Biology Reference
In-Depth Information
Chapter 18
Re-evaluation of the Neuronal
Centrosome as a Generator of
Microtubules for Axons and Dendrites
Peter W. Baas and Aditi Falnikar
Abstract A typical vertebrate neuron extends a single axon and multiple
dendrites, both of which are rich in highly organized arrays of microtubules that
serve essential functions. In simpler cell types, microtubules are organized by their
attachment to a centralized nucleating structure such as the centrosome. In axons
and dendrites, however, microtubules are not attached to the centrosome or any
recognizable organizing structure. Over a decade ago, we proposed that the
neuronal centrosome acts as a ''generator'' of microtubules for the axon and
dendrites. Our studies suggested that the neuronal centrosome is highly active,
especially during development, nucleating and releasing microtubules into the cell
body. The released microtubules are then actively transported into the axon and
dendrites by molecular motor proteins. In migrating neurons, most of the micro-
tubules are attached to the centrosome, suggesting that significant changes in the
nucleation or release of microtubules from the centrosome occur as neurons cease
migration and begin to form their axonal and dendritic arbors. Recent studies
suggest that the centrosome eventually becomes inactive as neurons mature, and
that microtubule numbers are increased by other mechanisms, such as the severing
of existing microtubules. Exactly how important the centrosome is for early stages
of differentiation remains unclear, and the possibility exists that the centrosome
may be re-activated in more mature neurons to meet particular challenges that may
arise. Here we review historical as well as contemporary data on the neuronal
centrosome, with emphasis on its potential role as a generator of microtubules.
P. W. Baas (
&
)
A. Falnikar
Department of Neurobiology and Anatomy,
Drexel University College of Medicine,
2900 Queen Lane, Philadelphia, PA 19129, USA
e-mail: pbaas@drexelmed.edu
