John Bixby, Ph.D.
Senior Associate Dean for Graduate & Postdoctoral Studies
Director of the Neuroscience Center
Primary Appointment: Molecular and Cellular Pharmacology
Secondary Appointment: The Miami Project to Cure Paralysis
Our lab is trying to achieve a molecular understanding of the ways in which specific neural connections are formed and maintained. To this end, we have studied two aspects of nerve cell differentiation: axon growth and synapse formation. Recently, we have focused on two major topics. First, we have studied the regulation of axon growth and guidance by protein tyrosine phosphatases (PTPs). These proteins help to control the signaling state of a large variety of other proteins inside the cell, and thus are part of a master regulatory system. Many PTPs are transmembrane proteins with large extracellular domains like those of signaling receptors; these "receptor protein tyrosine phosphatases" (RPTPs) seem particularly important for axon growth and guidance. Our studies concern ligand/receptor interactions, signal transduction mechanisms, and biological functions of these RPTPs.
In our new lab, we are working hardest on projects related specifically to regeneration of connections after injury. Major projects include the identification and regulation of inhibitory signaling mechanisms in the injured CNS, and the study of neuronal genes required for axonal regeneration.
I grew up in N.J., and earned a B.A. in Biology from Cornell University in 1975. Although this was early days for neuroscience, Cornell already had a bunch of neurobiologists on the faculty, and my degree included a concentration in neurobiology. As an undergraduate, I worked on a project to study the effects of auditory stimulation on development and hatching of Japanese quail. I have worked on neural development ever since. After graduation, I moved to California, where I stayed until 1988. I went to graduate school in Pasadena at Caltech, where I studied with David Van Essen. At Caltech I worked on the mechanisms underlying synapse elimination at the neuromuscular junction, as well as the anatomy and physiology of extrastriate visual cortex in monkeys. |
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In 1980 I moved down the coast to UCSD, where I did postdoctoral work with Nick Spitzer. My major interest here was in the early differentiation of Xenopus spinal neurons. Among other things, we showed that these spinal neurons can grow and thrive in the complete absence of extracellular calcium, and that calcium removal increases the rate of axon growth in these cells. Up to this point, I was a dyed-in-the-wool electrophysiologist, but I was becoming more and more interested in the nascent field of molecular neuroscience.In 1983, I decided to try to learn this new field, and I moved back up the coast, to Lou Reichardt's lab at UCSF. I stayed at UCSF for 5 years, where I not only learned a lot about molecular biology and biochemistry, but also managed to make some novel observations on the regulation of axon growth by extracellular matrix proteins and cell adhesion molecules.
I finally got a real job in 1988, when I moved to the Dept. of Molecular & Cellular Pharmacology at the University of Miami. Our work here has focused on axon growth regulation by cell adhesion molecules and related proteins, as well as the control of synapse formation at neuromuscular junctions.
In 2003, we managed to recruit Dr. Vance Lemmon from Case Western to the University of Miami. Vance and I decided to work together, and I was fortunate to be able to join the Miami Project to Cure Paralysis at this time. It is a great opportunity to apply what we learn about the basic processes of axon growth and guidance during development to the incredibly challenging problem of spinal cord regeneration after injury. My lab is merged with Vance Lemmon's lab, and we share equipment, lab space, lab meetings, and ideas. . |
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