Mysid shrimp (Americamysis bahia) have been utilized in routine marine toxicity assessments for decades. While mysids are a well-established model, there a key gaps in understanding how chemical exposure impacts their endocrine systems. Crustacean growth occurs through molting (i.e., shedding old exoskeleton), a process regulated by hormones, primarily ecdysteroids. Ecdysteroids are a class of steroid hormones that share similar chemical structures to vertebrate hormones (i.e., 17β-estradiol and testosterone), which have been suggested to disrupt molting in some invertebrates. Through powerful tools, like transcriptomics, potential genetic biomarkers may be identified following chemical exposure. These biomarkers could provide the basis for future research aimed at screening endocrine disrupting compounds using invertebrate models. The objectives of this work were to 1) assess whether known vertebrate endocrine disruptors (e.g., 17β-estradiol and trenbolone) would induce alterations in molting and growth and, 2) compare gene expression profiles between vertebrate endocrine disruptors and a model ecdysteroid (i.e., ponasterone A) using transcriptomic analysis. Ponasterone A induced predictable alterations in mass, molting, and ecdysteroid-related gene expression, reinforcing both the use of this compound as a positive control and these endpoints for assessing invertebrate endocrine disruptors. Vertebrate endocrine disruptors induced varied responses in the endpoints assessed, but neither acted in a manner comparable to ponasterone A. Future work may investigate the potential for differentially expressed genes identified in the transcriptomic analysis for screening of invertebrate endocrine disruptors.

Metabolic syndrome (MetS) is a cluster of concurrent cardiometabolic risk factors, including increased waist circumference, hypertension, elevated triglyceride level, reduced high-density lipoprotein (HDL) cholesterol level, and hyperglycemia. The key pathophysiology of MetS is insulin resistance, resulting in a disruption of glucose and lipid metabolism in the liver and adipose tissue, which increases the risk of type II diabetes, cardiovascular disease, and stroke. The development of insulin resistance and related conditions is multifaceted, but risk can be mitigated with lifestyle modifications, including improved nutrition. In the US, a typical American diet (TAD) is full of highly processed foods high in saturated fats and refined sugars and is associated with increased insulin resistance and obesity risk. In contrast, adherence to a plant-based Mediterranean diet (MD) rich in unsaturated fats, fiber, and non-refined carbohydrates has been found to reduce disease risk. Despite the contrasting nutritional compositions, the average macronutrient distributions of these two human diet styles are similar (approximately 50% kcal carbohydrates, 15% kcal protein, and 35% kcal fat). Due to the comparable macronutrient ratios but contrasting nutritional composition, direct comparative analysis could uncover metabolic and cellular differences relating to their associated health outcomes.

There are few rodent studies in the literature that directly compare a TAD and MD. Further, studies often utilize a high-fat diet, consisting of 40-60% kcal fat, or individual nutrient supplements, such as olive oil, rather than comprehensive diet models. To address these limitations, our lab developed comprehensive, macronutrient-matched TAD and MD models that more closely mimic human diets in the U.S. and Mediterranean, respectively. A previous study in our lab found that six months of TAD consumption resulted in elevated body weight, increased inflammation, and excess hepatic lipid deposition, in comparison to the MD. Our current study looked to further characterize MetS under this diet model, specifically investigating obesity, insulin resistance, and dyslipidemia markers. Male and female C57BL/6J mice consumed either the TAD or MD from the age of 4 to 7 months. We found that after three months on diet, there were elevations in hepatic steatosis and serum cholesterol levels in both males and females on the TAD. However, other findings suggested early signs of insulin resistance in TAD males, but not females. Future studies will investigate MetS after 6 months on diet to better elucidate insulin resistance development and potential sex differences.

