Do alien predators pose a particular risk to duck nests in Northern Europe? Results from an artificial nest experiment

Several alien predator species have spread widely in Europe during the last five decades and pose a potential enhanced risk to native nesting ducks and their eggs. Because predation is an important factor limiting Northern Hemisphere duck nest survival, we ask the question, do alien species increase the nest loss risk to ground nesting ducks? We created 418 artificial duck nests in low densities around inland waters in Finland and Denmark during 2017–2019 and monitored them for seven days after construction using wildlife cameras to record whether alien species visit and prey on the nests more often than native species. We sampled various duck breeding habitats from eutrophic agricultural lakes and wetlands to oligotrophic lakes and urban environments. The results differed between habitats and the two countries, which likely reflect the local population densities of the predator species. The raccoon dog (Nyctereutes procyonoides), an alien species, was the most common mammalian nest visitor in all habitats and its occurrence reduced nest survival. Only in wetland habitats was the native red fox (Vulpes vulpes) an equally common nest visitor, where another alien species, the American mink (Neovison vison), also occurred among nest visitors. Although cautious about concluding too much from visitations to artificial nests, these results imply that duck breeding habitats in Northern Europe already support abundant and effective alien nest predators, whose relative frequency of visitation to artificial nests suggest that they potentially add to the nest predation risk to ducks over native predators.

     

Quantitative genetics of the use of conspecific and heterospecific social cues for breeding site choice

Social information use for decision-making is common and affects ecological and evolutionary processes, including social aggregation, species coexistence, and cultural evolution. Despite increasing ecological knowledge on social information use, very little is known about its genetic basis and therefore its evolutionary potential. Genetic variation in a trait affecting an individual's social and nonsocial environment may have important implications for population dynamics, interspecific interactions, and, for expression of other, environmentally plastic traits. We estimated repeatability, additive genetic variance, and heritability of the use of conspecific and heterospecific social cues (abundance and breeding success) for breeding site choice in a population of wild collared flycatchers Ficedula albicollis. Repeatability was found for two social cues: previous year conspecific breeding success and previous year heterospecific abundance. Yet, additive genetic variances for these two social cues, and thus heritabilities, were low. This suggests that most of the phenotypic variation in the use of social cues and resulting conspecific and heterospecific social environment experienced by individuals in this population stems from phenotypic plasticity. Given the important role of social information use on ecological and evolutionary processes, more studies on genetic versus environmental determinism of social information use are needed.     

Synthesis of building blocks for solid-phase introduction of diethylenetriaminepentaacetic acid (DTPA) to oligonucleotides and oligopeptides

Synthesis of building blocks that allow site-specific incorporation of diethylenetriaminepentaacetic acid (DTPA) to oligonucleotides and oligopeptides using phosphoramidite and Fmoc chemistries, respectively, is described.     

Labeling of proteins and oligopeptides with luminescent lanthanide(III) chelates.

Synthesis of a building block that allows introduction of photoluminescent europium(III) and samarium(III) chelates to synthetic oligopeptides on solid phase using standard Fmoc chemistry is described. Upon completion of the oligopeptide synthesis, these conjugates were converted to the corresponding lanthanide(III) chelates by treatment with appropriate lanthanide(III) salt. Also synthesis of a new terpyridine-based europium(III) chelate designed for solution phase protein labeling is demonstrated.     

Requirements for receptor engagement during infection by adenovirus complexed with blood coagulation factor X

