mitotic actomyosin contractile ring

GO:0110085 · Cytoskeleton · Filament · Proposed

A cytoskeletal structure composed of actin filaments, myosin, and myosin-associated proteins that forms beneath the plasma membrane of many cells, including animal cells and yeast cells, in a plane perpendicular to the axis of the mitotic spindle, i.e. the cell division plane. Ring contraction is associated with centripetal growth of the membrane that divides the cytoplasm of the two future daughter cells. In animal cells, the mitotic contractile ring is located inside the plasma membrane at the location of the cleavage furrow. In Saccharomyces cerevisiae, Myo1 localizes to a ring at the future bud site before bud emergence; actin joins this ring at the mother-bud neck near the end of anaphase to form the cytokinetic actomyosin ring. [GO:0110085]

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
actin filaments	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	act1		UNKNOWN	Filamentous actin constituent of the mitotic cytokinetic contractile ring. `GO:0110085` GO:0110085 defines the mitotic actomyosin contractile ring as composed of actin filaments, myosin, and myosin-associated proteins. `DOI:10.1083/jcb.200602032` Wu and Pollard 2006 tracked fission-yeast actin-dependent coalescence of cortical cytokinesis nodes into a compact contractile ring.
myosin proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	myo2		UNKNOWN	Myosin constituent of the mitotic actomyosin ring that forms at the cytokinetic division plane. `GO:0110085` GO:0110085 defines the mitotic actomyosin contractile ring as composed of actin filaments, myosin, and myosin-associated proteins. `DOI:10.1083/jcb.200602032` Wu and Pollard 2006 observed Myo2-containing fission-yeast cytokinesis nodes mature and coalesce into the compact contractile ring.

Taxonomic distribution

NCBITaxon:4896 Schizosaccharomyces pombe — COMMON: Fission yeast assembles a compact actomyosin contractile ring from cytokinesis nodes during mitotic cytokinesis. [DOI:10.1083/jcb.200602032]

Canonical examples

NCBITaxon:4896 Schizosaccharomyces pombe — Fission-yeast mitotic model in which Myo2-containing cytokinesis nodes and actin coalesce into the contractile ring. [DOI:10.1083/jcb.200602032]

Functions

mitotic actomyosin cytokinesis — The mitotic actomyosin contractile ring assembles at the division plane and supports cytokinetic ring constriction.
- GO:0110085 GO:0110085 defines the ring by its mitotic cytokinesis location and association with division-plane membrane ingrowth.
- DOI:10.1083/jcb.200602032 Wu and Pollard 2006 characterized fission-yeast contractile-ring assembly during cytokinesis.

Mechanism graphs

Fission-yeast mitotic actomyosin-ring topology (ASSEMBLY)

Actin filaments and myosin form the fission-yeast mitotic actomyosin contractile ring.

Subject	Predicate	Object	Evidence
actin filaments	contributes to	mitotic actomyosin contractile ring	`GO:0110085` GO:0110085 defines the mitotic ring as an actin-containing cytoskeletal structure.
myosin proteins	contributes to	mitotic actomyosin contractile ring	`GO:0110085` GO:0110085 defines the mitotic ring as containing myosin.

Discussions

INTERPRETATION (RESOLVED): Keep the mitotic actomyosin contractile ring distinct from the generic actomyosin ring and from localized meiotic or bud-neck contractile rings. GO:0110085 denotes the mitotic subtype of the broader actomyosin contractile ring class. GO:0000142 denotes the cellular bud neck child structure and GO:0110086 denotes the meiotic sibling class.
CURATION_TODO (OPEN): Resolve exact source-neutral family groundings and myosin-associated protein boundaries for the mitotic actomyosin contractile ring. GO:0110085 includes myosin-associated proteins in the ring definition and fission-yeast mitotic rings include many node and actin-remodeling factors. This first mitotic subtype record keeps only broad actin and myosin constituents until accessory constituent versus associated-machinery boundaries are reviewed explicitly.
INTERPRETATION (RESOLVED): Distinguish the early budding-yeast Myo1 precursor ring from the later actin-containing contractile ring. The GO:0110085 definition inspected on 2026-10-11 says the budding-yeast mitotic contractile ring forms before mitosis. Bi et al. 1998 instead distinguish an early Myo1 ring from actin recruitment near the end of anaphase. Applying the early myosin-only timing to the actomyosin structure conflates assembly states.

Evidence

GO:0110085 Gene Ontology cellular-component term for the mitotic actomyosin contractile ring.
GO:0005826 Gene Ontology cellular-component parent for actomyosin contractile rings.
GO:0000142 Gene Ontology cellular-component child term for the localized cellular bud neck contractile ring.
GO:0110086 Gene Ontology cellular-component sibling term for meiotic actomyosin contractile rings.
DOI:10.1083/jcb.200602032 Wu and Pollard 2006, 'Assembly of the cytokinetic contractile ring from a broad band of nodes in fission yeast', Journal of Cell Biology.
DOI:10.1083/jcb.142.5.1301 Bi et al. 1998 distinguish Myo1 localization before bud emergence from actin recruitment near the end of anaphase in Saccharomyces cerevisiae. This primary evidence qualifies the budding-yeast timing clause of the GO-derived definition, not the separate fission-yeast model.

Curation history

2026-09-29T22:10:25Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-29T22:11:55Z codex · EXPANDED_RECORD — Added actomyosin-ring parentage, reviewed-label-only actin and myosin constituents, fission-yeast mitotic distribution and canonical example evidence, a cytokinesis function, GO/DOI evidence, a nonmechanistic actomyosin-ring topology graph, and boundary and component-grounding discussions.
2026-09-29T22:12:26Z codex · REFINED_RECORD — Tightened the boundary resolution note so GO:0110086 is described only as a meiotic sibling class rather than as an existing exact record.
2026-10-11T12:55:41Z codex · ADDRESS_SAVED_REVIEW — Addressed #2213: distinguished early budding-yeast Myo1 localization from late actin recruitment, with primary evidence and a preserved GO source-conflict discussion.

Source: data/structures/cytoskeleton/mitotic_actomyosin_contractile_ring.yaml