Identification and expression analysis of two steamer-like retrotransposons in the Chilean blue mussel (Mytilus chilensis).

BACKGROUND: Disseminated neoplasia (DN) is a proliferative cell disorder of the circulatory system of bivalve mollusks. The disease is transmitted between individuals and can also be induced by external chemical agents such as bromodeoxyuridine. In Mya arenaria, we have cloned and characterized an LTR-retrotransposon named Steamer. Steamer mRNA levels and gene copy number correlates with DN and can be used as a marker of the disease. So far, the only mollusk where a retrotransposon expression relates to DN is Mya arenaria. On the other hand, it has been reported that the Chilean blue mussel Mytilus chilensis can also suffers DN. Our aim was to identify retrotransposons in Mytilus chilensis and to study their expression levels in the context of disseminated neoplasia. RESULTS: Here we show that 7.1% of individuals collected in August 2018, from two farming areas, presents morphological characteristics described in DN. Using Steamer sequence to interrogate the transcriptome of M. chilensis we found two putative retrotransposons, named Steamer-like elements (MchSLEs). MchSLEs are present in the genome of M. chilensis and MchSLE1 is indeed an LTR-retrotransposon. Neither expression, nor copy number of the reported MchSLEs correlate with DN status but both are expressed at different levels among individual animals. We also report that in cultured M. chilensis haemocytes MchSLEs1 expression can be induced by bromodeoxyuridine. CONCLUSIONS: We conclude that SLEs present in Mytilus chilensis are differentially expressed among individuals and do not correlate with disseminated neoplasia. Treatment of haemocytes with a stressor like bromodeoxyuridine induces expression of MchSLE1 suggesting that in Mytilus chilensis environmental stressors can induce activation of LTR-retrotransposon.

Centuries of genome instability and evolution in soft-shell clam, Mya arenaria, bivalve transmissible neoplasia.

Transmissible cancers are infectious parasitic clones that metastasize to new hosts, living past the death of the founder animal in which the cancer initiated. We investigated the evolutionary history of a cancer lineage that has spread though the soft-shell clam (Mya arenaria) population by assembling a chromosome-scale soft-shell clam reference genome and characterizing somatic mutations in transmissible cancer. We observe high mutation density, widespread copy-number gain, structural rearrangement, loss of heterozygosity, variable telomere lengths, mitochondrial genome expansion and transposable element activity, all indicative of an unstable cancer genome. We also discover a previously unreported mutational signature associated with overexpression of an error-prone polymerase and use this to estimate the lineage to be >200 years old. Our study reveals the ability for an invertebrate cancer lineage to survive for centuries while its genome continues to structurally mutate, likely contributing to the evolution of this lineage as a parasitic cancer.

Improving lithium-ion cells by replacing polyethylene terephthalate jellyroll tape.

Polyethylene terephthalate (PET) tape is widely used by well-known lithium-ion battery manufacturers to prevent electrode stacks from unwinding during assembly. PET tape is selected since it has suitable mechanical and electrical properties, but its chemical stability has been largely overlooked. In the absence of effective electrolyte additives, PET can depolymerize into its monomer dimethyl terephthalate, which is an unwanted redox shuttle that induces substantial self-discharge in a lithium-ion cell. This study presents a chemical screening experiment to probe the PET decomposition mechanism involving in situ generated methanol and lithium methoxide from dimethyl carbonate, one of the most common electrolyte solvents in lithium-ion cells. By screening other polymers, it is found that polypropylene and polyimide (Kapton) are stable in the electrolyte. Finally, it is demonstrated that reversible self-discharge of LiFePO4-graphite cells can be virtually eliminated by replacing PET jellyroll tape with chemically stable polypropylene tape.

Horizontal transmission of disseminated neoplasia in the widespread clam Macoma balthica from the Southern Baltic Sea.

