Estuardo Robles

E-mail: erobles@wisc.edu

Research Project:

My research in the laboratory of Dr. Timothy M. Gomez is aimed at characterizing the cellular basis for growth cone motility and guidance. The growth cone is the highly dynamic structure at the tip of growing axons that regulates axonal extension and synaptic targeting in response to extracellular cues. Live confocal imaging allows us to examine the pathfinding and behavior of growing neurons within the developing embryo of Xenopus laevis, the African clawed frog. The rapid development of a simple primary nervous system makes the amphibian ideal for studying the effects of extracellular guidance cues and signal transduction mechanisms on axon guidance. In addition, the ability to examine neurons in tissue culture allows us to relate growth cone behavior to the cell biology underlying these complex behaviors. Confocal imaging of fluorescently labeled probes allows us to simultaneously monitor the dynamics of intracellular calcium, the cytoskeleton, and adhesion molecules during axon outgrowth. In addition, UV-photolysis of caged compounds such as caged-calcium and -cAMP enables precise examination of how these compounds regulate growth cone motility. Our recent studies have characterized local calcium signaling pathways within growth cone filopodia that function to regulate motility and guidance by locally altering tyrosine kinase signaling. Currently we are examining the roles of adhesion-related cytoskeletal proteins and Rho GTPases in growth cone motility in vitro, as well as the role of tyrosine kinase signaling during axon pathfinding in vivo.

Abstracts and Publications:

• Robles, E. and T.M. Gomez. Src and Cdc42 signals converge at the tips of filopodia to promote motility downstream of axon guidance cues. In Preparation.
• Gomez, T.M., D. Harrigan, J. Henley, and E. Robles. 2003. Working with Xenopus spinal neurons in live cell culture. Meth. Cell Biol. 71: 129-156.
• Robles, E., and T.M. Gomez. 2003. Src tyrosine kinase activity promotes growth cone motility by regulating filopodial extension and the formation of substratum contacts. Amer. Soc. Cell Biol. Abstr.
• Robles, E., and T.M. Gomez. 2003. Distinct aspects of growth cone motility are regulated by tyrosine phosphorylation. Soc. Neurosci. Abstr.
• Robles, E., Huttenlocher, A. and Gomez, T. M. 2003. Filopodial calcium transients regulate growth cone motility and guidance through local activation of calpain. Neuron 38: 597-609. [PDF]
• Gomez, T.M., and E. Robles. 2003. Imaging calcium dynamics in developing neurons. Methods Enzymol. 361: 407-422
• Robles, E., and T.M. Gomez. 2002. Filopodial calcium transients regulate growth cone adhesion and motility through local activation of calpain. Soc. Neurosci. Abstr.
• Robles, E. and T.M. Gomez. 2001. Filopodial calcium transients regulate growth cone adhesion and motility by local activation of calpain. Amer. Soc. for Cell Biol. Abstr.
• Gomez, T.M.*, E. Robles*, M-m. Poo, and N.C. Spitzer. 2001. Filopodial calcium transients promote substrate-dependent growth cone turning. Science 291: 1983-1987. [PDF]
  *These authors contributed equally.
• Robles, E., T.M. Gomez, and N.C. Spitzer. 2000. Filopodial calcium transients regulate growth cone adhesion and substrate dependent growth cone turning. Soc. Neurosci. Abstr.
• Robles, E., T.M. Gomez, and N.C. Spitzer. 1999. Global and local calcium transients promote substrate dependent growth cone turning. Amer. Soc. Cell Biol. Abstr.
• Robles, E., T.M. Gomez, and N.C. Spitzer. 1999. Global and local calcium transients promote substrate dependent growth cone turning. SACNAS Abstr.