Generation and characterization of an estrogen receptor alpha‐iCre knock‐in mouse

Two estrogen receptors, ESR1 and ESR2, are responsible for the classical actions of estrogens in mammalian species. They display different spatiotemporal expression patterns and nonoverlapping functions in various tissues and physiological conditions. In this study, a novel knock‐in mouse line that expresses codon‐improved Cre recombinase (iCre) under regulation of the natural Esr1 promoter (Esr1–iCre) was developed. Functional characterization of iCre expression by crossing them with reporter lines (ROSA26‐lacZ or Ai9‐RFP) showed that iCre is faithfully expressed in Esr1‐lineage cells. This novel transgenic mouse line will be a useful animal model for lineage‐tracing Esr1‐expressing cells, selective gene ablation in the Esr1‐lineage cells and for generating global Esr1 knockout mice.     

Review ‐ Helicobacter,inflammation, immunology and vaccines

Understanding the mechanisms involved in induction and regulation of the immune and inflammatory response to Helicobacter pylori is extremely important in determining disease outcomes. H pylori expresses a plethora of factors that influence the host response. Vaccines against H pylori are desperately needed for the prevention of gastric carcinogenesis, especially with the increasing trends in antimicrobial resistance. This review summarizes some important findings, published between 1 April 2019 and 31 March 2020, in the areas of H pylori‐mediated inflammation, immunity and vaccines.     

Cross‐Modality Effects of Prey Odour During the Intraspecific Interactions of a Mosquito‐Specialist Predator

One of the predictions from evolutionary game theory is that individuals will increase their willingness (i.e. become primed) to escalate aggression when they detect the presence of a limiting resource. Here, we test this prediction in the context of prey odour priming escalation decisions during vision‐based encounters by Evarcha culicivora. This East African jumping spider (Salticidae) feeds indirectly on vertebrate blood by actively choosing blood‐carrying female mosquitoes as preferred prey. Unlike many salticid species, it also expresses pronounced mutual mate choice. As predicted, we show here that, in the presence of odour from their preferred prey, both sexes of E. culicivora escalate during vision‐based same‐sex encounters. This is further evidence that the odour of blood‐carrying mosquitoes is salient to this salticid. For both sexes of E. culicivora, this particular prey may be a resource that matters in the context of intrasexual selection.     

Context‐dependent fruit–frugivore interactions: partner identities and spatio‐temporal variations

Fruit–frugivore interactions are crucial for the dynamics and regeneration of most forested ecosystems. Still, we lack an understanding of the potential variation in the sign and strength of such interactions in relation to variations in the spatial and temporal ecological context. Here, we evaluated spatial (three sites) and temporal (two fruiting seasons) local variation in the sign (seed predation versus dispersal) and strength (frequency and quantity) of the interactions among six frugivorous mammals and a community of Mediterranean fleshy‐fruited shrubs. We examined mammal faecal samples and quantified frequency of seed occurrence, number of seeds per faecal sample, seed species diversity and quality of seed treatment (i.e. percentage of undamaged seeds). The frequency of seed occurrence and number of seeds per faecal sample strongly varied among dispersers, sites, seasons and fruit species. For instance, fox Vulpes vulpes faeces showed between 6 and 40 times more seeds than wild boar Sus scrofa faeces in seasons or sites in which Rubus and Juniperus seeds were dominant. However, in seasons or sites dominated by Corema seeds, wild boar faeces contained up to seven times more seeds than fox faeces. Mammalian carnivores (fox and badger, Meles meles) treated seeds gently, acting mostly as dispersers, whereas deer (Cervus elaphus and Dama dama) acted mainly as seed predators. Interestingly, rabbit Oryctolagus cuniculus acted as either mostly seed disperser or seed predator depending on the plant species. Our results indicated that the sign of fruit–frugivore interactions depended mainly on the identity of the partners. For a particular fruit–frugivore pair, however, our surrogate of interaction strength largely varied with the spatio‐temporal context (year and habitat), leading to a low specificity across the seed–frugivore network. The high spatio‐temporal variability of seed dispersal (in quantity, quality and seed diversity) by different frugivores would confer resilience against unpredictable environmental conditions, such as those typical of Mediterranean ecosystems.     

