Protein expression profiles in the epidermis of cyclooxygenase-2 transgenic mice by 2-dimensional gel electrophoresis and mass spectrometry

Exposure of murine skin to tumor-promoting agents such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA) causes up-regulation of cyclooxygenase-2 (COX-2) and increased prostaglandin (PG) synthesis. Pharmacological inhibition of COX-2 significantly reduces skin tumor development. However, we previously demonstrated that K14.COX-2 transgenic (TG) mice that overexpressed COX-2 in the epidermis were unexpectedly resistant to tumor development under the classical 7,12-dimethylbenz[a]anthracene-TPA protocol. In the present study, we employed a proteomic approach of 2-dimensional gel electrophoresis (2-DE) and mass spectrometry to profile differentially expressed proteins in the epidermis of K14.COX-2 TG and wild-type control mice. Various 2-DE approaches were used to identify the maximum number of differentially expressed proteins: 20 for untreated samples, 3 for acetone-treated samples, and 22 for TPA-treated samples. These proteins include 14-3-3 sigma, numerous actin fragments, actin filament related proteins cofilin-1 and destrin, galectin-3, galectin-7, prohibitin, S100A6, S100A9, and many others. The differential expression of galectin-3, galectin-7, S100A9 was validated by Western blot analysis and/or immunohistochemical analysis. The current data suggest that some of the differentially expressed proteins might increase apoptosis and cell cycle arrest, which, in turn, may provide insight into the role of COX-2 in skin tumorigenesis.     

Identification, cloning, and functional expression of three glutathione transferase genes from Aspergillus fumigatus

Analysis of the genome of the human pathogen, Aspergillus fumigatus, revealed the presence of several putative glutathione transferase (GST) open reading frames. Three A. fumigatus GST genes, termed gstA, B, and C, were cloned and recombinant proteins expressed in Escherichia coli. Functional analysis of recombinant gstA-C confirms that the enzymes exhibit GST activity and glutathione peroxidase activity. RT-PCR confirmed low basal expression of gstA and gstC which was markedly up-regulated (at least 4x-10x) in the presence of either H2O2 or 1-chloro-2,4-dinitrobenzene (CDNB). GstB expression was only observed in the presence of CDNB. These results demonstrate for the first time the existence of three functional GSTs in A. fumigatus and strongly suggest a role for these enzymes in the response of the organism to both oxidative stress and xenobiotic presence.     

Mathematical Models for Cell Migration with Real-Time Cell Cycle Dynamics

The fluorescent ubiquitination-based cell cycle indicator, also known as FUCCI, allows the visualization of the G1 and S/G2/M cell cycle phases of individual cells. FUCCI consists of two fluorescent probes, so that cells in the G1 phase fluoresce red and cells in the S/G2/M phase fluoresce green. FUCCI reveals real-time information about cell cycle dynamics of individual cells, and can be used to explore how the cell cycle relates to the location of individual cells, local cell density, and different cellular microenvironments. In particular, FUCCI is used in experimental studies examining cell migration, such as malignant invasion and wound healing. Here we present, to our knowledge, new mathematical models that can describe cell migration and cell cycle dynamics as indicated by FUCCI. The fundamental model describes the two cell cycle phases, G1 and S/G2/M, which FUCCI directly labels. The extended model includes a third phase, early S, which FUCCI indirectly labels. We present experimental data from scratch assays using FUCCI-transduced melanoma cells, and show that the predictions of spatial and temporal patterns of cell density in the experiments can be described by the fundamental model. We obtain numerical solutions of both the fundamental and extended models, which can take the form of traveling waves. These solutions are mathematically interesting because they are a combination of moving wavefronts and moving pulses. We derive and confirm a simple analytical expression for the minimum wave speed, as well as exploring how the wave speed depends on the spatial decay rate of the initial condition.     

A Highlights from MBoC Selection: Chromosome replication and segregation govern the biogenesis and inheritance of inorganic polyphosphate granules

Prokaryotes and eukaryotes synthesize long chains of orthophosphate, known as polyphosphate (polyP), which form dense granules within the cell. PolyP regulates myriad cellular functions and is often localized to specific subcellular addresses through mechanisms that remain undefined. In this study, we present a molecular-level analysis of polyP subcellular localization in the model bacterium Caulobacter crescentus. We demonstrate that biogenesis and localization of polyP is controlled as a function of the cell cycle, which ensures regular partitioning of granules between mother and daughter. The enzyme polyphosphate kinase 1 (Ppk1) is required for granule production, colocalizes with granules, and dynamically localizes to the sites of new granule synthesis in nascent daughter cells. Localization of Ppk1 within the cell requires an intact catalytic active site and a short, positively charged tail at the C-terminus of the protein. The processes of chromosome replication and segregation govern both the number and position of Ppk1/polyP complexes within the cell. We propose a multistep model in which the chromosome establishes sites of polyP coalescence, which recruit Ppk1 to promote the in situ synthesis of large granules. These findings underscore the importance of both chromosome dynamics and discrete protein localization as organizing factors in bacterial cell biology.     

