Investigating the epigenetic regulation of manganese superoxide dismutase in aging rat tissue

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015The free radical theory of aging postulates that accumulation of oxidative damage in major cellular components is the predominant underlying cause of the aging phenotype. This damage is caused most commonly by reactive oxygen species (ROS) and antioxidant enzymes such as the superoxide dismutases (SOD) that neutralize ROS, are therefore vital. Manganese superoxide dismutase (MnSOD) is particularly critical as it is functional in the mitochondria, a major site for ROS generation. Numerous studies have demonstrated a tissue-specific decrease in the activity and mRNA levels of major antioxidants, including MnSOD, with aging, however the exact mechanism of this regulation is unclear. It was hypothesized that a general down-regulation of various antioxidant enzymes such as this may occur at the transcriptional level. In order to investigate SOD2 regulation, a comprehensively annotated rat SOD2 promoter region was established using the appropriate bioinformatics tools. Following this, SOD2 mRNA levels in tissues from young and old rat tissue were compared using quantitative PCR. The results showed increased and decreased SOD2 mRNA levels in old compared to young liver tissue and brain tissue, respectively, however these trends were not statistically significant. As MnSOD has been shown to be epigenetically downregulated in various age-related diseases it was hypothesized that the decrease in MnSOD mRNA levels seen in aging brain tissue may be a result of epigenetic regulation at the SOD2 (MnSOD gene) promoter, specifically, through DNA methylation. A methylation assay assessing the SOD2 gene promoter revealed no significant evidence of hypermethylation. Although this suggests that promoter methylation is an unlikely mechanism of SOD2 regulation in aging, further work would need to be implemented in order to prove this conclusively

Dual-specificity phosphatase 5 controls the localized inhibition, propagation, and transforming potential of ERK signaling

Deregulated extracellular signal-regulated kinase (ERK) signaling drives cancer growth. Normally, ERK activity is self-limiting by the rapid inactivation of upstream kinases and delayed induction of dual-specificity MAP kinase phosphatases (MKPs/DUSPs). However, interactions between these feedback mechanisms are unclear. Here we show that, although the MKP DUSP5 both inactivates and anchors ERK in the nucleus, it paradoxically increases and prolongs cytoplasmic ERK activity. The latter effect is caused, at least in part, by the relief of ERK-mediated RAF inhibition. The importance of this spatiotemporal interaction between these distinct feedback mechanisms is illustrated by the fact that expression of oncogenic BRAF(V600E), a feedback-insensitive mutant RAF kinase, reprograms DUSP5 into a cell-wide ERK inhibitor that facilitates cell proliferation and transformation. In contrast, DUSP5 deletion causes BRAF(V600E)-induced ERK hyperactivation and cellular senescence. Thus, feedback interactions within the ERK pathway can regulate cell proliferation and transformation, and suggest oncogene-specific roles for DUSP5 in controlling ERK signaling and cell fate

Does Sleep Improve Your Grammar? : Preferential Consolidation of Arbitrary Components of New Linguistic Knowledge

We examined the role of sleep-related memory consolidation processes in learning new form-meaning mappings. Specifically, we examined a Complementary Learning Systems account, which implies that sleep-related consolidation should be more beneficial for new hippocampally dependent arbitrary mappings (e.g. new vocabulary items) relative to new systematic mappings (e.g. grammatical regularities), which can be better encoded neocortically. The hypothesis was tested using a novel language with an artificial grammatical gender system. Stem-referent mappings implemented arbitrary aspects of the new language, and determiner/suffix+natural gender mappings implemented systematic aspects (e.g. tib scoiffesh + ballerina, tib mofeem + bride; ked jorool + cowboy, ked heefaff + priest). Importantly, the determiner-gender and the suffix-gender mappings varied in complexity and salience, thus providing a range of opportunities to detect beneficial effects of sleep for this type of mapping. Participants were trained on the new language using a word-picture matching task, and were tested after a 2-hour delay which included sleep or wakefulness. Participants in the sleep group outperformed participants in the wake group on tests assessing memory for the arbitrary aspects of the new mappings (individual vocabulary items), whereas we saw no evidence of a sleep benefit in any of the tests assessing memory for the systematic aspects of the new mappings: Participants in both groups extracted the salient determiner-natural gender mapping, but not the more complex suffix-natural gender mapping. The data support the predictions of the complementary systems account and highlight the importance of the arbitrariness/systematicity dimension in the consolidation process for declarative memories

Can a participatory approach contribute to food chain risk analysis?

We consider food chain risks and specifically address stakeholder participation in the risk analysis process. We combine social and natural science perspectives to explore the participation process in relation to food risks and, in particular, to consider how some specific participation processes might be scientifically evaluated and how stakeholder participation in general might be incorporated into food risk decision making. We have built considerations based on three large integrative case studies that examine aspects of participatory processes. Here we use the case studies collectively to illustrate observations and beliefs concerning the nature of the interaction of stakeholders with established quantitative risk methodologies. This account is not supported by any large volume of analysis. The views in the report are expressed in relation to an accepted risk analysis framework and also with respect to probabilistic modeling of risks and are illustrated where possible with anecdotal reports of actual case study events