The Fanconi anemia signaling network regulates the mitotic spindle assembly checkpoint

Indiana University-Purdue University Indianapolis (IUPUI)Fanconi anemia (FA) is a heterogenous genetic syndrome characterized by progressive bone marrow failure, aneuploidy, and cancer predisposition. It is incompletely understood why FA-deficient cells develop gross aneuploidy leading to cancer. Since the mitotic spindle assembly checkpoint (SAC) prevents aneuploidy by ensuring proper chromosome segregation during mitosis, we hypothesized that the FA signaling network regulates the mitotic SAC. A genome-wide RNAi screen and studies in primary cells were performed to systematically evaluate SAC activity in FA-deficient cells. In these experiments, taxol was used to activate the mitotic SAC. Following taxol challenge, negative control siRNA-transfected cells appropriately arrested at the SAC. However, knockdown of fourteen FA gene products resulted in a weakened SAC, evidenced by increased formation of multinucleated, aneuploid cells. The screen was independently validated utilizing primary fibroblasts from patients with characterized mutations in twelve different FA genes. When treated with taxol, fibroblasts from healthy controls arrested at the mitotic SAC, while all FA patient fibroblasts tested exhibited weakened SAC activity, evidenced by increased multinucleated cells. Rescue of the SAC was achieved in FANCA patient fibroblasts by genetic correction. Importantly, SAC activity of FANCA was confirmed in primary CD34+ hematopoietic cells. Furthermore, analysis of untreated primary fibroblasts from FA patients revealed micronuclei and multinuclei, reflecting abnormal chromosome segregation. Next, microscopy-based studies revealed that many FA proteins localize to the mitotic spindle and centrosomes, and that disruption of the FA pathway results in supernumerary centrosomes, establishing a role for the FA signaling network in centrosome maintenance. A mass spectrometry-based screen quantifying the proteome and phospho-proteome was performed to identify candidates which may functionally interact with FANCA in the regulation of mitosis. Finally, video microscopy-based experiments were performed to further characterize the mitotic defects in FANCA-deficient cells, confirming weakened SAC activity in FANCA-deficient cells and revealing accelerated mitosis and abnormal spindle orientation in the absence of FANCA. These findings conclusively demonstrate that the FA signaling network regulates the mitotic SAC, providing a mechanistic explanation for the development of aneuploidy and cancer in FA patients. Thus, our study establishes a novel role for the FA signaling network as a guardian of genomic integrity

Global Climate Change and the Southern Ocean: How Antarctic Fishes Physiologically Respond to a Changing Environment from the Cellular to the Organismal Level

Studies have projected that future changes in sea surface temperature and pCO2 levels will impact higher latitudes to a greater extent than in temperate regions. For notothenioid fishes of the Southern Ocean, evolution in extremely stable, cold waters has resulted in several adaptations which have left these fishes poorly prepared for global climate change. I have analyzed the metabolic and cellular response of Trematomus bernacchii, Pagothenia borchgrevinki and Trematomus newnesi to a long-term, multi-stressor scenario relevant to the predicted changes in the Southern Ocean. By combining whole animal respirometry with cellular level analysis of energy allocation, osmoregulatory mechanisms and cellular damage, I aimed to determine if acclimation to increased sea surface temperature (4°C), increased seawater pCO2 levels (1000 μatm), or a combination of these two parameters result in energetic trade-offs and exacerbated cellular damage. The data suggest a synergistic relationship exists between elevated temperature and pCO2, as the combination of these variables further elevates metabolic rates and delays the acclamatory response. Overall, long-term acclimation to experimental treatments resulted in a novel discovery: despite evolving in the same environment and on the same time-scale, these three species of notothenioid differ in their physiological response to global climate change, and defend different biochemical pathways when confronted with a changing environment. While T. bernacchii, P. borchgrevinki, and T. newnesi all showed small acclamatory capacities, there appear to be energetic trade-offs associated with this acclimation, and overall, it may not be possible for energetic demands to be met over long time scales, which could result in long-term impacts to population numbers

Career development assessment of at-risk students : implications for a dropout prevention model

Career development of at-risk and non-at-risk students was assessed using the Career Development Inventory (Thompson & Lindeman, 1981), The Salience Inventory (Nevill & Super, 1986a) and The Values Scale (Nevill & Super, 1986b) to provide recommendations for dropout prevention programs. Super's Career Development Assessment Model was used as a framework to investigate career development in relation to socioeconomic status, race, gender, role commitment and values of at-risk students compared to non-at-risk students. The total sample size was 93 participants. For the at-risk group, there were 13 ninth-graders and 20 10th-graders from Gillespie Park Education Center, an alternative school for at-risk students in Greensboro, North Carolina, including 13 black females, 14 black males, three white females and three white males. The majority of these students ranked from below average to low socioeconomic status. Sixty non-at-risk 10th-graders were randomly selected from the four Greensboro public high schools, including 19 black females, 11 black males, 16 white females, 12 white males, one Asian female and one East Indian male. The majority of these students ranked from average to high in socioeconomic status. Both groups averaged in ages from 15 to 16

Does Ocean Acidification Benefit Seagrasses in a Mesohaline Environment? A Mesocosm Experiment in the Northern Gulf of Mexico

