LRP5 Signaling in Osteosarcomagenesis: a Cautionary Tale of Translation from Cell Lines to Tumors

Previous reports document expression of low-density lipoprotein receptor-related protein 5 (LRP5) in osteosarcoma (OS) tissue. Expression of this Wnt receptor correlated with metastatic disease and poor disease-free survival. Forced expression of dominant-negative LRP5 (dnLRP5), which lacks the membrane binding domain of the native protein and therefore functions as a soluble receptor-sponge for Wnt ligands, reduced in vitro cellular invasion and in vivo xenograft tumor growth for osteosarcoma cell lines. Here, we use a genetically engineered mouse model of osteosarcomagenesis with and without expression of dnLRP5 to assess to what degree tumorigenesis is affected and whether Wnt/β-catenin signaling is circumvented or maintained. Each cohort of mice developed osteosarcoma at a similar ultimate prevalence, but after a slightly increased latency in those also expressing dnLRP5. On histology, there was no difference between groups, despite previous reports that the dnLRP5 osteosarcoma cells specifically undergo a mesenchymal-to-epithelial transition in vitro. Finally, immunohistochemistry showed the presence of cytosolic and nuclear β-catenin and nuclear Cyclin D1, markers consistent with preserved Wnt/β-catenin signaling despite constitutive blockade of the cell surface receipt of Wnt signaling ligand. These data suggest that canonical Wnt signaling plays a role in OS progression and that while blockade of singular nodes in signaling pathways can have dramatic effects on individual cell lines, real tumors readily evade such focused attacks.     

Spatiotemporal Variation in Shallow-Water Freshwater Fish Distribution and Abundance in a Large Subtropical Coastal Lagoon

Patos Lagoon is located off the southern Brazilian coast and represents one of the largest coastal lagoons in the world. We estimated hydrological and physicochemical conditions associated with spatial variation in the abundance and diversity of freshwater fishes along the lagoon, and inter-annual variability in abundances of freshwater fishes occurring in its estuarine zone. During our study, the region experienced two periods of average rainfall and two periods with above-average rainfall. The characids Astyanax eigenmaniorum and Oligosarcus jenynsii and the siluriform Parapimelodus nigribarbis were the most abundant freshwater fishes in the estuary during wet periods when water levels were higher and salinity was lower. Increases in abundance of these species in the estuarine area, all of which members of primary-division freshwater families, apparently were associated with pulses of reproduction and passive transport from freshwater habitats located near middle and upper lagoon reaches. Abundance of species from secondary freshwater families, such as poeciliids and cichlids, were less correlated with hydrological conditions, and their patterns of occurrence in the estuary suggest active migration from nearby freshwater habitats draining into this area. Findings indicate that freshwater discharge in the basin and expansion/retraction of freshwaters in the middle-upper lagoon determined patterns of freshwater fish abundance and species richness in the estuarine zone.     

Seasonal Variation of Cadmium, Copper, and Lead Concentrations in Fish from a Freshwater Lake

This paper aims to compare the Cd, Cu, and Pb concentration in the bone, gills, and muscle of the seven fish species sampled during normal and dry seasons. Cadmium, Cu, and Pb concentrations varied significantly depending on the type of the tissue and season. Bone samples of the Osteochilus hasseltii showed the highest concentrations of Pb (6.08 μg/g dw) during September (the dry season), whereas bone samples of the Puntioplites bulu showed the lowest concentrations of Cd (0.08 μg/g dw) during September. Muscle samples of the P. bulu indicated the highest concentrations of Cu (2.58 μg/g dw) during March (the normal season). On the other hand, muscle samples of Channa straitus sowed the lowest concentrations of Cd (0.04 μg/g dw) during July (the dry season). Gills samples of the O. hasseltii showed the highest concentration of Pb (6.56 μg/g dw) during March (the normal season), while gills samples of C. straitus indicated the lowest concentration of Cd (0.06 μg/g dw) during July (the dry season).     

