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. 2021 Mar 8;49(6):3338–3353. doi: 10.1093/nar/gkab141

Figure 3.

Figure 3.

A schematic representation of chromosome end structures (not to scale) is shown. (A–D) Simple fusion between nonhomologous chromosomes. (A, B) Inter-chromosomal fusion sites of the Caenorhabditis elegans ALT1 and ALT2 survivor lines. References represent CB4856 chromosomes. (A) Chromosome IL and IIR ends were fused to each other after a 50 644-bp deletion in the chromosome IL subtelomeric region and a 6387-bp deletion in the chromosome IIR subtelomeric region. (B) Chromosome VL and XR ends were fused to each other after a 156-bp deletion in the chromosome VL subtelomeric region and a 255-bp deletion in the chromosome XR subtelomeric region. (C) Inter-chromosomal fusion sites of the ALT3 survivor line. References represent N2 chromosomes. Chromosome IVL and XR ends were fused to each other after a 29,935-bp deletion in the chromosome IVL subtelomeric region and a 306-bp deletion in the chromosome XR subtelomeric region. (D) Inter-chromosomal fusion sites of the ALT4 survivor line. References represent N2 chromosomes. Chromosome IVL and VL ends were fused to each other after a 41,965-bp deletion in the chromosome IVL subtelomeric region and a 109 516-bp deletion in the chromosome VL subtelomeric region. (E–H) Complex inter-chromosomal fusion with discontinuous fragments. (E) The fusion site of chromosome IIIL and IVR ends in the Caenorhabditis elegans ALT1 survivor line contained a discontinuous fragment, which would have originated from the chromosome IVR end, but was located in the opposite direction. The origin of the discontinuous fragment was supposed to be chromosome IV:17 975 510–17 982 596 in the reference CB4856 genome. The fused chromosome IIIL end had a 1557-bp subtelomere deletion, and the chromosome IVR end had a 653-bp subtelomere deletion. References represent corresponding CB4856 chromosomes. (F) The fusion site of chromosome IIIL and IVR ends in the ALT2 survivor line contained not just the same discontinuous IVR fragment in the ALT1 survivor line, but also another discontinuous fragment, which originated from the chromosome IIIL end and was located in the same direction. The origin of the discontinuous IIIL fragment was supposed to be chromosome III:4679–8126 in the reference CB4856 genome. The fused chromosome IVR end had almost the same subtelomere deletion, but the chromosome IIIL end had a much shorter 650-bp subtelomere deletion than that of the ALT1 survivor line. References represent the corresponding CB4856 chromosomes. (G) The fusion site of chromosome IIR and VL ends in the ALT3 survivor line contained a discontinuous fragment, which would have originated from the chromosome VL end, but was located in the opposite direction. The origin of the discontinuous fragment was supposed to be chromosome IV:655–983 in the reference N2 genome. The fused chromosome IIR end had a 5282-bp subtelomere deletion, and the chromosome VL end had a 1086-bp subtelomere deletion. References represent the corresponding N2 chromosomes. (H) The fusion site of chromosome IIIL and VR ends in the ALT4 line. A discontinuous fragment would have originated from chromosome III:865–2999 in the reference N2 genome and was located in the opposite direction. The fused chromosome IIIL end had a 1640-bp subtelomere deletion, and the chromosome VR end had a 1249-bp subtelomere deletion. References represent corresponding N2 chromosomes.