BRCA1 protects genomic stability by signaling for the homologous recombination pathway, DNA repair, and transcriptional regulation. A pathogenic mutation in the BRCA1 region causes a higher predisposition to the development of breast and ovarian cancer. Our lab is exploring the different enzymatic functions of BRCA1 by looking at its role in histone ubiquitylation, leading to transcriptional regulation of certain parts of the genome. Join us to see our plan for connecting molecular mechanisms of a large, multi-functional gene to the phenotype of an organism. A homolog of BRCA1 is conserved in C. elegans as BRC-1. We propose that mononucleosome ubiquitylation is a key mechanism contributing to the cellular functions of BRC-1. Understanding the significance of mononucleosome ubiquitylation in BRC-1 with C. elegans gives insight into the mechanisms of genetic variations in BRCA1 and further expands C. elegans’ function as a model organism. We have generated a C. elegans mutant with two point mutations that alter the ability of BRC-1 protein to interact with the nucleosome and ubiquitinate histone H2A while retaining all other functions. We hypothesize this mutation increases DNA damage accumulation and disrupts transcriptional regulation to establish nucleosome ubiquitylation as a necessary precursor for these, but likely not all, BRC-1 functions. We compare three strains of C. elegans (wildtype, brc-1 knockout, and our mononucleosome ubiquitylation-deficient mutant) in different conditions designed to induce cellular stress or DNA damage accumulation. We find that BRC-1 nucleosome ubiquitylation contributes to embryonic survival under standard conditions as well as DNA damage-inducing conditions. We also share preliminary results regarding the role of nucleosome ubiquitylation in transcription regulation and reactive oxygen species generation. Our findings further the understanding of the many enzymatic functions of the large BRCA1 gene.

Mercury is emitted from various anthropogenic processes in temperate and tropical regions and is transported to northern latitudes via air and ocean currents. Although there are few point sources of mercury in the Arctic, elevated mercury levels have been observed in Arctic predators such as marine mammals, seabirds, fish, and spiders. This is concerning due to mercury’s known neurotoxic and teratogenic effects. Mercury deposited in the Arctic can be converted into its bioavailable form, methylmercury (MeHg), by aquatic bacteria. It can then be transferred into nearby terrestrial habitats by aquatic emergent insects. A previous study indicated that Arctic wolf spiders (Pardosa glacialis) collected from the shoreline of ponds had elevated concentrations of MeHg. In temperate zones, adult aquatic insects typically disperse within 30 meters of freshwater sources, suggesting that upland predators may consume fewer emergent aquatic insects, thereby reducing their contamination from these sources. While Arctic wolf spiders are ubiquitous predators across the tundra, it is unclear whether spiders collected in upland habitats are similarly contaminated with MeHg. The purpose of this study was to investigate the movement of mercury from aquatic to terrestrial food webs on the Pituffik Peninsula of northwest Greenland. Specifically, we examined the effects of shoreline proximity on mercury concentrations in Arctic wolf spiders. We collected Arctic wolf spiders and their insect prey at varying distances (0m, 10m, and 35m) from six freshwater ponds. We found a positive relationship between mercury concentrations and body size in P. glacialis. Spiders captured 35 meters away from the shoreline had significantly lower mercury concentrations than those captured at 0m or 10m from the shoreline. These results suggest that the dispersal of Arctic emergent aquatic insects declines with increasing distance from the shoreline and that emergent insects are an important source of mercury for Arctic wolf spiders.

The ClpXP protease plays a critical role in bacterial responses to external stressors, protein recycling, and virulence. The protease is highly conserved and composed of two subunits: ClpX, a regulatory ATPase, which recognizes and unfolds proteins, and ClpP, the proteolytic subunit. Our lab has identified that ClpX plays a role in resistance to cell-envelope targeting antibiotics and is critical for virulence in B. anthracis Sterne. However, it is unlikely that ClpX is directly mediating these effects. Rather, these effects are likely due to the dysregulation of the protein network maintained by ClpXP, which includes proteins involved in gene expression, such as transcription factors. Previously, we conducted a microarray and identified 119 differentially expressed genes between wild-type B. anthracis Sterne and a ΔclpX strain. One of the genes identified from the microarray is msrA/B, a fusion of the msrA and msrB methionine sulfoxide reductases (msr). Msr enzymes restore functionality to oxidized methionine residues; MsrA reduces S-form Met(O), and MsrB reduces R-form Met(O). Research with these enzymes has primarily focused on their role in resistance to reactive oxygen species (ROS). However, in S. aureus, msrA1 and msrB expression was induced upon exposure to oxacillin and other cell-wall active antimicrobial agents and not by ROS, indicating a potential connection between msrA/B and cell wall-targeting antibiotics. In B. anthracis Sterne, loss of msrA/B increases susceptibility to penicillin and vancomycin. However, this phenotype is not seen with cell-membrane targeting agents such as daptomycin, suggesting that the role of msrA/B in antimicrobial resistance may be limited to cell-wall active antibiotics. We are currently investigating the role in resistance to ROS but have seen no susceptibility to either H2O2 or paraquat. Future studies will look at changes in msrA/B expression in response to a variety of antibiotics and ROS stressors to better understand the role of this enzyme in regulating the response to these stressors in B. anthracis.