Disseminated neoplasia (DN) is one of the most challenging and unrecognised diseases occurring in aquatic fauna. It has been diagnosed in four bivalve species from the Gulf of Gdansk (Southern Baltic Sea) with the highest frequency in Macoma balthica (formerly Limecola balthica), reaching up to 94% in some populations. The aetiology of DN in the Baltic Sea has not yet been identified, with earlier studies trying to link its occurrence with environmental pollution. Taking into account recent research providing evidence that DN is horizontally transmitted as clonal cells between individuals in some bivalve species, we aimed to test whether DN is a bivalve transmissible neoplasia (BTN) in the population of M. balthica from the Gulf of Gdansk highly affected with cancer. We examined mitochondrial cytochrome c oxidase I (mtCOI) and elongation factor 1α (EF1α) sequences of genomes obtained from haemolymph and tissues of neoplastic and healthy individuals. Sequence analysis resulted in detection of an independent transmissible cancer lineage occurring in four neoplastic clams that is not present in healthy animals. This study describes the first case of BTN in the clam M. balthica (MbaBTN), providing further insights for studies on this disease.

Survival and Detection of Bivalve Transmissible Neoplasia from the Soft-Shell Clam Mya arenaria (MarBTN) in Seawater.

Many pathogens can cause cancer, but cancer itself does not normally act as an infectious agent. However, transmissible cancers have been found in a few cases in nature: in Tasmanian devils, dogs, and several bivalve species. The transmissible cancers in dogs and devils are known to spread through direct physical contact, but the exact route of transmission of bivalve transmissible neoplasia (BTN) has not yet been confirmed. It has been hypothesized that cancer cells from bivalves could be released by diseased animals and spread through the water column to infect/engraft into other animals. To test the feasibility of this proposed mechanism of transmission, we tested the ability of BTN cells from the soft-shell clam (Mya arenaria BTN, or MarBTN) to survive in artificial seawater. We found that MarBTN cells are highly sensitive to salinity, with acute toxicity at salinity levels lower than those found in the native marine environment. BTN cells also survive longer at lower temperatures, with 50% of cells surviving greater than 12 days in seawater at 10 °C, and more than 19 days at 4 °C. With one clam donor, living cells were observed for more than eight weeks at 4 °C. We also used qPCR of environmental DNA (eDNA) to detect the presence of MarBTN-specific DNA in the environment. We observed release of MarBTN-specific DNA into the water of laboratory aquaria containing highly MarBTN-diseased clams, and we detected MarBTN-specific DNA in seawater samples collected from MarBTN-endemic areas in Maine, although the copy numbers detected in environmental samples were much lower than those found in aquaria. Overall, these data show that MarBTN cells can survive well in seawater, and they are released into the water by diseased animals. These findings support the hypothesis that BTN is spread from animal-to-animal by free cells through seawater.

Prevalence and polymorphism of a mussel transmissible cancer in Europe.

Transmissible cancers are parasitic malignant cell lineages that have acquired the ability to infect new hosts from the same species, or sometimes related species. First described in dogs and Tasmanian devils, transmissible cancers were later discovered in some marine bivalves affected by a leukaemia-like disease. In Mytilus mussels, two lineages of bivalve transmissible neoplasia (BTN) have been described to date (MtrBTN1 and MtrBTN2), both of which emerged in a Mytilus trossulus founder individual. Here, we performed extensive screening of genetic chimerism, a hallmark of transmissible cancer, by genotyping 106 single nucleotide polymorphisms of 5,907 European Mytilus mussels. Genetic analysis allowed us to simultaneously obtain the genotype of hosts - Mytilus edulis, M. galloprovincialis or hybrids - and the genotype of tumours of heavily infected individuals. In addition, a subset of 222 individuals were systematically genotyped and analysed by histology to screen for possible nontransmissible cancers. We detected MtrBTN2 at low prevalence in M. edulis, and also in M. galloprovincialis and hybrids although at a much lower prevalence. No MtrBTN1 or new BTN were found, but eight individuals with nontransmissible neoplasia were observed at a single polluted site on the same sampling date. We observed a diversity of MtrBTN2 genotypes that appeared more introgressed or more ancestral than MtrBTN1 and reference healthy M. trossulus individuals. The observed polymorphism is probably due to somatic null alleles caused by structural variations or point mutations in primer-binding sites leading to enhanced detection of the host alleles. Despite low prevalence, two sublineages divergent by 10% fixed somatic null alleles and one nonsynonymous mtCOI (mitochondrial cytochrome oxidase I) substitution are cospreading in the same geographical area, suggesting a complex diversification of MtrBTN2 since its emergence and host species shift.

