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 Microtubule behaviour in live larval neuroblasts
Spindle organization and chromosome segregation during asymmetric division of a Drosophila larval neuroblast.
Recording of GFP-alphaTubulin84B (in green) and Histone2-RFP (in red) reveal the stable position of the spindle along the apico-basal axes before asymmetric division takes place. During anaphase chromosomes segregate to the poles and, at telophase, the aster that remains in the bigger daughter cell (neuroblast) becomes bigger and positions in the middle of the cytoplasm, whereas the aster segregating to the smaller daughter cell (GMC) decreases notably. After division both daughetr cells remain connected by the midbody.
Aster behaviour and spindle formation during asymmetric division of a Drosophila larval neuroblast.
Recording of GFP-alphaTubulin84B reveals that, early in the cell cycle, there is only one aster located apically in the cell, opposed to the cluster of basal GMCs. Shortly before the onset of mitosis, which can be told by the entry of GFP signal inside the nucleus, a second aster appears within the basal half of the cell which, after division, will be inherited by the daughter GMC.
Aster behaviour and spindle formation during asymmetric division of a Drosophila larval neuroblast.
Recording of GFP-alphaTubulin84B during two consecutive cell cycles reveals that the pattern of late formation of the basal aster repeats one cell cycle after another. As a result, spindle is always assembled along the apico-basal axes of the cell.
Aster behaviour and spindle formation during asymmetric division of a Drosophila larval neuroblast.
Recording of the microtubule binding protein jupiter-GFP reveals the presence of a single aster for most of the cell cycle. The second mitotic aster appears only shortly before nuclear envelope breakdown, at a basal position within the cell. This late appearing aster is inherited by the daughter GMC, whereas the apical aster that remains in the NB moves again to the apical cortex after cytokinesis.
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