Quick divergence but slow convergence during ecotype formation in lake and stream stickleback pairs of variable age

When genetic constraints restrict phenotypic evolution, diversification can be predicted to evolve along so-called lines of least resistance. To address the importance of such constraints and their resolution, studies of parallel phenotypic divergence that differ in their age are valuable. Here, we investigate the parapatric evolution of six lake and stream threespine stickleback systems from Iceland and Switzerland, ranging in age from a few decades to several millennia. Using phenotypic data, we test for parallelism in ecotypic divergence between parapatric lake and stream populations and compare the observed patterns to an ancestral-like marine population. We find strong and consistent phenotypic divergence, both among lake and stream populations and between our freshwater populations and the marine population. Interestingly, ecotypic divergence in low-dimensional phenotype space (i.e. single traits) is rapid and seems to be often completed within 100 years. Yet, the dimensionality of ecotypic divergence was highest in our oldest systems and only there parallel evolution of unrelated ecotypes was strong enough to overwrite phylogenetic contingency. Moreover, the dimensionality of divergence in different systems varies between trait complexes, suggesting different constraints and evolutionary pathways to their resolution among freshwater systems.

Toxicity of eosinophil MBP is repressed by intracellular crystallization and promoted by extracellular aggregation.

Eosinophils are white blood cells that function in innate immunity and participate in the pathogenesis of various inflammatory and neoplastic disorders. Their secretory granules contain four cytotoxic proteins, including the eosinophil major basic protein (MBP-1). How MBP-1 toxicity is controlled within the eosinophil itself and activated upon extracellular release is unknown. Here we show how intragranular MBP-1 nanocrystals restrain toxicity, enabling its safe storage, and characterize them with an X-ray-free electron laser. Following eosinophil activation, MBP-1 toxicity is triggered by granule acidification, followed by extracellular aggregation, which mediates the damage to pathogens and host cells. Larger non-toxic amyloid plaques are also present in tissues of eosinophilic patients in a feedback mechanism that likely limits tissue damage under pathological conditions of MBP-1 oversecretion. Our results suggest that MBP-1 aggregation is important for innate immunity and immunopathology mediated by eosinophils and clarify how its polymorphic self-association pathways regulate toxicity intra- and extracellularly.

Continuous eclogite melting and variable refertilisation in upwelling heterogeneous mantle

Large-scale tectonic processes introduce a range of crustal lithologies into the Earth's mantle. These lithologies have been implicated as sources of compositional heterogeneity in mantle-derived magmas. The model being explored here assumes the presence of widely dispersed fragments of residual eclogite (derived from recycled oceanic crust), stretched and stirred by convection in the mantle. Here we show with an experimental study that these residual eclogites continuously melt during upwelling of such heterogeneous mantle and we characterize the melting reactions and compositional changes in the residue minerals. The chemical exchange between these partial melts and more refractory peridotite leads to a variably metasomatised mantle. Re-melting of these metasomatised peridotite lithologies at given pressures and temperatures results in diverse melt compositions, which may contribute to the observed heterogeneity of oceanic basalt suites. We also show that heterogeneous upwelling mantle is subject to diverse local freezing, hybridization and carbonate-carbon-silicate redox reactions along a mantle adiabat.

Tubes or sheets: divergent aggregation pathways of an amphiphilic 2,7-substituted pyrene trimer

The self-assembly of an amphiphilic 2,7-linked pyrene trimer in an aqueous environment into two morphologically related forms is described. Supramolecular polymerization leads to the simultaneous formation of nanosheets and nanotubes.

