Genetic Endpoints Research Articles

Lineage-Specific Transcription Factors in Carcinogenesis

Each cancer is the result of an individually unique evolutionary process. Yet, as demonstrated by extensive genetic analyses of human specimens, the genetic endpoints of cancers across different tissues are remarkably specific, with individual cancer driver genes being typically associated with only a limited set of tumor types. Tissue and cellular contexts thus impose strong and genetically predictable evolutionary constraints on carcinogenesis. Lineage-specific transcription factors, central regulators of organismal development, tissue homeostasis, and regeneration, often also support cancer cell fitness in a lineage-specific manner. In this review, we discuss recent results on the interactions between transcriptional lineage factor programs and oncogenic pathways and how such interactions may determine the oncogenic competence of cancer-associated genetic alterations. These developments are starting to shed light on the molecular basis of tissue specificity in carcinogenesis, with relevance for cancer prevention and therapy.

Risk assessment and environmental consequences of the use of the Allium-derived compound propyl-propane thiosulfonate (PTSO) in agrifood applications

The organosulfur compound propyl-propane thiosulfonate (PTSO), mainly found in Allium cepa, has a promising use in the agrifood industry. To confirm its safety for livestock, consumers, and environment, toxicological assessment is needed. In this regard, endocrine-disrupting chemicals (EDCs) are in the spotlight of research. Therefore, as part of the risk assessment of PTSO, in the present work, an in vivo study was performed in mice exposed to PTSO to investigate its potential reproductive toxicity considering fertility, genetic and endocrine endpoints. Five-weeks-old CD1 mice (80 males, 80 females) were exposed for 11 or 16 weeks (males or females, respectively) to different doses of PTSO (0, 14, 28 and 55 mg PTSO/kg b.w./day; 20 animals per group and sex) through the food pellets. No clinical observations or mortality and no changes in absolute organ weights and relative organ weights/body weight or brain ratios occurred during the study. The estrous cycle did not undergo any significant toxicologically relevant change. Most of the sex hormones displayed normal values. Some alterations in the expression of some genes related to reproduction is only observed in females, but they do not appear to have consequences in the development of sex organs. Docking results showed the impossibility of stable binding to estrogen and androgen receptors. Considering all the results obtained, the safe profile of PTSO can be confirmed for different agrifood applications at the conditions assayed.

Research Progress of Zebrafish Model in Aquatic Ecotoxicology

In recent years, with the aggravation of environmental pollution, the study of aquatic ecotoxicology has become a hot topic. Some aquatic organisms, such as large fleas, toads, and zebrafish, have been developed and applied as model organisms. They have been increasingly used to study the bioaccumulation and toxicity of environmental pollutants due to the advantages of their small size, easy reproduction, short life cycle, low maintenance cost, and ability to combine genetic, cellular, and whole organism endpoints. This review summarizes the methods of zebrafish, as a model in aquatic ecotoxicology, using its developmental toxicity, biomarkers, genomics, and phenotype analysis to evaluate the toxicity of environmental pollutants, providing a reference value for researchers to select model animals for aquatic ecotoxicology research.

Marine Pollutant Tributyltin Affects DNA Methylation and Fitness of Banded Murex (Hexaplex trunculus) Populations

Banded murex, Hexaplex trunculus, is a marine gastropod whose reproductive fitness can be severely affected by very low concentrations of antifouling compound tributyltin (TBT). TBT has strong xenoandrogen impacts on snails, causing the development of imposex (e.g., the superimposition of male sexual characteristic in females), thereby affecting the fitness of entire populations. TBT is also known as a DNA-demethylating agent and an obesogenic factor. The aim of this study was to unravel the interactions between TBT bioaccumulation, phenotypic responses, and epigenetic and genetic endpoints in native populations of H. trunculus. Seven populations inhabiting environments along the pollution gradient were sampled in the coastal eastern Adriatic. These included sites of intense marine traffic and boat maintenance activity and sites with low anthropogenic impact. Populations inhabiting intermediately and highly polluted sites exhibited higher TBT burdens, higher incidences of imposex, and higher wet masses of snails than populations in lowly polluted sites. Other morphometric traits and cellular biomarker responses did not show clear differentiation among populations in relation to marine traffic/pollution intensity. An analysis of methylation sensitive amplification polymorphism (MSAP) revealed environmentally driven population differentiation and higher epigenetics than genetic within-population diversity. Moreover, decreases in genome-wide DNA methylation coincided with the imposex level and snail mass, suggesting an epigenetic background of the animal phenotypic response.