Use of Biochemical Endpoints to Determine Relationships between Contaminants and Impaired Fish Health in a Freshwater Stream

Bayou Bartholomew is a low gradient stream predominantly influenced by agricultural inputs and stormwater discharge from the urban areas of Pine Bluff, Arkansas. Preliminary studies indicated induction of hepatic cytochrome P450 1A protein (CYP1A) and CYP1A-catalyzed enzyme activity (ethoxyresorufin O-deethylase-EROD) in several fish species collected in the waterway, which meanders through residential areas of Pine Bluff, and forested regions in the outskirts of the city. Largemouth bass (Micropterus salmoides) showed CYP1A repression and a lack of correlation between CYP1A and EROD activity. In addition, hepatic heme oxygenase activity was elevated in several species and demonstrated an inverse relationship with hepatic CYP1A. Hepatic metallothionein was unchanged in any species collected from these locations. Four years after this evaluation, sediments were collected and analyzed for agents that could be mechanistically consistent with the biochemical responses observed. Utilizing seven criteria for causality, these data indicated that PCBs appear to be at least one group of agents responsible for the biological effects observed in fish species from the upper Bayou Bartholomew. While this supports causality under the criteria, further studies in this waterway would strengthen the relationship between this class of compound and the effects observed in resident fish species.     

Spatial Match-Mismatch between Juvenile Fish and Prey Provides a Mechanism for Recruitment Variability across Contrasting Climate Conditions in the Eastern Bering Sea

Understanding mechanisms behind variability in early life survival of marine fishes through modeling efforts can improve predictive capabilities for recruitment success under changing climate conditions. Walleye pollock (Theragra chalcogramma) support the largest single-species commercial fishery in the United States and represent an ecologically important component of the Bering Sea ecosystem. Variability in walleye pollock growth and survival is structured in part by climate-driven bottom-up control of zooplankton composition. We used two modeling approaches, informed by observations, to understand the roles of prey quality, prey composition, and water temperature on juvenile walleye pollock growth: (1) a bioenergetics model that included local predator and prey energy densities, and (2) an individual-based model that included a mechanistic feeding component dependent on larval development and behavior, local prey densities and size, and physical oceanographic conditions. Prey composition in late-summer shifted from predominantly smaller copepod species in the warmer 2005 season to larger species in the cooler 2010 season, reflecting differences in zooplankton composition between years. In 2010, the main prey of juvenile walleye pollock were more abundant, had greater biomass, and higher mean energy density, resulting in better growth conditions. Moreover, spatial patterns in prey composition and water temperature lead to areas of enhanced growth, or growth ‘hot spots’, for juvenile walleye pollock and survival may be enhanced when fish overlap with these areas. This study provides evidence that a spatial mismatch between juvenile walleye pollock and growth ‘hot spots’ in 2005 contributed to poor recruitment while a higher degree of overlap in 2010 resulted in improved recruitment. Our results indicate that climate-driven changes in prey quality and composition can impact growth of juvenile walleye pollock, potentially severely affecting recruitment variability.     

The Re-Emergence of H1N1 Influenza Virus in 1977: A Cautionary Tale for Estimating Divergence Times Using Biologically Unrealistic Sampling Dates

In 1977, H1N1 influenza A virus reappeared after a 20-year absence. Genetic analysis indicated that this strain was missing decades of nucleotide sequence evolution, suggesting an accidental release of a frozen laboratory strain into the general population. Recently, this strain and its descendants were included in an analysis attempting to date the origin of pandemic influenza virus without accounting for the missing decades of evolution. Here, we investigated the effect of using viral isolates with biologically unrealistic sampling dates on estimates of divergence dates. Not accounting for missing sequence evolution produced biased results and increased the variance of date estimates of the most recent common ancestor of the re-emergent lineages and across the entire phylogeny. Reanalysis of the H1N1 sequences excluding isolates with unrealistic sampling dates indicates that the 1977 re-emergent lineage was circulating for approximately one year before detection, making it difficult to determine the geographic source of reintroduction. We suggest that a new method is needed to account for viral isolates with unrealistic sampling dates.     