A multifunctional reporter mouse line for Cre‐ and FLP‐dependent lineage analysis

The Cre/lox and FLP/FRT recombination systems have been used extensively for both conditional knockout and cell lineage analysis in mice. Here we report a new multifunctional Cre/FLP dual reporter allele (R26^NZG) that exhibits strong and apparently ubiquitous marker expression in embryos and adults. The reporter construct, which is driven by the CAG promoter, was knocked into the ROSA26 locus providing an open chromatin domain for consistent expression and avoiding site‐of‐integration effects often observed with transgenic reporters. R26^NZG directs Cre‐dependent nuclear‐localized β‐galactosidase (β‐gal) expression, and can be converted into a Cre‐dependent EGFP reporter (R26^NG) by germline excision of the FRT‐flanked nlslacZ cassette. Alternatively, germline excision of the floxed PGKNEO cassette in R26^NZG generates an FLP‐dependent EGFP reporter (R26^ZG) that expresses β‐gal in FLP‐nonexpressing cells. Finally, by the simultaneous use of both Cre and FLP deleters, R26^NZG allows lineage relationships to be interrogated with greater refinement than is possible with single recombinase reporter systems. genesis 47:107–114, 2009. © 2009 Wiley‐Liss, Inc.     

Food quantity–quality co‐limitation: Interactive effects of dietary carbon and essential lipid supply on population growth of a freshwater rotifer

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Generation of an estrogen receptor beta‐iCre knock‐in mouse

A novel knock‐in mouse that expresses codon‐improved Cre recombinase (iCre) under regulation of the estrogen receptor beta (Esr2) promoter was developed for conditional deletion of genes and for the spatial and/or temporal localization of Esr2 expression. ESR2 is one of two classical nuclear estrogen receptors and displays a spatiotemporal expression pattern and functions that are different from the other estrogen receptor, ESR1. A cassette was constructed that contained iCre, a polyadenylation sequence, and a neomycin selection marker. This construct was used to insert iCre in front of the endogenous start codon of the Esr2 gene of a C57BL/6J embryonic stem cell line via homologous recombination. Resulting Esr2‐iCre mice were bred with ROSA26‐lacZ and Ai9‐RFP reporter mice to visualize cells of functional iCre expression. Strong expression was observed in the ovary, the pituitary, the interstitium of the testes, the head and tail but not body of the epididymis, skeletal muscle, the coagulation gland (anterior prostate), the lung, and the preputial gland. Additional diffuse or patchy expression was observed in the cerebrum, the hypothalamus, the heart, the adrenal gland, the colon, the bladder, and the pads of the paws. Overall, Esr2‐iCre mice will serve as a novel line for conditionally ablating genes in Esr2‐expressing tissues, identifying novel Esr2‐expressing cells, and differentiating the functions of ESR2 and ESR1. genesis 54:38–52, 2016. © 2016 Wiley Periodicals, Inc.     

Strain‐specific consumption and transformation of alga‐derived dissolved organic matter by members of the Limnohabitans‐C and Polynucleobacter‐B clusters of Betaproteobacteria

We investigated changes in quality and quantity of extracellular and biomass‐derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass‐derived OM concentrations from each alga were approximately 20 mg l^?1 and 1 mg l^?1 respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%–61% of identified compounds of the extracellular OM from each alga. In biomass‐derived OM of Rhodomonas and Chlamydomonas 71%–77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga‐derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%–76% and 38%–82% of all identified extracellular and biomass‐derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga‐derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation.     

