Microtubule organizing center
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206251656
2008-04-17T14:42:53Z
143.239.130.235
The '''microtubule-organizing center''' ('''MTOC''') is a structure found in [[eukaryote|eukaryotic]] cells from which [[microtubule]]s emerge. MTOCs have two main functions: The organization of eukaryotic [[flagellum|flagella]] and [[cilium|cilia]] and the organization of the [[mitosis|mitotic]] and [[meiosis|meiotic]] [[spindle apparatus]] separating the [[chromosome]]s during [[cell division]]. The MTOC is the site of [[microtubule nucleation]] and can be visualized in cells by [[Immunohistochemistry|immunohistochemical]] detection of [[Tubulin#.CE.B3-tubulin|γ-tubulin]]. In animals, the two most important types of MTOCs are the [[basal body|basal bodies]] associated with cilia and certain intercellular junctions in [[epithelial]] cells, and the [[centrosome]] associated with spindle formation.
===Centrosome===
{{main|Centrosome}}
Most animal cells during [[interphase]] have one centrosome, usually located near the [[cell nucleus|nucleus]], and generally associated closely with the [[Golgi apparatus]]. The centrosome usually has a pair of [[centriole]]s. 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 protein]]s [[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===
{{main|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===
{{main|Spindle pole body}}
In [[yeast]]s and some [[alga]]e, the MTOC is embedded into the [[nuclear envelope]] as a spindle pole body. In these organisms, the nuclear envelope does not 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.
==External links==
* {{MeshNumber|A11.284.195.190.750.585|Microtubule-Organizing+Center}}
[[Category:Cytoskeleton]]
[[Category:Organelles]]
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