A Comparison of Genetic Variation Between an Anadromous Steelhead, Oncorhynchus mykiss, Population and Seven Derived Populations Sequestered in Freshwater for 70 Years

In 1926 cannery workers from the Wakefield Fisheries Plant at Little Port Walter in Southeast Alaska captured small trout, Oncorhynchus mykiss, from a portion of Sashin Creek populated with a wild steelhead (anadromous O. mykiss) run. They planted them into Sashin Lake which had been fishless to that time and separated from the lower stream by two large waterfalls that prevented upstream migration of any fish. In 1996 we sampled adult steelhead from the lower creek and juvenile O. mykiss from an intermediate portion of the creek, Sashin Lake, and five lakes that had been stocked with fish from Sashin Lake in 1938. Tissue samples from these eight populations were compared for variation in: microsatellite DNA at 10 loci; D-loop sequences in mitochondrial DNA; and allozymes at 73 loci known to be variable in steelhead. Genetic variability was consistently less in the Sashin Lake population and all derived populations than in the source anadromous population. The cause of this reduction is unknown but it is likely that very few fish survived to reproduce from the initial transplant in 1926. Stockings of 50–85 fish into five other fishless lakes in 1938 from Sashin Lake did not result in a similar dramatic reduction in variability. We discuss potential explanations for the observed patterns of genetic diversity in relation to the maintenance of endangered anadromous O. mykiss populations in freshwater refugia.     

Within and Between Plant Variation in Seed Number, Seed Mass and Germinability of Primula elatior: Effect of Population Size

Abstract: In this study, natural variation of seed mass and seed number between and within individual plants of P. elatior, a common forest herb on rich soils in Flanders, was investigated for both small (< 50 flowering individuals) and large (> 1000 flowering individuals) populations. The relationship between seed number and seed mass at both the between and within population level was also quantified. We also investigated how population size affected germinability of seeds through the effects of seed mass. Seed number varied by a factor of twenty, whereas seed mass spanned, on average, a 3.5 range. In both cases variation was highest among populations, indicating that population size has important effects on seed number and seed mass. Next, seed number-seed mass tradeoffs were significantly influenced by population size, with small populations showing strong negative relationships whereas in large populations seed mass was only marginally influenced by seed number. As to germination, larger seeds showed larger germination percentages only for the smallest population. In all other populations, seed mass had little effect on germination.     

A 3D Hybrid Model for Tissue Growth: The Interplay between Cell Population and Mass Transport Dynamics

To provide theoretical guidance for the design and in vitro cultivation of bioartificial tissues, we have developed a multiscale computational model that can describe the complex interplay between cell population and mass transport dynamics that governs the growth of tissues in three-dimensional scaffolds. The model has three components: a transient partial differential equation for the simultaneous diffusion and consumption of a limiting nutrient; a cellular automaton describing cell migration, proliferation, and collision; and equations that quantify how the varying nutrient concentration modulates cell division and migration. The hybrid discrete-continuous model was parallelized and solved on a distributed-memory multicomputer to study how transport limitations affect tissue regeneration rates under conditions encountered in typical bioreactors. Simulation results show that the severity of transport limitations can be estimated by the magnitude of two dimensionless groups: the Thiele modulus and the Biot number. Key parameters including the initial seeding mode, cell migration speed, and the hydrodynamic conditions in the bioreactor are shown to affect not only the overall rate, but also the pattern of tissue growth. This study lays the groundwork for more comprehensive models that can handle mixed cell cultures, multiple nutrients and growth factors, and other cellular processes, such as cell death.     

