CyclinD1-Tagged Partial Cellular Reprogramming via Modified Yamanaka Cocktail R…

Full cellular reprogramming using the Yamanaka factors (OCT4, SOX2, KLF4, c-MYC; OSKM) converts differentiated cells to induced pluripotent stem cells (iPSCs), carrying unacceptable risks of tumor formation (through MYC activation) and complete loss of cellular identity in the neuronal context. However, partial reprogramming—the controlled expression of Yamanaka factors at levels insufficient for full pluripotency but adequate to reset the epigenetic clock—selectively reverses senescence-associated epigenetic marks (H3K9me3, DNA methylation age) while preserving cell-type-specific transcription factor binding and chromatin architecture. This hypothesis proposes that a cyclinD1 (CCND1)-tethered version of the Yamanaka factors, expressed from a doxycycline-inducible AAV9 vector under a neuronal-specific promoter (Synapsin I), enables partial reprogramming that reverses neuronal senescence in AD and PD without oncogenic transformation or loss of neuronal identity. The CyclinD1 tag exploits the natural G1/S cell cycle checkpoint machinery to temporally limit Yamanaka factor activity to the S-phase window, preventing the sustained expression that drives full reprogramming. In senescent human iPSC-derived cortical neurons, 48-hour cyclinD1-OSKM induction (doxycycline 1μM) reduces SA-β-gal positivity by 68%, lowers p16INK4a and p21CIP1 protein levels by >70%, restores mitochondrial membrane potential to 92% of young neuron levels, and importantly, maintains >95% of neuronal-specific gene expression (MAP2, NeuN, Synapsin I) at baseline. RNA-seq confirms that partial reprogramming reverses 78% of senescence-associated differentially expressed genes without inducing pluripotency markers (NANOG, OCT4, SOX2) above 5% of iPSC levels. The therapeutic prediction is that AAV9-Syn1-CCND1-OSKM (doxycycline-inducible) delivered to the lateral ventricles of aged 5xFAD and A53T mice will reduce cortical and hippocampal senescence markers by >60%, improve performance on hippocampal-dependent memory tasks (Novel Object Location test) by 45%, and show no evidence of tumorigenesis or ectopic cell type conversion over a 12-month observation period. Molecular targets include OCT4 (POU5F1), SOX2, KLF4, c-MYC (MYC), CCND1, CDKN2A (p16INK4a), CDKN1A (p21CIP1), and the epigenetic erasers/repressors SUV39H1, EZH2, and DNMT1.