A review of genetic and structural understanding of the role of myocilin in primary open angle glaucoma.

Primary open angle glaucoma (POAG) is the most common form of glaucoma and the second leading cause of blindness in the world. Discovery of the candidate gene MYOC (TIGR/MYOC) encoding the protein myocilin, believed to have a role in cytoskeletal function, might play a key role in understanding the pathogenesis of POAG. MYOC is expressed in many ocular tissues, including trabecular meshwork (TM), a specialised eye tissue essential in regulating intraocular pressure (IOP). Later it was shown to be the trabecular meshwork inducible-glucocorticoid response protein (TIGR). Mutations in MYOC have been identified as the cause of hereditary juvenile-onset open-angle glaucoma (JOAG). The unprocessed myocilin with signal peptide is a 55-kDa protein with 504 amino acids. Mature myocilin is known to form multimers. Wild type myocilin protein is normally secreted into the trabecular extracellular matrix (ECM) and there appears to interact with various ECM materials. It is believed that the deposition of high amounts of myocilin in trabecular ECM could affect aqueous outflow either by physical barrier and/or through cell-mediated process leading to elevation of IOP. The N-terminal region of the myocilin has sequence similarity to myosin (muscle protein) and the C-terminal of the protein has an olfactomedin-like domain. Structural and genetic studies of the MYOC gene and its protein product along with molecular modeling could lead to better understanding of the pathogenesis of POAG. This review highlights the current understanding of myocilin and the relevance of genetic and structural work.

Isolation, purification and preliminary studies on fish eye lens glycoprotein.

Glycoprotein from the eye lens of fish, Mystus cavasius, was isolated by extraction with 1% Triton X-100 in saline. The crude extract which was found to be electrophoretically heterogeneous was fractionated on a DEAE-cellulose column. One of the fractions obtained in major amount was further resolved by column chromatography using Sephadex G-150 into two homogeneous fractions (GP-1 and GP-2]. GP-1 contained carbohydrates (11.2%) and protein (77.5%). The constituent sugars were D-glucose, D-mannose, D-galactosamine and N-acetyl neuraminic acid. The principal amino acids were aspartic acid, serine, glutamic acid, glycine and alanine. The proportions of these residues were determined.