A Novel Mutation In The TIGR Gene In A Chinese Primary Open Angle Glaucoma Family

Background:Primary open angle glaucoma (POAG) is one of the leading causes of blindness worldwide. Defects in trabecular -meshwork inducible glucocorticoid response. (TIGR) gene (OMIM: ~*601652) have been shown to be associated with POAG. Many mutations in TIGR gene have been reported. However, in the literature, descriptions of disease-causing TIGR mutations in Chinese population are few.Purpose:To determine the possible TIGR molecular genetic defect underlying POAG in China and to identify the pathogenic mutation causing the disease.Methods:(1) Clinical and genetic study of the POAG familyA large POAG family was chosen from many POAG families we investigated during the last 8 years to be complete studied in thisprogram. The majority of 1 branch of this large Chinese POAG family was personally examined by two senior ophthalmologists. The diagnoses were made by both doctors according to the signs of elevated intraocular pressure (IOP), glaucomatous optic neuropathy and glaucomatous visual field defect. (2) Molecular genetic study of the POAG family1. Isolation of the genomic DNA: genomic DNA was extracted from the family members' blood by using DNA Isolation Kits for Mammalian Blood(Roche Biochimical, Inc).2. PCR primer design: PCR primers were designed to amplify all coding sequences of the TIGR gene plus the flanking sites.3. PCR amplification: PCR amplification was performed in a 50ul or 20ul volume4. Purification of the PCR products: PCR products were purified using Gel purification Kits(Omega, USA)5. Mutation screening: 100 normal control subjects were screened by single strand conformational polymorphism analysis for the mutation.Results:(1) Genetic analysis of the POAG familyThis 5 generation family was composed of 62 members, including 46 males and 16 females. There were 7POAG patients, 3 glaucoma suspects and 10 normal subjects among the family members who donated their blood samples. All POAG patients had elevated intraocular pressures that could not be adequately lowered by medications. Filtering surgery was performed on 6 of 7 affected family members. The remaining one has reached the late stage of POAG.(2) Molecular genetic analysis of the POAG familyA novel disease-causing missence mutation T455K in the third exon of the TIGR gene was identified in all affected family members, all glaucoma suspects and 4 individuals who have not shown apparently signs of glaucoma. None of the subjects without the mutation had glaucoma. Affected individuals with the T455K mutation showed variable onset between 26-59 years of age. The T455K mutation in TIGR gene was not found in the normal controls. A previously reported polymorphism 730+35 (A>G) in the second intron of the TIGR gene was detected in 4 individuals.Conclusion:The novel TIGR sequence alteration T455K that was highly...