Pilot projects 2009
Project 1: A mathematical model describing both the normal transition of cells from G2 into mitosis and the process that occurs following DNA damage.
Project 2: Epigenetics of the nutrient-carcinogen interactions: the role of choline in transplacental carcinogenesis associated with exposure to arsenic.
Project 3: Analysis of bias due to model resolution in assessments of global premature human mortalities from exposure to outdoor air pollutants.
Project 4: Inactivation of Timeless in murine melanocytes enhances melanomagenesis.
Project 5: Mapping methylated DNA sites associated with arsenical-induced skin disease.
Project 6: The Role of TOA in adiponectin and insulin signaling.
Project: A mathematical model describing both the normal transition of cells from G2 into mitosis and the process that occurs following DNA damage.
In order to study the G2 DNA damage checkpoint we created a mathematical model of the protein interactions involved in the G2 to M transition and the G2 DNA damage arrest mechanism. This proposal calls for the addition of DNA damage signaling pathways and additional compartments to the model as well as the modeling of G2 checkpoint function in various cell lines.
Project: Epigenetics of the nutrient-carcinogen interactions: the role of choline in transplacental carcinogenesis associated with exposure to arsenic.
Several nutrients and certain environmental carcinogens have been shown to modify DNA methylation pattern during the fetal development. However, a little is known about the in utero interactions between these nutrients and carcinogens and how these interactions affect the methylation of genomic DNA or specific genes. Inorganic arsenic (iAs) is a potent human carcinogen. Chronic exposure to arsenic has been associated mainly with skin, liver, lung and bladder cancers. Animal studies show that in utero exposure to iAs may be in part responsible for these effects. Exposures of pregnant CD1 mice to iAs in drinking water from gestation day GD8 to GD18 have been shown to markedly increase liver tumor incidence and multiplicity in their adult offsprings. Results from this and other laboratories confirmed that prenatal exposures of mice to iAs alter methylation and expression of several genes associated with a variety of human and rodent tumors. In addition, we observed significant changes in the concentration of S-adenosylhomocysteine (SAM) in the livers isolated from fetuses exposed in utero to iAs. These findings indicate that exposure to iAs alters DNA methylation by competing with DNA methyltransferases (DNMT) for SAM, the donor of methyl groups used for methylation of both DNA and iAs. Alternatively, iAs and/or its metabolites may modify the expression or activity of DNMTs, thus, altering the DNA methylation pattern. Choline is a precursor for SAM synthesis. Choline intake has been shown to modify SAM availability. The proposed project will use the mouse model for transplacental arsenic carcinogenesis to examine effects of choline supplementation on epigenetic events that may determine the susceptibility of adult offsprings to cancer. Specifically, effects of choline intake on the concentration of SAM, metabolism of iAs, methylation of CpG-islands in genomic DNA and gene expression will be examined in the livers of CD1 mouse fetuses during in utero exposure to iAs. Results of this work will be used to design a long-term cancer study that will examine the association between choline intake and epigenetic changes in fetuses exposed in utero to iAs, and development of liver cancer in adult offspring.
Project: Analysis of bias due to model resolution in assessments of global premature human mortalities from exposure to outdoor air pollutants.
Analysis of the global-scale effects of air quality on human health is increasingly relevant, and the PI has led health impact assessments using global atmospheric chemical transport models. These analyses are limited by coarse grid resolution, and fail to capture the fine-scale distributions of concentration and population, particularly in urban regions. We will analyze the bias in assessments of air pollution-related mortality caused by the coarse resolution of global models, by comparing with a finer-scale regional model over the US. Stage 1 will analyze the total mortality due to exposure to ozone and fine particulate matter over the US, quantify the bias due to the coarse model resolution of the global model, analyze this bias geographically and by season, and quantify the bias in using national baseline mortality rates rather than county-level rates. Stage 2 will quantify these biases for the effect of a change in precursor emissions on ozone-related mortality, which may have a different spatial structure than the total mortality. These analyses will support future proposed applications, such as modeling future air pollution mortality in global energy-economic scenarios.
Project: Inactivation of Timeless in murine melanocytes enhances melanomagenesis.
Effort in this pilot project will generate a novel murine “floxed” allele of an essential gene, Timeless. Timeless is a component of the replication fork protection complex that stabilizes DNA replication forks that are stalled at natural fork barriers and sites of UV-induced DNA damage. Reduced expression of Timeless should produce a condition of genomic instability leading to oncogenic events. UNC environmental melanoma investigators will use a conditionally activatable, melanocyte-specific CRE recombinase allele to selectively delete Timeless in melanocytes. Reduction in Timeless should enhance melanoma development and malignant progression. Additional studies will combine Timeless inactivation with other oncogenic events such as Ras activation to facilitate melanoma formation. To determine the contribution of Timeless to suppression of melanomagenesis, we propose the following specific aims: 1) to generate germ-line transmission of the floxed Timeless (TimLOXP) allele in C57Bl/6 mice; and 2) to breed TimLOXP mice with Tyr-Cre-ERT2 mice to generate mice with deletion of Timeless in melanocytes, and characterize the effects of somatic Timeless deletion in melanocytes. This project will determine whether an essential checkpoint mediator suppresses melanomagenesis in a murine model.
Project: Mapping methylated DNA sites associated with arsenical-induced skin disease.
Tens of millions of people worldwide are currently exposed to high levels of arsenic. Consumption of drinking water contaminated with inorganic arsenic (iAs) results in arsenicosis or chronic arsenic poisoning. Advanced stages of arsenicosis are associated with cancer of the skin. While the exact basis for iAs-induced skin disease is not known, a potential mechanism is that iAs causes epigenetic alterations that influence the expression levels of tumor-associated genes. We hypothesize that epigenomic alterations, specifically deregulation of DNA methylation, contribute in a significant way to the skin disease manifestations of arsenicosis. We will test this hypothesis by defining the epigenome-wide sites of DNA methylation that are associated with iAs-induced skin disease, using DNA isolated from residents of arsenicosis-endemic areas of Mexico. We will evaluate associations between DNA methylation, iAs exposure and metabolism, and skin disease. This pilot study will identify differential sites of DNA methylation that are associated with susceptibility to iAs-induced skin disease. This research is directly in line with the mission of the CEHS.
Project: The Role of TOA in adiponectin and insulin signaling.
Adiponectin is a hormone noted for its insulin-sensitizing, anti-atherogenic, anti-inflammatory and cancer resistant properties. Thus, environmental factors that lower circulating levels adiponectin contribute to the greatest public health problems in the US, type II diabetes, cardiovascular disease and cancer. Environmental factors that reduce circulating adiponectin include elements of the built environment that cause obesity, cigarette smoke, chemicals used to produce food and water containers and endotoxin on air particles. How does the reduction of circulating adiponectin cause disease? Our current model suggests that low adiponectin impairs the insulin signaling pathway giving rise to insulinemia and glycemia. We will examine the function of a new protein called TOA (target of adiponectin) in the adiponectin signaling pathway. We will specifically determine whether adiponectin and insulin lead to the phosphorylation of TOA (Aim 1), identify the intracellular location of TOA (Aim 2) and determine whether TOA controls glucose production by a glucose sensing mechanism (Aim 3). Investigating the signaling pathway that mediates the effects of adiponectin will lead to a better understanding of the interactions between environmental factors and the pathogenesis of human disease.
|Funded by NIEHS Grant # P30 ES010126|