Project description:Bioassay is a system for monitoring toxicity of chemicals in the environment via the biological responses of experimental organisms. These responses can be detected by analysis of genome-wide changes in mRNA expression levels using DNA microarray. We applied this system for evaluation of synergistic toxicity by cadmium and thiuram, as this combination showed mutual growth inhibition in yeast. Hierarchical cluster analysis using the mRNA expression profiles suggested the response of yeast to this combination is similar to that seen with cadmium treatment. Functional characterization of induced genes by this combination treatment also suggests the enhanced toxicity of cadmium. This toxicity was observed as the damage to mitochondrial functions which were not observed with either cadmium or thiuram treatments alone. The potential toxicity to mitochondria by this combinational treatment was confirmed as the result of mitochondrial curing. We could evaluate the synergistic toxicity by cadmium and thiuram and show the possible use of transcriptome bioassay for synergistic toxicity. Keywords: stress response
Project description:Thorium (232Th), an actinoide element, is among the most common and naturally occurring radioactive materials distributed in our environment. Thorium has been used as a radiographic contrast agent (thorotrast) from 1930 to 1955, and many studies on its effects to the human body have been reported. Once thorium is injected in the body, the risk of cancer is increased by the direct bombardment from alpha-particle with high linear energy transfer during decay of Thorium. However, these many reports focus on the irradiation damage by long-term exposure of thorium. The acute toxicity of thorium is greater risk from the chemical toxicity than from the radiological toxicity. Here, we evaluated the effect of thorium from the stand point of chemical toxicity using yeast DNA microarray. In this experiment, genes that contribute to “C-compound and carbohydrate metabolism”, “energy”, and “cell rescue, defense and virulence” were significantly induced. These genes were classified into oxidative stress, glycogen and trehalose metabolism, sugar transport, and cell wall damage. On the contrary, only one gene related to DNA damage was detected. These results indicate that thorium causes the damage of cell wall and induces the oxidative stress. In order to overcome oxidative stress, yeast cells promote the glycogen and trehalose metabolisms and shift to anaerobic fermentation. Keywords: stress response
Project description:Increasing evidences have shown that cadmium could caused male infertility. However, the exhaustive mechanisms have not been elucidated in mammals. Here, the mice testes and sperm RNA were used to investigate lncRNA expression profiles by stranded-specific RNA-seq on the transcriptome levels after exposure to cadmium. More LncRNA expression have been changed than mRNA genes by cadmium. Furthermore, many novel LncRNA were inducible expression, suggesting that LncRNA might be a good candidate for indicating the reproductive toxicity of cadmium. The present study provides a preliminary database for further exploring the mechanisms of reproductive toxicity caused by cadmium in mammalians.
Project description:Cadmium sulphide quantum dots (CdS QDs) are widely used in novel equipment. The relevance of the research lies in the need to develop risk assessments for nanomaterials (ENMs), using baker's yeast as model system. A whole-genome microarray experiment, performed on Saccharomyces cerevisiae (BY4742), showed how genes were regulated in response to CdS QDs.
Project description:Metals at high concentrations can exert toxic effects on microorganisms. It has been widely reported that lowering environmental pH reduces effects of cadmium toxicity in bacteria. Understanding the effects of pH-mediated cadmium toxicity on bacteria would be useful for minimizing cadmium toxicity in the environment and gaining insight into the interactions between organic and inorganic components of life. Growth curve analysis confirmed that cadmium was less toxic to Escherichia coli at pH 5 than at pH 7 in M9 minimal salts medium. To better understand the cellular mechanisms by which lowering pH decreases cadmium toxicity, we used DNA microarrays to characterize global gene expression patterns in E. coli in response to cadmium exposure at moderately acidic (5) and neutral (7) values of pH. Higher expression of several stress response genes including hdeA, otsA, and yjbJ at pH 5 after only 5 minutes was observed and may suggest that acidic pH more rapidly induces genes that confer cadmium resistance. Genes involved in transport were more highly expressed at pH 7 than at pH 5 in the presence of cadmium. Of the genes that showed an interaction between pH and cadmium effects, 46% encoded hypothetical proteins, which may have novel functions involved in mitigating cadmium toxicity.
