horsetail-astral microtubule array

GO:0032117 · Cytoskeleton · Other · Proposed

An array of astral microtubules that emanates from the spindle pole body during meiosis and facilitates horsetail nuclear movement. [GO:0032117]

Multipanel Figure 4 follows the S. pombe meiotic radial microtubule array and its transition to meiosis I. A shows endogenously tagged wild-type Hrs1 in green and mCherry-Atb2 microtubules in magenta: the prophase array and Hrs1 signal disappear before the later spindle. B and C compare proteasome-impaired and stabilized-Hrs1 cells. D-G contain synchronization plots, immunoblots, phosphatase treatment and a phosphorylation-site schematic, not additional array micrographs. Times in A-C are minutes after filming begins, not a universal meiotic clock. FLUORESCENCE · *Schizosaccharomyces pombe* (`NCBITaxon:4896`) · Charlotta Funaya, Shivanthi Samarasinghe, Sabine Pruggnaller, Midori Ohta, Yvonne Connolly, Jan Müller, Hiroshi Murakami, Agnes Grallert, Masayuki Yamamoto, Duncan Smith, et al.; CC BY, via PubMed Central · CC_BY_3_0 · source: PMC PMC3382715.1 fig4 · `DOI:10.1016/j.cub.2012.02.042`

Synonyms: HAA

Part of: GO:0030981 — cortical microtubule cytoskeleton (no local record)

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
Alpha tubulin	Protein	part of	`InterPro:IPR002452`	tub1, atb2, alp2		UNKNOWN	Alpha-tubulin class of the microtubule polymer forming the meiotic radial array. `DOI:10.1016/j.cub.2012.02.042` Figure 4A directly images mCherry-Atb2-labeled array microtubules in homothallic S. pombe cells. `GO:0005874` The microtubule definition supplies alpha/beta polymer composition, not HAA-specific dimensions or an isoform deletion phenotype.
Beta tubulin	Protein	part of	`InterPro:IPR002453`			UNKNOWN	Beta-tubulin class paired with alpha tubulin in the array microtubule polymer. `GO:0032117` The whole-array definition explicitly specifies astral microtubules. `GO:0005874` Alpha/beta tubulin composition applies to the array microtubules. No beta-tubulin isoform-specific localization or perturbation is inferred. `DOI:10.1016/j.cub.2012.02.042` Tomography and fluorescence establish the radial microtubule structure to which the generic polymer composition applies.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

Alpha tubulin

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P04689`	Tubulin alpha-2 chain	tub1	Schizosaccharomyces pombe 972h- (`NCBITaxon:284812`)	REVIEWED
Role and evidence (2 references) Reference-sequence exemplar for species-level Atb2 imaging; the exact reference stock is not asserted to be the experimental strain. `DOI:10.1016/j.cub.2012.02.042` Figure 4A follows mCherry-Atb2 in the meiotic radial array before its replacement by the meiosis-I spindle. This is not a census of all alpha-tubulin isoforms. `https://www.uniprot.org/uniprotkb/P04689/entry` Native accession, reviewed status, protein label, tub1 primary gene with atb2/alp2 aliases and reference taxon verified on 2026-10-08. The native InterPro response includes the exact Alpha tubulin family; experimental membership comes from the primary study.

Canonical examples

NCBITaxon:4896 Schizosaccharomyces pombe — Meiotic-prophase arrays studied in homothallic cells, including endogenously tagged Hrs1 and mCherry-Atb2 strain KT2901 for Figure 4A, and separately in synchronized pat1 mat-Pc diploids for ultrastructure. No fungal-wide prevalence or identity with the UniProt reference stock is asserted. [DOI:10.1016/j.cub.2012.02.042]

