EPHA2 Polymorphisms in Estonian Patients with Age-Related Cataract.

BACKGROUND: Ephrin receptors (Ephs) are tyrosine kinases that together with their ligands, ephrins, are considered important in cell-cell communication, especially during embryogenesis but also for epithelium homeostasis. Studies have demonstrated the involvement of mutations or common variants of the gene encoding Eph receptor A2 (EPHA2), in congenital cataract and in age-related cataract. This study investigated a number of disease-associated single nucleotide polymorphisms (SNPs) in EPHA2 in patients with age-related cataract. MATERIALS AND METHODS: The study included 491 Estonian patients who had surgery for age-related cataract, classified as nuclear, cortical, posterior subcapsular and mixed lens opacities, and 185 controls of the same ethnical origin. Seven SNPs in EPHA2 (rs7543472, rs11260867, rs7548209, rs3768293, rs6603867, rs6678616, rs477558) were genotyped using TaqMan Allelic Discrimination. Statistical analyses for single factor associations used χ(2)-test and logistic regression was performed including relevant covariates (age, sex and smoking). RESULTS: In single-SNP allele analysis, only the rs7543472 showed a borderline significant association with risk of cataract (p = 0.048). Regression analysis with known risk factors for cataract showed no significant associations of the studied SNPs with cataract. Stratification by cataract subtype did not alter the results. Adjusted odds ratios were between 0.82 and 1.16 (95% confidence interval 0.61-1.60). CONCLUSIONS: The present study does not support a major role of EphA2 in cataractogenesis in an Estonian population.

A novel ARC gene polymorphism is associated with reduced risk of Alzheimer's disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease, and is clinically characterized by cognitive disturbances and the accumulation of the amyloid ß (Aß) peptides in plaques in the brain. Recent studies have shown the links between AD and the immediate-early gene Arc (activity-regulated cytoskeleton-associated protein), involved in synaptic plasticity and memory consolidation. For example, AD mouse models show a decreased expression of Arc mRNA in the brain. In additional, acute Aß application to brain slices leads to a widespread ARC protein diffusion, unlike the normal defined localization to synapses. In this study, we investigated genetic variation in human ARC and the risk of developing AD. To this end, we genotyped 713 subjects diagnosed with AD and 841 controls without dementia. ARC was sequenced in a group of healthy individuals, and seven previously known SNPs and three novel SNPs were identified. Two of the newly found SNPs were intronic and one, +2852(G/A), was located in the 3'UTR. Three tag SNPs were selected, including the novel SNP +2852(G/A), to relate to risk of AD, Mini Mental State Examination (MMSE) scores and cerebrospinal fluid (CSF) biomarker levels of total tau (T-tau), hyperphosphorylated tau181 (P-tau(181)) and Aß(1-42). The AA genotype of the newly found 3'-UTR SNP +2852(A/G), was associated with a decreased risk of AD (p (c) = 0.005; OR = 0.74; 95 % CI: 0.61-0.89). No associations of single SNPs or haplotypes with MMSE score or CSF biomarkers were found. Here we report a novel ARC SNP associated with a reduced risk of developing AD. To our knowledge, this is the first study associating a gene variant of ARC with any disease. The location of the SNP within the 3'UTR indicates that dendritic targeting of ARC mRNA could be involved in the molecular mechanisms underlying this protective function. However, further investigation of the importance of this SNP for ARC function, ARC processing and the pathology of AD is needed.

No association of LOXL1 gene polymorphisms with Alzheimer's disease.

