Editing Centrosome

{{Short description|Cell organelle in animal cell helping in cell division}}
{{See also|Centrosome cycle |Centriole}}
{{distinguish|Centisome|Centromere}}{{Cell biology|centrosome=Yes}}
In [[cell biology]], the '''centrosome''' (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre<ref>{{Cite web|title=Structure of Plants and Fungi{{!}}Digitális Tankönyvtár|url=https://regi.tankonyvtar.hu/hu/tartalom/tamop412A/2011-0073_structure_of_plants_fungi/ch03s05.html|access-date=2021-01-30|website=regi.tankonyvtar.hu|language=hu}}</ref>) is an [[organelle]] that serves as the main [[microtubule organizing center]] (MTOC) of the animal [[cell (biology)|cell]], as well as a regulator of [[cell cycle|cell-cycle]] progression. The centrosome provides structure for the cell. It is thought to have evolved only in the [[metazoa]]n lineage of [[Eukaryote|eukaryotic cells]].<ref name="pmid17977464">{{Cite book
| last1 = Bornens | first1 = M.
| last2 = Azimzadeh | first2 = J.
| year = 2008
| pages = [https://archive.org/details/eukaryoticmembra00gasp/page/119 119–129]
| chapter = Origin and Evolution of the Centrosome
| title = Eukaryotic Membranes and Cytoskeleton
| series = Advances in Experimental Medicine and Biology
| volume = 607
| chapter-url = https://archive.org/details/eukaryoticmembra00gasp |chapter-url-access = limited
| doi = 10.1007/978-0-387-74021-8_10
| pmid = 17977464
| isbn = 978-0-387-74020-1
}}</ref> [[Fungus|Fungi]] and [[plant]]s lack centrosomes and therefore use other structures to organize their microtubules.<ref name="pmid12224551">{{Cite book 
| pages = 257–289 
| doi = 10.1016/S0074-7696(02)20008-X 
| series = International Review of Cytology 
| volume = 220 
| title = Acentrosomal microtubule nucleation in higher plants 
| year = 2002 
| author1 = Schmit 
| isbn = 9780123646248 
| pmid = 12224551
}}</ref><ref name="pmid15473833">{{Cite journal
| year = 2004
| pages = 1–28 
| doi = 10.1146/annurev.cellbio.20.022003.114106
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| pmid =  15473833| issue = 1
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| title = THE BUDDING YEAST SPINDLE POLE BODY: Structure, Duplication, and Function
| journal = Annual Review of Cell and Developmental Biology| first1 = S. L.
}}</ref> Although the centrosome has a key role in efficient [[mitosis]] in animal cells, it is not essential in certain fly and flatworm species.<ref name="pmid16546079">{{Cite journal
| pmid =  16546079 
| doi = 10.1016/j.cub.2006.01.053
| year = 2006
| last2 =  Goshima
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| pages = 564–569
| volume = 16| first3 = A. D. | first2 = G.| last1 = Mahoney| first4 = R. D.
| journal = Current Biology
| title = Making Microtubules and Mitotic Spindles in Cells without Functional Centrosomes| first1 = N. M.
| doi-access = free
}}</ref><ref name=azimzadehscience2012/><ref name=stowerspr2012/>