Human adenoviruses from multiple species bind to coagulation factor X (FX), yet the importance of this interaction in adenovirus dissemination is unknown. Upon contact with blood, vectors based on adenovirus serotype 5 (Ad5) binds to FX via the hexon protein with nanomolar affinity, leading to selective uptake of the complex into the liver and spleen. The Ad5:FX complex putatively targets heparan sulfate proteoglycans (HSPGs). The aim of this study was to elucidate the specific requirements for Ad5:FX-mediated cellular uptake in this high-affinity pathway, specifically the HSPG receptor requirements as well as the role of penton base-mediated integrin engagement in subsequent internalisation. Removal of HS sidechains by enzymatic digestion or competition with highly-sulfated heparins/heparan sulfates significantly decreased FX-mediated Ad5 cell binding in vitro and ex vivo. Removal of N-linked and, in particular, O-linked sulfate groups significantly attenuated the inhibitory capabilities of heparin, while the chemical inhibition of endogenous HSPG sulfation dose-dependently reduced FX-mediated Ad5 cellular uptake. Unlike native heparin, modified heparins lacking O- or N-linked sulfate groups were unable to inhibit Ad5 accumulation in the liver 1h after intravascular administration of adenovirus. Similar results were observed in vitro using Ad5 vectors possessing mutations ablating CAR- and/or α(v) integrin binding, demonstrating that attachment of the Ad5:FX complex to the cell surface involves HSPG sulfation. Interestingly, Ad5 vectors ablated for α(v) integrin binding showed markedly delayed cell entry, highlighting the need for an efficient post-attachment internalisation signal for optimal Ad5 uptake and transport following surface binding mediated through FX. This study therefore integrates the established model of α(v) integrin-dependent adenoviral infection with the high-affinity FX-mediated pathway. This has important implications for mechanisms that define organ targeting following contact of human adenoviruses with blood.     

Survival probability in a small shorebird decreases with the time an individual carries a tracking device

Effects of tracking devices on survival are generally considered to be small. However, most studies to date have been conducted over a time-period of only one year, neglecting the possible accumulation of negative effects and consequently stronger negative impacts on survival when the individuals have carried the tracking devices for longer periods. We studied the effects of geolocators in a closely monitored and colour-ringed southern dunlin Calidris alpina schinzii population breeding in Finland. Our capture–recapture data spans 2002–2018 and includes individual histories of 338 colour-ringed breeding adult dunlins (the term ‘recapture' includes resightings of colour-ringed and individually recognizable birds). These data include 53 adults that were fitted with leg-flag mounted geolocators in 2013–2014. We followed their fates together with other colour-ringed birds not equipped with geolocators until 2018. Geolocators were removed within 1–2 years of attachment or were not removed at all, which allowed us to examine whether carrying a geolocator reduces survival and whether the reduction in survival becomes stronger when geolocators are carried for more than one year. We fit multi-state open population capture–recapture models to the encounter history data. When assessing geolocator effects, we accounted for recapture probabilities, time since marking, and sex and year effects on survival. We found that carrying a geolocator reduced survival, which contrasts with many studies that examined return rates after one year. Importantly, survival declined with the time the individual had carried a geolocator, suggesting that the negative effects accumulate over time. Hence, the longer monitoring of birds carrying a geolocator may explain the difference from previous studies. Despite their larger mass, females tended to be more strongly affected by geolocators than males. Our results warrant caution in conducting tracking studies and suggest that short-term studies examining return rates may not reveal all possible effects of tracking devices on survival.     

Keratinocyte growth factor induces gene expression signature associated with suppression of malignant phenotype of cutaneous squamous carcinoma cells

Keratinocyte growth factor (KGF, fibroblast growth factor-7) is a fibroblast-derived mitogen, which stimulates proliferation of epithelial cells. The expression of KGF by dermal fibroblasts is induced following injury and it promotes wound repair. However, the role of KGF in cutaneous carcinogenesis and cancer progression is not known. We have examined the role of KGF in progression of squamous cell carcinoma (SCC) of the skin. The expression of KGF receptor (KGFR) mRNA was lower in cutaneous SCCs (n = 6) than in normal skin samples (n = 6). Expression of KGFR mRNA was detected in 6 out of 8 cutaneous SCC cell lines and the levels were downregulated by 24-h treatment with KGF. KGF did not stimulate SCC cell proliferation, but it reduced invasion of SCC cells through collagen. Gene expression profiling of three cutaneous SCC cell lines treated with KGF for 24 h revealed a specific gene expression signature characterized by upregulation of a set of genes specifically downregulated in SCC cells compared to normal epidermal keratinocytes, including genes with tumor suppressing properties (SPRY4, DUSP4, DUSP6, LRIG1, PHLDA1). KGF also induced downregulation of a set of genes specifically upregulated in SCC cells compared to normal keratinocytes, including genes associated with tumor progression (MMP13, MATN2, CXCL10, and IGFBP3). Downregulation of MMP-13 and KGFR expression in SCC cells and HaCaT cells was mediated via ERK1/2. Activation of ERK1/2 in HaCaT cells and tumorigenic Ha-ras-transformed HaCaT cells resulted in downregulation of MMP-13 and KGFR expression. These results provide evidence, that KGF does not promote progression of cutaneous SCC, but rather suppresses the malignant phenotype of cutaneous SCC cells by regulating the expression of several genes differentially expressed in SCC cells, as compared to normal keratinocytes.     

