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T Matsuo, N Fujiwara, T Umeda, M Nagayama, H Ohtsuki; Protein Expression, Genomic Structure, and Genomic Polymorphisms of Oculomedin . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3379.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To elucidate protein expression, genomic structure, and genomic polymorphisms of a novel gene, "oculomedin", which has been cloned as a mechanical stretch response gene from human trabecular cells in culture (Biochem Biophys Res Commun 1999;259:349-351). Methods: Polyclonal antibody was prepared by immunizing rabbits with a chemically synthesized 15-mer peptide which was a part of 44-mer amino acid sequence of oculomedin. Protein expression was revealed by Western blotting after polyacrylamide gel electrophoresis of protein extracts of mechanically stretched trabecular cells and control trabecular cells in culture as well as the extract of the retinal tissue. Protein localization was studied immunohistochemically in the human eye section. Genomic localization was done by radiation hybrid panel mapping, and genomic structure was determined by search in the GenBank database. Genomic polymorphisms of the coding region in 165 patients with different types of glaucoma were detected by polymerase chain reaction (PCR) amplification and direct sequencing. Results: Oculomedin protein was detected by Western blotting only in mechanically stretched trabecular cells, but not in control trabecular cells in culture. The retina had also its expression. Immunohistochemically, oculomedin protein was localized to the trabecular meshwork, corneal epithelium, and retinal photoreceptor layer. The genome of oculomedin consisted of two exons which were located on chromosome 1q25, distal to MYOC. The second exon contained the coding region. Heterozygous nucleotide substitutions with no amino acid change were found at one or two of 3 locations in 45 (58%) of 77 primary open angle glaucoma (POAG) patients, at one or both of 2 locations in 4 (33%) of 12 primary angle-closure glaucoma (PACG) patients, at one or both of 2 locations in 16 (55%) of 29 normal tension glaucoma (NTG) patients, and at one or both of 2 locations in 17 (70%) of 24 secondary glaucoma (SG) patients. In contrast, heterozygous nucleotide substitutions resulting in amino acid changes were found at one of 4 locations in 4 (5%) of the 77 POAG patients, but were detected in none of the PACG, NTG, or SG patients. Conclusions: Oculomedin was expressed in the trabecular meshwork and the retina, similar to myocilin, suggesting that oculomedin might play a role in the function of the trabecular meshwork. Amino acid changes of oculomedin protein found only in patients with POAG suggest that oculomedin might be responsible for the development of this type of glaucoma.
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