DNA Oxidative Damage as a Sensitive Genetic Endpoint to Detect the Genotoxicity Induced by Titanium Dioxide Nanoparticles.

The genotoxicity of nanomaterials has attracted great attention in recent years. As a possible occupational carcinogen, the genotoxic effects and underlying mechanisms of titanium dioxide nanoparticles (TiO2 NPs) have been of particular concern. In this study, the effect of TiO2 NPs (0, 25, 50 and 100 µg/mL) on DNA damage and the role of oxidative stress were investigated using human bronchial epithelial cells (BEAS-2B) as an in vitro model. After detailed characterization, the cytotoxicity of TiO2 NPs was detected. Through transmission electron microscopy (TEM), we found that TiO2 NPs entered the cytoplasm but did not penetrate deep into the nucleus of cells. The intracellular levels of reactive oxygen species (ROS) significantly increased in a dose-dependent manner and the ratios of GSH/GSSG also significantly decreased. The results of the normal comet assay were negative, while the Fpg-modified comet assay that specifically detected DNA oxidative damage was positive. Meanwhile, N-acetyl-L-cysteine (NAC) intervention inhibited the oxidative stress and genotoxicity induced by TiO2 NPs. Therefore, it was suggested that TiO2 NPs could induce cytotoxicity, oxidative stress and DNA oxidative damage in BEAS-2B cells. DNA oxidative damage may be a more sensitive genetic endpoint to detect the genotoxicity of TiO2 NPs.

Determination of potential thresholds for N-ethyl-N-nitrosourea and ethyl methanesulfonate based on a multi-endpoint genotoxicity assessment platform in rats

The main goal of the study was to investigate the genotoxic response of N-ethyl-N-nitrosourea (ENU) and ethyl methanesulfonate (EMS) at low doses in a multi-endpoint genotoxicity assessment platform in rats and to derive potential thresholds and related metrics. Male Sprague–Dawley rats were treated by daily oral gavage for 28 consecutive days with ENU (0.25 ~ 8 mg/kg bw) and EMS (5 ~ 160 mg/kg bw), both with six closely spaced dose levels. Pig-a gene mutation assay, micronucleus test, and comet assay were performed in several timepoints. Then, the dose–response relationships were analyzed for possible points of departure (PoD) using the no observed genotoxic effect level and benchmark dose (BMD) protocols with different critical effect sizes (CES, 0.05, 0.1, 0.5, and 1SD). Overall, dose-dependent increases in all investigated endpoints were found for ENU and EMS. PoDs varied across genetic endpoints, timepoints, and statistical methods, and selecting an appropriate lower 95% confidence limit of BMD needs a comprehensive consideration of the mode of action of chemicals, the characteristics of tests, and the model fitting methods. Under the experimental conditions, the PoDs of ENU and EMS were 0.0036 mg/kg bw and 1.7 mg/kg bw, respectively.