Centrosomes are composed of two [[centriole]]s arranged at [[right angle]]s to each other, and surrounded by a dense, highly structured<ref>{{Cite journal|last1=Lawo|first1=Steffen|last2=Hasegan|first2=Monica|last3=Gupta|first3=Gagan D.|last4=Pelletier|first4=Laurence|date=November 2012|title=Subdiffraction imaging of centrosomes reveals higher-order organizational features of pericentriolar material|url=https://pubmed.ncbi.nlm.nih.gov/23086237/|journal=Nature Cell Biology|volume=14|issue=11|pages=1148–1158|doi=10.1038/ncb2591|issn=1476-4679|pmid=23086237|s2cid=11286303|access-date=2020-08-07|archive-date=2021-07-25|archive-url=https://web.archive.org/web/20210725103608/https://pubmed.ncbi.nlm.nih.gov/23086237/|url-status=live}}</ref> mass of [[protein]] termed the [[pericentriolar material]] (PCM). The PCM contains proteins responsible for [[microtubule nucleation]] and anchoring<ref>{{Cite journal
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| pmid = 1967194
| year = 1990
| last1 = Eddé | first1 = B.
| last2 = Rossier
| last3 = Le Caer
| last4 = Desbruyères
| last5 = Gros
| last6 = Denoulet
| title = Posttranslational glutamylation of alpha-tubulin
| volume = 247
| issue = 4938
| pages = 83–85
| journal = Science
|bibcode = 1990Sci...247...83E }}</ref> — including [[Tubulin#γ-Tubulin|γ-tubulin]], [[pericentrin]] and [[ninein]]. In general, each centriole of the centrosome is based on a nine-triplet microtubule assembled in a cartwheel structure, and contains [[centrin]], [[cenexin]] and [[tektin]].<ref name=rieder>{{Cite journal 
| pmid = 11567874 
| date=Oct 2001 | first2 = S. | last3=Khodjakov | first3 = A. 
| title = The centrosome in vertebrates: more than a microtubule-organizing center 
| volume = 11 
| issue = 10 
| pages = 413–419 
| issn = 0962-8924 
| journal = Trends in Cell Biology 
| doi = 10.1016/S0962-8924(01)02085-2
| last1=Rieder | first1=C. L. | last2=Faruki }}</ref>
In many cell types, the centrosome is replaced by a [[cilium]] during cellular differentiation. However, once the cell starts to divide, the cilium is replaced again by the centrosome.<ref>{{cite journal | pmid = 24982683 | doi=10.1016/j.ddmec.2013.03.002 | volume=10 | title=Cell Cycle Regulation of the Centrosome and Cilium | pmc=4073209 | year=2013 | journal=Drug Discov Today Dis Mech | pages=e119–e124  | last1 = Avidor-Reiss | first1 = T | last2 = Gopalakrishnan | first2 = J| issue=3–4 }}</ref>

==History==
The centrosome was discovered jointly by [[Walther Flemming]] in 1875 <ref>Flemming, W. (1875). Studien uber die Entwicklungsgeschichte der Najaden. Sitzungsgeber. Akad. Wiss. Wien 71, 81–147</ref><ref name="Bloodgood">{{cite book |last1=Bloodgood |first1=RA |title=From central to rudimentary to primary: the history of an underappreciated organelle whose time has come. The primary cilium. |chapter=From Central to Rudimentary to Primary: The History of an Underappreciated Organelle Whose Time Has Come.The Primary Cilium |series=Methods in Cell Biology |date=2009 |volume=94 |pages=3–52 |doi=10.1016/S0091-679X(08)94001-2 |pmid=20362083|isbn=9780123750242 }}</ref> and [[Edouard Van Beneden]] in 1876,<ref>Van Beneden, E. (1876). Contribution a l'histoire de la vesiculaire germinative et du premier noyau embryonnaire. Bull. Acad. R. Belg (2me series) 42, 35–97.</ref><ref name="Bloodgood"/> and later described and named in 1888 by [[Theodor Boveri]].<ref>{{cite book
  | last = Boveri
  | first = Theodor
  | author-link = Theodor Boveri
  | title = Zellen-Studien II: Die Befruchtung und Teilung des Eies von Ascaris megalocephala.
  | publisher = Gustav Fischer Verlag
  | location = Jena
  | year = 1888
  | volume = H.2 c.2
 | url = https://www.biodiversitylibrary.org/item/29952
  | access-date = 2018-01-14
  | archive-date = 2021-08-26
  | archive-url = https://web.archive.org/web/20210826031459/https://www.biodiversitylibrary.org/item/29952
  | url-status = live
  }}</ref>

==Functions==
{{Further|Centrosome cycle}}
[[Image:Molly Sheehan Wikipedia 1.jpg|right|thumb|300px|Role of the centrosome in cell cycle progression]]
 
Centrosomes are associated with the [[nuclear membrane]] during the [[prophase]] stage of the cell cycle. During [[mitosis]], the nuclear membrane breaks down, and the centrosome-nucleated [[microtubule]]s can interact with the [[chromosome]]s to build the [[mitotic spindle]].

The mother centriole, the older of the two in the centriole pair, also has a central role in making [[cilia]] and [[flagella]].<ref name=rieder/>

