Fkbp8: novel isoforms, genomic organization, and characterization of a forebrain promoter in transgenic mice

The immunophilin homolog FKBP8 has been implicated in the regulation of apoptosis. Here we show that the 38-kDa form of FKBP8 (FKBP38) derives from a truncated ORF. The extended FKBP8 ORFs are 46 and 44 kDa in mouse and 45 kDa in human. Although the genomic organization of mouse and human FKBP8 is evolutionarily conserved, additional first exons are encoded by the murine locus. A 4.4-kb murine Fkbp8 gene fragment, containing a GC-rich potential promoter, directed expression of a LacZ reporter gene to forebrain neurons in transgenic mice. Expression of the transgene was observed in CA1 pyramidal neurons of the hippocampus in transgenic mice from three lines. One transgenic founder mouse exhibited widespread forebrain expression of the LacZ transgene that resembles the pattern for the endogenous Fkbp8 gene. Thus promoter/enhancer elements for forebrain expression are located around the first exons of the mouse Fkbp8 gene.     

Interaction between isopod grazing and wave action: a structuring force in macroalgal communities in the southern Baltic Sea

The macroalgal belt in the southern Baltic Sea may be partly structured by the interaction of physical and biological factors. A field study, spanning the 1990s, describes a rapid decline of the Fucus spp. stands along the wave-exposed Swedish southeast coast. During this period, a relative dominance of Fucus vesiculosus L. shifted to a relative dominance of Fucus serratus L. The decline of F. vesiculosus coincided with observations of large numbers of the grazing isopods Idotea baltica (Pallas) and Idotea granulosa Rathke, or with field observations of frequent grazing marks on Fucus fronds. I. baltica, but not I. granulosa, tended to aggregate in the declining Fucus spp. stands, indicating a strong preference for Fucus spp. In a mesocosm experiment I. baltica, when given a choice, grazed both Fucus species at weak water motion. At strong water motion grazing was concentrated on F. vesiculosus. It is hypothesized that one of the reasons I. baltica preferred F. vesiculosus to F. serratus at strong water motion may have been differences in habitat quality, like width of thallus, influencing the ability to cling to the plant. Smaller thallus, as in F. vesiculosus, thus is the preferred habitat for grazing of I. blatica. We postulate that the existence of F. serratus in the area may be favoured by strong wave action and moderate but not strong grazing by I. baltica, relaxing the interspecific competition from F. vesiculosus.     

Involvement of CXCR4 Chemokine Receptor in Metastastic HER2-Positive Esophageal Cancer

A functional linkage of the structurally unrelated receptors HER2 and CXCR4 has been suggested for breast cancer but has not been evaluated for esophageal carcinoma. The inhibition of HER2 leads to a reduction of primary tumor growth and metastases in an orthotopic model of esophageal carcinoma. The chemokine receptor CXCR4 has been implicated in metastatic dissemination of various tumors and correlates with poor survival in esophageal carcinoma. The aim of this study was to investigate a correlation between the expression levels of HER2 and CXCR4 and to evaluate the involvemnent of CXCR4-expression in HER2-positive esophageal carcinoma. The effects of HER2-inhibition with trastuzumab and of CXCR4-inhibition with AMD3100 on primary tumor growth, metastatic homing, and receptor expression were evaluated in vitro and in an orthotopic model of metastatic esophageal carcinoma using MRI for imaging. The clinical relevance of HER2- and CXCR4-expression was examined in esophageal carcinoma patients. A significant correlation of HER2- and CXCR4-expression in primary tumor and metastases exists in the orthotopic model. Trastuzumab and AMD3100 treatment led to a significant reduction of primary tumor growth, metastases and micrometastases. HER2-expression was significantly elevated under AMD3100 treatment in the primary tumor and particularly in the metastases. The positive correlation between HER2- and CXCR4-expression was validated in esophageal cancer patients. The correlation of CXCR4- and HER2-expression and the elevation of HER2-expression and reduction of metastases through CXCR4-inhibition suggest a possible functional linkage and a role in tumor dissemination in HER2-positive esophageal carcinoma.     

Cloning and expression of the gene for a fibronectin-binding protein from Staphylococcus aureus.

