Name: how cells set the division plane
Uploaded: 2021-04-07T12:12:02.000Z
Duration: 2 min 13 s
Channel: JoVE

K12 Standards

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High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-4

Determining the Plane of Cell Division

Dzieląca się komórka, dokładnie określająca swoją płaszczyznę podziału komórki, jest niezbędna do pomyślnego rozdzielenia chromosomów i dystrybucji zawartości cytoplazmatycznej do komórek potomnych.
U zwierząt płaszczyzna podziału znajduje się na równiku komórki pomiędzy posegregowanymi chromosomami, a jej położenie jest określane podczas anafazy. Mikrotubule tworzące wrzeciono mitotyczne oddziałują z korą komórkową i odgrywają decydującą rolę w określaniu bruzdy rozszczepienia.
Do wyjaśnienia wyznaczenia płaszczyzny podziału komórki stosuje się trzy różne modele – model stymulacji astralnej, model relaksacji biegunowej i model stymulacji wrzeciona centralnego.
W modelu stymulacji astralnej promieniste układy astralnych mikrotubul oddziałują z korą równikową i indukują powstawanie bruzdy rozszczepienia.
W modelu relaksacji biegunowej mikrotubule astralne wysyłają sygnały hamujące do biegunów komórkowych i w ten sposób hamują powstawanie bruzdy rozszczepienia na obu biegunach. Prowadzi to do skurczu kory mózgowej na równiku komórki.
Gdy rozpocznie się anafaza, międzybiegunowe mikrotubule obecne między posegregowanymi chromosomami przekształcają się w nakładające się na siebie antyrównoległe mikrotubule, znane również jako wrzeciono centralne. W modelu stymulacji wrzeciona centralnego, wrzeciono centralne stymuluje tworzenie bruzd łupliwych w korze równikowej. 
Ogólny konsensus jest taki, że wszystkie trzy procesy działają razem, aby określić płaszczyznę podziału komórki. To wielotorowe podejście może sprawić, że system będzie reagował na wahania stężenia białka, a także wielkości komórek, a tym samym zwiększy dokładność podziału komórek.
Udział każdej metody zależy od typu i rozmiaru komórki. Na przykład w zarodkach C. elegans występuje duży wachlarz astralnych mikrotubul, a zatem może odgrywać bardziej aktywną rolę w określaniu płaszczyzny podziału komórki.

<ol>
	<li>Biologia molekularna komórki, Alberts, wydanie 6. Strony 997-999.</li>
	<li>Molekularna Biologia Komórki, Lodish, wydanie 8. Stron - 903.</li>
	<li>Geelen, Danny. "Położenie płaszczyzny podziału jest determinowane przez miejsce podziału korowego na błonie plazmatycznej". W: Biotechnologia i zrównoważone rolnictwo 2006 i później, s. 121-124. Springer, Dordrecht, 2007.</li>
	<li>Balasubramanian, Mohan K., Erfei Bi i Michael Glotzer. "Analiza porównawcza cytokinezy w pączkujących drożdżach, drożdżach rozszczepialnych i komórkach zwierzęcych." Current Biology 14, nr 18 (2004): R806-R818.</li>
	<li>Pieśń, Jan. "Rusztowania septynowe i płaszczyzny łupliwości w Saccharomyces." Komórka 84, nr 2 (1996): 187-190.</li>
	<li>Rincon, Sergio A. i Anne Paoletti. "Mid1/anilina i przestrzenna regulacja cytokinezy u drożdży rozszczepieniowych." Cytoszkielet 69, nr 10 (2012): 764-777.</li>
	<li>Galli, Matilde i Sander van den Heuvel. "Określenie płaszczyzny rozszczepienia we wczesnych zarodkach C. elegans." Roczny przegląd genetyki 42 (2008): 389-411.</li>
</ol>