Project description:Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. Oligomers of Amyloid-β peptides (Aβ) are thought to play a pivotal role in AD pathogenesis, yet the mechanisms involved remain unclear. Two major isoforms of Aβ associated with AD are Aβ40 and Aβ42, the latter being more prone to form oligomers and toxic. Humanized yeast models are currently applied to unravel the cellular mechanisms behind Aβ toxicity. Here, we took a systems biology approach to study two yeast AD models which expressed either Aβ40 or Aβ42 in bioreactor cultures. Strict control of oxygen availability and culture pH, strongly affected the chronological lifespan and reduced confounding effects of variations during cell growth. Reduced growth rates and biomass yields were observed upon expression of Aβ42, indicating a redirection of energy from growth to maintenance. Quantitative physiology analyses furthermore revealed reduced mitochondrial functionality and ATP generation in Aβ42 expressing cells, which matched with observed aberrant fragmented mitochondrial structures. Genome-wide expression levels analysis showed that Aβ42 expression triggers strong ER stress and unfolded protein responses (UPR). Expression of Aβ40 induced only mild ER stress, leading to activation of UPR target genes that cope with misfolded proteins, which resulted in hardly affected physiology. The combination of well-controlled cultures and AD yeast models strengthen our understanding of how cells translate different levels of Aβ toxicity signals into particular cell fate programs, and further enhance their role as a discovery platform to identify potential therapies.
Project description:Alzheimer’s disease (AD) is hallmarked by progressive neurodegeneration. Aggregation of amyloid-β peptides (Aβ) is thought to play a pivotal role in driving AD pathogenesis, yet the underlying mechanisms remain unclear. Here, we use yeast genome-scale screening to study global synthetic genetic interactions and identify toxicity modifiers of Aβ42. We find that the gene encoding riboflavin kinase (FMN1) and its metabolic product flavin mononucleotide (FMN) are connected to AD. These relationship between Aβ42 and FMN was previously unknown. As a cofactor for flavoenzymes, FMN supplementation appears to attune many cellular processes to ameliorate Aβ42 toxicity. RNA-seq analysis further confirms FMN’s cytoprotective mechanisms. Our findings provide increased understanding of FMN regulated cellular pathways which are associated with potential targets for AD treatment.
Project description:Exposure to cadmium is associated with a variety of human diseases. At low concentrations, cadmium activates the transcription of stress-responsive genes, which can prevent or repair the adverse effects caused by this metal. Using C. elegans, 290 genes were identified that are differentially expressed (≥1.5-fold) following a 4 or 24 hour exposure to cadmium. Several of these genes are known to be involved in metal detoxification, including mtl-1, mtl-2, cdr-1 and ttm-1, confirming the efficacy of the study. The majority, however, were not previously associated with metal-responsiveness and are novel. Gene Ontology analysis mapped these genes to cellular/ion trafficking, metabolic enzymes and proteolysis categories. RNAi-mediated inhibition of 50 cadmium-responsive genes resulted in an increased sensitivity to cadmium toxicity, demonstrating that these genes are involved in the resistance to cadmium toxicity. Several functional protein interacting networks were identified by interactome analysis. Within one network, the signaling protein KEL-8 was identified. Kel-8 protects C. elegans from cadmium toxicity in a mek-1 (MAPKK)-dependent manner. Because many C. elegans genes and signal transduction pathways are evolutionarily conserved, these results may contribute to the understanding of the functional roles of various genes in cadmium toxicity in higher organisms. Keywords: gene expression time course
Project description:The toxicity of the heavy metal cadmium is well established. However, the molecular basis for how this toxicity perturbs cellular viability is still not well understood. This project investigates the cellular and molecular impacts of cadmium stress in the bacterial pathogen, Streptococcus pneumoniae. We find that cadmium depletes cellular manganese and zinc stores, leading to disruption of metalloproteins and the corresponding biochemical pathways. Furthermore, the over-accumulation of cadmium within the cells appears to facilitate mismetallation events, whereby native metal cofactors are displaced by cadmium, leading to reduced or abrogated enzymatic activity. These metalloproteomic analyses have been conducted in conjunction with transcriptomics and metabolomics to elucidate the global impacts of cadmium stress within a prokaryotic organism.