The gene encoding the fibronectin-binding protein (FNBP) from Staphylococcus aureus strain 8325-4 was isolated from a gene bank in pBR322. The original clone, containing a 6.5-kb insert, gave a functional product present in the periplasm of Escherichia coli. Analysis of polypeptides isolated after affinity chromatography on fibronectin-Sepharose followed by ion-exchange chromatography revealed two gene products, 87 and 165 kd in mol. wt. The amino acid compositions of these two polypeptides and a native FNBP from S. aureus strain Newman were very similar. Antibodies raised against the native FNBP from strain Newman precipitated the 125I-labelled 165-kd polypeptide, and unlabeled 165- and 87-kd polypeptides as well as native FNBP inhibited the immunoprecipitation reactions. The region of the fnbp-gene encoding the fibronectin-binding activity has been identified and subcloned in an expression vector based on the staphylococcal protein A gene. The resulting product in E. coli is an extracellular fusion protein consisting of two IgG-binding domains of protein A followed by a fibronectin-binding region. The fusion protein binds to fibronectin and completely inhibits the binding of fibronectin to intact cells of S. aureus.     

Seasonal Community and Population Dynamics of Pelagic Bacteria and Archaea in a High Mountain Lake

The seasonal variations in community structure and cell morphology of pelagic procaryotes from a high mountain lake (Gossenköllesee, Austria) were studied by in situ hybridization with rRNA-targeted fluorescently labeled oligonucleotide probes (FISH) and image-analyzed microscopy. Compositional changes and biomass fluctuations within the assemblage were observed both in summer and beneath the winter ice cover and are discussed in the context of physicochemical and biotic parameters. Proteobacteria of the beta subclass (beta-proteobacteria) formed a dominant fraction of the bacterioplankton (annual mean, 24% of the total counts), whereas alpha-proteobacteria were of similar relative importance only during spring (mean, 11%). Bacteria of the Cytophaga-Flavobacterium cluster, although less abundant, constituted the largest fraction of the filamentous morphotypes during most of the year, thus contributing significantly to the total microbial biomass. Successive peaks of threadlike and rod-shaped archaea were observed during autumn thermal mixing and the period of ice cover formation, respectively. A set of oligonucleotide probes targeted to single phylotypes was constructed from 16S rRNA-encoding gene clone sequences. Three distinct populations of uncultivated microbes, affiliated with the alpha- and beta-proteobacteria, were subsequently monitored by FISH. About one-quarter of all of the beta-proteobacteria (range, 6 to 53%) could be assigned to only two phylotypes. The bacterial populations studied were annually recurrent, seasonally variable, and vertically stratified, except during the periods of lake overturn. Their variability clearly exceeded the fluctuations of the total microbial assemblage, suggesting that the apparent stability of total bacterioplankton abundances may mask highly dynamic community fluctuations.Until recently, microbial ecologist studying aquatic bacteria faced a basic dilemma: they could either measure the abundance, biomass, growth rates, activity, etc. of the “average” bacterium under in situ conditions (e.g., see reference 13), ignoring the phylogenetic and physiological diversity of microbial communities, or they could isolate and ecophysiologically characterize individual bacterial strains (e.g., see reference 36) but were then not able to tell if these microorganisms were also common in the environment. Consequently, little knowledge has been gathered about the spatial and temporal abundance fluctuations of defined phylogenetic groups and of individual bacterial species in natural habitats. Molecular biological techniques used to identify microbes in environmental samples have recently provided new tools to study bacterioplankton biodiversity (e.g., see references 1, 9, 14, 15, and 19) and the in situ abundances of bacteria and archaea that could not be adequately distinguished before (2, 4, 5, 25). Microbiologists are now in a position to potentially elucidate the biogeography (24), population dynamics, and successions (28) not only of a few morphologically conspicuous microbes but of a large number of species, most of which might still be uncharacterized.Fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes selectively visualizes bacterial cells with defined phylogenetic affiliations (3, 5). Based on a rapidly growing set of 16S (and, to a lesser extend, 23S) rRNA sequence data, it is probably the phylogenetically most sophisticated (22) approach for whole-cell in situ identification. On the other hand, FISH of plankton samples can be performed with minimal laboratory requirements (16), and evaluation relies on epifluorescence microscopy, which is a standard technique of aquatic microbial ecologists, e.g., for counting (30) and sizing (33) of picoplankton. In contrast to other identification approaches, FISH largely conserves the gestalt of the targeted microorganisms, i.e., their morphologies, cell sizes (26, 34), and cellular rRNA content (7, 32). So, despite the limitations of the method (as discussed in reference 5), its potential for the identification and cytometric analysis of planktonic microbes is just about to be recognized.Recent investigations have reported that various freshwater microbial communities are dominated by bacteria which are phylogenetically affiliated with the alpha and beta subclasses of the class Proteobacteria (alpha- and beta-proteobacteria, respectively) and with members of the Cytophaga-Flavobacterium cluster (2, 6, 16, 19). These observations were based on single or short-term sampling schemes. The instantaneous community composition of the bacterioplankton, however, may not be representative for different seasons, and the typical ranges of annual community variability remain to be established.The size distribution of planktonic bacteria, and particularly the appearance of filamentous cells, has come into the focus of aquatic microbial ecology in the context of studies of predator-prey interactions. It has been shown both in the laboratory (18, 37) and in field experiments (20) that the filamentous morphotype is a phenotypic adaptation of some microbes to protistan grazing, but there are probably numerous other causes for bacteria to elongate far beyond their typical sizes (e.g., see reference 23). Threadlike bacteria have been observed throughout the year in the plankton of a hypertrophic lake (41) but were also found in midwinter in an oligotropic alpine lake (31).In earlier studies, we demonstrated FISH to be an appropriate tool for the monitoring of spatial (2) and short-term temporal (26) dynamics of different phylogenetic groups of the planktonic microbial community in a high mountain lake. Here we report on the seasonal and vertical abundance distributions of pelagic members of Bacteria and Archaea in Gossenköllesee and analysis of the community structure at different levels of taxonomic resolution. We applied published domain- and group-specific oligonucleotide probes (5) but also used the sequence information from a 16S rRNA-encoding gene (rDNA) library obtained from Gossenköllesee bacterioplankton 1 year earlier to construct specific probes targeted at individual bacterial populations. Particular attention was paid to the changes in abundance and taxonomic composition of the filamentous bacterial morphotypes which were recognized as a permanently important fraction of the planktonic procaryotes in Gossenköllesee. Additionally, we monitored the seasonal changes in the biomass size distributions of the nonfilamentous fraction of the pelagic microbial community.     

