Genetically-Defined Deficiency of Mannose-Binding Lectin Is Associated with Protection after Experimental Stroke in Mice and Outcome in Human Stroke

Background

The complement system is a major effector of innate immunity that has been involved in stroke brain damage. Complement activation occurs through the classical, alternative and lectin pathways. The latter is initiated by mannose-binding lectin (MBL) and MBL-associated serine proteases (MASPs). Here we investigated whether the lectin pathway contributes to stroke outcome in mice and humans.

Methodology/Principal Findings

Focal cerebral ischemia/reperfusion in MBL-null mice induced smaller infarctions, better functional outcome, and diminished C3 deposition and neutrophil infiltration than in wild-type mice. Accordingly, reconstitution of MBL-null mice with recombinant human MBL (rhMBL) enhanced brain damage. In order to investigate the clinical relevance of these experimental observations, a study of MBL2 and MASP-2 gene polymorphism rendering the lectin pathway dysfunctional was performed in 135 stroke patients. In logistic regression adjusted for age, gender and initial stroke severity, unfavourable outcome at 3 months was associated with MBL-sufficient genotype (OR 10.85, p = 0.008) and circulating MBL levels (OR 1.29, p = 0.04). Individuals carrying MBL-low genotypes (17.8%) had lower C3, C4, and CRP levels, and the proinflammatory cytokine profile was attenuated versus MBL-sufficient genotypes.

Conclusions/Significance

In conclusion, genetically defined MBL-deficiency is associated with a better outcome after acute stroke in mice and humans.     

Bcr/Abl interferes with the Fanconi anemia/BRCA pathway: implications in the chromosomal instability of chronic myeloid leukemia cells

Chronic myeloid leukemia (CML) is a malignant clonal disorder of the hematopoietic system caused by the expression of the BCR/ABL fusion oncogene. Although it is well known that CML cells are genetically unstable, the mechanisms accounting for this genomic instability are still poorly understood. Because the Fanconi anemia (FA) pathway is believed to control several mechanisms of DNA repair, we investigated whether this pathway was disrupted in CML cells. Our data show that CML cells have a defective capacity to generate FANCD2 nuclear foci, either in dividing cells or after DNA damage. Similarly, human cord blood CD34(+) cells transduced with BCR/ABL retroviral vectors showed impaired FANCD2 foci formation, whereas FANCD2 monoubiquitination in these cells was unaffected. Soon after the transduction of CD34(+) cells with BCR/ABL retroviral vectors a high proportion of cells with supernumerary centrosomes was observed. Similarly, BCR/ABL induced a high proportion of chromosomal abnormalities, while mediated a cell survival advantage after exposure to DNA cross-linking agents. Significantly, both the impaired formation of FANCD2 nuclear foci, and also the predisposition of BCR/ABL cells to develop centrosomal and chromosomal aberrations were reverted by the ectopic expression of BRCA1. Taken together, our data show for the first time a disruption of the FA/BRCA pathway in BCR/ABL cells, suggesting that this defective pathway should play an important role in the genomic instability of CML by the co-occurrence of centrosomal amplification and DNA repair deficiencies.     

Comparative population structure, abundance and vertical distribution of six copepod species in the North Atlantic: Evidence for intraguild predation?

The abundance, vertical distribution and stage composition of the copepods Euchaeta norvegica, Metridia lucens and Pleuromamma robusta and the abundance and vertical distribution of Acartia sp., Oithona spp. and Oncaea sp. were analysed for a period of 4.5 years (1971-1974), based on data previously collected at weather station India in the North Atlantic (59°N, 19°W). The results were compared with previously published results on Calanus finmarchicus during the same study. The factor analysis showed two well-differentiated groups. The cohort development and abundance of C. finmarchicus, E. norvegica and Oncaea were related to successive phytoplankton blooms. On the contrary, the cohort development and abundance of M. lucens, P. robusta, Acartia spp. and Oithona spp. were not related to phytoplankton concentration and showed negative relationships with Calanus abundance. We suggest that C. finmarchicus, which largely dominates the biomass at station India, could play a key role in the structuring of the community: as prey for the carnivorous E. norvegica, vectoring the spring bloom to deep waters through faecal pellet consumption by the coprophagous Oncaea spp., and through intraguild predation on the early stages of other omnivorous copepods such as Acartia, Oithona, M. lucens and P. robusta.     

