The diameter of the actin ring, i.e., the contractile ring
, became smaller than those at anaphase.
Cytokinesis is achieved by an actin-myosin contractile ring
that physically divides the cell into two daughter cells following separation of the sister chromatids during anaphase.
At the telophase of the second mitotic division (MT2), the width of the midbody that formed between each blastomere decreased with the contraction of the contractile ring
as in the first cleavage.
This concentration of centralspindlin, in turn, recruits the Rho GEF Ect2, which mediates the activation of Rho required for the functioning of the contractile ring
that drives furrowing during cytokinesis (Yuce et al., 2005; Green et al., 2012).
The cleavages take place by constriction of the contractile ring
(CR) formed in the cortex at the division site.
Cleavage furrow: timing of emergence of contractile ring
actin filaments and establishment of the contractile ring
by filament bundling in sea urchin eggs.
These stages are thought to be critical for docking of the meiotic spindle with the cell cortex, and for meiotic apparatus-cortex signaling that mediates the positioning and generation of the contractile ring
. These processes occur by as yet unknown mechanisms.
[Ca.sup.2+] is a key regulator of cytokinesis, the process by which the contractile ring
constricts the cell to form the cleavage furrow.
We refer to this self-organized network of actin filaments as a pseudo-contractile ring because of the following two fundamental properties that it shares with the contractile ring
: (i) it exhibits myosin-II-mediated, anti-parallel sliding of actin filaments (3, 4), and (ii) it assembles during the M-phase of the cell cycle.