An Excess of Deleterious Variants in VEGF-A Pathway Genes in Down-Syndrome-Associated Atrioventricular Septal Defects

About half of people with trisomy 21 have a congenital heart defect (CHD), whereas the remainder have a structurally normal heart, demonstrating that trisomy 21 is a significant risk factor but is not causal for abnormal heart development. Atrioventricular septal defects (AVSD) are the most commonly occurring heart defects in Down syndrome (DS), and ∼65% of all AVSD is associated with DS. We used a candidate-gene approach among individuals with DS and complete AVSD (cases = 141) and DS with no CHD (controls = 141) to determine whether rare genetic variants in genes involved in atrioventricular valvuloseptal morphogenesis contribute to AVSD in this sensitized population. We found a significant excess (p < 0.0001) of variants predicted to be deleterious in cases compared to controls. At the most stringent level of filtering, we found potentially damaging variants in nearly 20% of cases but fewer than 3% of controls. The variants with the highest probability of being damaging in cases only were found in six genes: COL6A1, COL6A2, CRELD1, FBLN2, FRZB, and GATA5. Several of the case-specific variants were recurrent in unrelated individuals, occurring in 10% of cases studied. No variants with an equal probability of being damaging were found in controls, demonstrating a highly specific association with AVSD. Of note, all of these genes are in the VEGF-A pathway, even though the candidate genes analyzed in this study represented numerous biochemical and developmental pathways, suggesting that rare variants in the VEGF-A pathway might contribute to the genetic underpinnings of AVSD in humans.     

Uncovering Atomic‐Scale Stability and Reactivity in Engineered Zinc Oxide Electrocatalysts for Controllable Syngas Production

In this study, scalable, flame spray synthesis is utilized to develop defective ZnO nanomaterials for the concurrent generation of H₂ and CO during electrochemical CO₂ reduction reactions (CO₂RR). The designed ZnO achieves an H₂/CO ratio of ≈1 with a large current density (j) of 40 mA cm^?2 during long‐term continuous reaction at a cell voltage of 2.6 V. Through in situ atomic pair distribution function analysis, the remarkable stability of these ZnO structures is explored, addressing the knowledge gap in understanding the dynamics of oxide catalysts during CO₂RR. Through optimization of synthesis conditions, ZnO facets are modulated which are shown to affect reaction selectivity, in agreement with theoretical calculations. These findings and insights on synthetic manipulation of active sites in defective metal‐oxides can be used as guidelines to develop active catalysts for syngas production for renewable power‐to‐X to generate a range of fuels and chemicals.     

Human exploitation shapes productivity–biomass relationships on coral reefs

Coral reef fisheries support the livelihoods of millions of people in tropical countries, despite large‐scale depletion of fish biomass. While human adaptability can help to explain the resistance of fisheries to biomass depletion, compensatory ecological mechanisms may also be involved. If this is the case, high productivity should coexist with low biomass under relatively high exploitation. Here we integrate large spatial scale empirical data analysis and a theory‐driven modelling approach to unveil the effects of human exploitation on reef fish productivity–biomass relationships. We show that differences in how productivity and biomass respond to overexploitation can decouple their relationship. As size‐selective exploitation depletes fish biomass, it triggers increased production per unit biomass, averting immediate productivity collapse in both the modelling and the empirical systems. This ‘buffering productivity’ exposes the danger of assuming resource production–biomass equivalence, but may help to explain why some biomass‐depleted fish assemblages still provide ecosystem goods under continued global fishing exploitation.     

Exploring movement patterns and changing distributions of baleen whales in the western North Atlantic using a decade of passive acoustic data

Six baleen whale species are found in the temperate western North Atlantic Ocean, with limited information existing on the distribution and movement patterns for most. There is mounting evidence of distributional shifts in many species, including marine mammals, likely because of climate‐driven changes in ocean temperature and circulation. Previous acoustic studies examined the occurrence of minke (Balaenoptera acutorostrata) and North Atlantic right whales (NARW; Eubalaena glacialis). This study assesses the acoustic presence of humpback (Megaptera novaeangliae), sei (B. borealis), fin (B. physalus), and blue whales (B. musculus) over a decade, based on daily detections of their vocalizations. Data collected from 2004 to 2014 on 281 bottom‐mounted recorders, totaling 35,033 days, were processed using automated detection software and screened for each species' presence. A published study on NARW acoustics revealed significant changes in occurrence patterns between the periods of 2004–2010 and 2011–2014; therefore, these same time periods were examined here. All four species were present from the Southeast United States to Greenland; humpback whales were also present in the Caribbean. All species occurred throughout all regions in the winter, suggesting that baleen whales are widely distributed during these months. Each of the species showed significant changes in acoustic occurrence after 2010. Similar to NARWs, sei whales had higher acoustic occurrence in mid‐Atlantic regions after 2010. Fin, blue, and sei whales were more frequently detected in the northern latitudes of the study area after 2010. Despite this general northward shift, all four species were detected less on the Scotian Shelf area after 2010, matching documented shifts in prey availability in this region. A decade of acoustic observations have shown important distributional changes over the range of baleen whales, mirroring known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats like fixed fishing gear, shipping, and noise pollution.