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L. Tranchina, F. Oddone, E. Giardina, M. Centofanti, R. Iervolino, G. Manni, G. Novelli; The Genetic Role of MYOC Mt1 Variant in Pigmentary Dispersion Syndrome and Pigmentary Glaucoma: Italian Study. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5112.
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A major susceptibility locus (GLC1A) of primary open angle glaucoma (POAG) mapped on chromosome 1q23-q25 have been identified in different populations with further analysis disclosing mutations in MYOC gene (1q24.3). The MYOC mutations account for 1,1%-4% of POAG, depending on the population. A major variant in the promoter region of the MYOC gene, TIGR/MYOC mt1 (-1000 C/G), is associated with more rapid progression of the glaucoma disease state. This variant accelerates worsening for both optic disc and visual field measures of disease progression.To evaluate the genetic role of mt1 (-1000C/G) on Pigmentary Glaucoma (PG) and Pigmentary dispersion syndrome (PDS) as in POAG in the Italian population
Genomic DNA was extracted from peripheral blood lymphocytes by standard phenol-chloroform extraction. For this study 59 PG/PDS patients, 177 POAG, and 125 controls have been recruited by the Department of Ophthalmology of Tor Vergata University of Rome.Mt1 mutation was analysed using a Real-Time TaqMan genotyping assay (Applied Biosystems, Foster City, CA). We compared genotype and allele frequencies between patients and controls, and among the different types of glaucoma using a Χ2 test.
Genotype frequency of heterozygous (G/C) was 0,12 in PG/PDS, 0,14 in POAG, and 0,23 in controls. As expected on the basis of the genotype frequencies we observed interesting odds ratio (OR) values: 0,44 for PDS and 0,54 for POAG. Our findings in PG/PDS do not support the effect of mt1 variant as an indicator of poor IOP control and greater visual field damage.
Genetic data suggest a protective role for the G allele in PG/PDS as revealed by low OR (0,44). MYOC gene product has been proposed to cause increased intraocular pressure (IOP) by obstruction of aqueous outflow. The latter suggest that G allele may lead to a differential expression of MYOC gene in trabecular cells resulting in a resistance to increased IOP in mt1 carriers.
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