Association of polymorphisms in APOE, p53, and p21 with primary open-angle glaucoma in Turkish patients.

PURPOSE: To investigate the association between Apolipoprotein E (APOE), tumor suppressor protein p53 (p53), and cyclin-dependent kinase inhibitor 1A (p21) genes and primary open-angle glaucoma (POAG) in a cohort of Turkish subjects. METHODS: Seventy-five POAG patients (49 women, 26 men) and 119 healthy subjects (67 women, 52 men) were genotyped with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Allele and genotype frequencies between healthy subjects and glaucoma patients were compared by the chi(2) test, and intraocular pressure (IOP), cup/disc ratio (C/D) and visual field indices (MD and PSD) were compared among different APOE, p53, and p21 genotypes in POAG group. A p value <0.05 was considered as statistically significant. RESULTS: The mean ages were 63.8+/-9.5 and 61.8+/-10.2 years in POAG and control groups, respectively (p=0.18). There were no significant differences in the distribution of APOE, p53, and p21 genotypes between the healthy subjects and POAG patients (p=0.38, p=0.12, and p=0.2, respectively). There were no significant differences in maximum IOP, MD, and PSD values among different groups of p53 and p21 genotypes (p>0.05). POAG subjects with the epsilon2epsilon3 genotype had a worse PSD value (median=2.2) than those with the epsilon3epsilon4 genotype (median=1.77; p=0.01) and POAG subjects with the epsilon3epsilon3 genotype had worse MD and PSD values (median= -7.4 and 3.4, respectively) than those with the epsilon3epsilon4 genotype (median= -4.1 and 1.77, respectively; p=0.034 and 0.028, respectively). CONCLUSIONS: Our study found no link between polymorphisms in APOE, p53, and p21 genes and POAG in Turkish patients, although a larger sample is required to elucidate the role of these polymorphisms in the pathogenesis and course of glaucoma.

Exclusion of LCA5 locus in a consanguineous Turkish family with macular coloboma-type LCA.

BACKGROUND: Leber's congenital amaurosis (LCA) is an inherited retinal dystrophy, which causes severe visual impairment in early childhood. Recent molecular genetic studies have linked 11 loci (AIPL1, CRB1, CRX, GUCY2D, RPE65, RDH12, RPGRIP1, TULP1, LCA3, LCA5, and LCA9) to LCA. LCA5 is a new locus, which maps to the 6q11-q16 chromosomal region and was found to be associated with macular coloboma-type LCA in a Pakistani family. Herein, we describe the molecular genetic features of a consanguineous Turkish family in which four children have macular coloboma-type LCA. METHODS: Haplotype analysis was performed on the DNA of the family members using microsatellite markers against GUCY2D, RPE65, and LCA5. Genomic DNA was screened for mutations by means of single-strand conformational polymorphism (SSCP) analysis in exons of the RPE65 and CRX genes. RESULTS: In haplotype analysis, no linkage to LCA5 or GUCY2D loci was detected. None of the tested markers showed homozygosity or segregation between affected siblings. PCR-SSCP mutation analysis revealed no mutations in the screened RPE65 and CRX genes. CONCLUSION: We excluded LCA5 as the genetic cause of macular coloboma-type LCA in this Turkish family. Macular coloboma-type LCA shows genetic heterogeneity and it is not possible to establish a phenotype-genotype correlation with LCA5 and macular coloboma.

The Arg753GLn polymorphism of the human toll-like receptor 2 gene in tuberculosis disease.

Toll-like receptor 2 (TLR2), a member of the Toll-like receptor family, plays an important role in recognition of, and subsequent immune response activation against, mycobacteria. The genetic polymorphism of TLR2 (arginine to glutamine substitution at residue 753 (Arg753Gln)) has been associated with a negative influence on TLR2 function, which may, in turn, determine the innate host response to mycobacteria. The aim of the present study was to investigate the Arg753Gln single nucleotide polymorphism of the TLR2 gene in tuberculosis (TB) patients compared to healthy controls. A retrospective case/control study was carried out. The Arg753Gln polymorphism of the TLR2 gene was studied in 151 TB patients compared to 116 ethnically and age-matched healthy control subjects. The TLR2 polymorphism (adenine (A) allele) was observed in 17.9 and 7.7% of TB patients and controls, respectively. When the ratios of the three genotypes were compared between the two groups, the AA genotype was found to be more significantly associated with TB. Allele frequencies for guanine (G) and A were found to be 0.95 and 0.05 in the control group and 0.86 and 0.14 in the TB patient group, respectively. The risk of developing TB disease was increased 6.04- and 1.60-fold for carriers of the AA and GA genotypes, respectively. In conclusion, the present data suggest that the arginine to glutamine substitution at residue 753 polymorphism of the Toll-like receptor 2 gene influences the risk of developing tuberculosis.

