Chromosome organization and function in time and space: meiosis, mitosis and E.coli

摘要 染色体是我们遗传物质的储存库。我们认为它们是“活的、会呼吸的东西” 它们在时间和空间上的波动构成了它们最基本的功能。通过比较减数分裂和 哺乳动物有丝分裂染色体和大肠杆菌类核，我们试图确定基本的共同点。 减数分裂是有性繁殖的基础。其独特的特点是母体的配对和重组 和父系同源基因，包括发生交叉位点的交叉干扰现象 在染色体上间隔均匀。我们用4D长时间尺度分析了这种图案化过程 在我们新的线虫平台和真菌Sordaria的细胞遗传学研究中进行可视化。我们正在调查 我们新的力学模型和我们发现的同源结构/DNA桥，同时分析 新发现的球员和识别更多的球员。对于配对，使用我们新的低信噪比斑点检测算法和FROS 在萌芽酵母的标签中，我们探索伙伴搜索和同源鉴定。在索达里亚，我们有史以来第一次 减数分裂长非编码RNA的全面筛选将识别参与模式形成和/或 配对。其他研究探讨了减数分裂从有丝分裂到稳定同源多倍体的进化。 有丝分裂染色体开始处于扩散但空间有序的状态(G1)，但最终进化为 紧凑的、并排的姐妹染色单体准备进行分离。我们正在寻找我们的姐妹间 结构/DNA桥及其在轴向扭转应力作用下的出现。使用活细胞 哺乳动物染色体成像，包括我们新的4D长时间标度荧光散斑平台 显微镜下，我们正在探索我们的发现，中期染色体是折叠的，而不是卷曲的，并将询问 在有/没有我们提出的压缩/扩张周期的情况下，G1染色体何时/如何获得其处置。 正如我们发现的那样，大肠杆菌染色体也经历了全球压缩/扩张周期。现在，由 高通量4D成像生长在琼脂糖槽中的细胞，以及膜包裹的L形式，我们是 研究这些循环的(超卷依赖)机制；它们在姐妹分离和 细胞分裂；类核/膜相互作用在这两个方面的作用。我们还在努力 在体外重建类核周期，并询问周期是否也发生在其他细菌中。 在上述许多研究中，染色体可以被视为机械对象，受 驱动局部和全局运动、突变或通过应力重新分布的变形力(应力)， 空间图案。为了直接检测和分析这种效应，我们正在开发锌-锰机械。 发光纳米晶体作为一种非侵入性的体内应力传感器。一旦开发完成，该工具将应用于 检测哺乳动物染色体中的波和/或其他尚未想象的应激模式。 我们独特的研究将为不孕不育和出生缺陷(减数分裂)问题提供新的切入点， 遗传不稳定性与癌症(有丝分裂细胞)和抗生素耐药性(E.Coli L形式)有关。

Abstract Chromosomes are the repositories of our genetic material. We consider them to be "living, breathing objects" whose fluctuations in time and space underlie their most basic functions. By comparing meiotic and mammalian mitotic chromosomes and E.coli nucleoids we seek to identify fundamental commonalities. Meiosis underlies sexual reproduction. Its unique hallmarks are pairing and recombination of maternal and paternal homologs, including the phenomenon of crossover interference in which crossover sites occur with even spacing along the chromosomes. We analyze this patterning process by 4D long timescale visualization in our new C.elegans platform and by cytogenetic studies in the fungus Sordaria. We are probing our new mechanical model and our discovered inter-homolog structure/DNA bridges, concomitantly analyzing new-found players and identifying more. For pairing, with our new low SNR spot detection algorithm and FROS tags in budding yeast, we probe partner searching and homology identification. In Sordaria, our first-ever comprehensive screen of meiotic long noncoding RNAs will identify species involved in patterning and/or pairing. Other studies investigate the evolution of meiosis from mitosis and evolution of stable autopolyploidy. Mitotic chromosomes start in a diffuse but spatially ordered state (G1), but ultimately evolve into compact, side-by-side sister chromatids ready for segregation. We are pursuing our discovery of inter-sister structure/DNA bridges and their emergence via axial torsional stress by quantitative modeling. Using live cell imaging of mammalian chromosomes, including our new 4D long timescale platform for fluorescent speckle microscopy, we are exploring our finding that metaphase chromosomes are folded, not coiled, and will ask when/how G1 chromosomes acquire their disposition, with/without our proposed compaction/expansion cycles. E.coli chromosomes also undergo global compaction/expansion cycles, as we discovered. Now, by high throughput 4D imaging of cells growing in agarose grooves, and of membrane-enclosed L-forms, we are investigating the (supercoiling-dependent) mechanism of these cycles; their roles for sister segregation and cell division; and the roles of nucleoid/membrane interactions in both aspects. We are also working to reconstitute nucleoid cycles in vitro, and are asking if cycles also occur in other bacteria. For many of the above studies, chromosomes can be viewed as mechanical objects, subject to deforming forces (stresses) that drive local and global movement, abrupt changes or, via stress redistribution, spatial patterning. To directly detect and analyze such effects, we are developing ZnS-Mn mechano- luminescent nanocrystals as a non-invasive in vivo stress sensor. Once developed, this tool will be applied to detection of waves and/or other, yet-to-be imagined, stress patterns in mammalian chromosomes. Our unique studies will provide novel entry points into problems of infertility and birth defects (meiosis), genetic instability and cancer (mitotic cells) and antibiotic resistance (E.coli L-forms).