Ocean acidification is thought to benefit seagrasses because of increased carbon dioxide (CO2) availability for photosynthesis. However, in order to truly assess ecological responses, effects of ocean acidification need to be investigated in a variety of coastal environments. We tested the hypothesis that ocean acidification would benefit seagrasses in the northern Gulf of Mexico, where the seagrasses Halodule wrightii and Ruppia maritima coexist in a fluctuating environment. To evaluate if benefits of ocean acidification could alter seagrass bed composition, cores of H. wrightii and R. maritima were placed alone or in combination into aquaria and maintained in an outdoor mesocosm. Half of the aquaria were exposed to either ambient (mean pH of 8.1 ± 0.04 SD on total scale) or high CO2 (mean pH 7.7 ± 0.05 SD on total scale) conditions. After 54 days of experimental exposure, the δ13C values were significantly lower in seagrass tissue in the high CO2 condition. This integration of a different carbon source (either: preferential use of CO2, gas from cylinder, or both) indicates that plants were not solely relying on stored energy reserves for growth. Yet, after 41 to 54 days, seagrass morphology, biomass, photo-physiology, metabolism, and carbon and nitrogen content in the high CO2 condition did not differ from those at ambient. There was also no indication of differences in traits between the homospecific or heterospecific beds. Findings support two plausible conclusions: (1) these seagrasses rely heavily on bicarbonate use and growth will not be stimulated by near future acidification conditions or (2) the mesohaline environment limited the beneficial impacts of increased CO2 availability

The effects of thermal acclimation on cardio-respiratory performance in an Antarctic fish (Notothenia coriiceps).

The Southern Ocean has experienced stable, cold temperatures for over 10 million years, yet particular regions are currently undergoing rapid warming. To investigate the impacts of warming on cardiovascular oxygen transport, we compared the cardio-respiratory performance in an Antarctic notothenioid (Notothenia coriiceps) that was maintained at 0 or 5°C for 6.0-9.5 weeks. When compared at the fish's respective acclimation temperature, the oxygen consumption rate and cardiac output were significantly higher in 5°C-acclimated than 0°C-acclimated fish. The 2.7-fold elevation in cardiac output in 5°C-acclimated fish (17.4 vs. 6.5 ml min-1 kg-1) was predominantly due to a doubling of stroke volume, likely in response to increased cardiac preload, as measured by higher central venous pressure (0.15 vs. 0.08 kPa); tachycardia was minor (29.5 vs. 25.2 beats min-1). When fish were acutely warmed, oxygen consumption rate increased by similar amounts in 0°C- and 5°C-acclimated fish at equivalent test temperatures. In both acclimation groups, the increases in oxygen consumption rate during acute heating were supported by increased cardiac output achieved by elevating heart rate, while stroke volume changed relatively little. Cardiac output was similar between both acclimation groups until 12°C when cardiac output became significantly higher in 5°C-acclimated fish, driven largely by their higher stroke volume. Although cardiac arrhythmias developed at a similar temperature (~14.5°C) in both acclimation groups, the hearts of 5°C-acclimated fish continued to pump until significantly higher temperatures (CTmax for cardiac function 17.7 vs. 15.0°C for 0°C-acclimated fish). These results demonstrate that N. coriiceps is capable of increasing routine cardiac output during both acute and chronic warming, although the mechanisms are different (heart rate-dependent versus primarily stroke volume-dependent regulation, respectively). Cardiac performance was enhanced at higher temperatures following 5°C acclimation, suggesting cardiovascular function may not constrain the capacity of N. coriiceps to withstand a warming climate

Ocean Acidification Risk Assessment for Alaska's Fishery Sector

The highly productive fisheries of Alaska are located in seas projected to experience strong global change, including rapid transitions in temperature and ocean acidification-driven changes in pH and other chemical parameters. Many of the marine organisms that are most intensely affected by ocean acidification(OA) contribute substantially to the state’s commercial fisheries and traditional subsistence way of life. Prior studies of OA’s potential impacts on human communities have focused only on possible direct economic losses from specific scenarios of human dependence on commercial harvests and damages to marine species. However, other economic and social impacts, such as changes in food security or livelihoods, are also likely to result from climate change. This study evaluates patterns of dependence on marine resources within Alaska that could be negatively impacted by OA and current community characteristics to assess the potential risk to the fishery sector from OA. Here, we used a risk assessment framework based on one developed by the Intergovernmental Panel on Climate Change to analyze earth-system global ocean model hindcasts and projections of ocean chemistry, fisheries harvest data, and demographic information. The fisheries examined were: shellfish, salmon and other fin fish. The final index incorporates all of these data to compare overall risk among Alaska’s federally designated census areas. The analysis showed that regions in southeast and southwest Alaska that are highly reliant on fishery harvests and have relatively lower incomes and employment alternatives likely face the highest risk from OA.Although this study is an intermediate step toward our full understanding, the results presented here show that OA merits consideration in policy planning, as it may represent another challenge to Alaskan communities, some of which are already under acute socio-economic strains.This study is part of the Synthesis of Arctic Research (SOAR) and was funded in part by the U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program through Interagency Agreement No. M11PG00034 with the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), Office of Oceanic and Atmospheric Research (OAR), Pacific Marine Environmental Laboratory (PMEL).Ye

Sources of Error in Carbonate Chemistry: What happens when Biology and Chemistry meet?

Two different experimental systems were used to evaluate sources of error in carbonate chemistry measurements at Friday Harbor Labs, WA. One system, set up in Laboratory 6, examined the effects of different filters and a UV sterilizer. The second system explored the carbon input from feeding live versus dead algae in the presence of mussels, Mytilus trossulus. The use of an activated charcoal filter and UV sterilizer increased the pH of incoming seawater more than that of a pleated sediment filter and UV sterilizer. There were no discernable changes in the Dissolved Inorganic Carbon (DIC), and no trends could be seen in Total Alkalinity. Feeding live or dead algae produced similar results over most carbonate measurements. All treatments decreased treatment tank pH, increased tank pCO2, and increased tank DIC. However, feeding dead algae notably decreased treatment tank Total Alkalinity, while mussels that were fed live food did not show a difference in this parameter when compared to non-treated water