Calcium nanodomains in spindles
Bibliographic record
Abstract
Summary The role of calcium signaling in specific events of animal cell meiosis or mitosis (M-phase) is a subject of enduring controversy. Early efforts suggested that increases in intracellular free calcium ([Ca 2+ ] i ) promote spindle disassembly 1, 2 while subsequent work suggested that global [Ca 2+ ] i increases trigger nuclear envelope breakdown, spindle assembly, the metaphase-anaphase transition, and cytokinesis 3-6 . However, further studies led to the conclusion that elevation of [Ca 2+ ] i either has no role in these events, plays a permissive role in these events, or functions as an auxiliary signaling pathway that supplements other mechanisms 7 . One potential explanation of the controversy is that specific M-phase events might depend on highly localized increases in [Ca 2+ ] i , variously referred to as microdomains 8 or nanodomains 9 , as proposed recently 10 . Such domains are hypothesized to arise from rapid shuttling of calcium between closely positioned sources and sinks, rendering them potentially difficult to detect with traditional dyes and largely insensitive to slow chelators such as EGTA 9 . Here a novel microtubule-binding calcium sensor—TubeCamp--was used to test the hypothesis 10 that spindles are associated with calcium nanodomains. TubeCamp imaging revealed that spindles in Xenopus eggs, Xenopus embryos, and HeLa cells were all associated with calcium nanodomains at the spindle poles. Calcium nanodomains also formed in spindles assembled in cell extracts and at the center of monopolar spindles, suggesting that they are a basic feature of spindle self-assembly. Disruption of calcium nanodomains via perturbation of inositol-1,4,5-trisphosphate signaling or rapid chelation of [Ca 2+ ]i resulted in spindle disassembly in vivo and vitro. The results demonstrate the existence of spindle-associated calcium nanodomains and indicate that such domains are an essential and common feature of spindles in vertebrates.
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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 | 0.000 |
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".