The roles of FGF signaling in germ cell migration in the mouse

Fibroblast growth factor (FGF) signaling is thought to play a role in germ cell behavior. FGF2 has been reported to be a mitogen for primordial germ cells in vitro, whilst combinations of FGF2, steel factor and LIF cause cultured germ cells to transform into permanent lines of pluripotent cells resembling ES cells. However, the actual function of FGF signaling on the migrating germ cells in vivo is unknown. We show, by RT-PCR analysis of cDNA from purified E10.5 germ cells, that germ cells express two FGF receptors: Fgfr1-IIIc and Fgfr2-IIIb. Second, we show that FGF-mediated activation of the MAP kinase pathway occurs in germ cells during their migration, and thus they are potentially direct targets of FGF signaling. Third, we use cultured embryo slices in simple gain-of-function experiments, using FGF ligands, to show that FGF2, a ligand for FGFR1-IIIc, affects motility, whereas FGF7, a ligand for FGFR2-IIIb, affects germ cell numbers. Loss of function, using a specific inhibitor of FGF signaling, causes increased apoptosis and inhibition of cell shape change in the migrating germ cells. Lastly, we confirm in vivo the effects seen in slice cultures in vitro, by examining germ cell positions and numbers in embryos carrying a loss-of-function allele of FGFR2-IIIb. In FGFR2-IIIb(-/-) embryos, germ cell migration is unaffected, but the numbers of germ cells are significantly reduced. These data show that a major role of FGF signaling through FGFR2-IIIb is to control germ cell numbers. The data do not discriminate between direct and indirect effects of FGF signaling on germ cells, and both may be involved.     

Dysregulation of bacterial proteolytic machinery by a new class of antibiotics

Here we show that a new class of antibiotics-acyldepsipeptides-has antibacterial activity against Gram-positive bacteria in vitro and in several rodent models of bacterial infection. The acyldepsipeptides are active against isolates that are resistant to antibiotics in clinical application, implying a new target, which we identify as ClpP, the core unit of a major bacterial protease complex. ClpP is usually tightly regulated and strictly requires a member of the family of Clp-ATPases and often further accessory proteins for proteolytic activation. Binding of acyldepsipeptides to ClpP eliminates these safeguards. The acyldepsipeptide-activated ClpP core is capable of proteolytic degradation in the absence of the regulatory Clp-ATPases. Such uncontrolled proteolysis leads to inhibition of bacterial cell division and eventually cell death.     

100th anniversary of Robert Koch's Nobel Prize for the discovery of the tubercle bacillus

The year 2005 marks the 100th anniversary of Robert Koch's Nobel Prize. Here, we describe the scientific career of Robert Koch, the discoverer of the etiologic agent of tuberculosis but also of those of anthrax, cholera and wound infections. Equally important, Koch developed the methodologies and concepts that made medical microbiology a scientific discipline. Despite great efforts, however, Koch failed to conquer tuberculosis, which still causes enormous health problems worldwide 100 years after his Nobel award.     

Nucleosome, the main autoantigen in systemic lupus erythematosus, induces direct dendritic cell activation via a MyD88-independent pathway: consequences on inflammation

Nucleosome is the major autoantigen in systemic lupus erythematosus. It is found as a circulating complex in the sera of patients and seems to play a key role in disease development. In this study, we show for the first time that physiologic concentrations of purified nucleosomes directly induce in vitro dendritic cell (DC) maturation of mouse bone marrow-derived DC, human monocyte-derived DC (MDDC), and purified human myeloid DC as observed by stimulation of allogenic cells in MLR, cytokine secretion, and CD86 up-regulation. Importantly, nucleosomes act as free complexes without the need for immune complex formation or for the presence of unmethylated CpG DNA motifs, and we thus identified a new mechanism of DC activation by nucleosomes. We have clearly demonstrated that this activation is nucleosome-specific and endotoxin-independent. Particularly, nucleosomes induce MDDC to secrete cytokines known to be detected in high concentrations in the sera of patients. Moreover, activated MDDC secrete IL-8, a neutrophil chemoattractant also detected in patient sera, and thus might favor the inflammation observed in patients. Both normal and lupus MDDC are sensitive to nucleosome-induced activation. Finally, injection of purified nucleosomes to normal mice induces in vivo DC maturation. Altogether, these results strengthen the key role of nucleosomes in systemic lupus erythematosus and might explain how peripheral tolerance is broken in patients.     

PAProC: a prediction algorithm for proteasomal cleavages available on the WWW

The first version of PAProC (Prediction Algorithm for Proteasomal Cleavages) is now available to the general public. PAProC is a prediction tool for cleavages by human and yeast proteasomes, based on experimental cleavage data. It will be particularly useful for immunologists working on antigen processing and the prediction of major histocompatibility complex class I molecule (MHC I) ligands and cytotoxic T-lymphocyte (CTL) epitopes. Likewise, in cases in which proteasomal protein degradation has been indicated in disease, PAProC can be used to assess the general cleavability of disease-linked proteins. On its web site (http://www.paproc.de), background information and hyperlinks are provided for the user (e.g., to SYFPEITHI, the database for the prediction of MHC I ligands).     

Distribution patterns of the ΔF508 mutation in the CFTR gene on CF-linked marker haplotypes in the German population

Summary We have measured the frequency of the ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and its association with cystic fibrosis (CF)-linked marker haplotypes in the German population. Based on the analysis of 400 CF chromosomes, the frequency of the ΔF508 mutation is estimated to be 77.3%, the vast majority being associated with marker haplotype KM19-XV2c 2 1. Our data further suggest the presence of another frequent CF mutation associated with this marker haplotype.     

Very Low Ethanol Concentrations Affect the Viability and Growth Recovery in Post-Stationary-Phase Staphylococcus aureus Populations

Pharmaceuticals, culture media used for in vitro diagnostics and research, human body fluids, and environments can retain very low ethanol concentrations (VLEC) (≤0.1%, vol/vol). In contrast to the well-established effects of elevated ethanol concentrations on bacteria, little is known about the consequences of exposure to VLEC. We supplemented growth media for Staphylococcus aureus strain DSM20231 with VLEC (VLEC⁺ conditions) and determined ultramorphology, growth, and viability compared to those with unsupplemented media (VLEC⁻ conditions) for prolonged culture times (up to 8 days). VLEC⁺-grown late-stationary-phase S. aureus displayed extensive alterations of cell integrity as shown by scanning electron microscopy. Surprisingly, while ethanol in the medium was completely metabolized during exponential phase, a profound delay of S. aureus post-stationary-phase recovery (>48 h) was observed. Concomitantly, under VLEC⁺ conditions, the concentration of acetate in the culture medium remained elevated while that of ammonia was reduced, contributing to an acidic culture medium and suggesting decreased amino acid catabolism. Interestingly, amino acid depletion was not uniformly affected: under VLEC⁺ conditions, glutamic acid, ornithine, and proline remained in the culture medium while the uptake of other amino acids was not affected. Supplementation with arginine, but not with other amino acids, was able to restore post-stationary-phase growth and viability. Taken together, these data demonstrate that VLEC have profound effects on the recovery of S. aureus even after ethanol depletion and delay the transition from primary to secondary metabolite catabolism. These data also suggest that the concentration of ethanol needed for bacteriostatic control of S. aureus is lower than that previously reported.     

Homology between 4.3 μm minicircular and plastomic DNA in chloroplasts of Acetabularia cliftonii

Molecular Genetics and Genomics - In addition to high molecular weight plastomic DNA, chloroplasts of Acetabularia cliftonii also contain small supercoiled DNA molecules (Green 1976). Restriction...