Understanding obstacles to retroviral mediated gene therapy of globin disorders: Implications for design of therapeutic expression cassettes and retrovirus vectors
Bibliographic record
Abstract
To achieve successful retroviral-mediated gene therapy of globin disorders, the transduced β-globin gene must consistently express at therapeutic levels. The Locus Control Region (LCR) controls expression of the human β-like globin gene cluster. In this thesis, transgenic mouse experiments show that full activity from human LCR/β-globin transgenes requires 5′ HS1, the distal β-globin promoter and 3′ enhancer sequences. In vitro DNaseI footprinting experiments identify multiple factors bound to 5′HS1 and the distal promoter. Based on these data a modified LCR holocomplex model is proposed where factors mediate an architectural DNA loop between 5′HS1 and the distal β-globin promoter. A second obstacle to globin gene therapy is that MSCV and HIV-1 vectors dominantly silence linked LCR/β-globin transgenes in transgenic mice. Silencing of reporter genes by retroviral sequences in transgenic Drosophila and de novo methylase null embryonic stem (ES) cells demonstrate that silencing of C-type retroviruses occurs via a conserved mechanism that is not dependent on DNA methylation. A model is proposed where the silenced state is initiated by the formation of closed chromatin on vector sequences and maintained by methylation during differentiation. These findings identify β-globin gene expression cassettes that express to full levels for use in gene therapy and strongly suggest that vector silencing can be overcome by inhibiting the spread of repressive chromatin from the vector to the therapeutic gene.
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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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.004 | 0.005 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.006 |
| 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".