Biology Reference
In-Depth Information
centrosome, and also neurons that bear dendrites or multiple axons may differ from
those that do not bear dendrites and have the more classic single axon. Migratory
neurons appear to utilize their centrosome in the most traditional fashion, as the
vast majority of microtubules in the migratory neuron remain attached to the
centrosome (Tsai and Gleeson
2005
), while a small fraction of the microtubules
are apparently released from the centrosome so that they transit down the leading
process or slide their minus ends behind the centrosome (Falnikar et al.
2011
).
Overall, it appears that the centrosome is most important early in neuronal
development, especially during neuronal migration and early axonal differentia-
tion. After that, the preponderance of the data suggests that neurons gradually lose
their dependence on the centrosome in favor of self-sustaining mechanisms for
maintaining the microtubule arrays of the axon and the dendrites.
Whether or not the neuron needs a centrosome for the development of proper axons
or dendrites remains a debatable point, as merely being able to form an axon or dendrite
in culture may be a very different thing than being able to form the appropriate axon or
dendrite within the context of a functional nervous system. In addition, it is pertinent to
keep in mind that the biology community continues to be surprised by the plethora of
transgenic animals that are viable in the absence of proteins believed to play important
roles in cellular functions. Oftentimes, the importance of a particular protein (or in this
case, an organelle) is gleaned only after cells or entire organisms are challenged in
particular ways. This may be the case developmentally, and also in more mature
neurons in which the centrosome appears to have become vestigial. For example,
perhaps under certain circumstances, the centrosome is re-activated to enable the
neuron to meet a particular challenge, such as restructuring of the dendritic arbor in
response to learning or disease, or regeneration of an injured axon.
Acknowledgments The work in our laboratory is supported by grants from the National
Institutes of Health and the National Science Foundation.
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