Intraspecific Aggregation Alters Competitive Interactions in Experimental Plant Communities

We tested the prediction from spatial competition models that intraspecific aggregation may promote coexistence and thus maintain biodiversity with experimental communities of four annual species. Monocultures, three-species mixtures, and the four-species mixture were sown at two densities and with either random or intraspecifically aggregated distributions. There was a hierarchy of competitive abilities among the four species. The weaker competitors showed higher aboveground biomass in the aggregated distribution compared to the random distribution, especially at high density. In one species, intraspecific aggregation resulted in an 86% increase in the number of flowering individuals and a 171% increase in the reproductive biomass at high density. The competitively superior species had a lower biomass in the aggregated distribution than in the random distribution at high density. The data support the hypothesis that the spatial distribution of plants profoundly affects competition in such a way that weaker competitors increase their fitness while stronger competitors are suppressed when grown in the neighborhood of conspecifics. This implies that the spatial arrangement of plants in a community can be an important determinant of species coexistence and biodiversity.

Eclogitic diamonds from variable crustal protoliths in the northeastern Siberian craton: trace elements and coupled δ13C – δ18O signatures in diamonds and garnet inclusions

Diamonds of eclogitic assemblages are dominant in the placer diamond deposits of the northeastern Siberian platform. In this study we present new trace elements and stable isotopes (δ13C and δ18O) data for alluvial diamonds and their garnet inclusions from this locality. Cr-rich garnets of peridotitic affinity in the studied diamonds have a narrow range of δ18O values from 5.7‰ to 6.2‰, which is largely overlapping with the accepted mantle range. This narrow range suggests that the garnet inclusions showing different REE patterns and little variations in oxygen isotopes may have formed by different processes involving fluid/melts that, however, were in oxygen isotopic equilibrium with the mantle. The trace element composition of the eclogitic garnet inclusions supports a crustal origin for at least the high-Ca garnets, which show flat HREE patterns and in some cases a positive Eu-anomaly. High-Ca eclogitic garnets generally show heavier oxygen isotope compositions (δ18O 6.5–9.6‰) than what is observed in low-Ca garnets (δ18O 5.7–7.4‰). The variability in oxygen isotopes and trace elements is suggested to be inherited from contrasting crustal protoliths. The relationship between the high δ18O values of inclusions and the low δ13C values of the host diamonds implies that the high-Ca garnet inclusions were derived from intensely hydrated (e.g., δ18O > 7‰) and typically oxidised basaltic rock close to the seawater interface, and that the carbon for diamonds was closely associated with this protolith.

Sphingosine 1-Phosphate Produced by Sphingosine Kinase 2 Intrinsically Controls Platelet Aggregation In Vitro and In Vivo

RATIONALE Platelets are known to play a crucial role in hemostasis. Sphingosine kinases (Sphk) 1 and 2 catalyze the conversion of sphingosine to the bioactive metabolite sphingosine 1-phosphate (S1P). Although platelets are able to secrete S1P on activation, little is known about a potential intrinsic effect of S1P on platelet function. OBJECTIVE To investigate the role of Sphk1- and Sphk2-derived S1P in the regulation of platelet function. METHODS AND RESULTS We found a 100-fold reduction in intracellular S1P levels in platelets derived from Sphk2(-/-) mutants compared with Sphk1(-/-) or wild-type mice, as analyzed by mass spectrometry. Sphk2(-/-) platelets also failed to secrete S1P on stimulation. Blood from Sphk2-deficient mice showed decreased aggregation after protease-activated receptor 4-peptide and adenosine diphosphate stimulation in vitro, as assessed by whole blood impedance aggregometry. We revealed that S1P controls platelet aggregation via the sphingosine 1-phosphate receptor 1 through modulation of protease-activated receptor 4-peptide and adenosine diphosphate-induced platelet activation. Finally, we show by intravital microscopy that defective platelet aggregation in Sphk2-deficient mice translates into reduced arterial thrombus stability in vivo. CONCLUSIONS We demonstrate that Sphk2 is the major Sphk isoform responsible for the generation of S1P in platelets and plays a pivotal intrinsic role in the control of platelet activation. Correspondingly, Sphk2-deficient mice are protected from arterial thrombosis after vascular injury, but have normal bleeding times. Targeting this pathway could therefore present a new therapeutic strategy to prevent thrombosis.