HPRT gene mutation, sister chromatid exchange and comet assay in peripheral lymphocytes of radiation laborers at Al-Amal Cancer Hospital in Baghdad

A Study performed on 30 Iraqi radiation Labors had been exposed tо a low dose tо ionizing radiation at Al-Amal Cancer Hospital in Baghdad the use of three genetic endpoints. Covered 12 females and 18 males between the aged tо (22-57) years. In addition to 20 Healthy individuals from the population, dwelling Baghdad, covered, 7 females and 13 males, aged (19 - 55) years which are non-smokers, non- alcoholic. The cytogenetic analysis, including, HPRT gene mutation¸ comet assay and SCE have been carried out on peripheral blood lymphocytes of labors and control groups. The HPRT gene mutation assay showed a significant increase (p<0.05) in the radiation labors. There were found a significant increase (p<0.05) in comet tail length and tail moment values in thе human lymphocyte in these radiation Labors compared with thе control group. Also the SCE in human lymphocyte for radiation Laborers was significantly (p<0.05) higher than in a control group. Results obtained confirmed the cytogenetic analysis; including, HPRT gene mutation¸ comet assay and SCE are useful as biodosimetric markers for the detection of human exposure to low doses of ionizing radiation. It reflects the simultaneous exposure and actual levels of DNA damage present in radiological laborers' peripheral blood leukocytes by detecting temporary DNA damage and / or repair activity.

CYP1B1 converts procarcinogens into genotoxins in Saccharomyces cerevisiae

CYP1B1 activates many chemical carcinogens into potent genotoxins, and allelic variants are risk factors in lung, breast, and prostate cancer. However, few eukaryotic genetic instability endpoints have been directly measured for CYP1B1-activated metabolites. In this study, we expressed human CYP1B1 in yeast strains that measure DNA damage-associated toxicity and frequencies of chromosomal translocations. DNA damage-associated toxicity was measured in a rad4 rad51 strain, defective in both DNA excision and recombinational repair. Frequencies of chromosomal translocations were measured in diploid yeast strains containing two his3 fragments. These strains were exposed to benzo[a]pyrene-7,8-dihydrodiol (BaP-DHD), aflatoxin B1 (AFB1), and the heterocyclic aromatic amines, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). We observed that AFB1, BaP-DHD, IQ, and MeIQx conferred toxicity in the DNA repair mutant expressing CYP1B1. Translocation frequencies increased eight-fold and three-fold after exposure to 50 μM AFB1 and 33 μM BaP-DHD respectively. A DNA damage response was observed after AFB1 exposure, as measured by the induction of the small subunit of ribonucleotide reductase, Rnr3. While CYP1B1-mediated activation of BaP-DHD and heterocyclic aromatic amines was expected, activation of AFB1 to become a potent recombinagen was not expected. These studies demonstrate that chromosomal rearrangement is a useful genotoxic endpoint for CYP1B1-mediated carcinogen activation.

Abstract PO-219: The implications of genetic ancestry and allostatic load on clinical outcomes in the ECOG-ACRIN adjuvant breast cancer trial E5103

