Changes in histone abundance and post-translational modifications in Rana [Lithobates] catesbeiana tissues during temperature-mediated thyroid hormone-induced metamorphosis
Bibliographic record
Abstract
Amphibian metamorphosis involves thyroid hormone (TH)-dependent postembryonic remodeling of differentiated tissues as a tadpole transforms into a frog. Rana [Lithobates] catesbeiana (American bullfrog) metamorphosis can be precociously induced in premetamorphic tadpoles by treatment with exogenous TH. However, metamorphosis is temperature-dependent and does not occur at 5 °C, even with TH treatment. Remarkably, exposure to TH at 5 °C establishes a molecular memory that primes the tadpole for an accelerated metamorphosis when shifted to a permissive temperature (24 °C). Previous research suggests that histone post-translational modifications (PTMs) and the incorporation of histone variants are altered upon cold temperature exposure in the presence and absence of TH. Herein, we use mass spectrometry to analyze the histone composition of premetamorphic R. catesbeiana blood, liver, and tailfin following TH injection at a permissive temperature (24 °C), a non-permissive temperature (5 °C), and a shifted condition (5 → 24 °C). Using stringent selection criteria, we identified tissue- and temperature-specific changes in the abundance and putative PTMs of chromatin-binding proteins, including histones. Linker histone variant H1.0 abundance increased in all three tissues following TH treatment under permissive temperatures only. TH-dependent changes in the abundance of methyl-CpG binding protein 2 (MeCP2) and high mobility group (HMG) proteins were temperature- and tissue-specific. PTMs, including variations in H3K27 and H3K36 methylations in the liver, were differentially abundant following TH treatment under the different temperature conditions. We also identified newly discovered HMGB2 methylation marks that exhibited temperature-specific changes in abundance following TH treatment. These observations suggest that epigenetic variations may contribute to early TH signaling events and to molecular memory.
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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 | 0.001 |
| 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".