Dissection of a Complex Enhancer Element: Maintenance of Keratinocyte Specificity but Loss of Differentiation Specificity
Bibliographic record
Abstract
In this report, we explored the mechanisms underlying keratinocyte-specific and differentiation-specific gene expression in the skin. We have identified five keratinocyte-specific, open chromatin regions that exist within the 6 kb of 5' upstream regulatory sequence known to faithfully recapitulate the strong endogenous keratin 5 (K5) promoter and/or enhancer activity. One of these, DNase I-hypersensitive site (HSs) 4, was unique in that it acted independently to drive abundant and keratinocyte-specific reporter gene activity in culture and in transgenic mice, despite the fact that it was not essential for K5 enhancer activity. We have identified evolutionarily conserved regulatory elements and a number of their associated proteins that bind to this compact and complex enhancer element. The 125-bp 3' half of this element (referred to as 4.2) is by far the smallest known strong enhancer element possessing keratinocyte-specific activity in vivo. Interestingly, its activity is restricted to a subset of progeny of K5-expressing cells located within the sebaceous gland. The other half of HSs 4 (termed 4.1) possesses activity to suppress sebocyte-specific expression and induce expression in the channel (inner root sheath) cells surrounding the hair shaft. Our findings lead us to a view of keratinocyte gene expression which is determined by multiple regulatory modules, many of which contain AP-2 and/or Sp1/Sp3 binding sites for enhancing expression in skin epithelium, but which also harbor one or more unique sites for the binding of factors which determine specificity. Through mixing and matching of these modules, additional levels of specificity are obtained, indicating that both transcriptional repressors and activators govern the specificity.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".