Richard Burry, PhD

Current Research: A special property of nerve cells is the ability to extend cellular processes, which develop specialized endings, or synaptic terminals. The neuron can communicate electrical activity to other neurons through chemical synapses. Considerable information has been accumulated about the function of the synapse, but little is known of the signaling that stimulate these events.

Dr. Burry’s team has examined the distribution of GAP-43, a developmentally regulated neuronal protein. In cultured cerebellar neurons, GAP-43 is found at high levels in growth cones and filopodia, but is seen at low levels in older cultures. Presynaptic terminals have a decreasing amount of GAP-43, and it is only associated with the plasma membrane. GAP-43 is seen at highest levels in the growth cones and distal axons of developing neurons. It is lost from both the soma and proximal axons. The distribution of GAP-43 in developing neurons suggests it is involved in growth-cone activity and possibly in growth-cone functions. These results were obtained with a new immunocytochemical technique developed in Dr. Burry's laboratory. This procedure uses incubations of tissue with 1 nanometer gold particles and subsequent silver enhancement prior to embedding for standard EM.

Dr. Burry’s team has also examined the signaling leading to the expression of GAP-43. Neuronal differentiation is dependent on protein growth factors, which bind to receptor proteins on the surface of developing neurons. As a result of this binding, a cascade of signaling is activated, which changes the cell from a dividing neuroblast to a differentiating neuron.

Nerve growth factor (NGF) is one factor, which binds to a high-affinity receptor, trkA, and starts a signaling cascade. This leads to transcription of new proteins and activation of other signaling enzymes. The neuroendocrine cell line, PC12, differentiate into sympathetic-like neurons with long neurites following stimulation with NGF. NGF-activated signal cascade induces expression of many proteins from cytoskeletal to enzymes that synthesize neurotransmitters. The observation of neurite outgrowth is an indication that these events have been signaled in an appropriate order and that the correct proteins have been expressed.

Additional research includes the CRF as a growth factor in the developing cerebellum. CRF has been extensively studied in the stress pathway, but it is also a peptide neuromodulator in the adult cerebellum changing the excitability of Purkinje cells. In developing cerebellum, CRF has been seen in afferents at early stages of development prior to synapse formation. The CRF receptors are present on granule cells in the external granule cell layer. The early appearance of CRF in the developing cerebellum has lead to the suggestion that CRF has a role in signaling differentiation.

Current experiments are determining the role CRF plays in signaling neuronal differentiation. The initial experiments are examining the signaling pathways activated by the CRF in a cultured neuronal cell PC12 cell line transfected with CRF receptors. Specifically, researchers are looking for the activation or expression of transcription factors. To transfer this information to the developing cerebellum, they are testing the previously identified CRF signaling pathways in primary cultures of rat cerebellar granule cells. With this information, researchers will examine the responses of neurite growth and levels of expression of GAP-43.

Research Techniques:

Biochemistry and Molecular Biology: SDS-PAGE, 2D gel electrophoresis, immunoprecipitation, cell fractionation, western blot, preparation of plasmids, transfection, retroviral production and retroviral infection

Cell Culture: Primary cell cultures of CNS neurons, PC12 cells, neuroblastoma, glial and fibroblast cell lines, mutant cell cloning and generation of monoclonal and polyclonal antibodies

Microscopy: Silver-enhanced gold probe for electron microscopy immunocytochemistry, light microscopic immunocytochemistry, scanning laser confocal microscopy, time-lapse microscopy, scanning electron microscopy and computer-based image analysis

Education:
Postdoctoral Degree: University of Colorado, Health Sciences Center
University of Tennessee, Center for Health Sciences (Dr. John Wood)