MMP-13 Regulates Growth of Wound Granulation Tissue and Modulates Gene Expression Signatures Involved in Inflammation, Proteolysis, and Cell Viability

Proteinases play a pivotal role in wound healing by regulating cell-matrix interactions and availability of bioactive molecules. The role of matrix metalloproteinase-13 (MMP-13) in granulation tissue growth was studied in subcutaneously implanted viscose cellulose sponge in MMP-13 knockout (Mmp13(-/-)) and wild type (WT) mice. The tissue samples were harvested at time points day 7, 14 and 21 and subjected to histological analysis and gene expression profiling. Granulation tissue growth was significantly reduced (42%) at day 21 in Mmp13(-/-) mice. Granulation tissue in Mmp13(-/-) mice showed delayed organization of myofibroblasts, increased microvascular density at day 14, and virtual absence of large vessels at day 21. Gene expression profiling identified differentially expressed genes in Mmp13(-/-) mouse granulation tissue involved in biological functions including inflammatory response, angiogenesis, cellular movement, cellular growth and proliferation and proteolysis. Among genes linked to angiogenesis, Adamts4 and Npy were significantly upregulated in early granulation tissue in Mmp13(-/-) mice, and a set of genes involved in leukocyte motility including Il6 were systematically downregulated at day 14. The expression of Pdgfd was downregulated in Mmp13(-/-) granulation tissue in all time points. The expression of matrix metalloproteinases Mmp2, Mmp3, Mmp9 was also significantly downregulated in granulation tissue of Mmp13(-/-) mice compared to WT mice. Mmp13(-/-) mouse skin fibroblasts displayed altered cell morphology and impaired ability to contract collagen gel and decreased production of MMP-2. These results provide evidence for an important role for MMP-13 in wound healing by coordinating cellular activities important in the growth and maturation of granulation tissue, including myofibroblast function, inflammation, angiogenesis, and proteolysis.     

The structure of the glial cell line-derived neurotrophic factor-coreceptor complex: insights into RET signaling and heparin binding

Glial cell line-derived neurotrophic factor (GDNF), a neuronal survival factor, binds its co-receptor GDNF family receptor alpha1 (GFR alpha 1) in a 2:2 ratio and signals through the receptor tyrosine kinase RET. We have solved the GDNF(2).GFR alpha 1(2) complex structure at 2.35 A resolution in the presence of a heparin mimic, sucrose octasulfate. The structure of our GDNF(2).GFR alpha 1(2) complex and the previously published artemin(2).GFR alpha 3(2) complex are unlike in three ways. First, we have experimentally identified residues that differ in the ligand-GFR alpha interface between the two structures, in particular ones that buttress the key conserved Arg(GFR alpha)-Glu(ligand)-Arg(GFR alpha) interaction. Second, the flexible GDNF ligand "finger" loops fit differently into the GFR alphas, which are rigid. Third, and we believe most importantly, the quaternary structure of the two tetramers is dissimilar, because the angle between the two GDNF monomers is different. This suggests that the RET-RET interaction differs in different ligand(2)-co-receptor(2)-RET(2) heterohexamer complexes. Consistent with this, we showed that GDNF(2).GFR alpha1(2) and artemin(2).GFR alpha 3(2) signal differently in a mitogen-activated protein kinase assay. Furthermore, we have shown by mutagenesis and enzyme-linked immunosorbent assays of RET phosphorylation that RET probably interacts with GFR alpha 1 residues Arg-190, Lys-194, Arg-197, Gln-198, Lys-202, Arg-257, Arg-259, Glu-323, and Asp-324 upon both domains 2 and 3. Interestingly, in our structure, sucrose octasulfate also binds to the Arg(190)-Lys(202) region in GFR alpha 1 domain 2. This may explain how GDNF.GFR alpha 1 can mediate cell adhesion and how heparin might inhibit GDNF signaling through RET.