Spatial Distribution of Histone Isoforms on the Bovine Active and Inactive X Chromosomes
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Bibliographic record
Abstract
The inactive X chromosome (Xi) in female mammals serves as an important model for studying the role of histone isoforms in directing specific nuclear processes leading to inherited differences in transcription. In the present study, we investigated the distribution of some histone isoforms known to be involved in the process of human X inactivation on their bovine counterparts. To ascertain the identity of active and inactive X chromosome, their distribution was investigated on the X chromosomes in a cell line derived from a bovine female carrying an X;autosome translocation rcp(Xp+;23q-) which allowed the recognition of the maternal (translocated) and paternal (normal) X chromosome. The distribution patterns of histone H3 trimethylated at lysine 9 (H3K9me3) and trimethylated at lysine 27 (H3K27me3), and histone macroH2A1 and macroH2A2 (isoforms specific to heterochromatin) were determined by immunocytochemistry and compared to the temporal pattern of replication using BrdU pulse labeling prior to staining. Immunostaining revealed that H3K9me3, H3K27me3, and macroH2A1 are preferentially concentrated on the Xi, whereas the histone variant macroH2A2 is not a marker for this chromosome. H3K9me3, H3K27me3, and macroH2A1 were consistently located in bands along the Xi, while H3K9me3, macroH2A1 and macroH2A2 localized in the pericentromeric regions of the autosomes. H3K27me3 identified two intense bands on the Xi at Xp22 and Xq31, representing the early replication regions of the chromosome. H3K27me3 and macroH2A1 overlapped in the Xq31 region. It was concluded that different heterochromatin regions on the bovine inactive X chromosome can be identified by their histone isoform composition.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 it