wyznaczanie płaszczyzny podziału komórki

Umiejscowienie płaszczyzny podziału komórki jest krytycznym etapem podczas rozwoju i różnicowania komórek, szczególnie podczas mitozy, kiedy płaszczyzna jest niezbędna do określenia wielkości dwóch komórek potomnych. Płaszczyzna podziału komórki jest prostopadła do płaszczyzny segregacji chromosomów, ale różne typy organizmów mają różne mechanizmy podziału komórek w zależności od ich morfologii i funkcji. <h4>Komórki zwierzęce</h4> W komórkach zwierzęcych bruzda szczelinowa tworzy się wzdłuż płaszczyzny podziału komórki, zaczynając od kory komórkowej, obszaru poniżej błony komórkowej. Wrzeciono mitotyczne odgrywa decydującą rolę w określeniu płaszczyzny podziału komórki; dlatego zmiana osi wrzeciona mitotycznego może zmienić płaszczyznę podziału. Strategię tę stosują niektóre organizmy eukariotyczne, takie jak Caenorhabditis elegans, w celu przejścia z podziału komórkowego z symetrycznego na asymetryczny. Symetryczny podział komórek prowadzi do powstania dwóch identycznych komórek potomnych i jest często stosowany do hodowli tkanek zawierających wiele komórek tego samego typu. Natomiast podział asymetryczny powoduje różnorodność komórkową, ponieważ generuje dwie nieidentyczne komórki potomne. Na przykład komórki neuroepitelialne początkowo zwiększają swoją liczbę, przechodząc symetryczne podziały. Następnie wykorzystują podział asymetryczny, aby wytworzyć komórki potomne podobne do komórki macierzystej, a także różnicujące neurony. <h4>Drożdże</h4> U pączkujących drożdży, takich jak Saccharomyces cerevisiae, o płaszczyźnie podziału komórki decydują w fazie G1 białka septyny. Cytokinezę osiąga się poprzez utworzenie bruzdy rozszczepiającej w obszarze szyi pączkujących komórek drożdży; jednakże aparat mitotyczny nie odgrywa żadnej roli w określaniu płaszczyzny podziału komórki. Natomiast u drożdży rozszczepialnych, takich jak Schizosaccharomyces pombe, położenie jądra międzyfazowego decyduje o położeniu płaszczyzny podziału komórki w fazie G2. Podczas interfazy białko Mid1 jest zlokalizowane głównie w jądrze; jednakże podczas mitozy Mid1 jest eksportowany z jądra do kory komórki, gdzie rekrutuje składniki pierścienia aktomiozyny do przyśrodkowego obszaru komórki. Ostatecznie prowadzi to do podziału komórki macierzystej na dwie komórki potomne o podobnej wielkości. <h4>Rośliny</h4> W większości komórek roślinnych płaszczyzna podziału jest ustalana, zanim komórka przystąpi do mitozy. Wzdłuż równika komórki macierzystej tworzy się pasmo preprofazy, które wyznacza płaszczyznę podziału komórki. Pasmo preprofazy jest strukturą przypominającą pierścień złożoną z mikrotubul i F-aktyny. Daje początek wiązce mikrotubul zwanej fragmoplastem, która stanowi rusztowanie strukturalne dla ekspansji i pozycjonowania płytek komórkowych.

Wyznaczanie płaszczyzny podziału komórki

Ustawienie płaszczyzny podziału komórki jest krytycznym krokiem podczas rozwoju i różnicowania komórek, szczególnie podczas mitozy, gdy płaszczyzna jest ...

Education

JoVE Core

Molecular Biology

Biologia molekularna

Unit 2

Jednostka 2

Cell Division

Podział komórki

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

how cells set the division plane

How cells set the division plane during cell division affects daughter cell size and, in many cases, cell fate. The plane of division is perpendicular to the plane of chromosome segregation. Different organisms use different cues to place it, based on their shape and needs.

In animal cells, the cleavage furrow forms along the division plane from the cell cortex, the area just below the plasma membrane. The mitotic spindle is the main guide for this position. If the spindle axis changes, the division plane can change as well. Some eukaryotes, such as Caenorhabditis elegans, use this shift to move from symmetric division to asymmetric division.

Symmetric cell division makes two identical daughter cells and is often used to build tissues with many of the same cell type. Asymmetric division makes two different daughter cells and increases cell diversity. Neuroepithelial cells first divide symmetrically to raise their numbers. They later divide asymmetrically to form a daughter cell like the parent cell and another that will become a neuron.

In budding yeast, such as Saccharomyces cerevisiae, septin proteins decide the plane of division during the G1 phase. The cell then completes cytokinesis by forming a cleavage furrow at the bud neck. In this yeast, the mitotic apparatus does not set the division plane.

In fission yeast, such as Schizosaccharomyces pombe, the interphase nucleus helps decide where the division plane will form during the G2 phase. The Mid1 protein stays mainly in the nucleus during interphase. During mitosis, Mid1 moves to the cell cortex and recruits actomyosin ring components to the middle of the cell. This lets the mother cell divide into two similar-sized daughter cells.

