An epigenome-wide association study meta-analysis of educational attainment.

The epigenome is associated with biological factors, such as disease status, and environmental factors, such as smoking, alcohol consumption and body mass index. Although there is a widespread perception that environmental influences on the epigenome are pervasive and profound, there has been little evidence to date in humans with respect to environmental factors that are biologically distal. Here we provide evidence on the associations between epigenetic modifications-in our case, CpG methylation-and educational attainment (EA), a biologically distal environmental factor that is arguably among the most important life-shaping experiences for individuals. Specifically, we report the results of an epigenome-wide association study meta-analysis of EA based on data from 27 cohort studies with a total of 10 767 individuals. We find nine CpG probes significantly associated with EA. However, robustness analyses show that all nine probes have previously been found to be associated with smoking. Only two associations remain when we perform a sensitivity analysis in the subset of never-smokers, and these two probes are known to be strongly associated with maternal smoking during pregnancy, and thus their association with EA could be due to correlation between EA and maternal smoking. Moreover, the effect sizes of the associations with EA are far smaller than the known associations with the biologically proximal environmental factors alcohol consumption, body mass index, smoking and maternal smoking during pregnancy. Follow-up analyses that combine the effects of many probes also point to small methylation associations with EA that are highly correlated with the combined effects of smoking. If our findings regarding EA can be generalized to other biologically distal environmental factors, then they cast doubt on the hypothesis that such factors have large effects on the epigenome.

Methyl-CpG-binding protein MBD2 plays a key role in maintenance and spread of DNA methylation at CpG islands and shores in cancer.

Cancer is characterised by DNA hypermethylation and gene silencing of CpG island-associated promoters, including tumour-suppressor genes. The methyl-CpG-binding domain (MBD) family of proteins bind to methylated DNA and can aid in the mediation of gene silencing through interaction with histone deacetylases and histone methyltransferases. However, the mechanisms responsible for eliciting CpG island hypermethylation in cancer, and the potential role that MBD proteins play in modulation of the methylome remain unclear. Our previous work demonstrated that MBD2 preferentially binds to the hypermethylated GSTP1 promoter CpG island in prostate cancer cells. Here, we use functional genetic approaches to investigate if MBD2 plays an active role in reshaping the DNA methylation landscape at this locus and genome-wide. First, we show that loss of MBD2 results in inhibition of both maintenance and spread of de novo methylation of a transfected construct containing the GSTP1 promoter CpG island in prostate cancer cells and Mbd2-/- mouse fibroblasts. De novo methylation was rescued by transient expression of Mbd2 in Mbd2-/- cells. Second, we show that MBD2 depletion triggers significant hypomethylation genome-wide in prostate cancer cells with concomitant loss of MBD2 binding at promoter and enhancer regulatory regions. Finally, CpG islands and shores that become hypomethylated after MBD2 depletion in LNCaP cancer cells show significant hypermethylation in clinical prostate cancer samples, highlighting a potential active role of MBD2 in promoting cancer-specific hypermethylation. Importantly, co-immunoprecipiation of MBD2 shows that MBD2 associates with DNA methyltransferase enzymes 1 and 3A. Together our results demonstrate that MBD2 has a critical role in 'rewriting' the cancer methylome at specific regulatory regions.

Genetic effects on information processing speed are moderated by age--converging results from three samples.

Information processing is a cognitive trait forming the basis of complex abilities like executive function. The Trail Making Test (TMT) is a well-established test of information processing with moderate to high heritability. Age of the individual also plays an important role. A number of genetic association studies with the TMT have been performed, which, however, did not consider age as a moderating factor. We report the results of genome-wide association studies (GWASs) on age-independent and age-dependent TMT performance in two population-representative community samples (Munich Antidepressant Response Signature, MARS: N1 = 540; Ludwig Maximilians University, LMU: N2 = 350). Age-dependent genome-wide findings were then evaluated in a third sample of healthy elderly subjects (Sydney Memory and Ageing Study, Sydney MAS: N3 = 448). While a meta-analysis on the GWAS findings did not reveal age-independent TMT associations withstanding correction for multiple testing, we found a genome-wide significant age-moderated effect between variants in the DSG1 gene region and TMT-A performance predominantly reflecting visual processing speed (rs2199301, P(meta-analysis) = 1.3 × 10(-7)). The direction of the interaction suggests for the minor allele a beneficial effect in younger adults turning into a detrimental effect in older adults. The detrimental effect of the missense single nucleotide polymorphism rs1426310 within the same DSG1 gene region could be replicated in Sydney MAS participants aged 70-79, but not in those aged 80 years and older, presumably a result of survivor bias. Our findings demonstrate opposing effects of DSG1 variants on information processing speed depending on age, which might be related to the complex processes that DSG1 is involved with, including cell adhesion and apoptosis.