Variable phenotypic expressivity in inbred retinal degeneration mouse lines: A comparative study of C3H/HeOu and FVB/N rd1 mice

PURPOSE Recent advances in optogenetics and gene therapy have led to promising new treatment strategies for blindness caused by retinal photoreceptor loss. Preclinical studies often rely on the retinal degeneration 1 (rd1 or Pde6b(rd1)) retinitis pigmentosa (RP) mouse model. The rd1 founder mutation is present in more than 100 actively used mouse lines. Since secondary genetic traits are well-known to modify the phenotypic progression of photoreceptor degeneration in animal models and human patients with RP, negligence of the genetic background in the rd1 mouse model is unwarranted. Moreover, the success of various potential therapies, including optogenetic gene therapy and prosthetic implants, depends on the progress of retinal degeneration, which might differ between rd1 mice. To examine the prospect of phenotypic expressivity in the rd1 mouse model, we compared the progress of retinal degeneration in two common rd1 lines, C3H/HeOu and FVB/N. METHODS We followed retinal degeneration over 24 weeks in FVB/N, C3H/HeOu, and congenic Pde6b(+) seeing mouse lines, using a range of experimental techniques including extracellular recordings from retinal ganglion cells, PCR quantification of cone opsin and Pde6b transcripts, in vivo flash electroretinogram (ERG), and behavioral optokinetic reflex (OKR) recordings. RESULTS We demonstrated a substantial difference in the speed of retinal degeneration and accompanying loss of visual function between the two rd1 lines. Photoreceptor degeneration and loss of vision were faster with an earlier onset in the FVB/N mice compared to C3H/HeOu mice, whereas the performance of the Pde6b(+) mice did not differ significantly in any of the tests. By postnatal week 4, the FVB/N mice expressed significantly less cone opsin and Pde6b mRNA and had neither ERG nor OKR responses. At 12 weeks of age, the retinal ganglion cells of the FVB/N mice had lost all light responses. In contrast, 4-week-old C3H/HeOu mice still had ERG and OKR responses, and we still recorded light responses from C3H/HeOu retinal ganglion cells until the age of 24 weeks. These results show that genetic background plays an important role in the rd1 mouse pathology. CONCLUSIONS Analogous to human RP, the mouse genetic background strongly influences the rd1 phenotype. Thus, different rd1 mouse lines may follow different timelines of retinal degeneration, making exact knowledge of genetic background imperative in all studies that use rd1 models.

Variable effects of the conserved RNA hairpin element upon 3' end processing of histone pre-mRNA in vitro.

We have studied the requirements for efficient histone-specific RNA 3' processing in nuclear extract from mammalian tissue culture cells. Processing is strongly impaired by mutations in the pre-mRNA spacer element that reduce the base-pairing potential with U7 RNA. Moreover, by exchanging the hairpin and spacer elements of two differently processed H4 genes, we find that this difference is exclusively due to the spacer element. Finally, processing is inhibited by the addition of competitor RNAs, if these contain a wild-type spacer sequence, but not if their spacer element is mutated. Conversely, the importance of the hairpin for histone RNA 3' processing is highly variable: A hairpin mutant of the H4-12 gene is processed with almost wild-type efficiency in extract from K21 mouse mastocytoma cells but is strongly affected in HeLa cell extract, whereas an identical hairpin mutant of the H4-1 gene is affected in both extracts. The hairpin defect of H4-12-specific RNA in HeLa cells can be overcome by a compensatory mutation that increases the base complementarity to U7 snRNA. Very similar results were also obtained in RNA competition experiments: processing of H4-12-specific RNA can be competed by RNA carrying a wild-type hairpin element in extract from HeLa, but not K21 cells, whereas processing of H4-1-specific RNA can be competed in both extracts. With two additional histone genes we obtained results that were in one case intermediate and in the other similar to those obtained with H4-1. These results suggest that hairpin binding factor(s) can cooperatively support the ability of U7 snRNPs to form an active processing complex, but is(are) not directly involved in the processing mechanism.

Increased spread and replication efficiency of Listeria monocytogenes in organotypic brain-slices is related to multilocus variable number of tandem repeat analysis (MLVA) complex.