Aggregation of amyloid-beta is one of the major characteristics in brains of patients with Alzheimer's disease (AD). Although several mechanisms behind the formation of such aggregates have been suggested the regulatory factors are still unknown. The present study aimed at investigating the association of lysyl oxidase-like 1 (LOXL1) polymorphisms with AD diagnosis and cerebrospinal fluid biomarkers (CSF) for the disease. Proteins of the lysyl oxidase (LOX) family are involved in cross-linking extracellular matrix proteins to insoluble fibers and have been associated with neurodegenerative diseases including AD. Genetic polymorphisms in LOXL1 (rs1048661, rs3825942, and rs2165241) have been linked to exfoliation syndrome and exfoliation glaucoma, conditions that have shown association with AD. The polymorphisms were genotyped by Taqman allelic discrimination in a study sample including AD patients (n = 318) and controls (n = 575). In a subgroup of the population, the polymorphisms were analyzed in relation to APOE ε4 genotype and to CSF (T-tau, P-tau, and Aß(1-42)). No evidence for associations of these polymorphisms with risk for AD or any of the studied CSF biomarkers measured was found. These results do not support LOXL1 as being a major risk gene for AD.

Ubiquitin carboxyl-terminal esterase L1 (UCHL1) S18Y polymorphism in patients with cataracts.

BACKGROUND: Cataract is characterized by light-scattering protein aggregates. The ubiquitin-proteasome system has been proposed a role in proteolytic removal of these protein aggregates. Ubiquitin carboxyl-terminal esterase L1 (UCHL1) is a de-ubiquitinating enzyme with important functions in recycling of ubiquitin. A protective role of the p.S18Y polymorphism of the UCHL1 gene has been shown in Parkinson`s disease. The current study aimed to examine possible effects on cataract formation. METHODS: Patients with cataract (n = 493) and controls (n = 142) were analyzed for the UCHL1 p.S18Y polymorphism using dynamic allele-specific hybridization. RESULTS: Significant differences were observed in allele and genotype frequencies of the p.S18Y polymorphism between controls and cataract patients, where a positive UCHL1 allele A carrier status was associated with the cataract diagnosis (adjusted OR 1.7 [95% CI = 1.1-2.6] p = 0.02). No significant differences were seen in genotype distribution when stratifying for type of cataract. Nor did the mean age at cataract surgery differ between genotypes. CONCLUSION: The current study does not support a protective role for the UCHL1 S18Y polymorphism in cataract development, but may instead suggest a disease-promoting effect.

Ubiquitin carboxy-terminal hydrolase L1 (UCHL1) S18Y polymorphism in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by protein aggregates, i.e. senile plaques and neurofibrillary tangles. The ubiquitin-proteasome system has been proposed a role in proteolytic removal of these protein aggregates. Ubiquitin carboxy-terminal hydrolase L1 (UCHL1) is a de-ubiquitinating enzyme with important functions in recycling of ubiquitin. The S18Y polymorphism of the UCHL1 gene confers protection against Parkinson's disease. In this study, the genotype and allele frequencies of the UCHL1 S18Y polymorphism were investigated in 452 AD patients and 234 control subjects, recruited from four memory clinics in Sweden. Using a binary logistic regression model including UCHL1 allele A and APOE epsilon4 allele positivity, age and sex as covariates with AD diagnosis as dependent variable, an adjusted OR of 0.82 ([95% CI 0.55-1.24], P = 0.35) was obtained for a positive UCHL1 allele A carrier status. The present study thus do not support a protective effect of the UCHL1 S18Y polymorphism against AD.

No association of VEGF polymorphims with Alzheimer's disease.

The vascular hypothesis of Alzheimer's disease (AD) has brought the vascular endothelial growth factor (VEGF) into focus. The genomic region including the VEGF gene has been linked to AD and single nucleotide polymorphisms (SNPs) of the VEGF have in previous studies been associated with AD risk. To further evaluate these findings, we genotyped two SNPs in the VEGF gene (rs699947 [-2578]) and rs1570360 [-1154]) by TaqMan Allelic Discrimination in a study sample including AD patients (n = 801) and controls (n = 286). In a subgroup of the population these SNPs were analyzed in relation to APOE epsilon4 genotype, to cerebrospinal fluid biomarkers (T-tau, P-tau, and beta(42)-Amyloid) as well as to neuropathological markers for AD (neurofibrillary tangles and senile plaques). No significant associations with risk for AD or any of the studied biomarkers could be found in this study, thus not supporting VEGF as being a major risk gene for AD.

