email: pphelps@physci.ucla.edu
phone: (310) 825-7264
office: 3802 Life Science Building
homepage: http://www.physci.ucla.edu/research/phelps/index.php
research interests: Neuronal Development and Regeneration: Migration and axon outgrowth
Research Interests
My laboratory studies the mechanisms of neuronal migration and axonal elongation in rodent spinal cord. Current experiments focus on migratory errors in mice with single gene deletions of adhesion molecules such as Reelin. We have found several groups of spinal cord neurons that migrate abnormally in reeler mutants, including some in the superficial dorsal horn, an area involved in nociceptive (pain) processing. Furthermore, we have discovered a significant reduction in mechanical sensitivity and a pronounced increase in thermal nociception in reeler compared with control mice. Future studies will characterize the cause of the nociceptive changes which in turn should help elucidate the role that Reelin plays in nervous system development. A second focus in the lab is to determine if molecules that are important for axonal outgrowth during development are also required for regeneration after spinal cord injury. For example, the L1 cell adhesion molecule facilitates axonal outgrowth during development and we have found that it is re-expressed on regenerating axons following spinal cord injury. Our most recent studies involve transplantation of growth-promoting olfactory ensheathing glia (OEG) combined with extensive step training to promote axon regeneration following complete spinal cord transection in adult rodents. Together the repair strategies of OEG transplantation and training result in functional recovery of hindlimb stepping and axon regeneration across the lesion site.
Selected Publications
Runyan, S.R. and P.E. Phelps. 2009. Mouse olfactory ensheathing glia enhance axon outgrowth on a myelin substrate in vitro Expt. Neurology 216 95-104 .
Takeoka, A., Kubasak, M.D., Zhong, H., Roy, R.R., and Phelps, P.E.. 2009. Serotonergic innervation of the caudal spinal stump in rats after complete spinal transection: Effect of olfactory ensheathing glia J. Comp. Neurol 515 664-676 .
Kubasak, M.D., D.L Jindrich, H. Zhong, A. Takeoka, K.C. McFarland, C. Muñoz-Quiles, R.R. Roy, V.R. Edgerton, A. Ramón-Cueto, and P.E. Phelps. 2008. OEG transplantation and step training enhance hindlimb-stepping ability in adult spinal transected rats Brain 131 264-276 .
Akopians, A.L., A.H. Babayan, U. Beffert, J. Herz, A.I. Basbaum, and P.E. Phelps. 2008. Contribution of the Reelin signaling pathway to nociceptive processing Europ. J. Neurosci 27 523-537 [link].
Runyan, S.A., R.R. Roy, H. Zhong, and P.E. Phelps. 2007. L1 cell adhesion molecule is not required for small-diameter primary afferent sprouting after deafferentation Neuroscience 150 959-969 [link].
Villeda, S.A., L.A. Akopians, A.H. Babayan, A.I. Basbaum, P.E. Phelps. 2006. Absence of Reelin results in altered nociception and aberrant neuronal positioning in the dorsal spinal cord Neuroscience 139 1385-1396 .
Kubasak, MD, R. Brooks, S. Chen, S.A. Villeda, P.E. Phelps. 2004. Developmental distribution of Reelin-positive cells and their secreted product in the rodent spinal cord J Comp Neurol 468 165-178 .
Tran, T.S., S. Cohen-Cory and P.E. Phelps. 2004. Embryonic GABAergic spinal commissural neurons project rostrally to mesencephalic targets J. Comp. Neurol 475 327-339 [link].
Akopians, A, S.A. Runyan, P.E. Phelps. 2003. Expression of L1 decreases during postnatal development of rat spinal cord J. Comp. Neurol 467 375-388 .
de Leon, R.D., M.D. Kubasak, P.E. Phelps, W.K. Timoszyk, D.J. Reinkensmeyer, R.R. Roy, and V.R. Edgerton. 2002. Using robotics to teach the spinal cord to walk Brain Res. Reviews 40 267-273 .