CCR5-Δ32 genotype does not improve predictive value of IL28B polymorphisms for treatment response in chronic HCV infection.

IL28B polymorphisms strongly predict spontaneous and treatment-induced clearance of hepatitis C virus (HCV) infection. A recent study proposed a 32-base pair deletion in the CC-chemokine receptor 5 (CCR5) gene (CCR5-Δ32) interacting with the IL28B polymorphisms to influence spontaneous HCV clearance. The aim of this study was to clarify the role of CCR5-Δ32 in treatment-induced clearance of chronic hepatitis C (CHC). A cross-sectional cohort of 813 Caucasian patients with CHC genotype 1 (365 responders and 448 non-responders) who had received standard of care dual therapy with interferon (IFN)-α and ribavirin (RBV) was genotyped for the CCR5-Δ32 and IL28B polymorphisms to examine their interaction with respect to treatment response. CCR5-Δ32 did not influence treatment-induced recovery to IFN-α/RBV in CHC, and did not improve prediction of sustained virological response in the context of the IL28B polymorphisms in a multivariate model. CCR5-Δ32 homozygotes were significantly more frequent in those with CHC than healthy controls in the European cohorts (2.9% vs 0.4%, P<0.0001), but not in Australians of European ancestry. In conclusion, CCR5-Δ32 does not influence treatment response in the context of IL28B polymorphisms. Although CCR5-Δ32 may affect viral clearance within closely controlled geographical and genetic environments, we found no effect in larger cohorts treated with dual therapy.

Epigenetic-induced repression of microRNA-205 is associated with MED1 activation and a poorer prognosis in localized prostate cancer.

Deregulation of microRNA (miRNA) expression can have a critical role in carcinogenesis. Here we show in prostate cancer that miRNA-205 (miR-205) transcription is commonly repressed and the MIR-205 locus is hypermethylated. LOC642587, the MIR-205 host gene of unknown function, is also concordantly inactivated. We show that miR-205 targets mediator 1 (MED1, also called TRAP220 and PPARBP) for transcriptional silencing in normal prostate cells, leading to reduction in MED1 mRNA levels, and in total and active phospho-MED1 protein. Overexpression of miR-205 in prostate cancer cells negatively affects cell viability, consistent with a tumor suppressor function. We found that hypermethylation of the MIR-205 locus was strongly related with a decrease in miR-205 expression and an increase in MED1 expression in primary tumor samples (n=14), when compared with matched normal prostate (n=7). An expanded patient cohort (tumor n=149, matched normal n=30) also showed significant MIR-205 DNA methylation in tumors compared with normal, and MIR-205 hypermethylation is significantly associated with biochemical recurrence (hazard ratio=2.005, 95% confidence interval (1.109, 3.625), P=0.02), in patients with low preoperative prostate specific antigen. In summary, these results suggest that miR-205 is an epigenetically regulated tumor suppressor that targets MED1 and may provide a potential biomarker in prostate cancer management.

Betaine distribution in the Malvaceae.

Aerial parts of 26 taxa, distributed in 18 genera and all 5 tribes of the Malvaceae have been examined for the presence of betaines. Glycinebetaine was obtained in high yield (0.5-4.6%, dry weight) from all the plants studied, except Abelmoschus moschatus, in extracts of which glycinebetaine was not detected. Trigonelline was recorded for 16 of the plants tested, but the yields were low (0.005-0.07%, dry weight). Roots and flowers of a few of the species were also examined for betaines. The same compounds as those found in the aerial parts were usually detected, but the glycinebetaine contents of the roots and flowers were considerably lower.

The Toll/IL-1 receptor binding protein MyD88 is required for Xenopus axis formation.