Association of complement factor H Y402H gene polymorphism with Alzheimer's disease.

Alzheimer's disease (AD) and age-related macular degeneration (AMD) share several epidemiological and biochemical features. The present study aimed to assess the possible influence of the AMD-associated complement factor H (CFH) Y402H (1277T > C) polymorphism on the risk of AD. Caucasian subjects (n = 800) meeting the criteria for probable (n = 717) or definite (n = 83) AD and Caucasian non-demented controls (n = 1265) were included in this multi-center case-control study, in which genotype and allele frequencies of the CFH 1277T > C polymorphism were determined and related to diagnosis, APOE genotype, Mini-Mental State Examination score (MMSE) and the cerebrospinal fluid (CSF) biomarkers total-tau (T-tau), phospho-tau(181) (P-tau(181)), and beta-amyloid(1-42) (Abeta(1-42)). The AMD-associated CFH genotypes (1277CC and 1277TC) were overrepresented in subjects with AD as compared to control individuals (P = 0.029). Positive C carrier status was associated with an odds ratio (OR) for AD of 1.24 (95% confidence interval [CI] 1.02-1.50). When APOE epsilon4 carrier status was included in the regression model, this association was even stronger (OR 1.34, 95% CI: 1.08-1.65, P = 0.007). Subgroup analysis showed that the association between CFH C allele positivity and AD was only evident for individuals carrying the APOE epsilon4 allele. Positive C carrier status was also associated with lower levels of CSF Abeta(1-42) selectively in the control group in an APOE epsilon4-independent manner (P = 0.003). In conclusion, the CFH 1277T > C polymorphism seems to influence the risk of AD and there appears to be an interaction between CFH 1277C and APOE epsilon4 alleles. The CFH 1277C allele may predispose patients for co-morbidity in AD and AMD.

Variability in the kinesin light chain 1 gene may influence risk of age-related cataract.

PURPOSE: Kinesin-mediated cargo vesicle transport is fundamental to the maintenance of a proper lens fiber structure, which is essential for the transparency of the lens. Here, we test the hypothesis that the rs8702 polymorphism in the kinesin light chain 1 gene (KLC1), previously linked to Alzheimer disease (AD), may play a role in cataractogenesis. METHODS: Patients with nuclear (n=76), cortical (n=154), posterior subcapsular (n=117), and mixed (n=148) cataract as well as 183 controls were analyzed for the KLC1 rs8702 polymorphism using the dynamic allele-specific hybridization (DASH) technique. RESULTS: The GG genotype of rs8702 was significantly over-represented among cataract patients as compared to controls (63% versus 52%, respectively, p=0.008) and associated with an age-adjusted odds ratio for cataract development of 1.61 (95% confidence interval 1.12-2.31). This association was not confined to any particular cataract type. CONCLUSIONS: The KLC1 gene may be a novel susceptibility gene for age-related cataract.

Methylenetetrahydrofolate reductase genetic polymorphisms in patients with primary open-angle glaucoma.

PURPOSE: Hyperhomocysteinemia has been found in patients with primary open-angle glaucoma. The purpose of the present study was to determine if hyperhomocysteinemia-associated polymorphisms of the methylenetetrahydrofolate reductase gene (MTHFR) are overrepresented in primary open-angle glaucoma. METHODS: Patients with primary open-angle glaucoma (n = 243) and controls (n = 187) were analyzed for the MTHFR 677 C > T and 1298 A > C polymorphisms using minisequencing technique. RESULTS: No significant differences were observed in allele and genotype frequencies of the MTHFR 677C > T and 1298A > C polymorphisms between controls and the primary open-angle glaucoma group. CONCLUSIONS: If hyperhomocysteinemia is important in the pathogenesis of glaucoma, this study does not support a role for MTHFR polymorphisms in this context.