Population Variation in the Life History of a Land Fish,Alticus arnoldorum,and the Effects of Predation and Density

Life history variation can often reflect differences in age-specific mortality within populations, with the general expectation that reproduction should be shifted away from ages experiencing increased mortality. Investigators of life history in vertebrates frequently focus on the impact of predation, but there is increasing evidence that predation may have unexpected impacts on population density that in turn prompt unexpected changes in life history. There are also other reasons why density might impact life history independently of predation or mortality more generally. We investigated the consequences of predation and density on life history variation among populations of the Pacific leaping blenny, Alticus arnoldorum. This fish from the island of Guam spends its adult life out of the water on rocks in the splash zone, where it is vulnerable to predation and can be expected to be sensitive to changes in population density that impact resource availability. We found populations invested more in reproduction as predation decreased, while growth rate varied primarily in response to population density. These differences in life history among populations are likely plastic given the extensive gene flow among populations revealed by a previous study. The influence of predation and density on life history was unlikely to have operated independently of each other, with predation rate tending to be associated with reduced population densities. Taken together, our results suggest predation and density can have complex influences on life history, and that plastic life history traits could allow populations to persist in new or rapidly changing environments.     

Fish, Flows and Flood Plains: Links between Freshwater Fishes and their Environment in the Murray-Darling River System, Australia

Knowledge of the biology of native fishes of the Murray-Darling Basin is based largely on studies conducted under hatchery conditions and on a limited number of recreationally important species. From observations that increases in water level in aquaculture ponds initiate spawning in some species, and from limited studies of wild fishes and studies in overseas floodplain river systems, a perception has emerged of the importance of flooding and the flood plain in the life cycles of Murray-Darling fishes in general. However, there is little confirmatory evidence of the use of temporary floodplain habitats by larvae, juveniles or adults. The significance of in-channel habitats, especially for rearing, has received little attention. Murray-Darling fish species can be placed into three life history modes, based mainly on spawning style and time and developmental intervals of larvae at first feeding. Fish in each group may be able to take advantage of floods if the timing is right and prey are plentiful, however, the larvae of some species are able to recruit under non-flood conditions within the main river channel. This forms the basis of the low flow recruitment hypothesis, which attempts to explain why some species spawn during the warmest months and lowest flows and how they are able to recruit under these conditions. This hypothesis is then placed in the context of the current state of knowledge of the relationships between flow and the biology of Murray-Darling fishes, specifically cues for spawning, movement and recruitment. The lack of widespread evidence for floodplain use by any life history interval of fish may be due to a paucity of study, however, there are some fundamental factors, such as the predictability of timing and duration of high flow events as well as the lack of coincidence of high flows and high temperatures in some regions of the Basin, which may be important in determining the use of floodplain habitats by fish.     

Molecular Evolutionary Analysis of Vertebrate Transducins: A Role for Amino Acid Variation in Photoreceptor Deactivation

Transducin is a heterotrimeric G protein that plays a critical role in phototransduction in the rod and cone photoreceptor cells of the vertebrate retina. Rods, highly sensitive cells that recover from photoactivation slowly, underlie dim-light vision, whereas cones are less sensitive, recover more quickly, and underlie bright-light vision. Transducin deactivation is a critical step in photoreceptor recovery and may underlie the functional distinction between rods and cones. Rods and cones possess distinct transducin α subunits, yet they share a common deactivation mechanism, the GTPase activating protein (GAP) complex. Here, we used codon models to examine patterns of sequence evolution in rod (GNAT1) and cone (GNAT2) α subunits. Our results indicate that purifying selection is the dominant force shaping GNAT1 and GNAT2 evolution, but that GNAT2 has additionally been subject to positive selection operating at multiple phylogenetic scales; phylogeny-wide analysis identified several sites in the GNAT2 helical domain as having substantially elevated dN/dS estimates, and branch-site analysis identified several nearby sites as targets of strong positive selection during early vertebrate history. Examination of aligned GNAT and GAP complex crystal structures revealed steric clashes between several positively selected sites and the deactivating GAP complex. This suggests that GNAT2 sequence variation could play an important role in adaptive evolution of the vertebrate visual system via effects on photoreceptor deactivation kinetics and provides an alternative perspective to previous work that focused instead on the effect of GAP complex concentration. Our findings thus further the understanding of the molecular biology, physiology, and evolution of vertebrate visual systems.     