Abstract Introduction: Elevated allostatic load (AL) has been associated with poor tumor prognostic features in Black breast cancer patients and worse disease specific and overall survival among cancer patients. To date, there are no studies evaluating the relationship between genetic ancestry, allostatic load and clinical trial endpoints such as completion of chemotherapy per protocol or overall survival. Prior evaluations of the ECOG-ACRIN adjuvant breast cancer trial E5103 suggests African ancestry is associated with a worse invasive disease-free survival and lower odds of chemotherapy completion. The objective of this study is to evaluate the association of genetic ancestry and AL with trial completion per protocol and with overall survival among patients in E5103. Methods: ECOG-ACRIN E5103 was a clinical trial that compared doxorubicin and cyclophosphamide (AC) for four cycles, followed by 12 weeks of weekly paclitaxel with placebo (Arm A) to the same chemotherapy with either concurrent bevacizumab (Arm B) or with concurrent plus sequential bevacizumab (Arm C) among women with node positive or high-risk node negative HER2 negative disease. Genetic ancestry groups of African ancestry (AA), European ancestry (EA) and other ancestry (OA) were determined using genome-wide single nucleotide polymorphisms. AL, at trial entry, was comprised of the biomarkers body mass index, systolic blood pressure, diastolic blood pressure, creatinine, IL6, IL10, and TNF alpha. To calculate AL, patients were awarded a point if their biomarker value was above the 75 percentile of the study sample. Logistic regression and Cox-Proportional Hazard models (odds ratio(OR) and hazard ratio (HR) estimates with corresponding 95% confidence intervals (CI)) were used to assess association with chemotherapy completion and with overall mortality. Estimates for AL were adjusted for genetic ancestry. Results: There were 348 patients in the study. The majority of the sample was of EA (EA 80%, AA 10%, OA 10%). Median (range) of AL was 2(0-6). Patients of AA (2.1(1.3)) and EA (1.88(1.4)) had a higher mean (SD) AL score compared to OA patients (0.91(1.1). On adjusted analysis, a 1 unit increased in AL was associated with a 15% reduction in the odds of completing chemotherapy per protocol (OR 0.85, 95% CI 0.72-0.99). Additionally, a 1 unit increase in AL was associated with a 14% increase in the hazard of death (HR 1.14, 95%CI 1.02-1.29). There was no association between ancestry and chemotherapy completion (AA OR 0.95, 95%CI 0.47-1.93; OA 1.82, 95%CI 0.78-4.23; ref EA) or survival (AA HR 1.40, 95% CI 0.85-2.31), OA 0.89 (0.46-1.73; ref EA). Moreover, there was no interaction between AL and ancestry. Conclusion: Among patients enrolled in E5103, AL appeared to be a better predictor of chemotherapy completion and overall survival than genetic ancestry. These results suggest life course exposure to chronic stress has implication in clinical outcomes even within the context of equivalent access to and quality of care. Citation Format: Samilia Obeng-Gyasi, Anne ONeill, Kathy D. Miller, Bryan P. Schneider, Ann H. Patridge, Lava R. Timsina, George W. Sledge, Lynne Wagner, Ruth C. Carlos. The implications of genetic ancestry and allostatic load on clinical outcomes in the ECOG-ACRIN adjuvant breast cancer trial E5103 [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-219.

27-OR: Genome-Wide Association Analysis Identifies Ancestry-Specific Genetic Variation Associated with Medication Response in the Study to Understand the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH)

SUGAR-MGH is a pharmacogenetic resource for characterizing genetic influences on pharmacological perturbations relevant to type 2 diabetes (T2D). 1,000 participants who were naïve to T2D treatment received 5 mg glipizide, followed by 4 doses of 500 mg metformin and a 75-g oral glucose tolerance test (OGTT) a week later. Glucose and insulin were measured at pre-specified endpoints after glipizide and during the OGTT. Incretin levels were measured in a subset. We calculated physiologic endpoints reflecting insulin secretion, insulin sensitivity, and incretin secretion. The mean age was 47 years, 54% were women, >35% were non-white, and the mean BMI was 30.2 kg/m2. 890 participants underwent genome-wide genotyping using the Illumina Multi-Ethnic Genotyping Array, and high-quality imputation was performed with the TOPMed reference panel. Multiple linear regression using an additive model tested for association between genetic variants and endpoints. We identified 21 genome-wide significant variants, of which 3 met experiment-wide significance (P<8.3×10-9 for 2 drugs × 3 physiological hypotheses tested). The most significant association was between an African ancestry-specific variant (minor allele frequency=0.026) at rs149403252 and lower fasting glucose following metformin, adjusted for baseline glucose (P=1.9×10-9). We tested the influence of 429 known T2D-associated variants and found that the protective C allele of rs703972 near ZMIZ1 was associated with increased secretion of active GLP-1 in response to metformin (P=1.6×10-5), suggesting that an enhanced incretin response may be a mechanism by which this variant decreases T2D risk. We illustrate that a genome-wide approach in a multi-ethnic human perturbation study can uncover new variation associated with drug response and provide insight into mechanisms of action of known T2D genetic variation. Disclosure J. H. Li: None. V. Kaur: None. L. Brenner: Research Support; Self; Apple. J. M. Mercader: None. J. C. Florez: Consultant; Self; Goldfinch Bio, Inc., Other Relationship; Self; Novo Nordisk. Funding National Institutes of Health (R01DK088214, R03DK077675, P30DK036836, M01RR01066, 1UL1RR025758-04, 8UL1TR000170-05, T32DK007028)

Genetic toxicity testing using human in vitro organotypic airway cultures: Assessing DNA damage with the CometChip and mutagenesis by Duplex Sequencing.

