Biology Reference
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Fig. 18.1 Schematic illustration depicting how differences in microtubule behavior at the
centrosome may contribute to phenotypic differences in different cell types. A pluripotent
precursor cell shown on the left could give rise to either a motile non-neuronal cell or a neuron. In
the case of the non-neuronal cell shown on the right at top, forces pulling on the microtubules
draw the centrosome toward the leading edge of the cell as it moves. In the most typical situation
of the neuron (denoted as type 1), the microtubules are released and the centrosome is not
relocated. Nevertheless, the microtubules are translocated toward the leading edge, which
coalesces into a growth cone. The cell body remains stationary and the microtubules translocate
into the space between the cell body and the growth cone, which develops into the axon. In the
case of some neurons (denoted as type 2), a subset of microtubules nucleated by the centrosome
remains attached to the centrosome while others are released. The same forces that transport the
released microtubules into the early axon pull on the attached microtubules, drawing the
centrosome toward the axon
from the first immature neurite to form after the final mitotic division of the
neuroblast, and that the Golgi and endosomes (which generally accompany the
centrosome) clustered in the location where the first neurite formed. These
observations are surprising in light of the earlier findings on hippocampal and
other types of neurons, but are consistent with the observations on cerebellar
granule neurons described by Zmuda and Rivas (
1998
). Interestingly, they also
found that ablating the centrosome precluded normal polarization of the neuron.
