Bibliographic record
Abstract
The spindle apparatus is arguably the most important organelle in cell division. Despite the comprehensive characterization of microtubule regulatory proteins and protein complexes in the past decades, we are still far from being able to reconstitute a functional spindle using purified components. One important question remaining unanswered is whether calcium signaling participates in spindle assembly. Calcium signaling is involved in cell division but is thought to be dispensable for spindle assembly, mainly because excessive EGTA (ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid) is present in the popular in vitro spindle assembly system – Xenopus egg extracts. However, a recent report showed that injection of the fast calcium chelator 1,2-bis(o-aminopheyoxy)ethane-N,N,N’,N’-tetraacetic acid (BAPTA), but not the slow chelator EGTA, causes rapid depolymerization of spindle microtubules in Xenopus oocytes. Differential sensitivity to BAPTA is the defining characteristic of highly restricted, or nanodomain Ca²⁺ signaling, best known to function in presynaptic neurotransmitter release. However, no local Ca²⁺ signals have been identified to be functionally linked to spindle assembly. In this project, a novel microtubule-binding calcium sensor, TubeCamp1 (TC1), was designed to test the hypothesis that spindles are associated with calcium nanodomains. Consistent with the hypothesis, confocal imaging with TC1 revealed microtubule-proximal calcium increase at the spindle poles in Xenopus oocytes and HeLa cells. Calcium nanodomains also formed in spindles assembled in vitro and at the center of monoastral spindles, suggesting that they are a general feature of spindle assembly. Disruption of nanodomain calcium signaling, via rapid chelation of calcium or perturbation of inositol-1,4,5-trisphosphate pathway, resulted in rapid spindle disassembly in intact oocytes and in oocyte extracts. These results demonstrate the existence of spindle-associated calcium nanodomains and suggest that such domains are an important and common feature of spindles in vertebrates. In addition, a Ca²⁺ transient was identified during polar body emission in Xenopus oocytes by using a novel ratiometric probe Tubecamp4 (TC4) and mobile probes Oregon Green-2 and -6f. A close examination of its spatiotemporal pattern with membrane-targeted probes revealed that the Ca²⁺ transient was associated with polar body abscission whereby the polar body is separated from the oocyte, suggesting a role of Ca²⁺ in ensuring the correct number of chromosomes and proper division of cytoplasm. Collectively, these results expand our knowledge in highly localized Ca²⁺ control of spindle assembly and cell cycles, providing new angles for understanding disease pathology and drug intervention.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".