The organotypic human air‐liquid‐interface (ALI) airway tissue model has been used as an in vitro cell culture system for evaluating the toxicity of inhaled substances. ALI airway cultures are highly differentiated, which has made it challenging to evaluate genetic toxicology endpoints. In the current study, we assayed DNA damage with the high‐throughput CometChip assay and quantified mutagenesis with Duplex Sequencing, an error‐corrected next‐generation sequencing method capable of detecting a single mutation per 107 base pairs. Fully differentiated human ALI airway cultures were treated from the basolateral side with 6.25 to 100 μg/mL ethyl methanesulfonate (EMS) over a period of 28 days. CometChip assays were conducted after 3 and 28 days of treatment, and Duplex Sequencing after 28 days of treatment. Treating the airway cultures with EMS resulted in time‐ and concentration‐dependent increases in DNA damage and a concentration‐dependent increase in mutant frequency. The mutations observed in the EMS‐treated cultures were predominantly C → T transitions and exhibited a unique trinucleotide signature relative to the negative control. Measurement of physiological endpoints indicated that the EMS treatments had no effect on anti‐p63‐positive basal cell frequency, but produced concentration‐responsive increases in cytotoxicity and perturbations in cell morphology, along with concentration‐responsive decreases in culture viability, goblet cell and anti‐Ki67‐positive proliferating cell frequency, cilia beating frequency, and mucin secretion. The results indicate that a unified 28‐day study can be used to measure several important safety endpoints in physiologically relevant human in vitro ALI airway cultures, including DNA damage, mutagenicity, and tissue‐specific general toxicity.

Toxicity of petroleum hydrocarbons to Brachyuran crabs: a review of deleterious effects of oil-related xenobiotics on life stages

AbstractPetroleum hydrocarbons (PH) toxicity and bioaccumulation in aquatic organisms have been investigated for almost 50 years. Continuous oil spillages necessitate a further understanding of the toxicological effects of PH on brachyuran crabs. Crabs can be exposed to PH through various routes such as the water column, sediment and diet. Numerous investigations have been dedicated to evaluating PH toxicity on different life stages of crab species, but the majority of them have focused on the blue crab Callinectes sapidus as it represents an edible and favourable seafood commodity for human consumption. The objective of the review is to critically assess studies related to PH toxicity on different life stages of 41 crab species representing 13 families across the world. Several physiological, biochemical and genetic endpoints of marine crabs were evaluated in addition to the sublethal effects of PH on crab metabolism, behaviour, moulting, growth and survival. A concise summary of PH deleterious effects on different taxonomic species of marine crabs is discussed and provides evidence that crabs can be used as indicator organisms of biomarker significance for marine pollution. Overall, larval stages appeared to be the most sensitive to the deleterious effects of PH compared with juveniles and adults. However, adult stages have received more research attention than other life stages, followed by larval stages, and juvenile stages are the least investigated stages with respect to PH toxicity. Finally, hepatopancreas and gills were the organs where greatest accumulation of PH was recorded.

Biomonitoring findings for occupational lead exposure in battery and ceramic tile workers using biochemical markers, alkaline comet assay, and micronucleus test coupled with fluorescence in situ hybridisation.

