Name: chromatid movement by microtubule forces
Uploaded: 2021-04-07T12:12:02.000Z
Duration: 1 min 39 s
Channel: JoVE
Description: 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.

K12 Standards

Next Generation Science Standards

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-4

Anaphase A and B

La ségrégation chromosomique a lieu pendant l’anaphase : lorsque les chromatides sœurs se séparent et que les chromatides individuelles se déplacent vers les pôles opposés de la cellule.
La progression de l’anaphase constitue deux processus indépendants mais qui se chevauchent : l’anaphase A et l’anaphase B.
Au cours de l’anaphase A, en l’absence de cohésion des chromatides sœurs, deux forces polaires agissent sur les chromosomes.
La dépolymérisation des microtubules au niveau du kinétochore produit une force vers le pôle. Le flux de microtubules, issu de la dépolymérisation de l’extrémité négative, génère également une force vers le pôle. La combinaison de ces deux forces vers les pôles, accompagnée d’un raccourcissement des microtubules kinétochores, tire les chromatides individuelles vers les pôles du fuseau.
Lorsque les chromosomes filles se déplacent vers les pôles, l’anaphase B commence et les pôles du fuseau sont séparés, allongeant le fuseau. Les protéines motrices, la kinésine-5 et la dynéine, entraînent la séparation des pôles du fuseau.
Les protéines motrices de la kinésine-5 réticulent les extrémités positives des microtubules interpolaires qui se chevauchent. Ces protéines motrices dirigées vers l’extrémité positive génèrent une force vers l’arrière le long des microtubules, poussant les pôles du fuseau à l’écart. 
Les protéines motrices dynéines lient les extrémités positives des microtubules astraux avec les composants du cortex cellulaire. Ces protéines motrices dirigées vers l’extrémité négative génèrent une force, tirant les pôles du fuseau vers le cortex cellulaire.

<ol>
	<li>Alberts, Bruce. « Moteurs moléculaires. » Biologie moléculaire de la cellule. 4e édition. Bibliothèque nationale de médecine des États-Unis, 1er janvier 1970. [<a href="https://www.ncbi.nlm.nih.gov/books/NBK26888/">Source</a>]</li>
	<li>Joglekar, Ajit P, Kerry S Bloom et Ed Salmon. 2010. « Mécanismes de génération de force par des attaches kinétochores-microtubules end-on. » Opinion actuelle en biologie cellulaire 22 (1). Elsevier Ltd : 57 à 67. [<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822009/">Source</a>]</li>
	<li>Khodjakov, Alexey et Tarun Kapoor. 2005. « Flux de microtubules : à quoi est-ce bon ? » Current Biology 15 (23). Elsevier Inc. : R966 à R968. [<a href="https://www.sciencedirect.com/science/article/pii/S0960982205013928">Source</a>]</li>
</ol>

anaphase a et b

Les microtubules se forment par polymérisation bout à bout d’hétérodimères de tubuline. Les microtubules des kinétochores proviennent des pôles du fuseau et leurs extrémités positives se connectent aux kinétochores des chromatides sœurs. Les complexes protéiques Ndc80, présents sur le kinétochore, forment des liens de faible affinité avec l'extrémité positive de ces microtubules du kinétochore.

La dépolymérisation de l'extrémité positive libère des hétérodimères de tubuline de la région terminale du microtubule. À mesure que les sous-unités de tubuline sont perdues, les complexes Ndc80 se détachent et se rattachent aux sites situés en avant du segment dépolymérisant du microtubule. Le processus entraîne un déplacement vers les pôles, tirant le kinétochore et sa chromatide associée vers le pôle du fuseau.

Le flux des microtubules attire les chromatides vers les pôles du fuseau.

Les sous-unités de tubuline formant le réseau de microtubules se déplacent continuellement vers l'extrémité négative, présentant un flux de microtubules dirigé vers l'extrémité négative.

Le flux de microtubules se développe lorsque la dépolymérisation continue à l'extrémité négative est équilibrée par une polymérisation continue à l'extrémité positive. Un taux constant de dépolymérisation et de polymérisation maintient une longueur de microtubule fixe tandis que les sous-unités individuelles du réseau se déplacent vers l'extrémité de dépolymérisation.

Les microtubules des kinétochores soumis à un flux tirent les kinétochores et leurs chromatides associées dans la direction du flux, vers les pôles du fuseau.

Protéines motrices des microtubules – Dynein et Kinesin-5

Les dynéines sont des protéines motrices dirigées vers l'extrémité négative des microtubules. Les dynéines relient les extrémités positives des microtubules astraux aux composants cytosquelettiques du cortex cellulaire, positionnant ainsi les pôles du fuseau dans la cellule. Le mouvement dirigé vers l'extrémité négative des dynéines génère une force qui tire les pôles du fuseau vers le cortex cellulaire.

La kinésine-5 est une protéine motrice orientée vers le côté positif. La kinésine-5 interagit avec les extrémités positives des microtubules interpolaires anti-parallèles dans la zone médiane du fuseau. Ces moteurs de microtubules aident les microtubules interpolaires à glisser les uns sur les autres tout en générant une force écartant les pôles du fuseau.

Anaphase A et B

Les microtubules se forment par polymérisation de bout en bout d’hétérodimères de tubuline. Les microtubules de kinétochore proviennent des pôles du fuseau, et leur ...

Education

Enseignement

JoVE Core

Molecular Biology

Biologie moléculaire

Unit 2

Unité 2

Cell Division

Division cellulaire

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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.

Chromatid Movement by Microtubule Forces

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 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

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

See how kinetochore microtubules, Ndc80, microtubule flux, dynein, and kinesin-5 help move chromatids and position the spindle during anaphase.

Chromatid Movement by Microtubule Forces | JoVE K12

molecular biology

JoVE Core Biologie Moléculaire illustre les processus moléculaires au sein de la cellule grâce à des leçons vidéos claires et concises. Les applications de ces concepts sont ensuite démontrées grâce à des expériences concrètes en laboratoire.

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS1-4.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Intrinsically Disordered Proteins

Ribosomes

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Protein Complex Assembly

Protein and Protein Structures

Conjugated Proteins

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Cooperative Allosteric Transitions

Protein Kinases and Phosphatases

GTPases and their Regulation

Covalently Linked Protein Regulators

protein-complexes-with-interchangeable-parts

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Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

HS-LS1-1

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What is a Nervous System?

Overview

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The Parasympathetic Nervous System

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Physiology of the Circulatory System

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Anatomy of the Heart

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Blood Flow

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

Chromatid Movement by Microtubule Forces

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