|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 4. Relationship between spindle orientation and sibling cell fate in neural
stem cells. (A) Drosophila neuroblasts. Wild-type
neuroblasts (left) invariably align their spindle along the apical/basal
polarity axis, resulting in apical neuroblast (NB) and basal GMC cell fates.
The cell fates that are acquired when the spindle is misoriented (e.g. in
aurora A or mud mutants; right) have not been established.
Spindle, blue lines; cleavage furrow plane, dotted line; apical domain, green;
basal domain, red. (B) Vertebrate neuroepithelial cells. Conclusions
from three different studies are shown. AJs, red balls; apical domain, green;
basolateral domain, orange. SC, neuroepithelial cell; BP, basal progenitor; N,
neuron. Apical is uppermost. (a) In Kosodo et al.
(Kosodo et al., 2004), spindle
orientation was concluded to regulate sibling cell fates in mouse embryonic
neuroepithelial cells: if both siblings receive apical components (green),
they both self-renew as progenitors (SCs; left); but if one cell lacks apical
components, it differentiates into a neuron (N, middle and right). This type
of asymmetric division can occur when the spindle is positioned in a
near-planar orientation (middle) or in an apical/basal orientation (right).
Thus, spindle orientation alone is insufficient to predict cell fate outcome.
(b) Konno et al. (Konno et al.,
2008) concluded that spindle orientation regulates sibling cell
fates in mouse embryonic neuroepithelial cells: only siblings that inherit
both apical and basal components will self-renew as progenitors (left); cells
containing only apical domain become basal progenitors (BP; middle), whereas
cells containing only the basal process become neurons (N; middle and right).
(c) Morin et al. (Morin et al.,
2007) concluded that spindle orientation does not affect sibling
cell fates in the chick spinal cord. Normally, all divisions during early
neurogenesis have a planar spindle orientation and form two progenitors
(left). However, when the basolateral protein LGN (Gpsm2) was reduced by
siRNA, the spindle could align with the apical/basal axis, yet both siblings
still maintained progenitor identity by molecular marker expression (right),
although the non-apical sibling was displaced out of the ventricular zone.
Apical membrane and junction markers were not used in this study and thus are
not shown.
|