BACKGROUND Listeria (L.) monocytogenes causes fatal infections in many species including ruminants and humans. In ruminants, rhombencephalitis is the most prevalent form of listeriosis. Using multilocus variable number tandem repeat analysis (MLVA) we recently showed that L. monocytogenes isolates from ruminant rhombencephalitis cases are distributed over three genetic complexes (designated A, B and C). However, the majority of rhombencephalitis strains and virtually all those isolated from cattle cluster in MLVA complex A, indicating that strains of this complex may have increased neurotropism and neurovirulence. The aim of this study was to investigate whether ruminant rhombencephalitis strains have an increased ability to propagate in the bovine hippocampal brain-slice model and can be discriminated from strains of other sources. For this study, forty-seven strains were selected and assayed on brain-slice cultures, a bovine macrophage cell line (BoMac) and a human colorectal adenocarcinoma cell line (Caco-2). They were isolated from ruminant rhombencephalitis cases (n = 21) and other sources including the environment, food, human neurolisteriosis cases and ruminant/human non-encephalitic infection cases (n = 26). RESULTS All but one L. monocytogenes strain replicated in brain slices, irrespectively of the source of the isolate or MLVA complex. The replication of strains from MLVA complex A was increased in hippocampal brain-slice cultures compared to complex C. Immunofluorescence revealed that microglia are the main target cells for L. monocytogenes and that strains from MLVA complex A caused larger infection foci than strains from MLVA complex C. Additionally, they caused larger plaques in BoMac cells, but not CaCo-2 cells. CONCLUSIONS Our brain slice model data shows that all L. monocytogenes strains should be considered potentially neurovirulent. Secondly, encephalitis strains cannot be conclusively discriminated from non-encephalitis strains with the bovine organotypic brain slice model. The data indicates that MLVA complex A strains are particularly adept at establishing encephalitis possibly by virtue of their higher resistance to antibacterial defense mechanisms in microglia cells, the main target of L. monocytogenes.

Caplacizumab for Acquired Thrombotic Thrombocytopenic Purpura.

BACKGROUND Acquired thrombotic thrombocytopenic purpura (TTP) is caused by aggregation of platelets on ultralarge von Willebrand factor multimers. This microvascular thrombosis causes multiorgan ischemia with potentially life-threatening complications. Daily plasma exchange and immunosuppressive therapies induce remission, but mortality and morbidity due to microthrombosis remain high. METHODS Caplacizumab, an anti-von Willebrand factor humanized single-variable-domain immunoglobulin (Nanobody), inhibits the interaction between ultralarge von Willebrand factor multimers and platelets. In this phase 2, controlled study, we randomly assigned patients with acquired TTP to subcutaneous caplacizumab (10 mg daily) or placebo during plasma exchange and for 30 days afterward. The primary end point was the time to a response, defined as confirmed normalization of the platelet count. Major secondary end points included exacerbations and relapses. RESULTS Seventy-five patients underwent randomization (36 were assigned to receive caplacizumab, and 39 to receive placebo). The time to a response was significantly reduced with caplacizumab as compared with placebo (39% reduction in median time, P=0.005). Three patients in the caplacizumab group had an exacerbation, as compared with 11 patients in the placebo group. Eight patients in the caplacizumab group had a relapse in the first month after stopping the study drug, of whom 7 had ADAMTS13 activity that remained below 10%, suggesting unresolved autoimmune activity. Bleeding-related adverse events, most of which were mild to moderate in severity, were more common with caplacizumab than with placebo (54% of patients vs. 38%). The frequencies of other adverse events were similar in the two groups. Two patients in the placebo group died, as compared with none in the caplacizumab group. CONCLUSIONS Caplacizumab induced a faster resolution of the acute TTP episode than did placebo. The platelet-protective effect of caplacizumab was maintained during the treatment period. Caplacizumab was associated with an increased tendency toward bleeding, as compared with placebo. (Funded by Ablynx; ClinicalTrials.gov number, NCT01151423.).