The Toll/Dorsal pathway regulates dorsoventral axis formation in the Drosophila embryo. We had previously obtained evidence that a homologous pathway exists in Xenopus, however, its role during normal frog development had not been established. Here we report the cloning of Xenopus MyD88 (XMyD88), whose mammalian homologs are adaptor proteins linking Toll/IL-1 receptors and IRAK kinases. We show that in the frog embryo overexpression of a dominant-negative form of XMyD88 blocked Toll receptor activity, specifically inhibited axis formation and reduced expression of pivotal organizer genes. The observed stage-dependency of interference suggests a function for maternal XMyD88 soon after fertilization. We conclude that XMyD88 activity is required for normal Spemann organizer formation, implying an essential role for maternal Toll/IL-1 receptors in Xenopus axis formation.

Conserved Spätzle/Toll signaling in dorsoventral patterning of Xenopus embryos.

The Spätzle/Toll signaling pathway controls ventral axis formation in Drosophila by generating a gradient of nuclear Dorsal protein. Dorsal controls the downstream regulators dpp and sog, whose patterning functions are conserved between insects and vertebrates. Although there is no experimental evidence that the upstream events are conserved as well, we set out to ask if a vertebrate embryo can respond to maternal components of the fly Dorsal pathway. Here we demonstrate a dorsalizing activity for the heterologous Easter, Spätzle and Toll proteins in UV-ventralized Xenopus embryos, which is inhibited by a co-injected dominant Cactus variant. We conclude that the Dorsal signaling pathway is a component of the conserved dorsoventral (d/v) patterning system in bilateria.

Isolated fracture of the radial diaphysis in dogs.

Four cases of isolated fracture of the radial diaphysis were diagnosed. All cases were successfully managed conservatively. Direct trauma was not a feature in any of the cases. The history, presenting signs and fracture morphology in each case were similar suggesting a common aetiology. The case histories are reviewed and a possible aetiology discussed.

Intravesicular pH and iron uptake by immature erythroid cells.

The intravesicular pH of intact rabbit reticulocytes was measured by two methods; one based on the intracellular:extracellular distribution of DMO (5, 5, dimethyl + oxazolidin-2,4-dione), methylamine, and chloroquine and the other by quantitative fluorescence microscopy of cell-bound transferrin. The latter method was also applied to nucleated erythroid cells from the fetal rat liver. A pH value of approximately 5.4 was obtained with both methods and in both types of cells. Treatment of the cells with lysosomotrophic agents, metabolic inhibitors, and ionophores elevated the intravesicular pH and inhibited iron uptake from transferrin. When varying concentrations of NH4Cl were used, a close correlation was observed between the inhibition of iron uptake and elevation of the intravesicular pH. At pH 5.4 iron release from rabbit iron-bicarbonate transferrin in vitro was much more rapid than from iron-oxalate transferrin. The bicarbonate complex donates its iron to rabbit reticulocytes approximately twice as quickly as the oxalate complex. It is concluded that the acidic conditions within the vesicles provide the mechanism for iron release from the transferrin molecule after its endocytosis and that the low vesicular pH is dependent on cellular metabolism.

The effect of lysosomotrophic bases and inhibitors of transglutaminase on iron uptake by immature erythroid cells.

The mechanism by which weak bases block iron uptake by immature erythroid cells was investigated using rabbit and rat reticulocytes and erythroblasts from the fetal rat liver. A large variety of bases was found to inhibit iron uptake but to have a much smaller or no effect on transferrin uptake by the cells. Quinacrine and chloroquine were active at the lowest concentrations. Dansylcadaverine, an inhibitor of transglutaminase, was also active at low concentration. However, the results do not indicate a role for transglutaminase in the iron uptake process. Instead they show that the major effect of the bases is to inhibit iron release from transferrin molecules on or within the cells. The possible mechanism of this effect was investigated by measurement of intracellular ATP levels, intracellular pH and by morphological studies utilizing fluorescent and electron microscopy. The bases caused little change in ATP levels, but elevated intracellular pH, probably due to accumulation within intracellular vesicles, which were shown to accumulate fluorescent weak bases, to swell under the action of the bases and to be the site of intracellular localization of transferrin. It is concluded that the bases tested in this work inhibit iron release from transferrin in intracellular vesicles by increasing their pH rather than by blocking transglutaminase and thereby restricting endocytosis. Reduction of transferrin uptake by the cells when it occurs is probably due to inhibition of recycling of transferrin receptors to the outer cell membrane.