The centrosome is copied only once per [[cell cycle]], so that each daughter cell inherits one centrosome, containing two structures called centrioles. The centrosome replicates during the [[S phase]] of the cell cycle. During the [[prophase]] in the process of cell division called [[mitosis]], the centrosomes migrate to opposite poles of the cell. The mitotic spindle then forms between the two centrosomes. Upon division, each daughter cell receives one centrosome. Aberrant numbers of centrosomes in a cell have been associated with [[cancer]]. Doubling of a centrosome is similar to [[DNA replication]] in two respects: the [[semiconservative replication|semiconservative]] nature of the process and the action of [[CDK2]] as a regulator of the process.<ref>{{Cite journal
| pmid = 11371338
| date=May 2001 | first = T.
| title = Centrosome duplication. A centriolar pas de deux
| volume = 105
| issue = 4
| pages = 417–420
| issn = 0092-8674
| journal = Cell
| doi = 10.1016/S0092-8674(01)00366-X
| author1=Stearns | s2cid=1622118 | doi-access = free
}}</ref> But the processes are essentially different in that centrosome doubling does not occur by template reading and assembly. The mother centriole just aids in the accumulation of materials required for the assembly of the daughter centriole.<ref>{{Cite journal| first1 = A.| last1 = Rodrigues-martins | first2 = M.| first3 = G.| first4 = D. M.| first5 = M.
| journal = Science
| last5 = Bettencourt-dias
| last2 = Riparbelli
| last4 = Glover
| last3 = Callaini
| s2cid = 6965044 | title = Revisiting the Role of the Mother Centriole in Centriole Biogenesis
| volume = 316
| pages = 1046–50
| year = 2007 
| doi = 10.1126/science.1142950
| pmid =  17463247
| issue =  5827
|bibcode = 2007Sci...316.1046R | hdl = 10400.7/955 | url = https://resolver.caltech.edu/CaltechAUTHORS:20201002-140639487 | hdl-access = free
}}</ref>

[[Image:Cytokinesis-electron-micrograph.jpg|thumb|right|400px|Centrosome (shown by arrow) next to nucleus]]

Centrioles, however, are not required for the progression of mitosis. When the centrioles are irradiated by a laser, mitosis proceeds normally with a morphologically normal spindle. Moreover, development of the fruit fly ''[[Drosophila]]'' is largely normal when centrioles are absent due to a mutation in a gene required for their duplication.<ref name="pmid16814722">{{Cite journal
| last3 = Vinogradova
| last7 = Raff | first1 = R.
| last2 = Lau | first2 = J. | first3 = T.
| last5 = Woods
| last4 = Gardiol | first4 = A. | first5 = G.
| last1 = Basto | first6 = A. | first7 = W.
| title = Flies without centrioles
| journal = Cell
| last6 = Khodjakov
| volume = 125
| issue = 7
| pages = 1375–1386
| date=Jun 2006 | issn = 0092-8674
| pmid = 16814722
| doi = 10.1016/j.cell.2006.05.025
| s2cid = 2080684 | doi-access = free
}}</ref> In the absence of the centrioles, the microtubules of the spindle are focused by [[molecular motor|motor]]s, allowing the formation of a bipolar spindle. Many cells can completely undergo interphase without centrioles.<ref name=rieder/>

Unlike centrioles, centrosomes are required for survival of the organism. Cells without centrosomes lack radial arrays of [[astral microtubules]]. They are also defective in spindle positioning and in the ability to establish a central localization site in cytokinesis. The function of centrosomes in this context is hypothesized to ensure the fidelity of [[cell division]], because it greatly increases the efficacy. Some cell types arrest in the following cell cycle when centrosomes are absent. This is not a universal phenomenon.

When the nematode ''[[Caenorhabditis elegans|C. elegans]]'' egg is fertilized, the sperm delivers a pair of centrioles. These centrioles will form the centrosomes, which will direct the first cell division of the [[zygote]], and this will determine its polarity. It's not yet clear whether the role of the centrosome in polarity determination is microtubule-dependent or independent.

In human reproduction, the [[sperm]] supplies the centriole that creates the centrosome and microtubule system of the zygote.<ref>{{Cite book|chapter=The biology of fertilization in humans|editor=Patrizio, Pasquale|title=A color atlas for human assisted reproduction: laboratory and clinical insights|publisher=Lippincott Williams & Wilkins|year=2003|isbn=978-0-7817-3769-2|page=3|chapter-url=https://books.google.com/books?id=2SBoQ8H-KMIC&pg=PA3|author1=Hewitson, Laura|author2=Schatten, Gerald P.|name-list-style=amp|access-date=2013-11-09|display-editors=etal|archive-date=2024-03-21|archive-url=https://web.archive.org/web/20240321115533/https://books.google.com/books?id=2SBoQ8H-KMIC&pg=PA3#v=onepage&q&f=false|url-status=live}}</ref>

== Centrosome alterations in cancer cells ==

[[Theodor Boveri]], in 1914, described centrosome aberrations in [[cancer]] cells. This initial observation was subsequently extended to many types of human tumors.<ref name=Nigg2002>{{Cite journal
 | title = Centrosome aberrations: cause or consequence of cancer progression?
 | year = 2002
 | author = Nigg, E.A.
 | journal = Nat Rev Cancer
 | pages = 815–821
 | volume = 2
 | pmid = 12415252
 | doi = 10.1038/nrc924
 | issue = 11
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 }}</ref> Centrosome alterations in cancer can be divided in two subgroups — i.e., structural or numeric aberrations — yet both can be found simultaneously in a tumor.