Automated solid-phase synthesis of metabolically stabilized triazolo-peptidomimetics

The use of 1,4-disubstituted 1,2,3-triazoles as trans-amide bond surrogates has become an important tool for the synthesis of metabolically stabilized peptidomimetics. These heterocyclic bioisosters are generally incorporated into the peptide backbone by applying a diazo-transfer reaction followed by CuAAC (click chemistry) with an α-amino alkyne. Even though the manual synthesis of backbone-modified triazolo-peptidomimetics has been reported by us and others, no procedure has yet been described for an automated synthesis using peptide synthesizers. In order to efficiently adapt these reactions to an automated setup, different conditions were explored, putting special emphasis on the required long-term stability of both the diazo-transfer reagent and the Cu(I) catalyst in solution. ISA·HCl is the reagent of choice to accomplish the diazo-transfer reaction; however, it was found instable in DMF, the most commonly used solvent for SPPS. Thus, an aqueous solution of ISA·HCl was used to prevent its degradation over time, and the composition in the final diazo-transfer reaction was adjusted to preserve suitable swelling conditions of the resins applied. The CuAAC reaction was performed without difficulties using [Cu (CH₃CN)₄]PF₆ as a catalyst and TBTA as a stabilizer to prevent oxidation to Cu(II). The optimized automated two-step procedure was applied to the synthesis of structurally diverse triazolo-peptidomimetics to demonstrate the versatility of the developed methodology. Under the optimized conditions, five triazolo-peptidomimetics (8–5 amino acid residues) were synthesized efficiently using two different resins. Analysis of the crude products by HPLC-MS revealed moderate to good purities of the desired triazolo-peptidomimetics (70–85%). The synthesis time ranged between 9 and 12.5 h.     

Structure of the connector of bacteriophage T7 at 8A resolution: structural homologies of a basic component of a DNA translocating machinery

The three-dimensional structure of the bacteriophage T7 head-to-tail connector has been obtained at 8A resolution using cryo-electron microscopy and single-particle analysis from purified recombinant connectors. The general morphology of the T7 connector is that of a 12-folded toroidal homopolymer with a channel that runs along the longitudinal axis of the particle. The structure of the T7 connector reveals many structural similarities with the connectors from other bacteriophages. Docking of the atomic structure of the varphi29 connector into the three-dimensional reconstruction of T7 connector reveals that the narrow, distal region of the two oligomers are almost identical. This region of the varphi29 connector has been suggested to be involved in DNA translocation, and is composed of an alpha-beta-alpha-beta-beta-alpha motif. A search for alpha-helices in the same region of the T7 three-dimensional map has located three alpha-helices in approximately the same position as those of the varphi29 connector. A comparison of the predicted secondary structure of several bacteriophage connectors, including among others T7, varphi29, P22 and SPP1, reveals that, despite the lack of sequence homology, they seem to contain the same alpha-beta-alpha-beta-beta-alpha motif as that present in the varphi29 connector. These results allow us to suggest a common architecture related to a basic component of the DNA translocating machinery for several viruses.     

North Atlantic Oscillation and spring bloom phytoplankton composition in the English Channel

The spring phytoplankton composition has been investigated ata 50 m deep station off Plymouth in the English Channel for6 years (1993–1999). The percentage of diatoms duringthe spring bloom was significantly correlated with the NorthAtlantic Oscillation index. A similar relationship between phytoplanktonand North Atlantic Oscillation has also been found in a Swedishlake, suggesting a possible link between atmospheric forcingand phytoplankton composition.     

Widespread evidence for horizontal transfer of transposable elements across Drosophila genomes

Background  

Horizontal transfer (HT) could play an important role in the long-term persistence of transposable elements (TEs) because it provides them with the possibility to avoid the checking effects of host-silencing mechanisms and natural selection, which would eventually drive their elimination from the genome. However, despite the increasing evidence for HT of TEs, its rate of occurrence among the TE pools of model eukaryotic organisms is still unknown.     

Some ideas about the role of lipids in the life cycle of Calanus finmarchicus

A conceptual model of the possible role of lipids in the lifecycle of Calanus finmarchicus is proposed. Lipid storage couldplay a key role at various levels: (i) by triggering diapausethrough variations in cholesterol and fatty acid derived hormonelevels; (ii) by determining the overwintering depth in relationto the convective mixed layer; and (iii) by playing an importantrole in the population adaptation to the hydrological conditionsof the basin. A number of ways to test the validity of the proposedhypotheses are proposed. Written responses to this article should be submitted to theEditorial Office within two months of publication. For furtherinformation, please see the Editorial ‘Horizons’in Journal of Plankton Research, Volume 26, Number 3, Page 257.     

Impact of chromatin context on Cas9-induced DNA double-strand break repair pathway balance

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