Identifying key questions in the ecology and evolution of cancer.

The application of evolutionary and ecological principles to cancer prevention and treatment, as well as recognizing cancer as a selection force in nature, has gained impetus over the last 50 years. Following the initial theoretical approaches that combined knowledge from interdisciplinary fields, it became clear that using the eco-evolutionary framework is of key importance to understand cancer. We are now at a pivotal point where accumulating evidence starts to steer the future directions of the discipline and allows us to underpin the key challenges that remain to be addressed. Here, we aim to assess current advancements in the field and to suggest future directions for research. First, we summarize cancer research areas that, so far, have assimilated ecological and evolutionary principles into their approaches and illustrate their key importance. Then, we assembled 33 experts and identified 84 key questions, organized around nine major themes, to pave the foundations for research to come. We highlight the urgent need for broadening the portfolio of research directions to stimulate novel approaches at the interface of oncology and ecological and evolutionary sciences. We conclude that progressive and efficient cross-disciplinary collaborations that draw on the expertise of the fields of ecology, evolution and cancer are essential in order to efficiently address current and future questions about cancer.

Intercellular viral spread and intracellular transposition of Drosophila gypsy.

It has become increasingly clear that retrotransposons (RTEs) are more widely expressed in somatic tissues than previously appreciated. RTE expression has been implicated in a myriad of biological processes ranging from normal development and aging, to age related diseases such as cancer and neurodegeneration. Long Terminal Repeat (LTR)-RTEs are evolutionary ancestors to, and share many features with, exogenous retroviruses. In fact, many organisms contain endogenous retroviruses (ERVs) derived from exogenous retroviruses that integrated into the germ line. These ERVs are inherited in Mendelian fashion like RTEs, and some retain the ability to transmit between cells like viruses, while others develop the ability to act as RTEs. The process of evolutionary transition between LTR-RTE and retroviruses is thought to involve multiple steps by which the element loses or gains the ability to transmit copies between cells versus the ability to replicate intracellularly. But, typically, these two modes of transmission are incompatible because they require assembly in different sub-cellular compartments. Like murine IAP/IAP-E elements, the gypsy family of retroelements in arthropods appear to sit along this evolutionary transition. Indeed, there is some evidence that gypsy may exhibit retroviral properties. Given that gypsy elements have been found to actively mobilize in neurons and glial cells during normal aging and in models of neurodegeneration, this raises the question of whether gypsy replication in somatic cells occurs via intracellular retrotransposition, intercellular viral spread, or some combination of the two. These modes of replication in somatic tissues would have quite different biological implications. Here, we demonstrate that Drosophila gypsy is capable of both cell-associated and cell-free viral transmission between cultured S2 cells of somatic origin. Further, we demonstrate that the ability of gypsy to move between cells is dependent upon a functional copy of its viral envelope protein. This argues that the gypsy element has transitioned from an RTE into a functional endogenous retrovirus with the acquisition of its envelope gene. On the other hand, we also find that intracellular retrotransposition of the same genomic copy of gypsy can occur in the absence of the Env protein. Thus, gypsy exhibits both intracellular retrotransposition and intercellular viral transmission as modes of replicating its genome.

Low-Temperature Atomic Layer Deposited Oxide on Titanium Nitride Electrodes Enables Culture and Physiological Recording of Electrogenic Cells.

The performance of electrode arrays insulated by low-temperature atomic layer deposited (ALD) titanium dioxide (TiO2) or hafnium dioxide (HfO2) for culture of electrogenic cells and for recording of extracellular action potentials is investigated. If successful, such insulation may be considered to increase the stability of future neural implants. Here, insulation of titanium nitride electrodes of microelectrode arrays (MEAs) was performed using ALD of nanometer-sized TiO2 or hafnium oxide at low temperatures (100-200°C). The electrode properties, impedance, and leakage current were measured and compared. Although electrode insulation using ALD oxides increased the electrode impedance, it did not prevent stable, physiological recordings of electrical activity from electrogenic cells (cardiomyocytes and neurons). The insulation quality, estimated from leakage current measurements, was less than 100 nA/cm2 in a range of 3 V. Cardiomyocytes were successfully cultured and recorded after 5 days on the insulated MEAs with signal shapes similar to the recordings obtained using uncoated electrodes. Light-induced electrical activity of retinal ganglion cells was recorded using a complementary metal-oxide semiconductor-based MEA insulated with HfO2 without driving the recording electrode into saturation. The presented results demonstrate that low-temperature ALD-deposited TiO2 and hafnium oxide are biocompatible and biostable and enable physiological recordings. Our results indicate that nanometer-sized ALD insulation can be used to protect electrodes for long-term biological applications.

