Fig. 1: Fusion-seq long-read (FSLR) uncovers CCRs in telomere crisis.

a A diagram of the telomere shortening-induced fusion assay, showing the position of primers and their distance to the start of telomere repeats (grey). b Telomere fusions were amplified using 17p6, XpYpM and 21q1 PCR primers from HCA2 fibroblasts transiting telomere crisis and visualised by Southern blot. This experiment was repeated independently with similar results for four times. c Scatter plot showing FSLR quantification of the number of alignments in the indicated number of telomere fusion molecules, which were isolated from the four fibroblasts indicated (alignment numbers are represented on a log2 scale, value of 2 represents fusion with no insertion, value ≥ 3 represent fusion with ≥ 1 insertion). The width of data point distribution is proportionate to the number of points at that Y value. d Quantification of the chromosomal origin of flanking DNA in telomere fusion molecules. Data plotted are means +/- standard error of the mean (SEM, n = 4 biological replicates), M mitochondrial DNA. e Scatter plot showing the size of flanking DNA which originates from 17p (n = 201946), XpYp (n = 84857) and 21q family telomeres (n = 78009) from four biological replicates. The black lines indicate the expected size of the flanking DNA from PCR primer site up to the start of telomere repeats. f Quantification of the chromosomal origin of individual DNA insertions in telomere fusion molecules. Data plotted are means +/- standard error of the mean (SEM, n = 4 biological replicates). g Scatter plot showing the size of individual DNA insertions from WI38 (n = 11416), MRC5 (n = 16149), HCA2 (n = 21791) and IMR90 (n = 49017) with the median indicated by the dotted line. Diagrams showing how DNA molecules from different chromosomes are connected in complex 18 (h) and complex 12 (j). Direction of the arrows indicates the orientation of the DNA (right = +, left = -), chr chromosome. Genome browser (GW) plots showing the location of individual DNA alignments from complex 18 (i) or complex 12 (k) (highlighted with red text in Fig. 1h, j) at their mapped genomic loci. Source data are provided as a Source data file.