Hoorcollege MCR: Dynamics of Cell division - Agathe Chaigne
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Course
Molecular cell research
Institution
Universiteit Utrecht (UU)
This is a summary of Agathe Chaigne's lecture on the dynamics of cell division. This lecture was given in English, so that's why the summary is also in English. Almost everything about the lecture is covered here, including supporting pictures and headings to show what it's about.
Dynamics of Cell Division
Cytokinesis and abscission
Abscission is a sequential process making the final cut between
daughter cells. This is done by an actomyosin ring, which is
created by signaling from the central spindle.
The intercellular bridge is called the midbody, and after abscission
a midbody remnant is present. The midbody is a dense molecular
thing.
The central spindle is in the middle of the cell (spindle =
microtubules). PRC1 is a protein that gives information about
the length of microtubules and MKLP1 and MKLP2 are
motorproteins which makes contraction possible. And this first
part is signaling to the cortex of the cell. The second part is
about the constriction and formation of the midbody. After this,
there is a recruitment of the ESCRT complex and abscission
takes place. In the figure, you can see important proteins
associated with the processes.
The first part is to position the spindle at the right position in the
cell. This is mediated by microtubules, which creates the
spindle. The microtubules push on the cortex and they recruit
some cortex proteins, which create a complex consisting of the
proteins LGN, Gai and NuMa. The complex can recruit dynein, which walks towards the
centrosome and the other side pulls on the microtubules. The spindle always pulls and
pushes. This all happens in the metaphase, but also comparable in anaphase.
In the central spindle formation, antiparallel
microtubules are bundled by PRC1. Another
proteins called CPC and centralspindlin are
recruited to overlap the zone and are
required for microtubule bundling.
Eventually, PRC 1 recruits KIF4, which
limits microtubule growth so a narrow
overlap zone is created. At the same time,
Ect2 binds centralspindlin and is loaded into
the equatorial membrane. Ect2 then converts RhoA-GDP into RhoA-GTP, which triggers the
contractile ring assembly.
So centralspindlin organizes the microtubules and signals to the cortex.
To create two sister cells, the chromosomes need to be separated which is facilitated by
spindle elongation. The chromosome passenger complex (CPC complex) moves from the
chromosomes to the central spindle during anaphase. It stays in the middle where the
microtubules overlaps. When the bridge is formed, CPC stays in the middle, and eventually
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