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Mol Biol Cell 2017 Mar 01;285:613-623. doi: 10.1091/mbc.E16-06-0466.
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The ultrastructural organization of actin and myosin II filaments in the contractile ring: new support for an old model of cytokinesis.

Henson JH , Ditzler CE , Germain A , Irwin PM , Vogt ET , Yang S , Wu X , Shuster CB .

Despite recent advances in our understanding of the components and spatial regulation of the contractile ring (CR), the precise ultrastructure of actin and myosin II within the animal cell CR remains an unanswered question. We used superresolution light microscopy and platinum replica transmission electron microscopy (TEM) to determine the structural organization of actin and myosin II in isolated cortical cytoskeletons prepared from dividing sea urchin embryos. Three-dimensional structured illumination microscopy indicated that within the CR, actin and myosin II filaments were organized into tightly packed linear arrays oriented along the axis of constriction and restricted to a narrow zone within the furrow. In contrast, myosin II filaments in earlier stages of cytokinesis were organized into small, discrete, and regularly spaced clusters. TEM showed that actin within the CR formed a dense and anisotropic array of elongate, antiparallel filaments, whereas myosin II was organized into laterally associated, head-to-head filament chains highly reminiscent of mammalian cell stress fibers. Together these results not only support the canonical "purse-string" model for contractile ring constriction, but also suggest that the CR may be derived from foci of myosin II filaments in a manner similar to what has been demonstrated in fission yeast.

PubMed ID: 28057763
PMC ID: PMC5328620
Article link: Mol Biol Cell

Species referenced: Echinodermata
Genes referenced: cep152 gsnl LOC100887844 LOC115919910 LOC115925415 LOC577676 LOC586660 LOC590297 LOC590309 LOC591682 rhoa septin2
Antibodies: phospho-LOC592760 Ab1 septin2 Ab1

Article Images: [+] show captions
References [+] :
Beach, Nonmuscle myosin II isoforms coassemble in living cells. 2015, Pubmed