RECQL4 depletion or malfunction increases inter-kinetochore distance. RECQL4 depletion or malfunction increases inter-kinetochore distance. (A) Cycled spindles are assembled as in Fig 3C and D and incubated for an additional 10 min with or without 6 μg/ml nocodazole. Samples were fixed, spun down on coverslips, stained for a kinetochore marker Ndc80 and DAPI, and analyzed by confocal microscopy. Maximum intensity projections are shown in the upper row. Single confocal slices (lower row) were used to detect kinetochore pairs (arrow heads) for further analysis. Quantitation shows the inter-kinetochore distance (right) and the relative angles of sister kinetochore pairs (left), measured with respect to the spindle pole to pole axis. n > 30 kinetochore pairs from > 6 structures. Note that after RECQL4 depletion, sister kinetochore pairs do not align to the pole to pole axis. Scale bar, 20 μm. ****P < 0.0001; **P < 0.01; NS (not significant) P > 0.05 (t test, two-tailed). (B) Immunofluorescence staining of control (GM00323, GM01864) and Rothmund–Thomson syndrome patient (AG05013, AG18371) fibroblasts with the kinetochore marker CREST and checkpoint marker BubR1. Scale bar, 5 μm. (C) Inter-kinetochore distance was measured in metaphase cells of control (GM00323, GM01864) and Rothmund–Thomson syndrome patient (AG05013, AG18371) fibroblasts based on CREST signals for the kinetochore pairs attached to microtubules (identified by the absence of the BubR1 signal) after 3D reconstruction. (n) indicates the number of kinetochore pairs measured per fibroblast line. P < 0.001 (t test, two-tailed). Hideki Yokoyama et al. LSA 2019;2:e201800120 © 2019 Yokoyama et al.