Inducible gene modification in the gastric epithelium of Tff1‐CreERT2, Tff2‐rtTA,Tff3‐luc mice

Temporal and spatial regulation of genes mediated by tissue‐specific promoters and conditional gene expression systems provide a powerful tool to study gene function in health, disease, and during development. Although transgenic mice expressing the Cre recombinase in the gastric epithelium have been reported, there is a lack of models that allow inducible and reversible gene modification in the stomach. Here, we exploited the gastrointestinal epithelium‐specific expression pattern of the three trefoil factor (Tff) genes and bacterial artificial chromosome transgenesis to generate a novel mouse strain that expresses the CreERT2 recombinase and the reverse tetracycline transactivator (rtTA). The Tg(Tff1‐CreERT2;Tff2‐rtTA;Tff3‐Luc) strain confers tamoxifen‐inducible irreversible somatic recombination and allows simultaneous doxycycline‐dependent reversible gene activation in the gastric epithelium of developing and adult mice. This strain also confers luciferase activity to the intestinal epithelium to enable in vivo bioluminescence imaging. Using fluorescent reporters as conditional alleles, we show Tff1‐CreERT2 and Tff2‐rtTA transgene activity in a partially overlapping subset of long‐term regenerating gastric stem/progenitor cells. Therefore, the Tg(Tff1‐CreERT2;Tff2‐rtTA;Tff3‐Luc) strain can confer intermittent transgene expression to gastric epithelial cells that have undergone previous gene modification, and may be suitable to genetically model therapeutic intervention during development, tumorigenesis, and other genetically tractable diseases. Birth Defects Research (Part A) 106:626–635, 2016. © 2016 Wiley Periodicals, Inc.     

LOS oligosaccharide modification enhances dendritic cell responses to meningococcal native outer membrane vesicles expressing a non‐toxic lipid A

Outer membrane vesicles (OMV) are released by many bacteria, and contain immunogenic antigens in addition to harmful inflammatory factors, like lipopolysaccharides. Chemically detoxified OMV have been used in vaccines against Neisseria meningitidis (Nm); however, little is known about their interaction with antigen presenting cells. In this study, we investigated the interaction of Nm OMV with human dendritic cells (DC) to gain further understanding of their biological activity. We engineered a novel serogroup B Nm that is unencapsulated (siaD), expresses pentacylated lipid A (lpxL1), hence conferring reduced toxicity, and expresses an lgtB oligosaccharide structure designed to target OMV to DC via DC‐SIGN. We show that the lgtB moiety is critical for internalization of NOMV by DC. Furthermore, the lgtB moiety significantly enhances DC maturation, IL‐10 and IL‐23 production in the presence of a pentacylated lipid A. While different DC phenotypes were observed for each NOMV, this had little effect on Th1 and Th2 cell differentiation; however, lgtBsignificantly increased Th17 cell expansion in the presence of pentacylated lipid A. We believe that lpxL1/lgtB NOMV should be considered further as a vaccine vector, particularly considering the importance of lgtB in antigen uptake and further human studies on antigen‐specific responses should be considered.     

Mutant Alleles at the Brown Locus Encoding Tyrosinase‐Related Protein‐1 (TRP‐1) Affect Proliferation of Mouse Melanocytes in Culture *

Tyrosinase related protein‐1 (TRP‐1) is a melanocyte‐specific gene product involved in eumelanin synthesis. Mutation in the Tyrp1 gene is associated with brown pelage in mouse and oculocutaneous albinism Type 3 in humans (OCA3). It has been demonstrated that TRP‐1 expresses DHICA oxidase activity in the murine system. However, its actual function in the human system is still unclear. The study was designed to determine the effects of mutation at two Typr1 alleles, namely the Tyrp1^b (brown) and Tyrp1^b‐cj (cordovan) compared with wild type Tyrp1^B (black) on melanocyte function and melanin biosynthesis. The most significant finding was that both of the Tyrp1 mutations (i.e. brown expressing a point mutation and cordovan expressing decreased amount of TRP‐1 protein) resulted in attenuation of cell proliferation rates. Neither necrosis nor apoptosis was responsible for the observed decrease in cell proliferation rates of the brown and cordovan melanocytes. Ultrastructural evaluation by electron microscopic analysis revealed that both mutations in Tyrp1 affected melanosome maturation without affecting its structure. These observations demonstrate that mutation in Tyrp1 compromised tyrosinase activity within the organelle. DOPA histochemistry revealed differences in melanosomal stages between black and brown melanocytes but not between black and cordovan melanocytes. There were no significant differences in tyrosine hydroxylase activities of tyrosinase and TRP‐1 in wild type black, brown and cordovan melanocyte cell lysates. We conclude that mutations in Tyrp1 compromise cell proliferation and melanosomal maturation in mouse melanocyte cultures.     