=== Structural aberrations ===
Usually, structural aberrations appear due to uncontrolled expression of centrosome components, or due to post-translational modifications (such as phosphorylations) that are not adequate for the components. These modifications may produce variations in centrosome size (usually too large, due to an excess of pericentriolar material). In addition, because centrosomal proteins have a tendency to form aggregates, centrosome-related bodies (CRBs) are often observed in ectopic places.<ref name=Casenghi2003>{{Cite journal
 | title = Polo-like kinase 1 regulates Nlp, a centrosome protein involved in microtubule nucleation
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 | last1 = Casenghi     | first1 =  M.
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 | last5 =  Korner     | first5 =  R.
 | last6 =  Nigg     | first6 =  E.A. | pmid=12852856
 | issue = 1
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 }}</ref> Both enlarged centrosomes and CRBs are similar to the centrosomal structures observed in tumors.<ref name=Lingle2002>{{Cite journal
 | title = Centrosome amplification drives chromosomal instability in breast tumor development
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 | last9 =  Salisbury     | first9 =  J.L. | doi=10.1073/pnas.032479999 | pmc=122305
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 }}</ref> Even more, these structures can be induced in culture cells by overexpression of specific centrosomal proteins, such as CNap-1 or Nlp.<ref name=Casenghi2003 /><ref name=Fry1998>{{Cite journal
 | title = C-Nap1, a Novel Centrosomal Coiled-Coil Protein and Candidate Substrate of the Cell Cycle–regulated Protein Kinase Nek2
 | year = 1998
 | journal = J Cell Biol
 | pages = 1563–1574
 | volume = 141
 | last1 = Fry     | first1 =  A.M.
 | last2 =  Mayor     | first2 =  T.
 | last3 =  Meraldi     | first3 =  P.
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 }}</ref> These structures may look very similar, yet detailed studies reveal that they may present very different properties, depending on their proteic composition. For instance, their capacity to incorporate γ-TuRC complexes (see also: [[tubulin#γ-Tubulin|γ-tubulin]]) can be very variable, and so their capacity to nucleate [[microtubule]]s<ref name=Lingle2002 /> therefore affects the shape, polarity and motility of implicated tumor cells in different ways.

=== Numeric aberrations ===
The presence of an inadequate number of centrosomes is very often linked to the appearance of [[genome instability]] and the loss of tissue differentiation.<ref name=Lingle2002 /><ref>{{Cite journal
 | title = Centrosome amplification and instability occurs exclusively in aneuploid, but not in diploid colorectal cancer cell lines, and correlates with numerical chromosomal aberrations
 | year = 2000
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 }}</ref> However, the method to count the centrosome number (with two centrioles to each centrosome) is often not very precise, because it is frequently assessed using [[fluorescence microscope|fluorescence microscopy]], which does not have high enough [[optical resolution]] to resolve centrioles that are very close to each other. Nevertheless, it is clear that the presence of an excess of centrosomes is a common event in human tumors. It has been observed that loss of the [[TP53|tumor-suppressor p53]] produces superfluous centrosomes,<ref>{{Cite journal
 |title        = Abnormal centrosome amplification in the absence of p53
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}}</ref> as well as deregulating other proteins implicated in [[cancer]] formation in humans, such as [[BRCA1]] and [[BRCA2]]. (For references, see <ref name=Nigg2002 />.) An excess of centrosomes can be generated by very different mechanisms: specific reduplication of the centrosome, cytokinesis failure during [[cell division]] (generating an increase in chromosome number), cell fusion (such as in cases of infection by specific viruses) or ''de novo'' generation of centrosomes. At this point, there is insufficient information to know how prevalent these mechanisms are ''in vivo'', but it is possible that the increase in centrosome numbers due to a failure during cell division might be more frequent than appreciated, because many "primary" defects in one cell (deregulation of the [[cell cycle]], defective [[DNA]] or [[chromatin]] metabolism, failure in the [[spindle checkpoint]], etc.) would generate a failure in cell division, an increase in [[ploidy]] and an increase in centrosome numbers as a "secondary" effect.<ref>{{Cite journal
 | title = Aurora-A overexpression reveals tetraploidization as a major route to centrosome amplification in p53–/– cells
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==Evolution==
The [[evolution]]ary history of the centrosome and the [[centriole]] has been traced for some of the signature genes — e.g., the [[centrins]].<ref name="pmid17977464"/> Centrins participate in [[calcium signaling]] and are required for centriole duplication.<ref>{{Cite journal
| pmid = 12176356
| year = 2002
| last1 = Salisbury | first1 = J. L.
| last2 = Suino
| last3 = Busby
| last4 = Springett
| title = Centrin-2 is required for centriole duplication in mammalian cells
| volume = 12
| issue = 15
| pages = 1287–1292
| journal = Current Biology
| doi = 10.1016/S0960-9822(02)01019-9 | first2 = K. M. | first3 = R. | first4 = M.
| s2cid = 1415623
| doi-access = free
}}</ref> There exist two main subfamilies of centrins, both of which are present in the early-branching [[eukaryote]] ''[[Giardia intestinalis]]''. Centrins have therefore been present in the common ancestor of eukaryotes. Conversely, they have no recognizable [[homology (biology)|homolog]]s in [[archea]] and [[bacteria]] and are thus part of the "eukaryotic signature genes". Although there are studies on the evolution of the centrins and centrioles,<ref name="pmid17977464"/><ref name="pmid19196504">{{Cite journal| first1 = W. F.
| title = Centriole evolution
| last1 = Marshall
| journal = Current Opinion in Cell Biology
| volume = 21
| issue =  1
| pages = 14–15
| year = 2009
| pmid =  19196504
| pmc =  2835302 
| doi = 10.1016/j.ceb.2009.01.008
}}</ref> no studies have been published on the evolution of the [[pericentriolar material]].

