State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 4300071, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Biochim Biophys Acta Mol Cell Res. 2019 Dec;1866(12):118518. doi: 10.1016/j.bbamcr.2019.07.013. Epub 2019 Jul 31.
The eukaryotic genome is compacted in the form of chromatin within the nucleus. Whether the spatial distribution of the genome is ordered or not has been a longstanding question. Answering this question would enable us to understand nuclear organization and cellular processes more deeply. Here, we applied a modified CRISPR/dCas9 system to label the randomly selected genomic loci in diploid living cells, which were visualized by high-resolution wide-field imaging. To analyze the spatial positions of three pairs of genomic loci, three sets of parameters were progressively measured: i) the linear distance between alleles; ii) the radial distribution of the genomic loci; and iii) the linear distances between three pairs of genomic loci on nonhomologous chromosomes. By accurate labeling, geometric measuring and statistical analysis, we demonstrated that the distribution of these genomic loci in the 3D space of the nucleus is relatively stable in both late G1 and early S phases. Collectively, our data provided visual evidence in live cells, which implies the orderly spatial organization of chromatin in the nucleus. The combination of orderliness and flexibility ensures the methodical and efficient operation of complex life systems. How the nucleus adopts this ordered 3D structure in living cells is thought-provoking.
真核生物基因组在细胞核内以染色质的形式压缩。基因组的空间分布是否有序一直是一个长期存在的问题。回答这个问题可以使我们更深入地了解核组织和细胞过程。在这里，我们应用改良的 CRISPR/dCas9 系统标记二倍体活细胞中随机选择的基因组位点，通过高分辨率宽场成像进行可视化。为了分析三对基因组位点的空间位置，我们逐步测量了三组参数：i）等位基因之间的线性距离；ii）基因组位点的径向分布；iii）非同源染色体上三对基因组位点之间的线性距离。通过精确标记、几何测量和统计分析，我们证明了这些基因组位点在细胞核的 3D 空间中的分布在晚 G1 和早 S 期相对稳定。总之，我们的数据在活细胞中提供了直观的证据，表明染色质在细胞核中的空间组织是有序的。有序性和灵活性的结合确保了复杂生命系统的有条不紊和高效运作。细胞核如何在活细胞中采用这种有序的 3D 结构是值得思考的。
