Hypothesis

Overexpression of the pioneer transcription factor FOXM1 in aged somatic cells reduces epigenetic noise by recruiting TET-mediated DNA demethylation to enhancer regions, thereby restoring mutual information between transcription factors and target genes and rescuing youthful gene regulatory network topology.

Mechanistic Rationale

FOXM1 binds nucleosomal DNA and opens chromatin at senescence-associated sites, as shown in human dermal fibroblasts [https://pubmed.ncbi.nlm.nih.gov/40133272/]. Recent work links epigenetic drift to stochastic DNA methylation variability that degrades TF‑target mutual information [https://pubmed.ncbi.nlm.nih.gov/41542164/]. We propose FOXM1’s transactivation domain physically interacts with TET2, guiding it to CpG‑rich enhancers that gain methylation with age. This targeted demethylation lowers directional stochastic variability, increases enhancer‑promoter contact fidelity, and boosts the information flow measured as mutual information between TFs and their targets.

Experimental Design

1. Model – Use 20‑month‑old mice with a doxycycline‑inducible FOXM1 transgene driven by a ubiquitous promoter (Rosa26‑rtTA; TetO‑FOXM1). Include littermate controls receiving doxycycline but lacking the transgene.
2. Induction – Administer doxycycline for 4 weeks to achieve sustained FOXM1 overexpression in liver, muscle and skin.
3. Multi‑omics – Perform single‑cell ATAC‑seq, scRNA‑seq, and whole‑genome bisulfite sequencing (scBS‑seq) on isolated cell populations (hepatocytes, satellite cells, fibroblasts).
4. Network Analysis – Compute mutual information between each TF and its predicted target genes across conditions using the modified MI estimator from [https://pubmed.ncbi.nlm.nih.gov/41542164/]. Quantify epigenetic noise as the variance of methylation levels at CpG sites within FOXM1‑bound enhancers.
5. Phenotypic Readouts – Measure fibrosis (hydroxyproline content), muscle grip strength, and skin elasticity.

Expected Outcomes

• FOXM1 overexpression will decrease the standard deviation of methylation at enhancer CpGs by ≥15% relative to controls, indicating reduced epigenetic noise.
• Mutual information between FOXM1 (and other TFs) and target genes will increase by ≥10% in aged cells, approaching youthful levels measured in 3‑month‑old mice.
• Concomitant improvements in tissue function (e.g., 20% reduction in liver fibrosis area, 15% increase in grip strength) will be observed.
• If FOXM1 fails to lower methylation variance or raise MI, the hypothesis is falsified.

Potential Pitfalls and Alternatives

• Doxycycline‑induced overexpression may cause off‑target proliferation effects; include a FOXM1 DNA‑binding mutant as a negative control.
• Cell‑type heterogeneity could mask noise reduction; single‑cell resolution is essential.
• Compensatory upregulation of other pioneer factors (e.g., FOXA2) might occur; monitor their expression to rule out indirect effects.

This hypothesis directly tests whether manipulating a specific TF can epigenetically stabilize enhancer states, thereby rescuing the information‑theoretic decay that underlies aging‑associated GRN rewiring.