Functions

dynein-driven meiotic oscillatory nuclear movement GO:0030989 — Provides the radial microtubule array that leads spindle-pole and nuclear oscillations during S. pombe meiotic prophase, acting with dynein-dynactin machinery.
- GO:0032117 The exact structure definition specifies facilitation of horsetail nuclear movement.
- DOI:10.1016/j.cub.2005.07.058 Readable primary abstract: Hrs1 loss impairs HAA formation and compromises horsetail movement; ectopic Hrs1 produces HAA-like arrays and nuclear oscillation in interphase. Full text was not accessible, so no detailed motor-interface or quantitative claim is extracted.
- DOI:10.1016/j.cub.2012.02.042 The main-text study follows the Hrs1-dependent radial array during meiotic prophase and its replacement at meiosis I. Chromosome pairing and recombination are not asserted as directly quantified array-only outcomes here.

Mechanism graphs

Hrs1-dependent radial array organization (ASSEMBLY)

S. pombe meiotic-prophase radial-array organization. Hrs1-dependent rMTOC assembly is upstream organizing context, not an assertion that the whole center or SPB is an array constituent. Tomography, immunolocalization and deletion phenotypes support minus-end organization; a purified Hrs1 bridge, nucleation sufficiency and universal microtubule counts are not established.

Subject	Predicate	Object	Evidence
Hrs1-dependent rMTOC assembly	generates	Radial microtubule organizing center near the SPB	`DOI:10.1016/j.cub.2012.02.042` Results sections 2.1-2.2: Hrs1 immunolabels the amorphous region, whereas hrs1 deletion removes that region and the radial arrangement despite residual SPB-associated microtubules.
Radial microtubule organizing center near the SPB	supports	Radial organization of microtubule minus ends	`DOI:10.1016/j.cub.2012.02.042` Tomography places predominantly capped ends in the cytoplasmic rMTOC region; gamma-tubulin enrichment and its altered localization after hrs1 deletion support the organizing-center interpretation, not purified nucleation or attachment sufficiency.
Radial organization of microtubule minus ends	organizes	horsetail-astral microtubule array	`DOI:10.1016/j.cub.2012.02.042` Wild-type-Hrs1 tomograms show varied microtubule orientations around the center; hrs1 deletion loses radial organization. Residual nonradial microtubules are not a retained normal HAA.
Alpha tubulin	contributes_to	microtubule	`GO:0005874` Generic microtubule composition supports this class-level edge; Figure 4A of the primary study separately establishes Atb2 localization in this array.
Beta tubulin	contributes_to	microtubule	`GO:0005874` This is class-level polymer composition, not an isoform-specific HAA experiment or a claim about beta-tubulin essentiality.
microtubule	contributes_to	horsetail-astral microtubule array	`DOI:10.1016/j.cub.2012.02.042` Tomography in Figure 1 and live-cell Atb2 imaging in Figure 4 establish a multi-microtubule array. The whole array is not one filament, a spindle or its organizing center.