Genetic Variants in Epidermal Growth Factor Receptor Pathway Genes and Risk of Esophageal Squamous Cell Carcinoma and Gastric Cancer in a Chinese Population

The epidermal growth factor receptor (EGFR) signaling pathway regulates cell proliferation, differentiation, and survival, and is frequently dysregulated in esophageal and gastric cancers. Few studies have comprehensively examined the association between germline genetic variants in the EGFR pathway and risk of esophageal and gastric cancers. Based on a genome-wide association study in a Han Chinese population, we examined 3443 SNPs in 127 genes in the EGFR pathway for 1942 esophageal squamous cell carcinomas (ESCCs), 1758 gastric cancers (GCs), and 2111 controls. SNP-level analyses were conducted using logistic regression models. We applied the resampling-based adaptive rank truncated product approach to determine the gene- and pathway-level associations. The EGFR pathway was significantly associated with GC risk (P = 2.16×10⁻³). Gene-level analyses found 10 genes to be associated with GC, including FYN, MAPK8, MAP2K4, GNAI3, MAP2K1, TLN1, PRLR, PLCG2, RPS6KB2, and PIK3R3 (P<0.05). For ESCC, we did not observe a significant pathway-level association (P = 0.72), but gene-level analyses suggested associations between GNAI3, CHRNE, PAK4, WASL, and ITCH, and ESCC (P<0.05). Our data suggest an association between specific genes in the EGFR signaling pathway and risk of GC and ESCC. Further studies are warranted to validate these associations and to investigate underlying mechanisms.     

Proposal for Teaching Evolutionary Biology: A bridge between research and educational practice

We present quantitative results for the doctoral thesis of the first-named author of this article. The objective was to recommend and test a teaching proposal for core knowledge of evolutionary biology in secondary education. The focus of the study is ‘Problem cores in teaching’. The ‘Weaving evolutionary thinking’ teaching unit, designed for and tested in this study, entailed: selecting basic evolutionary knowledge from the model of evolution through variation and natural selection; designing a coordinated set of activities, teaching resources and evaluation tools; leading a process of teacher training; and building bridges between: the teaching model, research into the teaching of evolutionary biology, our own teaching experience and that of the secondary school teacher who participated in the project. The data collected through questionnaires show significant differences in favour of the experimental group, which means that the proposal may be favourably assessed in the context of Mexican education, in terms of feasibility, relevance and the pedagogical transformation of knowledge.     

Life-History Variation inChrysoperla carnea:Implications for Rearing and Storing a Mexican Population

A population ofChrysoperla carneafrom San Pedro, Coahuila, Mexico, showed phenological responses that differ from those of previously studied North American biotypes. Short daylengths that induce diapause in other biotypes resulted in low incidences of diapause in the San Pedro population. Diapause induction required a decrease in daylength (from long to short days). Constant long days produced variable reproductive responses, whereas an increase in daylength (from short to long day) resulted in high incidences of reproduction. Providing prey to adults that had been reared under short days consistently increased the incidences of reproduction. Storage of either diapausing or nondiapausing adults at low temperature (5°C) for 13 weeks yielded better survivorship and reproductive performance than in unstored (24°C) controls. For efficient production, the San Pedro population ofC. carneamay be reared either with an increase in daylength or with the regular intervention of a storage period. To induce diapause in individuals destined for storage, larvae may be reared under long-day photoperiod and the prepupae transferred to short days.     

PopulationProfiler: A Tool for Population Analysis and Visualization of Image-Based Cell Screening Data

Image-based screening typically produces quantitative measurements of cell appearance. Large-scale screens involving tens of thousands of images, each containing hundreds of cells described by hundreds of measurements, result in overwhelming amounts of data. Reducing per-cell measurements to the averages across the image(s) for each treatment leads to loss of potentially valuable information on population variability. We present PopulationProfiler—a new software tool that reduces per-cell measurements to population statistics. The software imports measurements from a simple text file, visualizes population distributions in a compact and comprehensive way, and can create gates for subpopulation classes based on control samples. We validate the tool by showing how PopulationProfiler can be used to analyze the effect of drugs that disturb the cell cycle, and compare the results to those obtained with flow cytometry.     