In most plant cells, the division plane is set before the cell enters mitosis. A preprophase band forms along the cell equator and marks where division will occur. This ring-like structure contains microtubules and F-actin. It helps form the phragmoplast, which supports cell plate growth and placement.

How Cells Set the Division Plane

mitosis and cytokinesis

Mitosis and Cytokinesis Stages

Mitosis and cytokinesis are the two main steps of cell division. Mitosis is the process that divides the nucleus, while cytokinesis splits the rest of the cell. During mitosis, the cell’s genetic material is separated into two sets. This helps form two new nuclei with the same genetic information. Cytokinesis then completes division by separating the cytoplasm, which creates two daughter cells. These stages work together to make cell division possible in growing and repairing tissues.

duplication of chromatin structure

Chromatin Rebuilding During DNA Replication

Chromatin rebuilding during DNA replication helps cells copy DNA and pass on chromosome structure to daughter cells. During cell division, the genome must be disrupted and then reassembled across the whole chromosome. This process allows chromatin to be inherited, rebuilt, and maintained in new cells. The basic unit of chromatin is the nucleosome. A nucleosome contains DNA wrapped around an octamer of histone proteins, with short linker DNA between neighboring nucleosomes. The histone proteins...

cohesins

Cohesins in Meiosis and Genetic Disorders

Cohesin protein complexes act like molecular glue that keeps sister chromatids together. They are important in both mitosis and meiosis. In mitosis, cohesin complexes are removed from chromosomes before anaphase begins. Meiosis has two rounds of chromosome separation. Meiosis I separates homologous chromosomes, while Meiosis II separates sister chromatids. This process produces four daughter cells. The Meiosis I cohesin complex is made of four subunits: Smc1, Smc3, Rec8, and Scc3. Rec8...

condensins

How Condensins Shape Mitotic Chromosomes

Condensins shape chromosomes during mitosis, the stage when a cell divides. These large protein complexes use ATP, the cell’s energy molecule, to help turn loose post-interphase DNA into compact, separate chromosomes. They organize and segregate chromosomal DNA so it can be passed on correctly. Plant and animal cells contain two condensin complexes: condensin I and condensin II. Each complex has five subunits. Two are SMC, or Structural Maintenance of Chromosomes, subunits. One is a kleisin...

the mitotic spindle

How the Mitotic Spindle Separates Chromosomes

The mitotic spindle is a microtubule-based structure that helps separate chromosomes during cell division. It forms in eukaryotic cells and moves sister chromatids to opposite ends of the parent cell. This leaves each new cell nucleus with the correct genetic material. A bipolar spindle has two poles, and that shape is important for chromosome segregation. In many animal cells, two centrosomes are present when mitosis begins. Each centrosome helps organize a circular set of microtubules at one...

centrosome duplication

Centrosome Duplication in the Cell Cycle

Centrosome duplication is a key part of the animal cell cycle. The centrosome is the main microtubule organizing center, or MTOC, in animal cells. It contains two cylindrical centrioles at its core. Each centriole has nine sets of three microtubules held together by proteins. The two centrioles sit at right angles and are surrounded by the pericentriolar matrix, or PCM, a shapeless protein cloud. Duplication starts early in the cell cycle so each daughter cell can receive a centrosome after...

microtubule instability

Microtubule Growth and Shrinkage

Microtubules are hollow, cylindrical filaments in the cell. They are about 25 nm wide and can range from 200 nm to 25 μm in length. Their main building blocks are GTP-bound tubulin subunits that form αβ-heterodimers, which then assemble into protofilaments. These protofilaments join by lateral bonds to create stable microtubule cylinders. Microtubules are highly dynamic because they repeatedly assemble and break down. They can even grow on one end while shrinking on the other at the same time.

spindle assembly

How the Mitotic Spindle Forms

The mitotic spindle forms through centrosome-mediated, chromatin-mediated, and microtubule-mediated pathways. These pathways often work at the same time. Together, they build a strong spindle apparatus for cell division. In most cells, centrosomes are the main sites where microtubules begin to grow. During the G2 to prophase transition, centrosomes mature and make more microtubules. The growing microtubules extend from both centrosomes, and their plus-ends search for chromosomes by attaching...

attachment of sister chromatids

Kinetochore-Microtubule Binding in Mitosis

Kinetochore-microtubule binding helps chromosomes line up and separate during mitosis. After the nuclear envelope breaks down, condensed chromosomes are exposed to the bipolar microtubules of the mitotic spindle. The kinetochore is a large, disc-shaped protein complex at the centromere region of each sister chromatid, and it serves as the microtubule binding site. Usually, the plus-end of a single microtubule inserts into the kinetochore. In some cases, a kinetochore first makes lateral...