Apolipoprotein E polymorphisms in patients with primary open-angle glaucoma.

PURPOSE: To investigate apolipoprotein E (APOE) polymorphisms, which are known to influence the risk of Alzheimer disease (AD), in patients with primary open-angle glaucoma (POAG). DESIGN: Retrospective case-control association study. METHODS: Patients with POAG (n = 242) and controls (n = 187) were analyzed for the APOE epsilon 2/epsilon 3/epsilon 4 polymorphisms using minisequencing technique. RESULTS: The Alzheimer-associated APOE epsilon 4 allele had similar frequencies in the POAG group and in the control group. There was no difference between cases and controls with regard to APOE genotypes. CONCLUSIONS: If a common pathogenic mechanism exists for the two age-related neurodegenerative diseases, POAG and AD, it does not involve APOE polymorphisms.

Methylenetetrahydrofolate reductase genetic polymorphisms in patients with cataract.

PURPOSE: Hyperhomocysteinemia is commonly associated with polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene. The level of homocysteine can be lowered by dietary intake of folate. A protective effect of folate supplementation has been reported against cataract. Here we investigate MTHFR polymorphisms in human cataract. DESIGN: Retrospective case-control association study. METHODS: Patients with nuclear (n = 77), cortical (n = 155), posterior subcapsular (n = 119), and mixed (n = 151) cataract, and 187 controls were analyzed for the MTHFR 677C-->T and 1298A-->C polymorphisms using minisequencing technique. RESULTS: The wild-type MTHFR 677CC/1298AA genotype was strongly overrepresented among cataract cases (P = .003). This effect was most pronounced in the mixed cataract group (P < .001). Hyperhomocysteinemia-associated genotypes had similar frequencies in cataract and control groups. CONCLUSIONS: The previously reported protective effect of folate against cataract is not due to overrepresentation of hyperhomocysteinemia-associated MTHFR genotypes. Instead, the strong predominance of wild-type MTHFR in cataract may suggest impaired DNA synthesis as a cataractogenic factor.

The apolipoprotein E polymorphism and the cholesterol-raising effect of coffee.

BACKGROUND: The response of serum cholesterol to diet may be affected by the apolipoprotein E (APOE) epsilon2/epsilon3/epsilon4 polymorphism, which also is a significant predictor of variation in the risk of coronary heart disease (CHD) and CHD death. Here, we test the hypothesis that the APOE polymorphism may modulate the cholesterol-raising effect of coffee. OBJECTIVE: We determined the effect of a coffee abstention period and a daily intake of 600 mL coffee on serum cholesterol and triglycerides with respect to the APOE polymorphism. DESIGN: 121 healthy, non-smoking men (22%) and women (78%) aged 29-65 years, took part in a study with four intervention periods: 1 and 3) a coffee free period of three weeks, 2 and 4) 600 mL coffee/day for four weeks. RESULTS: APOE epsilon2 positive individuals had significantly lower total cholesterol concentration at baseline (4.68 mmol/L and 5.28 mmol/L, respectively, p = 0.01), but the cholesterol-raising effect of coffee was not influenced significantly by APOE allele carrier status. CONCLUSIONS: The APOE epsilon 2 allele is associated with lower serum cholesterol concentration. However, the APOE polymorphism does not seem to influence the cholesterol-raising effect of coffee.

The methylenetetrahydrofolate reductase C677T polymorphism is a major determinant of coffee-induced increase of plasma homocysteine: a randomized placebo controlled study.