Manufacture of lead-containing products has long been associated with various health risks. To get an insight into the related genotoxic risks, we conducted a biomonitoring study in 50 exposed workers and 48 matched controls using a battery of endpoints that sensitively detect the extent of genome instability in peripheral blood lymphocytes. The levels of primary DNA damage were estimated with the alkaline comet assay, while cytogenetic abnormalities were determined with the cytokinesis-block micronucleus (CBMN) cytome assay. Additionally, CBMN slides of 20 exposed and 16 control participants were subjected to fluorescence in situ hybridisation (FISH), coupled with pancentromeric probes to establish the incidence of centromere-positive micronuclei, nuclear buds, and nucleoplasmic bridges. Blood lead levels (B-Pb) were measured with atomic absorption spectrometry. To further characterise cumulative effects of occupational exposure, we measured erythrocyte protoporphyrin (EP) concentrations and delta-aminolevulinic acid dehydratase (ALAD) activity in blood. We also assessed the influence of serum folate (S-folate) and vitamin B12 (S-B12) on genome stability. Compared to controls, occupationally exposed workers demonstrated significantly higher B-Pb (298.36±162.07 vs 41.58±23.02), MN frequency (18.71±11.06 vs 8.98±7.50), centromere positive MN (C+ MN) (8.15±1.8 vs 3.69±0.47), and centromere negative MN (C- MN) (14.55±1.80 vs 4.56±0.89). Exposed women had significantly higher comet tail intensity (TI) and length (TL) than control women. Furthermore, workers showed a positive correlation between age and nuclear buds and MN, between MN and years of exposure, and between S-B12 levels and TI and ALAD activity, while a negative correlation was found between TI and B-Pb. These findings suggest that occupational settings in the manufacture of lead-containing products pose significant genotoxic risks, which calls for developing more effective work safety programmes, including periodical monitoring of B-Pb and genetic endpoints.

Biological Basis for Threshold Responses to Methylating Agents.

The cellular outcomes of chemical exposure are as much about the cellular response to the chemical as it is an effect of the chemical. We are growing in our understanding of the genotoxic interaction between chemistry and biology. For example, recent data has revealed the biological basis for mutation induction curves for a methylating chemical, which has been shown to be dependent on the repair capacity of the cells. However, this is just one end point in the toxicity pathway from chemical exposure to cell death. Much remains to be known in order for us to predict how cells will respond to a certain dose. Methylating agents, a subset of alkylating agents, are of particular interest, because of the variety of adverse genetic end points that can result, not only at increasing doses, but also over time. For instance, methylating agents are mutagenic, their potency, for this end point, is determined by the cellular repair capacity of an enzyme called methylguanine DNA-methyltransferase (MGMT) and its ability to repair the induceed methyl adducts. However, methyl adducts can become clastogenic. Erroneous biological processing will convert mutagenic adducts to clastogenic events in the form of double strand breaks (DSBs). How the cell responds to DSBs is via a cascade of protein kinases, which is called the DNA damage response (DDR), which will determine if the damage is repaired effectively, via homologous recombination, or with errors, via nonhomologous end joining, or whether the cell dies via apoptosis or enters senescence. The fate of cells may be determined by the extent of damage and the resulting strength of DDR signaling. Therefore, thresholds of damage may exist that determine cell fate. Such thresholds would be dependent on each of the repair and response mechanisms that these methyl adducts stimulate. The molecular mechanism of how methyl adducts kill cells is still to be fully resolved. If we are able to quantify each of these thresholds of damage for a given cell, then we can ascertain, of the many adducts that are induced, what proportion of them are mutagenic, what proportion are clastogenic, and how many of these clastogenic events are toxic. This review examines the possibility of dose and damage thresholds for methylating agents, from the perspective of the underlying evolutionary mechanisms that may be accountable.