Fusobacterium nucleatum infection of gingival epithelial cells leads to NLRP3 inflammasome‐dependent secretion of IL‐1β and the danger signals ASC and HMGB1

Fusobacterium nucleatum is an invasive anaerobic bacterium that is associated with periodontal disease. Previous studies have focused on virulence factors produced by F. nucleatum, but early recognition of the pathogen by the immune system remains poorly understood. Although an inflammasome in gingival epithelial cells (GECs) can be stimulated by danger‐associated molecular patterns (DAMPs) (also known as danger signals) such as ATP, inflammasome activation by this periodontal pathogen has yet to be described in these cells. This study therefore examines the effects of F. nucleatum infection on pro‐inflammatory cytokine expression and inflammasome activation in GECs. Our results indicate that infection induces translocation of NF‐κB into the nucleus, resulting in cytokine gene expression. In addition, infection activates the NLRP3 inflammasome, which in turn activates caspase‐1 and stimulates secretion of mature IL‐1β. Unlike other pathogens studied until now, F. nucleatum activates the inflammasome in GECs in the absence of exogenous DAMPs such as ATP. Finally, infection promotes release of other DAMPs that mediate inflammation, such as high‐mobility group box 1 protein and apoptosis‐associated speck‐like protein, with a similar time‐course as caspase‐1 activation. Thus, F. nucleatum expresses the pathogen‐associated molecular patterns necessary to activate NF‐κB and also provides an endogenous DAMP to stimulate the inflammasome and further amplify inflammation through secretion of secondary DAMPs.     

Postnatal male germ‐cell expression of cre recombinase in Tex101‐iCre transgenic mice

We have generated a transgenic mouse line that expresses improved Cre recombinase (iCre) under the control of the testis‐expressed gene 101 (Tex101) promoter. This transgenic mouse line was named Tex101‐iCre. Using the floxed ROSA reporter mice, we found that robust Cre recombinase activity was detected in postnatal testes with weak or no activity in other tissues. Within the testis, Cre recombinase was active in spermatogenic cells as early as the prospermatogonia stage at day 1 after birth. In 30‐ and 60‐day‐old mice, positive Cre recombinase activity was detected not only in prospermatogonia but also in spermatogenic cells at later stages of spermatogenesis. There was little or no Cre activity in interstitial cells. Breeding wild‐type females with homozygous floxed fibroblast growth factor receptor 2 (Fgfr2) males carrying the Tex101‐iCre transgene did not produce any progeny with the floxed Fgfr2 allele. All the progeny inherited a recombined Fgfr2 allele, indicating that complete deletion of the floxed Fgfr2 allele by Tex101‐iCre can be achieved in the male germline. Furthermore, FGFR2 protein was not detected in spermatocytes and spermatids of adult Fgfr2^fl/fl;Tex101‐iCre mice. Taken together, our results suggest that the Tex101‐iCre mouse line allows the inactivation of a floxed gene in spermatogenic cells in adult mice, which will facilitate the functional characterization of genes in normal spermatogenesis and male fertility. genesis 48:717–722, 2010. © 2010 Wiley‐Liss, Inc.     

Poly‐3‐hydroxyalkanoate synthases from Pseudomonas putida U: substrate specificity and ultrastructural studies