The phenotype of arg555trp mutation in a large Turkish family with corneal granular dystrophy.

PURPOSE: A large Turkish family with 52 members, 26 of whom had Groenouw type 1 corneal granular dystrophy was evaluated by genetic linkage studies and mutation analyses. Phenotype-genotype correlations were also assessed. METHODS: DNA from peripheral blood lymphocytes of 22 family members was used in establishing linkage to chromosome 5q31. Single-strand conformation polymorphism analysis was done to detect mutations in exons 4 and 12 of the human transforming growth factor beta-induced gene located on chromosome 5q31. Automated sequencing was performed on exon 12 of an affected patient. RESULTS: Patients yonger than 15 years of age had typical linear, granular opacities whereas adults had coarser, deeper granular stromal deposits. These changes were not associated with recurrent erosions or significant visual disabilities. The family was linked to chromosome 5q31 and a DNA shift was observed on exon 12 of affected patients. CGG to TGG transition producing R555W mutation was found. CONCLUSIONS: Segregation of Arg555Trp has been described as causing Groenouw type I corneal dystrophy of variable severity in patients of various ethnic backgrounds. In this large Turkish pedigree, the Arg555Trp mutation was associated with a mild phenotype that became clinically evident at five years of age but which remained asymptomatic in terms of corneal erosions.

Vitamin C induced oxidation of eye lens gamma crystallins.

Crystallins are long-lived proteins of the eye lens that have specific structures that maintain lens transparency. Lens crystallins are known to undergo changes with age that include oxidation. Oxidation may contribute to cataract development. In this study the effect of metal-catalysed oxidation of vitamin C (ascorbate) on gamma-crystallins was investigated based on polyacrylamide gel electrophoresis and electrospray mass spectrometry. Cross-linking, aggregation and denaturation occurred when two members of the gamma-crystalline family, gamma B and gamma S, were challenged with copper (II) and ascorbate. These proteins form a dimer, with copper alone or with the addition of ascorbate, which may be an early marker of oxidation. It was found that alpha-ketoglutarate and pyruvate were very effective in the inhibition of oxidation.

Investigation of ascorbate-Cu (II) induced cleavage of DNA by scanning tunneling microscopy.

Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR amplified fragment of human beta-globin gene was used as a model for time dependent cleavage reaction by ascorbate and copper. Cleavage reactions were carried out in a medium containing 0.5 microgram/20 microliters DNA, 20 nM Tris-HC1 pH, 7.8 and ascorbate-Cu (II) in the final concentrations of 1 mM and 30 microM, respectively. The mixtures were incubated at 37 degrees C for 5, 15 and 30 min. For STM studies, 3 pg/5 microliters DNA samples were deposited on the gold coated mica and dried in a water flow vacuum drier. The STM was operated in air at atmospheric pressure with a tip-to-substrate bias of 100 mV and tunneling currents of < 10 pA. Etched tips of Pt/Ir wires were used in a constant current mode. The degradated DNA structure can be distinguished from the intact DNA and the sizes of the degradation products can be identified in the STM micrographs. The size of fragments decreased from approximately 3000 A to 34 A in ascorbate-Cu (II) medium, after 30 min of incubation.

A new electrochemical method for the production of stable ascorbate free radicals.

A new method for the production of ascorbate free radicals is established. The radical is produced from ascorbate in deionized water by applying constant potential electrolysis under a nitrogen atmosphere. Prior to electrolysis, a cyclic voltammogram (CV) of the ascorbic acid was obtained. Electrolysis potentials were selected as the oxidation peak potential of the ascorbic acid obtained by CV. The detection of the radical was done by electron spin resonance (esr) and uv spectroscopies.

Possible role of glutathione in cofactor regeneration of dopamine beta-hydroxylase.

The activity of the enzyme dopamine beta-hydroxylase was determined in rat brain stem by a sensitive coupled radiometric assay. The appropriate copper and dilution parameters have been determined for this tissue. Reduced glutathione has been shown to activate the enzyme homogenate at concentrations of 24-240 microM. This paper shows that glutathione cannot contribute to the inhibitory activity coming from the brain stem. A mechanism is proposed for the role of glutathione in cofactor regeneration of dopamine beta-hydroxylase.