Assessment of Cytotoxic and Genotoxic Potential of Heavy Metals in Plants: A Review

Heavy metal stress is one of the major problems affecting the agricultural productivity of plants. Soil is contaminated by heavy metals, such as, Cd, Cr, Pb, Hg, and As. Plants suffer from oxidative stress upon exposure to heavy metals and lead to cellular damage. Heavy metals induce clastogenecity, aneugenicity, recombinogenicity, gene mutation, and DNA damage. There are several genetic endpoints that can be used as biomarkers of cytotoxicity and genotoxicity, e.g., comet assays, micronuclei frequency, meiotic analysis, mitotic analysis, and chromosomal aberrations. Plants are very useful in environmental monitoring and assessment as they provide a very wide range of genetic endpoints. They may be used as biosensors of the genetic toxicity of environmental pollutants.

Developmental, Morphological and Physiological Traits in Plants Exposed for Five Generations to Chronic Low-Level Ionising Radiation.

The effects of ionising radiation (IR) on plants are important for environmental protection but also in agriculture, horticulture, space science, and plant stress biology. Much current understanding of the effects of IR on plants derives from acute high-dose studies but exposure to IR in the environment frequently occurs at chronic low dose rates. Chronic low dose-rate studies have primarily been field based and examined genetic or cytogenetic endpoints. Here we report research that investigated developmental, morphological and physiological effects of IR on Arabidopsis thaliana grown over 7 generations and exposed for five generations to chronic low doses of either 137Cs (at a dose rate of c. 40 μGy/h from β/γ emissions) or 10 μM CdCl2. In some generations there were significant differences between treatments in the timing of key developmental phases and in leaf area or symmetry but there were, on the basis of the chosen endpoints, no long-term effects of the different treatments. Occasional measurements also detected no effects on root growth, seed germination rates or redox poise but in the generation in which it was measured exposure to IR did decrease DNA-methylation significantly. The results are consistent with the suggestion that chronic exposure to c. 40 μGy/h can have some effects on some traits but that this does not affect function across multiple generations at the population level. This is explained by the redundancy and/or degeneracy between biological levels of organization in plants that produces a relatively loose association between genotype and phenotype. The importance of this explanation to understanding plant responses to stressors such as IR is discussed. We suggest that the data reported here provide increased confidence in the Derived Consideration Reference Levels (DCRLs) recommended by the International Commission for Radiological Protection (ICRP) by providing data from controlled conditions and helping to contextualize effects reported from field studies. The differing sensitivity of plants to IR is not well understood and further investigation of it would likely improve the use of DCRLs for radiological protection.

Genotoxicity of source, treated and distributed water from four drinking water treatment plants supplied by surface water in Sardinia, Italy

High levels of disinfection by-products (DBPs) are constantly found in drinking water distributed in Sardinia, an Italian island with a tourist vocation and critical issues related to the drinking water supply. To reduce the concentration of trihalomethanes the disinfectant in use was changed – chlorine dioxide was adopted instead of hypochlorite. However, this caused the appearance of other DBPs (e.g., chlorites) in water distributed to the population. Thus, the use of monochloramine as a secondary disinfectant (associated with chlorine dioxide as the primary disinfectant) was evaluated in four drinking water treatment plants supplied by artificial basins located in the central-northern part of Sardinia. Raw, disinfected and distributed waters were studied for genotoxicity using a battery of in vitro tests on different cells (bacteria, plant and mammalian cells) to detect different genetic endpoints (i.e., point and chromosome mutations and DNA damage). Moreover, a chemical and microbiological characterisation of water samples was performed. All samples of water distributed to the people showed mutagenic or genotoxic effects in different cells/organisms. In particular, chromosome aberrations in plant cells and DNA damage in human cells were observed. In this study, the use of chloramines associated with other disinfectants did not eliminate the mutagenicity present in the raw water and when the raw water was not mutagenic it introduced mutagenic/genotoxic substances. A careful management of drinking water is needed to reduce health hazards associated with the mutagenicity of drinking water.

