Chromosome order in HeLa cells changes during mitosis and early G1, but is stably maintained during subsequent interphase stages

Abstract

hether chromosomes maintain their nuclear positions during interphase and from one cell cycle to the next has been controversially discussed. To address this question, we performed long-term live-cell studies using a HeLa cell line with GFP-tagged chromatin. Positional changes of the intensity gravity centers of fluorescently labeled chromosome territories (CTs) on the order of several m were observed in early G1, suggesting a role of CT mobility in establishing interphase nuclear architecture. Thereafter, the positions were highly constrained within a range of ‫ف‬ 1 m until the end of G2. To analyze possible changes of chromosome arrangements from one cell cycle to the next, nuclei were photobleached in G2 W maintaining a contiguous zone of unbleached chromatin at one nuclear pole. This zone was stably preserved until the onset of prophase, whereas the contiguity of unbleached chromosome segments was lost to a variable extent, when the metaphase plate was formed. Accordingly, chromatin patterns observed in daughter nuclei differed significantly from the mother cell nucleus. We conclude that CT arrangements were stably maintained from mid G1 to late G2/early prophase, whereas major changes of CT neighborhoods occurred from one cell cycle to the next. The variability of CT neighborhoods during clonal growth was further confirmed by chromosome painting experiments.

The significance of telomeric aggregates in the interphase nuclei of tumor cells

“…This is an open question, since the available data do not allow for a consensus in interpretation. While some research groups do not find substantial chromosomal movements [Abney et al, 1997;Gerlich et al, 2003], others find chromosomal reorganization during the cell cycle [Ferguson and Ward, 1992;Vourc'h et al, 1993;Bridger et al, 2000;Chubb et al, 2002;Walter et al, 2003;Essers et al, 2005], cellular differentiation [Stadler et al, 2004], and during quiescence and senescence [Bridger et al, 2000].…”

Topologically associated domains enriched for lineage-specific genes reveal expression-dependent nuclear topologies during myogenesis

“…How lineage-specific genome topologies emerge is largely not understood. Although it has been observed that chromatin organization in cycling cells maintains a defined organization from interphase through mitosis and to daughter nuclei, this pattern has not been reproducibly demonstrated (35,36,48). Moreover, analyzing the role of the cell cycle in establishing a new nuclear topology during cellular development has remained an intractable problem owing to the tight coupling of proliferation and differentiation.…”

“…Importantly, it has been observed that in a stably cycling population of cells, the interphase organization of the genome can reemerge as a facsimile in daughter nuclei (35). Although this behavior may be probabilistic and dependent on methodology (36,37), it is likely that a given cell type "remembers" its genomic organization (38) to reestablish a cell-specific expression profile. Proliferation is a hallmark of cellular differentiation and has been suggested to play a role in self-organizing genome topologies (30,39).…”

Form follows function: the genomic organization of cellular differentiation

“…Two recent studies utilized an H2B-GFP fusion protein and photobleaching to analyze the overall order of chromosomes through the cell cycle. In an analysis of HeLa cells, chromosomes were shown to maintain their localization in daughter cells in approximately half the nuclei studied (Walter et al 2003). Furthermore, chromosomes were shown to be mobile during the early Gap 1 cell cycle (G1).…”