Skeletal Pathologies in a Population of Alouatta palliata: Behavioral, Ecological, and Evolutionary Implications

We examined the pathological conditions in a sample of 200 skulls of Alouatta palliata recovered from Barro Colorado Island (BCI), Panama, to investigate the prevalence of disease and injury in a free-ranging monkey population. Forty-five individuals (22.5%) have some type of nondental pathological condition, indicating that illness and injury are relatively common in this population. Ten individuals, all older adult males, exhibit clear signs of antemortem trauma in the form of healed fractures. We attribute the trauma primarily to fighting, and its frequency (16.4% of adult males) contradicts previous assertions that BCI howlers are nonaggressive. Nine of the 37 scorable immature individuals (24%) have signs of a larval infestation, supporting the suggestion that ectoparasites play an important role in BCI howler mortality. Other pathological conditions in the sample include shifted muscle attachments, periostitis, arthritis, neoplasm, periapical abscesses, and facial deformity, as well as various dental abnormalities.     

Using Nested Models and Laboratory Data for Predicting Population Effects of Contaminants on Fish: A Step Toward a Bottom-Up Approach for Establishing Causality in Field Studies

Predicting the effects of contaminants on fish populations is difficult due to their complex life history and high interannual variation in their population abundances. We present an approach that extrapolates laboratory data on contaminant effects, including behavioral effects, to the population level by using a series of nested statistical and simulation models. The approach is illustrated using PCB effects on Atlantic croaker. Laboratory experiments were performed that estimated PCB effects on fecundity, egg mortality, and the swimming speed and predator evasion behavior of larvae. A statistical model converted impaired predator evasion to reduced probability of escaping a predatory fish. An individual-based model then converted the output of the statistical model into changes in larval stage duration and survival, which were used to change elements of the matrix model. A matrix projection model simulated population dynamics for 100 years for baseline conditions and for two hypothetical PCB exposure scenarios. PCB effects were imposed in the model by reducing the fecundity of exposed adults, increasing egg mortality, and increasing the larval stage duration and mortality rate. Predicted population effects of PCBs were small relative to the interannual variation. Our analysis is a step toward understanding population responses to stressors and for ultimately establishing causality in field situations.     

Association of CHRNA5-A3-B4 Variation with Esophageal Squamous Cell Carcinoma Risk and Smoking Behaviors in a Chinese Population

Background

CHRNA5-A3-B4, the gene cluster encoding nicotinic acetylcholine receptor subunits, is associated with lung cancer risk and smoking behaviors in people of European descent. Because cigarette smoking is also a major risk factor for esophageal squamous cell carcinoma (ESCC), we investigated the associations between variants in CHRNA5-A3-B4 and ESCC risk, as well as smoking behaviors, in a Chinese population.

Methods

A case-control study of 866 ESCC patients and 952 healthy controls was performed to study the association of polymorphisms (rs667282 and rs3743073) in CHRNA5-A3-B4 with cancer risk using logistic regression models. The relationships between CHRNA5-A3-B4 polymorphisms and smoking behaviors that can be quantified by cigarettes smoked per day (CPD) and pack-years of smoking were separately estimated with Kruskal-Wallis tests among all 840 smokers.

Results

CHRNA5-A3-B4 rs667282 TT/TG genotypes were associated with significantly increased risk of ESCC [adjusted odds ratio (OR) = 1.32, 95% confidence interval (CI) = 1.03 – 1.69, P = 0.029]. The increased ESCC risk was even higher among younger subjects (≤60 years) (OR = 1.44, 95% CI = 1.04 – 1.98, P = 0.024). These effects were not found in another polymorphism rs3743073. No evident association between the two polymorphisms and smoking behaviors was observed.

Conclusions

These results support the hypothesis that CHRNA5-A3-B4 is a susceptibility gene cluster for ESCC. The relationship between CHRNA5-A3-B4 and smoking behaviors in a Chinese population needs further investigation.