Discussions

CURATION_TODO (RESOLVED): Keep the whole meiotic array distinct from its organizer, constituent filaments and neighboring structures. Parsed checks over 907 records and whole-repository searches including ignored and hidden files found only prior read-ahead notes, not an existing HAA record. GO:0032117 is exact; GO:0005818 is its native is-a parent and GO:0030981 its native part-of target. No extra HAA part-of meiotic-spindle claim is inferred from ancestor relations. OTHER denotes a multi-filament system, not one microtubule, the nuclear-movement process, the telomere bouquet, the SPB or the rMTOC. Native GO wording that microtubules emanate from the SPB is retained, while the 2012 ultrastructure resolves their organization near but distinct from the SPB core.
CURATION_TODO (RESOLVED): Separate the array polymer inventory from the organizing-center composition. The initial constituent inventory covers alpha/beta-tubulin polymer classes. The 2012 study localizes Hrs1 and gamma tubulin to the rMTOC and tests Hrs1-dependent organization. These proteins are not automatically asserted to be array-lattice constituents; the center remains external assembly context in the graph. Whole-SPB, nuclear-envelope and bouquet membership is not inferred from spatial proximity or recruitment dependence. This boundary does not deny a physical connection to the array minus ends. A separate source-defined rMTOC record and more detailed membership evidence can refine the representation later.
CURATION_TODO (OPEN): Extend array-associated machinery and isoform coverage only with direct membership and role evidence. This is a bounded polymer inventory, not a complete HAA proteome. The Atb2 reference sequence is not the experimental strain. Beta-tubulin class composition does not justify an Nda3 example without an inspected isoform-specific experiment. Dynein-dynactin participates in movement, but its detailed array-resident composition and assembly essentiality need separate primary-source review before adding machinery rows. Unpublished observations about dynein-assisted radial rearrangement and suggested Hrs1/NudE similarity in the 2012 Discussion are not treated as verified family or component assignments.
KNOWLEDGE_GAP (OPEN): Resolve the physical minus-end attachment and nucleation mechanisms within the organizing region. Ultrastructure, immunolocalization and Hrs1 perturbations establish radial organization but not a purified molecular bridge or sufficiency of an isolated nucleation complex. Yeast-two-hybrid interactions with Kms1 and Alp4 do not establish complete native binding geometry. Gamma-tubulin enrichment is not a census of a fixed ring stoichiometry. Distances and microtubule counts in selected tomograms are assay-specific and are not imported as universal HAA dimensions.
CURATION_TODO (RESOLVED): Keep Hrs1 downregulation and meiotic transition phenotypes source-bounded. Hrs1 degradation and phosphorylation jointly downregulate the radial organizing system near meiosis I. Stabilized nonphosphorylatable Hrs1 can delay bipolar spindle formation; this is not a universal complete block, and outcomes depend on temperature and the spindle checkpoint. Phosphomimetic effects do not prove that every identified phosphorylation has the same native role. Ectopic Hrs1 produces HAA-like arrays in vegetative cells but does not turn every such cell into a native meiotic HAA exemplar. The later spindle is not the HAA, and disappearance of array signal is not direct proof that every tubulin subunit is degraded.
CURATION_TODO (RESOLVED): Preserve experimental, access and imaging limits. Only S. pombe is an organism exemplar; no clade prevalence, fixed whole-array copy number, trait or pathway relation is inferred. Homothallic live-cell imaging and synchronized engineered pat1 mat-Pc diploid EM experiments are distinct. Main Figure 2 text/captions specify 80 minutes for immuno-EM, whereas supplemental methods and the deletion-control caption specify 120 minutes; no single universal sampling time is assigned. Tomography used high-pressure freezing followed by freeze substitution and resin sections, not vitreous cryo-ET. The 2005 source is abstract-only; the 2012 main text, strain table and supplemental methods were read, but movies, raw data and most supplemental image panels remain uninspected. Figure 4 is unchanged CC BY 3.0 material and mixes live-cell images with biochemical and schematic panels; no dimension is inferred from its unquantified scale bars.

Evidence

GO:0032117 Native non-obsolete identity, exact synonym, definition, is-a aster and part-of cortical microtubule cytoskeleton verified through OAK on 2026-10-08.
DOI:10.1016/j.cub.2012.02.042 PMID 22425159; native PMC3382715.1 main text and captions read, with supplemental strain table and methods on pages 13-22. Selected supplemental pages and the unchanged Figure 4 were visually inspected. Movies and raw data were not inspected.
DOI:10.1016/j.cub.2005.07.058 PMID 16111942; published citation and DOI verified at NCBI. The primary abstract was readable, but the direct publisher returned 403; full text and supplements remain unread. Used only for abstract-scoped naming and function statements.

Curation history

2026-10-08T02:05:54Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-08T02:08:20Z codex · EXPANDED_RECORD — Added two tubulin classes, one verified protein example, a source-bounded function and six-edge assembly graph, explicit boundary discussions and an unchanged checksum-verified CC BY 3.0 figure.

Source: data/structures/cytoskeleton/horsetail_astral_microtubule_array.yaml