The substrate specificity of the two polymerases (PhaC1 and PhaC2) involved in the biosynthesis of medium‐chain‐length poly‐hydroxyalkanoates (mcl PHAs) in Pseudomonas putida U has been studied in vivo. For these kind of experiments, two recombinant strains derived from a genetically engineered mutant in which the whole pha locus had been deleted (P. putida U Δpha) were employed. These bacteria, which expresses only phaC1 (P. putida U Δpha pMC‐phaC1) or only phaC2 (P. putida U Δpha pMC‐phaC2), accumulated different PHAs in function of the precursor supplemented to the culture broth. Thus, the P. putida U Δpha pMC‐phaC1 strain was able to synthesize several aliphatic and aromatic PHAs when hexanoic, heptanoic, octanoic decanoic, 5‐phenylvaleric, 6‐phenylhexanoic, 7‐phenylheptanoic, 8‐phenyloctanoic or 9‐phenylnonanoic acid were used as precursors; the highest accumulation of polymers was observed when the precursor used were decanoic acid (aliphatic PHAs) or 6‐phenylhexanoic acid (aromatic PHAs). However, although it synthesizes similar aliphatic PHAs (the highest accumulation was observed when hexanoic acid was the precursor) the other recombinant strain (P. putida U Δpha pMC‐phaC2) only accumulated aromatic PHAs when the monomer to be polymerized was 3‐hydroxy‐5‐phenylvaleryl‐CoA. The possible influence of the putative three‐dimensional structures on the different catalytic behaviour of PhaC1 and PhaC2 is discussed.     

Effects of quantitative and qualitative differences in volatiles from host‐ and non‐host‐infested maize on the attraction of the larval parasitoid Cotesia kariyai

Cotesia kariyai Watanabe (Hymenoptera: Braconidae) is a specialist larval parasitoid of Mythimna separata Walker (Lepidoptera: Noctuidae). Cotesia kariyai wasps use herbivore‐induced plant volatiles (HIPVs) to locate hosts. However, complex natural habitats are full of volatiles released by both herbivorous host‐ and non‐host‐infested plants at various levels of intensity. Therefore, the presence of non‐hosts may affect parasitoid decisions while foraging. Here, the host‐finding efficiency of naive C. kariyai from HIPVs influenced by host‐ and non‐host‐infested maize [Zea mays L. (Poaceae)] plants was investigated with a four‐arm olfactometer. Ostrinia furnacalis Guenée (Lepidoptera: Crambidae) was selected as a non‐host species. One unit (1 U) of host‐ or non‐host‐infested plant was prepared by infesting a potted plant with five host or seven non‐host larvae. In two‐choice bioassays, host‐infested plants fed upon by different numbers of larvae, and various units of host‐ and non‐host‐infested plants (infestation units; 1 U, 2 U, and 3 U) were arranged to examine the effects of differences in volatile quantity and quality on the olfactory responses of C. kariyai with the assumption that volatile quantity and quality changes with differences in numbers of insects and plants. Cotesia kariyai was found to perceive quantitative differences in volatiles from host‐infested plants, preferring larger quantities of volatiles from larger numbers of larvae or plants. Also, the parasitoids discriminated between healthy plants, host‐infested plants, and non‐host‐infested plants by recognising volatiles released from those plants. Cotesia kariyai showed a reduced preference for host‐induced volatiles, when larger numbers of non‐host‐infested plants were present. Therefore, quantitative and qualitative differences in volatiles from host‐ and non‐host‐infested plants appear to affect the decision of C. kariyai during host‐habitat searching in multiple tritrophic systems.     

A compact unc45b‐promoter drives muscle‐specific expression in zebrafish and mouse

Summary: Gene therapeutic approaches to cure genetic diseases require tools to express the rescuing gene exclusively within the affected tissues. Viruses are often chosen as gene transfer vehicles but they have limited capacity for genetic information to be carried and transduced. In addition, to avoid off‐target effects the therapeutic gene should be driven by a tissue‐specific promoter in order to ensure expression in the target organs, tissues, or cell populations. The larger the promoter, the less space will be left for the respective gene. Thus, there is a need for small but tissue‐specific promoters. Here, we describe a compact unc45b promoter fragment of 195 bp that retains the ability to drive gene expression exclusively in skeletal and cardiac muscle in zebrafish and mouse. Remarkably, the described unc45b promoter fragment not only drives muscle‐specific expression but presents heat‐shock inducibility, allowing a temporal and spatial quantity control of (trans)gene expression. Here, we demonstrate that the transgenic expression of the smyd1b gene driven by the unc45b promoter fragment is able to rescue the embryonically lethal heart and skeletal muscle defects in smyd1b‐deficient flatline mutant zebrafish. Our findings demonstrate that the described muscle‐specific unc45b promoter fragment might be a valuable tool for the development of genetic therapies in patients suffering from myopathies. genesis 54:431–438, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.