Some methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms are associated with hyperhomocysteinemia. Trials have shown a plasma homocysteine raising effect of coffee. We determined the effect of a daily intake of 600 ml coffee and a supplementation of 200 microg folic acid or placebo on plasma homocysteine (tHcy) with respect to the MTHFR C677T and A1298C polymorphisms. One hundred and twenty healthy, non-smoking men (22%) and women (78%) aged 29-65 years, took part in a controlled, randomized, blinded study with two intervention periods: i) a coffee-free period of three weeks, ii) 600 ml coffee/day and a supplement of 200 microg folic acid/d or placebo for four weeks. The results showed that tHcy at baseline was significantly higher for the 677TT genotype group compared to the 677CC genotype group (p=0.0045) and that this group responded with significantly larger increase in tHcy upon coffee exposure than the 677CC and 677CT genotype groups (p=0.0045 and p=0.0041, respectively). Supplementation with 200 microg folic acid compared to placebo reduced the tHcy increasing effect of coffee in the 677TT genotype group. The A1298C polymorphism did not affect tHcy concentration significantly at any stage in the study. In conclusion, the homocysteine increasing effect of coffee is particularly seen in individuals with the homozygous 677TT genotype. Supplementation with 200 microg folic acid/d decreases this tHcy increment.

Transcobalamin polymorphism and serum holo-transcobalamin in relation to Alzheimer's disease.

Isoforms of the vitamin B(12) carrier protein transcobalamin (TC) might influence its cellular availability and contribute to the association between disrupted single-carbon metabolism and Alzheimer's disease (AD). We therefore investigated the relationships between the TC 776C>G (Pro259Arg) genetic polymorphism, total serum cobalamin and holo-TC levels, and disease onset in 70 patients with clinically diagnosed AD and 74 healthy elderly controls. TC 776C>G polymorphism was also determined for 94 histopathologically confirmed AD patients and 107 controls. Serum holo-TC levels were significantly higher in TC 776C homozygotes (p = 0.04). Kaplan-Meier survival functions differed between homozygous genotypes (Cox's F-Test F(42, 46) = 2.1; p = 0.008) and between 776C homozygotes and heterozygotes (Cox's F test F(46, 108) = 1.7; p = 0.02). Proportionately fewer TC 776C homozygotes appear to develop AD at any given age, but this will require confirmation in a longitudinal study.

Influence of the apolipoprotein E epsilon4 allele on human embryonic development.

Human apolipoprotein E (apoE) exists in three major isoforms encoded by distinct alleles (APOE epsilon2, epsilon3 and epsilon4) and has important functions in nerve development and repair. Inheritance of the 4 allele is a major risk factor for the development of Alzheimer's disease. To investigate the role of APOE polymorphisms in embryonic development, we analyzed the APOE genotypes of 81 spontaneously aborted embryos and 110 adult controls using a solid-phase minisequencing technique. The epsilon4 allele was significantly less frequent in the spontaneous abortion group than in the control group (P=0.009), while the frequency of epsilon3 was significantly increased (P=0.005), suggesting that epsilon4 may have protective effects during embryogenesis. These protective effects might counterbalance the deleterious age-related effects of the epsilon4 allele in natural selection.

Increased frequency of combined methylenetetrahydrofolate reductase C677T and A1298C mutated alleles in spontaneously aborted embryos.

The pathogenesis of spontaneous abortion is complex, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms are commonly associated with defects in folate dependent homocysteine metabolism and have been implicated as risk factors for recurrent embryo loss in early pregnancy. In the present study we have determined the prevalence of combined MTHFR C677T and A1298C polymorphisms in DNA samples from spontaneously aborted embryos (foetal death between sixth and twentieth week after conception) and adult controls using solid-phase minisequencing technique. There was a significant odds ratio of 14.2 (95% CI 1.78-113) in spontaneously aborted embryos comparing the prevalence of one or more 677T and 1298C alleles vs the wild type combined genotype (677CC/1298AA), indicating that the MTHFR polymorphisms may have a major impact on foetal survival. Combined 677CT/1298CC, 677TT/1298AC or 677TT/1298CC genotypes, which contain three or four mutant alleles, were not detected in any of the groups, suggesting complete linkage disequilibrium between the two polymorphisms. The present finding of high prevalence of mutated MTHFR genotypes in spontaneously aborted embryos emphasises the potential protective role of periconceptional folic acid supplementation.