The poor intrinsic growth capacity of adult central nervous system (CNS) neurons is a major contributor to failed axon regeneration in the brain and spinal cord. Primary sensory neurons in the dorsal root ganglia (DRG) are ideally suited to elucidate the intrinsic neuronal growth mechanisms that underlie regenerative ability. The differential regenerative capacity of the peripheral and central branches of sensory neurons implies that axotomies of the two branches result in different responses in the neuronal cell body. The feasibility of boosting the growth state and regenerative ability of CNS neurons is demonstrated by the striking observation that DRG neurons that have undergone peripheral process axotomy (a """"""""conditioning lesion"""""""") are able to regenerate their subsequently axotomized central process despite a hostile CNS environment. The goal of this proposal is to utilize cellular and molecular approaches to define the molecular switch that controls axon growth in DRG neurons that have undergone peripheral axotomy. First, a candidate approach will be used to identify both changes in the phosphorlyation state of retrogradely transported signaling proteins after axotomy and identify changes in the activity state of stimulus-induced transcription factors that may initiate the growth state. Second, microarray expression profile analysis will be used as an unbiased approach to identify transcription factors that are important in early changes in the DRG growth state after peripheral axotomy. Finally, the functional significance of the transcription factors identified will be tested in a primary neuronal culture assay using Sindbis virus-mediated over-expression analysis and Lentivirus-mediated delivery of interfering RNA (RNAi) knockdown. Finally, promising transcription factors will be tested in an in-vivo spinal cord lesion model using adenovirus-mediated gene transfer to demonstrate the relevance of these candidates to axonal regeneration after spinal cord injury. The long term goal of the applicant is to understand basic molecular and cellular mechanisms that promote axon regeneration, which is critical to devising new therapies for diseases in both the CNS (stroke, spinal cord injury, chronic progressive multiple sclerosis) and PNS (peripheral neuropathies) that currently carry poor prognosis secondary to axonal damage. The immediate goal is to obtain training in the application of state-of-the-art techniques in neurobiology to clinically relevant problems. The candidate's career development plan, guidance from Drs. Tessier Lavigne and Mobley, clinical training plan, and commitment from the Stanford Department of Neurology, will allow the realization of this goal. ? ?
| Zou, Hongyan; Ho, Carole; Wong, Karen et al. (2009) Axotomy-induced Smad1 activation promotes axonal growth in adult sensory neurons. J Neurosci 29:7116-23 |
| Fry, Elizabeth J; Ho, Carole; David, Samuel (2007) A role for Nogo receptor in macrophage clearance from injured peripheral nerve. Neuron 53:649-62 |
