In yeast, several of these localize to the cellular bud and cell cortex to direct nuclear migration, spindle orientation, nuclear division and cell division during cytokinesis.
However, the extent to which spindle orientation controls division symmetry or cell fate, and the upstream factors regulating this process, are still elusive.
Abd-B also non-cell-autonomously controls critical features within the niche, including centrosome orientation and division rates of germline stem cells.
Here, we show that distinct subpopulations of astral microtubules exist, which have differential functions in regulating spindle orientation and division symmetry.
Finally, there is clear clustering of cells along the x-axis, suggesting that the orientation of division at the eight-cell stage has reasonable predicative power (Fig. 5A).
It is believed that the orientation of division of polarised blastomeres in the 8- and 16-cell stage embryo determines the fate of daughter cells, based on how asymmetrically distributed lineage determinants are segregated.
In fact, as we describe in detail in Material and Methods and the relevant figure legends, all of our imaging sets, live and fixed, were 3D stacks, and therefore our tracing of the orientation of divisions is valid.
The relationship between cell polarity and orientation of cell division determines whether a neural stem cell undergoes symmetric or asymmetric cell division during development.
Apparently, the orientation of the division plane within the niche is responsible for maintaining this diversity; planar division generates two identical daughter cells, while apical-basal division generates asymmetric cell fates.
Because cell polarity is critical to cell division orientation, one could speculate that a disruption in oriented cell division by PALS1 ablation may have contributed to the observed phenomenon.
