transcriptional and epigenetic regulation of axon regeneration

• DOI: 10.7936/ytad-w503
• Publication Date: 2019-01-01
• Authors: Mahar, Marcus
• Keywords: Next-Generation Sequencing; 571; Neuroscience and Neurobiology; Genetics; AAV; Epigenetics; Reprogramming; Spinal Cord Injury; Molecular Biology

The mammalian nervous system is a highly intricate network consisting of over a hundred billion specialized cells called neurons. One unique characteristic of neurons is their highly polarized morphology; unlike other cells, neurons project long axonal extensions. These structures allow them to connect and communicate with not only other neurons, but also various cell types in the body and give rise to all motor, sensory, and higher order function. Because axons can extend up to three feet, they are also vulnerable to injury from sources such as traumatic brain and spinal cord injuries, stroke, or neurodegenerative diseases. Indeed, patients who have experienced these injuries often suffer debilitating, irreversible loss of function. Interestingly, whereas neurons which reside in the central nervous system are incapable of regenerating after axon injury, neurons of the peripheral nervous system activate a robust pro-regenerative response capable of promoting long distance regeneration and functional recovery. The molecular mechanisms which underlie this pro-regenerative response may provide key insights into how a pro-regenerative response could be stimulated in injured central nervous system neurons. A comprehensive overview of the known molecular mechanisms involved in this response is reviewed in Chapter 1.As mammals age, the synaptic connections between neurons mature. Following axon injury in peripheral nervous system neurons, the genes involved in synaptic function are turned off and genes required for inducing axon growth are activated. These widespread epigenetic and transcriptional changes require a coordinated effort of epigenetic and transcriptional regulators including epigenetic modifiers, transcription factors, and microRNAs. In Chapter 2, we demonstrated that these changes are, in part, a result of the rapid downregulation of microRNA-9 which occurs following axon injury. At baseline in adult peripheral nervous system neurons, microRNA-9 is highly expressed and actively represses various genes ...