It is evident that some parts of the centrosome are highly diverged in the model species ''[[Drosophila melanogaster]]'' and ''[[Caenorhabditis elegans]]''. For example, both species have lost one of the centrin subfamilies that are usually associated with centriole duplication. ''Drosophila melanogaster'' mutants that lack centrosomes can even develop to morphologically normal adult flies, which then die shortly after birth because their sensory neurons lack [[cilia]].<ref name="pmid16814722"/> Thus, these flies have evolved functionally redundant machinery, which is independent of the centrosomes.

==Associated nucleotides==

Research in 2006 indicated that centrosomes from [[Atlantic surf clam]] eggs contain [[Nucleic acid sequence|RNA sequences]]. The sequences identified were found in "few to no" other places in the cell, and do not appear in existing [[genome]] databases. One identified RNA sequence contains a putative [[RNA polymerase]], leading to the hypothesis of an RNA-based genome within the centrosome.<ref>{{Cite journal| first1 = M. C.| last1 = Alliegro | first2 = M. A.| first3 = R. E.
| title = Centrosome-associated RNA in surf clam oocytes
| last2 = Alliegro
| journal = Proceedings of the National Academy of Sciences
| last3 = Palazzo
| volume = 103| issue = 24
| pages = 9034–9038
| year = 2006| pmid = 16754862| pmc = 1482561 
| doi = 10.1073/pnas.0602859103
|bibcode = 2006PNAS..103.9034A | doi-access = free }}</ref> However, subsequent research has shown that centrosome do not contain their own DNA-based genomes. While it was confirmed that RNA molecules associate with centrosomes, the sequences have still been found within the nucleus. Furthermore, centrosomes can form ''de novo'' after having been removed (e.g., by laser irradiation) from normal cells.<ref name="pmid19196504"/>

== References ==
{{reflist|2|refs=

<ref name=azimzadehscience2012>{{Cite journal|last1=Azimzadeh |first1=Juliette |last2=Wong |first2=Mei Lie |last3=Downhour
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 |title=Centrosome Loss in the Evolution of Planarians |journal=[[Science (journal)|Science]] |volume=335 |issue=6067 |pages=461–463 |pmid= 22223737|doi=10.1126/science.1214457 |year=2012 |pmc=3347778|bibcode=2012Sci...335..461A }}</ref>

<ref name=stowerspr2012>{{Cite journal |author=staff |date=5 January 2012 |title=Flatworms' minimalist approach to cell division reveals the molecular architecture of the human centrosome |format=press release |publisher=[[Stowers Institute for Medical Research]] |url=http://www.stowers.org/media/news/jan-5-2012 |archive-url=https://web.archive.org/web/20120127120757/http://www.stowers.org/media/news/jan-5-2012 |url-status=dead |archive-date=January 27, 2012 |access-date=6 January 2012 }}</ref>

}}

{{Centrosome}}
{{Organelles}}

[[Category:Centrosome| ]]