Mechanisms of Activity-Dependent Transcription and DNA Repair in Neuronal Longevity - Project Summary The overarching goal of this proposal is to define new mechanisms that promote neuronal DNA repair and transcriptional fidelity across lifespan. The number of diagnoses for age-dependent neurodegenerative disease and dementia is projected to more than double by 2050, underscoring our immediate need to understand the cellular and molecular basis of brain aging. A critical aspect of age-dependent cognitive decline is the decreased ability of neurons to adapt to experience-driven changes in neuronal activity. Neuronal activity promotes plasticity, in part, via the de novo induction of cell-type-specific transcriptional programs that mediate learning and memory. However, the induction of such activity-dependent programs drives DNA damage at gene regulatory elements. Neuronal activity is thus a risky endeavor: long-lived neurons must adapt to new cues to facilitate life-long learning and yet maintain a pristine genome. Although accumulating DNA damage is a hallmark of aging and neurodegeneration, our knowledge of the mechanisms that limit damage in post-mitotic neurons is surprisingly limited. How neurons balance transcription and repair, especially in the context of aging neural circuits, is a fundamental unanswered question with major implications for cognitive aging and neurodegenerative disease. Here, we will leverage our lab’s recent discovery that neurons couple activity-dependent transcription to DNA repair through the neuronal chromatin modifier, NPAS4:NuA4. Deletion of NPAS4:NuA4 components in mouse models leads to dysregulated transcriptional responses to activity and increased DNA double-strand breaks across the genome, culminating in drastically reduced organismal longevity. Npas4 expression is reduced in aged neurons, suggesting dysregulation of transcriptional control and genome protection by NPAS4:NuA4 contributes to age-associated neuronal dysfunction. However, the mechanisms by which this protective complex stimulates both transcription and repair remain unclear. We hypothesize that NPAS4:NuA4 promotes genome stability via homology-directed repair factors and enhances transcriptional fidelity during aging via chromatin control of RNA Polymerase II (RNAPII) speed. In Aim 1, we will examine a role for the homology-directed repair factor RAD52 downstream of NPAS4:NuA4 in active neurons and test the consequences of perturbing this pathway on cellular aging phenotypes. In Aim 2, we will assess age-dependent changes to the regulation of activity-dependent transcriptional programs, especially those mediated by NPAS4:NuA4. These mechanistic studies will enhance foundational knowledge of genome control in post- mitotic cells and position us to design strategies that slow or prevent molecular damage in aged and diseased human neurons.