Effect of Liquid Electrolyte Soaking on the Interfacial Resistance of Li7La3Zr2O12 for All-Solid-State Lithium Batteries.

The impact of liquid electrolyte soaking on the interfacial resistance between the garnet-structured Li7La3Zr2O12 (LLZO) solid electrolyte and metallic lithium has been studied. Lithium carbonate (Li2CO3) formed by inadvertent exposure of LLZO to ambient conditions is generally known to increase interfacial impedance and decrease lithium wettability. Soaking LLZO powders and pellets in the electrolyte containing lithium tetrafluoroborate (LiBF4) shows a significantly reduced interfacial resistance and improved contact between lithium and LLZO. Raman spectroscopy, X-ray diffraction, and soft X-ray absorption spectroscopy reveal how Li2CO3 is continuously removed with increasing soaking time. On-line mass spectrometry and free energy calculations show how LiBF4 reacts with surface carbonate to form carbon dioxide. Using a very simple and scalable process that does not involve heat-treatment and expensive coating techniques, we show that the Li-LLZO interfacial resistance can be reduced by an order of magnitude.

A single clonal lineage of transmissible cancer identified in two marine mussel species in South America and Europe.

Transmissible cancers, in which cancer cells themselves act as an infectious agent, have been identified in Tasmanian devils, dogs, and four bivalves. We investigated a disseminated neoplasia affecting geographically distant populations of two species of mussels (Mytilus chilensis in South America and M. edulis in Europe). Sequencing alleles from four loci (two nuclear and two mitochondrial) provided evidence of transmissible cancer in both species. Phylogenetic analysis of cancer-associated alleles and analysis of diagnostic SNPs showed that cancers in both species likely arose in a third species of mussel (M. trossulus), but these cancer cells are independent from the previously identified transmissible cancer in M. trossulus from Canada. Unexpectedly, cancers from M. chilensis and M. edulis are nearly identical, showing that the same cancer lineage affects both. Thus, a single transmissible cancer lineage has crossed into two new host species and has been transferred across the Atlantic and Pacific Oceans and between the Northern and Southern hemispheres.

From the raw bar to the bench: Bivalves as models for human health.

Bivalves, from raw oysters to steamed clams, are popular choices among seafood lovers and once limited to the coastal areas. The rapid growth of the aquaculture industry and improvement in the preservation and transport of seafood have enabled them to be readily available anywhere in the world. Over the years, oysters, mussels, scallops, and clams have been the focus of research for improving the production, managing resources, and investigating basic biological and ecological questions. During this decade, an impressive amount of information using high-throughput genomic, transcriptomic and proteomic technologies has been produced in various classes of the Mollusca group, and it is anticipated that basic and applied research will significantly benefit from this resource. One aspect that is also taking momentum is the use of bivalves as a model system for human health. In this review, we highlight some of the aspects of the biology of bivalves that have direct implications in human health including the shell formation, stem cells and cell differentiation, the ability to fight opportunistic and specific pathogens in the absence of adaptive immunity, as source of alternative drugs, mucosal immunity and, microbiome turnover, toxicology, and cancer research. There is still a long way to go; however, the next time you order a dozen oysters at your favorite raw bar, think about a tasty model organism that will not only please your palate but also help unlock multiple aspects of molluscan biology and improve human health.

Chronic CRH depletion from GABAergic, long-range projection neurons in the extended amygdala reduces dopamine release and increases anxiety.

