Neuroblast asymmetric cell division

FIG. 1. Localization of key proteins involved in the neuroblast asymmetric cell division. During late interphase a complex of proteins including Insc, Baz (and Pins) are localized to the apical cell cortex. This complex acts to mediate the basal cortical localization of the cell fate determinants Numb (and its partner Pon), Pros (and its partner Miranda) and pros RNA (and its partner Staufen) during mitosis. During interphase, Numb is cytoplasmic and Pros is localized to the apical cortex. 

In Pins - embryos the initiation steps of apical complex formation occur normally. However, this complex cannot be maintained in mitotic neuroblasts. Hence, the importance of the maintenance of this complex for asymmetric cell division can be ascertained by assessing how Pins- neural progenitors divide. Pins- embryos exhibit all of the defects seen in insc mutants. Mitotic spindle orientation is defective. In the cells of mitotic domain 9 the 90° reorientation, which normally occurs in wild-type resulting in the orientation of the spindle along the apical—basal axis (Fig. 3A), fails to occur in the mutant (Fig. 3B). Mitotic spindle orientation of neuroblasts in the segmented CNS, deduced from DNA staining, also often fails to... 

Asymmetric cell division in Drosophila neuroblasts depends on localization of the apical protein complex (Baz/ParG/ PKC3) and two sets of basal proteins. The basal proteins are incorporated into the ganglion mother cell (GMC) and contain proteins that determine cell fate (see Figure 22-24). 

Asymmetric cell division often relies on cytoskeletal elements to generate or maintain asymmetric distribution of cellular factors. In S. cerevisiae, what factor is localized to the bud by myosin motors In Drosophila neuroblasts, what factors are localized aplcally by microtubules ... 

Doe, C. Q., and B. Bowerman. 2001. Asymmetric cell division fly neuroblast meets worm zygote. Curr. Opin. Cell Biol. 13 68-75. 

Wodarz A, Ramrath A, Kuchinke U, Knust E 1999 Bazooka provides an apical cue for Inscuteable localization in Drosophila neuroblasts. Nature 402 544—547 Yu F, Morin X, Cai Y, Y ang X, Chia W 2000 Analysis of partner of inscuteable, a novel player of Drosophila asymmetric divisions, reveals two distinct steps in Inscuteable apical localisation. Cell 100 399-409... 

Dehner Neuroblast divisions are asymmetric not just because the cell determinants are distributed asymmetrically, but also the size of the GMC is very different, as is the nuclear size. Is nuclear size difference present from the outset If you look at cells in telophase, are the nuclei the same size ... 

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