forces acting on chromosomes

Chromosome Movement During Mitosis

Chromosome movement during mitosis depends on several small forces that act at different times and positions in the cell. In prometaphase, these forces help chromosomes move to the equatorial plane and line up at the metaphase plate. Because the forces change with location and stage, chromosome behavior also changes as mitosis continues. Microtubules and motor proteins create two main kinds of force on chromosomes: poleward force and anti-poleward force, also called polar-ejection force.

separation of sister chromatids

Anaphase Start and Chromatid Release

Anaphase starts when sister chromatids are released from one another and pulled toward opposite spindle poles. Before that happens, cohesion along the chromosomal arms is reduced from prophase to metaphase, which helps the sister chromatids resolve. A residual cohesin link still holds them together until the metaphase-to-anaphase transition. This leftover connection helps prevent early separation and reduces the risk of aneuploidy, or the wrong number of chromosomes, in daughter cells. At the...

the spindle assembly checkpoint

How Cells Safeguard Chromosome Separation

The spindle assembly checkpoint helps cells safeguard chromosome separation during anaphase. It acts as a molecular surveillance system. The checkpoint checks whether the steps needed for chromosome segregation are complete before the cell moves on. Many proteins work together to control this checkpoint. If mutations affect these proteins, a cell may enter anaphase too early. Chromosomes can then separate before the needed steps are finished. When this happens, the daughter cells may receive...

anaphase a and b

Chromatid Movement by Microtubule Forces

Chromatid movement during anaphase depends on microtubule forces at the spindle. Kinetochore microtubules grow from the spindle poles, and their plus ends attach to kinetochores on sister chromatids. The kinetochore protein complex Ndc80 makes low-affinity links with the microtubule plus end.

the contractile ring

How Cells Build the Contractile Ring

Contractile rings are built from microfilaments and help separate daughter cells during cytokinesis. This ring forms as the cell cycle moves forward, but the exact timing and coordination with other cell cycle events are still not fully understood. RhoA, a small GTPase in the Ras superfamily, controls contractile ring assembly and function. The inactive form of RhoA is bound to GDP. A guanine nucleotide exchange factor, or Rho-GEF, is located in the cortex region, where the next cell division...

determining the plane of cell division

How cells set the division plane during cell division affects daughter cell size and, in many cases, cell fate. The plane of division is perpendicular to the plane of chromosome segregation. Different organisms use different cues to place it, based on their shape and needs. In animal cells, the cleavage furrow forms along the division plane from the cell cortex, the area just below the plasma membrane. The mitotic spindle is the main guide for this position. If the spindle axis changes, the...

the phragmoplast

How Plant Cells Build a New Wall

Plant cells build a new wall during cytokinesis with help from the phragmoplast. This plant structure forms from the central spindle and related cell parts as the cell finishes dividing. In animal cells, the comparable structure is the midbody, but in plants the phragmoplast expands outward to guide new wall formation. The mature phragmoplast has a donut-like shape. It has an outer leading region, a middle transition zone, and an inner lagging region. New microtubules are assembled...

distribution of cytoplasmic content

How Organelles Are Split During Cytokinesis

Cytokinesis splits a cell’s chromosomes and organelles into two daughter cells. Before cell division, organelles grow and divide. They cannot be made from scratch, so each daughter cell must inherit at least one copy to survive. Many details of this organelle sorting process are still not fully known. The cytoplasm contains organelles, salts, proteins, and water. Small organelles such as peroxisomes and lysosomes can be shared by simple diffusion. Because cells contain many copies of these...

anaphase promoting complex

APC Activates Chromosome Separation

The anaphase-promoting complex, or APC, helps control cell cycle progression by destroying specific proteins at the right time. These proteins are tagged with ubiquitin by ubiquitin ligases and then broken down by the proteasome. The SCF (Skp1/Cullin/F-box) complex and APC are two major ubiquitin ligases involved in this process. SCF stays active throughout the cell cycle, but APC turns on during the metaphase-to-anaphase transition. APC becomes active when Cdc20 or Cdh1 binds to it. These...

key terms and concepts

Learn how animal cells, yeast, and plant cells position the division plane using the spindle, septins, nucleus, and preprophase band.

How Cells Set the Division Plane | JoVE K12

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HS-LS1-2

How Cells Set the Division Plane

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