Cbp-dependent histone acetylation mediates axon regeneration induced by environmental enrichment in rodent spinal cord injury models

After a spinal cord injury, axons fail to regenerate in the adult mammalian central nervous system, leading to permanent deficits in sensory and motor functions. Increasing neuronal activity after an injury using electrical stimulation or rehabilitation can enhance neuronal plasticity and result in some degree of recovery; however, the underlying mechanisms remain poorly understood. We found that placing mice in an enriched environment before an injury enhanced the activity of proprioceptive dorsal root ganglion neurons, leading to a lasting increase in their regenerative potential. This effect was dependent on Creb-binding protein (Cbp)-mediated histone acetylation, which increased the expression of genes associated with the regenerative program. Intraperitoneal delivery of a small-molecule activator of Cbp at clinically relevant times promoted regeneration and sprouting of sensory and motor axons, as well as recovery of sensory and motor functions in both the mouse and rat model of spinal cord injury. Our findings showed that the increased regenerative capacity induced by enhancing neuronal activity is mediated by epigenetic reprogramming in rodent models of spinal cord injury. Understanding the mechanisms underlying activity-dependent neuronal plasticity led to the identification of potential molecular targets for improving recovery after spinal cord injury.

Loss of Kdm5c Causes Spurious Transcription and Prevents the Fine-Tuning of Activity-Regulated Enhancers in Neurons

During development, chromatin-modifying enzymes regulate both the timely establishment of cell-type-specific gene programs and the coordinated repression of alternative cell fates. To dissect the role of one such enzyme, the intellectual-disability-linked lysine demethylase 5C (Kdm5c), in the developing and adult brain, we conducted parallel behavioral, transcriptomic, and epigenomic studies in Kdm5c-null and forebrain-restricted inducible knockout mice. Together, genomic analyses and functional assays demonstrate that Kdm5c plays a critical role as a repressor responsible for the developmental silencing of germline genes during cellular differentiation and in fine-tuning activity-regulated enhancers during neuronal maturation. Although the importance of these functions declines after birth, Kdm5c retains an important genome surveillance role preventing the incorrect activation of non-neuronal and cryptic promoters in adult neurons.