Artificially Introduced Aneuploid Chromosomes Assume a Conserved Position in Colon Cancer Cells

BACKGROUND: Chromosomal aneuploidy is a defining feature of carcinomas. For instance, in colon cancer, an additional copy of Chromosome 7 is not only observed in early pre-malignant polyps, but is faithfully maintained throughout progression to metastasis. These copy number changes show a positive correlation with average transcript levels of resident genes. An independent line of research has also established that specific chromosomes occupy a well conserved 3D position within the interphase nucleus. METHODOLOGY/PRINCIPAL FINDINGS: We investigated whether cancer-specific aneuploid chromosomes assume a 3D-position similar to that of its endogenous homologues, which would suggest a possible correlation with transcriptional activity. Using 3D-FISH and confocal laser scanning microscopy, we show that Chromosomes 7, 18, or 19 introduced via microcell-mediated chromosome transfer into the parental diploid colon cancer cell line DLD-1 maintain their conserved position in the interphase nucleus. CONCLUSIONS: Our data is therefore consistent with the model that each chromosome has an associated zip code (possibly gene density) that determines its nuclear localization. Whether the nuclear localization determines or is determined by the transcriptional activity of resident genes has yet to be ascertained

Figure 5

<p>Raw distributions of 3D-distance measurements. CT-7 in DLD-1 & DLD-1+7, CT-18 in DLD-1 & DLD-1+18, CT-19 in DLD-1 & DLD-1+19. X-axis: cell line, Y-axis: Normalized radial distance (%) of chromosome territories from the geometric center of the nucleus.</p

Figure 1

<p>A: Schematic representation of the experimental design. DLD-1 (parental cell line) was subjected to MMCT to generated derivative cell lines DLD-1+7, DLD-1+18 and DLD-1+19. 3D-FISH was performed on each of the derivative cell lines with the probe combinations indicated. B: <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000199#pone-0000199-t001" target="_blank">Table</a> showing comparisons of DNA content and gene density between Chromosome 7, 18 and 19.</p

Figure 3

<p>A: Maximum intensity projection of a representative confocal image stack with Chromosome territories 7 (Red, Spectrum orange) and 19 (Green, Rhodamine Green) from DLD-1+19 B: A 3D reconstruction of the nucleus and chromosome territories from the image shown in A (X-Y orientation). C: A scheme adopted for 3D distance measurements of chromosome territories in Red (R₁ and R₂) and Green (G₁, G₂, and G₃) from the geometric center of the nucleus (N_c), to the nuclear periphery (N_P). Points on the nuclear periphery (eg. N_pR₁) are extensions from the nuclear center through the geometric center of the chromosome territory. D: 3D reconstruction in B shown in X-Z orientation.</p