Everything about Microtubule Organizing Center totally explained
The
microtubule-organizing center (
MTOC) is a structure found in
eukaryotic cells from which
microtubules emerge. MTOCs have two main functions: The organization of eukaryotic
flagella and
cilia and the organization of the
mitotic and
meiotic spindle apparatus separating the
chromosomes during
cell division. The MTOC is the site of
microtubule nucleation and can be visualized in cells by
immunohistochemical detection of
γ-tubulin. In animals, the two most important types of MTOCs are the
basal bodies associated with cilia and certain intercellular junctions in
epithelial cells, and the
centrosome associated with spindle formation.
Centrosome
Most animal cells during
interphase have one centrosome, usually located near the
nucleus, and generally associated closely with the
Golgi apparatus. The centrosome usually has a pair of
centrioles. Microtubules are anchored with their "minus" ends in the centrosome, and because microtubules dissociate preferentially at this end, this anchoring has a stabilizing effect, and MTOC-associated microtubules can grow very quickly. The polarity of the microtubules is important for
membrane bound transport, as the
motor proteins
kinesin and
dynein typically move preferentially in either the "plus" or "minus" direction along a microtubule, allowing vesicles to be directed to or from the
endoplasmic reticulum and Golgi apparatus.
Basal body
In epithelial cells, MTOCs also anchor and organize the microtubules that make up cilia. As with the centrosome, these MTOCs stabilize and give direction to the microtubules, in this case to allow unidirectional movement of the cilium itself, rather than vesicles moving along it.
Spindle pole body
In
yeasts and some
algae, the MTOC is embedded into the
nuclear envelope as a spindle pole body. In these organisms, the nuclear envelope doesn't break down during mitosis and the spindle pole body serves to connect cytoplasmic with nuclear microtubules.
Plant MTOCs
Plant cells lack centrioles or spindle pole bodies. Instead, the nuclear envelope itself appears to function as the main MTOC for
microtubule nucleation and spindle organization during plant cell mitosis.
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