Climate-dependent dispersal rates in metapopulations of burnet moths

Predicted climate change implies warmer weather and a higher frequency of extreme weather situations. The consequences of the warm July in 2003 was investigated in contrast to the cold July in 2004 in southern Sweden with focus on the dispersal rate of two species of burnet moths (Zygaenidae). During an extensive mark-release-recapture program in metapopulations of burnet moths substantial differences in inter habitat patch dispersal rates were observed. For two species of Zygaena it was 2.14 and 2.18 times higher during the warm year. Measured patch dispersal rate significantly declined towards the edges of the large study-area, suggesting that individuals disperse outside the study-area. No significant differences in dispersal rates were found between the two species studied. The dispersal rates were similar for both females and males, and no density dependent effects on dispersal or effects of amount of nectar rich flowers were found. Dispersal events appeared as distinct movements, often reaching several kilometres. We conclude that dispersal depend on climatic conditions. Exceptionally warm years may be especially important for survival of certain species in metapopulation systems and this may be crucial for the survival of populations during scenarios of climate change.     

The Net Landscape Carbon Balance—Integrating terrestrial and aquatic carbon fluxes in a managed boreal forest landscape in Sweden

The boreal biome exchanges large amounts of carbon (C) and greenhouse gases (GHGs) with the atmosphere and thus significantly affects the global climate. A managed boreal landscape consists of various sinks and sources of carbon dioxide (CO₂), methane (CH₄), and dissolved organic and inorganic carbon (DOC and DIC) across forests, mires, lakes, and streams. Due to the spatial heterogeneity, large uncertainties exist regarding the net landscape carbon balance (NLCB). In this study, we compiled terrestrial and aquatic fluxes of CO₂, CH₄, DOC, DIC, and harvested C obtained from tall‐tower eddy covariance measurements, stream monitoring, and remote sensing of biomass stocks for an entire boreal catchment (~68 km²) in Sweden to estimate the NLCB across the land–water–atmosphere continuum. Our results showed that this managed boreal forest landscape was a net C sink (NLCB = 39 g C m^?2 year^?1) with the landscape–atmosphere CO₂ exchange being the dominant component, followed by the C export via harvest and streams. Accounting for the global warming potential of CH₄, the landscape was a GHG sink of 237 g CO₂‐eq m^?2 year^?1, thus providing a climate‐cooling effect. The CH₄ flux contribution to the annual GHG budget increased from 0.6% during spring to 3.2% during winter. The aquatic C loss was most significant during spring contributing 8% to the annual NLCB. We further found that abiotic controls (e.g., air temperature and incoming radiation) regulated the temporal variability of the NLCB whereas land cover types (e.g., mire vs. forest) and management practices (e.g., clear‐cutting) determined their spatial variability. Our study advocates the need for integrating terrestrial and aquatic fluxes at the landscape scale based on tall‐tower eddy covariance measurements combined with biomass stock and stream monitoring to develop a holistic understanding of the NLCB of managed boreal forest landscapes and to better evaluate their potential for mitigating climate change.