These results provide insight into how the spindle size is maintained at metaphase.
In contrast, the spindle length in TPX2 depleted oocytes expressing YFP-TPX2ΔN reached 36±5 µm, which corresponds to a classical meiosis I spindle size [8].
10.7554/eLife.00290.019 Figure 7. Metaphase spindle orientation in stage 3 embryos depends on spindle size.
Altering spindle size in developing embryos impaired spindle orientation during metaphase, but chromosome segregation remained robust.
The measure spindle activity (termed SpA) captures the duration as well as amplitude of identified spindles and thus reflects the activity or intensity of the spindle process (spindle activity = mean spindle duration × mean spindle amplitude).
Representative images of decreased spindle size in fixed hemisected embryos.
The freehand ROI tool was used to measure spindle area.
Taking advantage of this mechanism to modify spindle size without functionally perturbing the spindle allowed us to uncover an important role for spindle size in maintaining spindle orientation in the large cells of early Xenopus development.
(C ) Addition of 1 µM recombinant importin α to steady-state spindles in stage 8 extracts decreases kif2a recruitment to spindles in addition to increasing spindle size.
However, chromosome segregation was robust to decreases in spindle size indicating that spindle architecture remained viable and a large spindle is not essential for division of large cells.
