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. 2021 Mar 3;22(4):e51400. doi: 10.15252/embr.202051400

Figure 2. Central MTOCs originate from spindle poles.

Figure 2

  1. Live imaging of MTOC and kinetochore dynamics. MTOCs (mNG‐Cep192, green) and kinetochores (tdTomato‐CENP‐C, magenta) in B6D2F1 oocytes are shown. Time in h:mm after NEBD. Circles indicate central MTOCs, which are positioned in the middle region of the spindle later than 4 h after NEBD. Arrows indicate displacement of the MTOCs. Scale bar, 10 μm.
  2. Tracking analysis of central MTOCs. In the left graph, the positions of central MTOCs in (A) along the spindle axis are shown over time. MTOC positions were used to calculate distance to the spindle equator. In the right graph, lines showing temporal changes in MTOC‐equator distance are aligned based on the time when the MTOC reached a position closest to the spindle equator. Horizontal lines at 7 and at −7 μm denote the thresholds used for the definition of the middle and polar regions of the spindle.
  3. Central MTOCs originate from spindle poles and transiently stay in the middle region of the spindle. As in (B), the trajectories of central MTOCs (n = 25 MTOCs of 8 oocytes from three independent experiments) were analyzed and their temporal changes in MTOC–equator distance are shown (Left graph). Central MTOCs were categorized into two groups: (1) ones that came from polar regions of the spindle (n = 21, middle graph) and (2) others that stayed in the middle region throughout the period before reaching a position closest to the equator (n = 4, right graph).
  4. Origin of central MTOCs. Origins were categorized based on the results shown in (C). Note that 7 central MTOCs came from outside of the spindle and are not included in (C).
  5. Destination of central MTOCs. The tracks of central MTOCs that originated from polar regions were used (n = 21 MTOCs). The pole of origin was defined as Pole 1, while the other pole was defined as Pole 2. MTOC positions along the spindle axis (positive values for those closer to Pole 1) over time are shown. Horizontal lines at 7 and at −7 μm denote the thresholds used for the definition of the middle and polar regions of the spindle. Note that central MTOCs moved back to the original pole (Pole 1) or switched their positions to the opposite pole (Pole 2).
  6. Destination of central MTOCs that originated from a polar region was categorized as in (E).

Data information: See also Movie EV2.

Source data are available online for this figure.