Abstract 12802: Intron-Mediated Enhancement of <i>Titin</i> ( <i>TTN</i> ) Regulates Sarcomere Formation and Function
Bibliographic record
Abstract
Background: Heterozygous truncating variants in the sarcomere protein titin (TTN) are the most common genetic cause of heart failure, a major cause of morbidity and mortality. This causality indicates that even two-fold changes in the amount of TTN can profoundly disturb cardiac physiology. Although a critical role of TTN in sarcomere formation and cardiomyocyte contractility is well established, the mechanisms regulating transcription of the TTN gene remain poorly understood. Methods: We performed bioinformatics analysis to identify a putative transcriptional enhancer of TTN . Next, we created biallelic deletion of the enhancer in human induced pluripotent stem cell derived cardiomyocytes and performed enhancer reporter assays both in vitro and in vivo to demonstrate necessity and sufficiency of the enhancer in TTN gene expression, respectively. Furthermore, we performed massive parallel reporter assay to define critical transcriptional factors of the TTN enhancer activity and analyzed whole genome sequencing (WGS) data of human patients with unexplained dilated cardiomyopathy (DCM). Results: We identified an intron mediated enhancer that promotes cardiac-specific TTN expression. Global deletion of this element downregulated TTN expression in cardiomyocytes and impaired sarcomere development, while transgenic expression promoted cardiac expression in mice. Using mutational scanning we defined key transcription factor binding sites, including NKX2-5 and MEF2 motifs that promote TTN expression in cardiomyocytes. Consistent with these functions, analyses of WGS data in 69 patients with unexplained DCM revealed one rare variant that disrupted the conserved MEF2 transcriptional factor binding motif. Conclusions: Discovery of a TTN enhancer advances our understanding of cardiomyocyte development, provides an opportunity to modulate TTN transcriptional activity, and ultimately develop therapeutic strategies to treat dilated cardiomyopathy caused by TTN haploinsufficiency.
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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) | 0.002 | 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".