Centers around the elucidation of mechanisms of genetic retinal diseases that lead to blindness with the ultimate goal of developing effective therapies for them. Has included the identification of the causative genes, mutational analyses of the genes in patients, construction of transgenic and knock-out animal models, use of the models to elucidate the pathophysiological mechanisms by which specific gene mutations lead to retinal degeneration, and therapeutic manipulation of the animal models. Began with the cloning of the first causative gene (ornithine aminotransferase) for inherited retinal disease, gyrate atrophy, including the construction and study of an antisense-based transgenic model. Early application of subtractive cloning approach to isolate a number of retinal genes which were subsequently shown to cause retinal degeneration; these included rom-1, a rod photoreceptor disc membrane protein associated with retinitis pigmentosa, recoverin, a calcium-binding inhibitor of rhodopsin kinase, X-arrestin, a cone-specific arrestin, HRG4/UNC119, a photoreceptor synaptic and inner segment protein that is mutated in cone-rod dystrophy, and HRG5, a regulator of retinal G-protein signaling. Construction and study of a transgenic and knock-out model of HRG4/UNC119 led to the elucidation of the function of this protein, including a role in mitochondrial energetics in the synapse and translocation of the photoreceptor G protein, transducin, from the inner segment to the outer segment via binding of the G-protein acyl group. In both cases, the pathophysiological basis of the retinal degeneration was demonstrated, serving as prototypical examples of the type of investigations we pursue.

Gene expression profiling has also been used extensively to study eye processes and diseases, especially age-related macular degeneration (AMD). Through the use of a custom expression profiling strategy (CHANGE), candidate genes were identified for AMD. A conditional over-expression transgenic model was constructed for a candidate gene that showed a correlative increase in AMD, and induction of over-expression of this gene in the model produced a phenotype (choroidal neovascularization, CNV) that is a hallmark of wet AMD, making the model ideal for investigation of the mechanism of the CNV. This model, along with a laser model of CNV, is being used to test the efficacy of therapy based on inhibiting the candidate gene. Since smoking is the best established environmental factor for AMD, the expression profiling approach has also been applied to mice exposed to tobacco smoke to identify AMD candidate genes. Candidate genes identified through smoking have been compared to previously identified AMD candidates, and genes showing consistency are being studied by approaches described above, including construction of animal models.

Higashide, T., Murakami, A., McLaren, M.J., Inana, G. Cloning of the

cDNA for a novel photoreceptor protein. J. Biol. Chem. 271:1797-1804

Higashide, T.,McLaren, M.J., and Inana, G. Localization of HRG4, a

photoreceptor protein homologous to Unc-119, in ribbon synapse.

Invest. Ophthalmol. Vis. Sci. 39:690-698 (1998).

Kobayashi, A., Higashide, T., Hamasaki, D., Sakuma, H., Kubota, S.,

An, W., Fujimaki, T., McLaren, M.J., Weleber, R.G., and Inana, G.

HRG4(UNC119) mutation found in cone-rod dystrophy causes retinal

degeneration in a transgenic model. Invest. Ophthalmol. Vis. Sci.

Ishiba, Y., Higashide, T., Mori, N., Kobayashi, A., Kubota, S., McLaren, M.J.,

Satoh, H., Wong, F., and Inana, G. Targeted inactivation of synaptic HRG4(UNC119)

causes dysfunction in the distal photoreceptor and slow retinal degeneration,

revealing a new function. Exp. Eye Res. 84:473-485, 2007.