Relative proximity of chromosome territories influences chromosome exchange partners in radiation-induced chromosome rearrangements in primary human bronchial epithelial cells

Abstract

It is well established that chromosomes exist in discrete territories (CTs) in interphase and are positioned in a cell-type specific probabilistic manner. The relative localisation of individual CTs within cell nuclei remains poorly understood, yet many cancers are associated with specific chromosome rearrangements and there is good evidence that relative territorial position influences their frequency of exchange. To examine this further, we characterised the complexity of radiation-induced chromosome exchanges in normal human bronchial epithelial (NHBE) cells by M-FISH analysis of PCC spreads and correlated the exchanges induced with their preferred interphase position, as determined by 1/2-colour 2D-FISH analysis, at the time of irradiation. We found that the frequency and complexity of aberrations induced were reduced in ellipsoid NHBE cells in comparison to previous observations in spherical cells, consistent with aberration complexity being dependent upon the number and proximity of damaged CTs, i.e. lesion proximity. To ask if particular chromosome neighbourhoods could be identified we analysed all radiation-induced pair-wise exchanges using SCHIP (statistics for chromosome interphase positioning) and found that exchanges between chromosomes (1;13), (9;17), (9;18), (12;18) and (16;21) all occurred more often than expected assuming randomness. All of these pairs were also found to be either sharing similar preferred positions in interphase and/or sharing neighbouring territory boundaries. We also analysed a human small cell lung cancer cell line, DMS53, by M-FISH observing the genome to be highly rearranged, yet possessing rearrangements also involving chromosomes (1;13) and (9;17). Our findings show evidence for the occurrence of non-random exchanges that may reflect the territorial organisation of chromosomes in interphase at time of damage and highlight the importance of cellular geometry for the induction of aberrations of varying complexity after exposure to both low and high-LET radiation.

Intermingling of chromosome territories

“…Moreover, the aberration complexity was shown to be dependent on the number and proximity of damaged chromosome territories. Interestingly, rearrangements involving chromosomes (1;13) and (9;17) were also observed in highly rearranged DMS53 human SCLC (small cell lung cancer) cell line genome, indicating the importance of cellular geometry for the induction of translocations …”

“…Interestingly, rearrangements involving chromosomes (1;13) and (9;17) were also observed in highly rearranged DMS53 human SCLC (small cell lung cancer) cell line genome, indicating the importance of cellular geometry for the induction of translocations. 48 Interestingly, it was demonstrated that MYC, BCL, immunoglobulin light (IGL, IGK), and heavy chain (IGH) loci which are frequently translo- it was shown that a significant fraction of extra-territorial FGFR3 is engaged in close loci pairs colocalizing with IGH. This suggests that extraterritorial positioning of FGFR3 in patient B-cells may provide a mechanism for generating close loci pairs with IGH and thus it is indirectly promoting translocation events between these two genes.…”

Complex correlations: replication timing and mutational landscapes during cancer and genome evolution

“…Longstanding cytogenetic evidence [48–56], recently confirmed with chromatin conformation capture [47,57–63], indicates that fusion partners are usually in close spatial proximity before the breaks occur. Since chromatin is organized in the nucleus such that domains of similar RT are in close proximity [4], there is a strong preference for partners to replicate at the same time [47], which is also reported in evolutionary fusion partners between mouse and human [5].…”

Telomere elongation through hTERT immortalization leads to chromosome repositioning in control cells and genomic instability in Hutchinson‐Gilford progeria syndrome fibroblasts, expressing a novel SUN1 isoform

“…24‐colour karyotyping (multiplex fluorescence in situ hybridization [M‐FISH]) was used to paint mitotic chromosomes of the T08 cell line using a modified method of the Metasystems protocol as described previously …”