GENE EXPRESSION IN AXOTOMIZED RETINAL GANGLION CELLS

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Death of retinal ganglion cells is the final common pathway underlying virtually all diseases of the optic nerve, including anterior ischemic optic neuropathy, optic neuritis, and compressive optic neuropathy. Despite a wealth of studies examining the direct effect of hypoxia, excitotoxins, and other injuries on retinal ganglion cells, the effect on these cells of axonal injury, which underlies most optic neuropathies, is far less clearly understood. Attempts to promote regeneration of ganglion cell axons after axotomy presupposes an intact ganglion cell soma; only by preventing ganglion cell death can it be expected that regenerative strategies will succeed. Therefore the overall goal of this proposal is to use recently developed techniques to better understand the subcellular events underlying death of retinal ganglion cells due to axonal injury. The working hypothesis is that axotomy of retinal ganglion cells causes expression of genes that turn on a program for cell death, and that these genes and their products can be characterized. The long-term goal is to modulate these genes or their products and therefore allow rescue of retinal ganglion cells when the optic nerve is injured. The first specific aim is to identify genes differentially expressed in axotomized retinal ganglion cells. A subtracted copy DNA (cDNA) library will be made from messenger RNA (mRNA) extracted from axotomized and control rat retinas. Candidate cDNAs will be screened with Northern blotting or ribonuclease protection assay using RNA probes. The second specific aim is to study the tissue, species, and developmental expression of the identified genes. Gene sequences will be used to look for homologies to other genes associated with cell death. The third specific aim is to express the protein products of the genes and determine their localization and possible function. The health-relatedness of this project is to diseases affecting the anterior and retrobulbar optic nerve. While these disorders directly damage axons contained within the optic nerve, the irreversible loss of vision reflects the death of ganglion cells contained within the retina. Understanding the subcellular nature of the ganglion cell response to axonal injury will allow development of therapies for these diseases. The opportunity to receive formal training in molecular biology and carry out this research program will also further the applicant's goal of becoming an independent investigator.