An investigation of physiological effects of the Deepwater Horizon oil spill on a long-distance migratory seabird, the northern gannet

Exposure to oil can have long-term impacts on migratory birds. Following the 2010 Deepwater Horizon blowout in the Gulf of Mexico (GOM), we investigated potential impacts of oil exposure on a population of northern gannets (Morus bassanus) that breed on Bonaventure Island (Québec, Canada) and winter in GOM and along the U.S. Atlantic coast (AC). Blood and feather samples were collected from adults previously equipped with geolocators to determine wintering locations. Parent and alkylated polycyclic aromatic hydrocarbons (PAHs); trace metals; stable isotopes of carbon, nitrogen, and hydrogen; and immune, thyroid, steroid, retinoid, and genetic endpoints were measured. PAH and trace metal concentrations did not differ between gannets using different wintering sites. Feather stable isotope values varied significantly between birds from different wintering locations. Gannets wintering in GOM showed higher feather corticosterone and plasma thyroid hormone levels, which may indicate increased energetic demands and/or greater exposure to environmental stressors.

Multifaceted implications of the competition between native and invasive crayfish: a glimmer of hope for the native’s long-term survival

Biological invasions represent a complex phenomenon driven by multiple factors. In this study, a real-time invasion process between a native (Pontastacus leptodactylus) and an invasive (Faxonius limosus) crayfish species was investigated in the Lower Danube (South-East Europe) through an interdisciplinary approach, by measuring various ecological, genetic, physiological and biometric endpoints. The results revealed that the prolonged competition in old invaded sites of the river (at least a decade) either drove the native species to extinction, or, unexpectedly, allowed its survival as highly fragmented populations. However, for the latter situation, several biological and ecological traits differed in the remnant populations: increased trophic position and elemental imbalance for two major macronutrients (C:N molar ratio), low growth, as strongly contracted trophic niche widths and low overlap degree with the invasive crayfish. The data suggest that the prolonged competition induced potential resource partitioning between species, potentially driving their coexistence, as the development of larger and heavier claws within the native males’ population. On the contrary, in more recently invaded sectors of the Lower Danube (3 years), the trophic niche of the native species was significantly larger compared to old invaded sites and characterised by high level of niche overlap, indicating almost identical diet with the invasive crayfish, but characterised by the lowest trophic position compared to other invasion sectors. The genetic diversity of the native crayfish populations was strongly reduced in the invaded sectors of the river, but without signs of genetic bottleneck, which may be explained by a drift-mutational equilibrium reached as a consequence of diminishing population size. Our findings suggest strong coexistence potential in the future for both species in the Lower Danube.

Application of the adverse outcome pathway framework to genotoxic modes of action.

In May 2017, the Health and Environmental Sciences Institute's Genetic Toxicology Technical Committee hosted a workshop to discuss whether mode of action (MOA) investigation is enhanced through the application of the adverse outcome pathway (AOP) framework. As AOPs are a relatively new approach in genetic toxicology, this report describes how AOPs could be harnessed to advance MOA analysis of genotoxicity pathways using five example case studies. Each of these genetic toxicology AOPs proposed for further development includes the relevant molecular initiating events, key events, and adverse outcomes (AOs), identification and/or further development of the appropriate assays to link an agent to these events, and discussion regarding the biological plausibility of the proposed AOP. A key difference between these proposed genetic toxicology AOPs versus traditional AOPs is that the AO is a genetic toxicology endpoint of potential significance in risk characterization, in contrast to an adverse state of an organism or a population. The first two detailed case studies describe provisional AOPs for aurora kinase inhibition and tubulin binding, leading to the common AO of aneuploidy. The remaining three case studies highlight provisional AOPs that lead to chromosome breakage or mutation via indirect DNA interaction (inhibition of topoisomerase II, production of cellular reactive oxygen species, and inhibition of DNA synthesis). These case studies serve as starting points for genotoxicity AOPs that could ultimately be published and utilized by the broader toxicology community and illustrate the practical considerations and evidence required to formalize such AOPs so that they may be applied to genetic toxicity evaluation schemes. Environ. Mol. Mutagen. 61:114-134, 2020. © 2019 Wiley Periodicals, Inc.