Temporal Dynamics of Rejuvenation and Cell Identity Loss in Aged Neurons

Aging in post-mitotic neurons causes impaired nucleocytoplasmic transport, telomere shortening, chromatin disorganization, epigenetic changes, and cellular senescence. Partial reprogramming with Yamanaka factors (OSKM) reverses these hallmarks, yet prolonged exposure causes "identity loss" where neurons aberrantly express genes from other lineages. Analysis of published datasets reveals that partially reprogrammed retinal neurons express gut, muscle, liver, blood, and olfactory genes, a critical barrier to clinical translation. We hypothesize that reprogramming factor exposure duration determines the balance between rejuvenation and identity loss.This K01 uses optogenetic control of reprogramming factors in HSV vectors to define temporal kinetics of safe neuronal rejuvenation. Aim 1 maps rejuvenation versus identity loss in aged human neurons using 4-hour to 3-day exposures, measuring DNA methylation, chromatin, telomeres, senescence markers, and identity markers. Aim 2 tests whether partial reprogramming reverses aging in vivo in peripheral neurons by delivering optogenetically controlled HSV-OSK/M to aged mouse dorsal root ganglia, using single-nucleus multi-omics comparing transduced versus non-transduced neurons. Aim 3 determines persistence by tracking epigenetic age and senescence over 24 weeks.This work establishes foundational principles for safe cellular rejuvenation by defining kinetics separating rejuvenation from dedifferentiation, provides mechanistic insight distinguishing aging-associated from identity-defining chromatin states, establishes translatable human neuron methods, and defines principles applicable to other post-mitotic tissues. Training in aging biology combined with existing expertise in viral vectors and optogenetics positions the candidate to lead an independent program in translational aging research.