The interplay between corticotropin-releasing hormone (CRH) and the dopaminergic system has predominantly been studied in addiction and reward, while CRH-dopamine interactions in anxiety are scarcely understood. We describe a new population of CRH-expressing, GABAergic, long-range-projecting neurons in the extended amygdala that innervate the ventral tegmental area and alter anxiety following chronic CRH depletion. These neurons are part of a distinct CRH circuit that acts anxiolytically by positively modulating dopamine release.

Horizontal transfer of retrotransposons between bivalves and other aquatic species of multiple phyla.

The LTR retrotransposon Steamer is a selfish endogenous element in the soft-shell clam genome that was first detected because of its dramatic amplification in bivalve transmissible neoplasia afflicting the species. We amplified and sequenced related retrotransposons from the genomic DNA of many other bivalve species, finding evidence of horizontal transfer of retrotransposons from the genome of one species to another. First, the phylogenetic tree of the Steamer-like elements from 19 bivalve species is markedly discordant with host phylogeny, suggesting frequent cross-species transfer throughout bivalve evolution. Second, sequences nearly identical to Steamer were identified in the genomes of Atlantic razor clams and Baltic clams, indicating recent transfer. Finally, a search of the National Center for Biotechnology Information sequence database revealed that Steamer-like elements are present in the genomes of completely unrelated organisms, including zebrafish, sea urchin, acorn worms, and coral. Phylogenetic incongruity, a patchy distribution, and a higher similarity than would be expected by vertical inheritance all provide evidence for multiple long-distance cross-phyla horizontal transfer events. These data suggest that over both short- and long-term evolutionary timescales, Steamer-like retrotransposons, much like retroviruses, can move between organisms and integrate new copies into new host genomes.

Low-Cost GRIN-Lens-Based Nephelometric Turbidity Sensing in the Range of 0.1-1000 NTU.

Turbidity sensing is very common in the control of drinking water. Furthermore, turbidity measurements are applied in the chemical (e.g., process monitoring), pharmaceutical (e.g., drug discovery), and food industries (e.g., the filtration of wine and beer). The most common measurement technique is nephelometric turbidimetry. A nephelometer is a device for measuring the amount of scattered light of suspended particles in a liquid by using a light source and a light detector orientated in 90° to each other. Commercially available nephelometers cost usually-depending on the measurable range, reliability, and precision-thousands of euros. In contrast, our new developed GRIN-lens-based nephelometer, called GRINephy, combines low costs with excellent reproducibility and precision, even at very low turbidity levels, which is achieved by its ability to rotate the sample. Thereby, many cuvette positions can be measured, which results in a more precise average value for the turbidity calculated by an algorithm, which also eliminates errors caused by scratches and contaminations on the cuvettes. With our compact and cheap Arduino-based sensor, we are able to measure in the range of 0.1-1000 NTU and confirm the ISO 7027-1:2016 for low turbidity values.

Heterozygosity for the Mood Disorder-Associated Variant Gln460Arg Alters P2X7 Receptor Function and Sleep Quality.

A single nucleotide polymorphism substitution from glutamine (Gln, Q) to arginine (Arg, R) at codon 460 of the purinergic P2X7 receptor (P2X7R) has repeatedly been associated with mood disorders. The P2X7R-Gln460Arg variant per se is not compromised in its function. However, heterologous expression of P2X7R-Gln460Arg together with wild-type P2X7R has recently been demonstrated to impair receptor function. Here we show that this also applies to humanized mice coexpressing both human P2X7R variants. Primary hippocampal cells derived from heterozygous mice showed an attenuated calcium uptake upon agonist stimulation. While humanized mice were unaffected in their behavioral repertoire under basal housing conditions, mice that harbor both P2X7R variants showed alterations in their sleep quality resembling signs of a prodromal disease stage. Also healthy heterozygous human subjects showed mild changes in sleep parameters. These results indicate that heterozygosity for the wild-type P2X7R and its mood disorder-associated variant P2X7R-Gln460Arg represents a genetic risk factor, which is potentially able to convey susceptibility to mood disorders.SIGNIFICANCE STATEMENT Depression and bipolar disorder are the most common mood disorders. The P2X7 receptor (P2X7R) regulates many cellular functions. Its polymorphic variant Gln460Arg has repeatedly been associated with mood disorders. Genetically engineered mice, with human P2X7R, revealed that heterozygous mice (i.e., they coexpress the disease-associated Gln460Arg variant together with its normal version) have impaired receptor function and showed sleep disturbances. Human participants with the heterozygote genotype also had subtle alterations in their sleep profile. Our findings suggest that altered P2X7R function in heterozygote individuals disturbs sleep and might increase the risk for developing mood disorders.

