This laboratory is focused mainly on the investigation of macular function and macular degenerations. Macular degenerations, especially age-related macular degenerations, are a major cause of blindness in the United States. Our basic approach is to isolate differentially expressed genes between macula and peripheral retina. The differentially expressed genes are being analyzed to determine both their functions in the macula and their chromosomal localization to see if they are possible candidates for known retinal or macular degenerations. We are also systematically searching the Best's vitelliform macular dystrophy (a juvenile form of macular degeneration) locus at 11q13 in an effort to isolate the gene causing this disease. Using a solid-phase cDNA subtraction technique developed in our laboratory, we have isolated 13 unknown macular enriched genes and 10 known genes. One of these genes is not detectable by northern blot analysis in any tissue except primate macula. We are studying one of the known genes (Olf-1/EBF), previously cloned in rodents and identified as an olfactory neuron specific transcription factor, which is also involved in early B-cell differentiation. This gene is a high-level transcription factor involved in regulating genes in signal transduction pathways. The Olf-1 gene is highly expressed in primate macula versus peripheral retina. We have cloned the human cDNA, which is significantly longer than those reported for mouse and rat, as well as the human Olf-1 gene. The gene is relatively large, approximately 350 kb in length and contains 16 exons. Northern blot analysis shows relatively high levels of expression of Olf-1 in the macula but nearly undetectable levels of expression in peripheral retina. Immunocytochemical localization of Olf-1 indicates that it is present in the inner plexiform layer of the macula and its expression disappears gradually towards the peripheral retina. Gel-shift assays also support the functional expression of Olf-1 in macula and its low expression in peripheral retina. Additional experiments are in progress to determine the specific role of Olf-1 in the macula. In the past year we have isolated and characterized two genes at the Best's macular dystrophy locus at 11q13. One of these was the hsRPB7, a subunit of the RNA polymerase II complex, and the other is a novel neuron-specific tropomyosin-like protein. After extensive mutational analysis of 9 Best's patients from 6 different families, no mutations were found. We are continuing our search for additional retina-expressed genes at this locus and have identified three additional candidates for further analysis.
