质溶液的复粘弹性系数联系起来的响应函数的显式表达式。然后，我们推导出染色质速度场的流谱密度的一般表达式。我们用这个理论分析了作者之一和她的同事最近获得的实验结果。我们发现，对于天然染色质和耗尽的染色质，实验数据的时间依赖关系可以用一个简单的复模模型Maxwell流体很好地拟合，尽管在波矢依赖方面存在一些差异。ATP耗竭细胞的温度波动主要是纵向的。ATP活性细胞在力偶极子的驱动下表现出强烈的横向长波速度波动。波数大于几个反微米的涨落以浓度涨落为主，其频谱与热涨落相同，但强度增加。
Following recent observations of large scale correlated motion of chromatin inside the nuclei of live differentiated cells, we present a hydrodynamic theory-the two-fluid model-inwhich the content of a nucleus is described as a chromatin solution with the nucleoplasm playing the role of the solvent and the chromatin fiber that of a solute. This system is subject to both passive thermal fluctuations and active scalar and vector events that are associated with free energy Consumption, such as ATP hydrolysis. Scalar events drive the longitudinal viscoelastic modes (where the chromatin fiber moves relative to the solvent) while vector events generate the transverse modes (where the chromatin fiber moves together with the solvent). Using linear response methods, we derive explicit expressions for the response functions that connect the chromatin density and velocity correlation functions to the corresponding correlation functions of the active sources and the complex viscoelastic moduli of the chromatin solution. We then derive general expressions for the flow spectral density of the chromatin velocity field. We use the theory to analyze experimental results recently obtained by one of the present authors and her co-workers. We find that the time dependence of the experimental data for both native and ATP-depleted chromatin can be well-fitted using a simple model-the Maxwell fluid-for the complex modulus, although there is some discrepancy in terms of the wavevector dependence. Thermal fluctuations of ATP-depleted cells are predominantly longitudinal. ATP-active cells exhibit intense transverse long wavelength velocity fluctuations driven by force dipoles. Fluctuations with wavenumbers larger than a few inverse microns are dominated by concentration fluctuations with the same spectrum as thermal fluctuations but with increased intensity.