Chemical versus Electrochemical Electrolyte Oxidation on NMC111, NMC622, NMC811, LNMO, and Conductive Carbon.

We compare the stability of alkyl carbonate electrolyte on NMC111, -622, and -811, LNMO, and conductive carbon electrodes. We prove that CO2 and CO evolution onset potentials depend on the electrode material and increase in the order NMC811 < NMC111 ≈ NMC622 < conductive carbon ≈ LNMO, which we rationalize by two fundamentally different oxidation mechanisms, the chemical and the electrochemical electrolyte oxidation. Additionally, in contrast to the widespread understanding that transition metals in cathode active materials catalyze the electrolyte oxidation, we will prove that such a catalytic effect on the electrochemical electrolyte oxidation does not exist.

Role of missing carotenoid in reducing the fluorescence of single monomeric photosystem II core complexes.

The fluorescence of monomeric photosystem II core complexes (mPSIIcc) of the cyanobacterium Thermosynechococcus elongatus, originating from redissolved crystals, is investigated by using single-molecule spectroscopy (SMS) at 1.6 K. The emission spectra of individual mPSIIcc are dominated by sharp zero-phonon lines, showing the existence of different emitters compatible with the F685, F689, and F695 bands reported formerly. The intensity of F695 is reduced in single mPSIIcc as compared to single PSIIcc-dimers (dPSIIcc). Crystal structures show that one of the ß-carotene (ß-Car) cofactors located at the monomer-monomer interface in dPSIIcc is missing in mPSIIcc. This ß-Car in dPSIIcc is in van der Waals distance to chlorophyll (Chl) 17 in the CP47 subunit. We suggest that this Chl contributes to the F695 emitter. A loss of ß-Car cofactors in mPSIIcc preparations will lead to an increased lifetime of the triplet state of Chl 17, which can explain the reduced singlet emission of F695 as observed in SMS.

Don't Just Survive, Thrive: Understanding How Acute Psychiatric Nurses Develop Resilience.

With one in five Canadians estimated to experience mental illness, retention of registered nurses in the acute psychiatric hospital setting becomes a pressing issue. The key for these nurses to survive and potentially even thrive in practice has been identified as resilience. From interviews with four registered nurses, maintaining a "vast" perspective, becoming an "expert" of self, clarifying "belief systems", and being "present" through "staying awake" were identified as key in developing resilience. Although participants expressed that the development of resilience is an individual process, the concept of development was similar. Developing personal resilience may be a matter of self-development.

Evidence of horizontal transmission of the cancer-associated Steamer retrotransposon among ecological cohort bivalve species.

Bivalve specimens from legacy frozen tissue collections, and others freshly obtained, were surveyed for the presence of the Steamer long terminal repeat (LTR)-retrotransposon associated with disseminated hemic neoplasia of the soft-shelled clam Mya areneria. Of 22 species investigated using primers for the pol region, only Atlantic M. arenaria, Atlantic and North Sea razor clams Ensis directus, and Baltic clams Macoma balthica from the North Sea were found to possess copies of Steamer in their genomes. Notably, close relatives like Mya truncata and Siliqua patula did not exhibit evidence of Steamer. Amplified Steamer sequences were uniformly identical in all M. areneria specimens, and were highly variable across specimens of E. directus. Variation in the latter included nucleotide polymorphisms among and within individuals as well as length variation in 2 specimens corresponding to the deletion of a predicted stable hairpin structure. Results implicate Atlantic razor clams as the proximal source for horizontal transmission of Steamer among ecologically similar yet markedly distantly related bivalves. The consequences of cross-species transmission of the Steamer retrotransposon are unknown, and the finding of Steamer in 3 bivalve species suggests that further spread is possible.