Agencies outline Mars initiative

The US and European space agencies launch an initiative that could lead to joint missions to explore the Red Planet.

Study pinpoints UK wind hotspots

An Energy Saving Trust study identifies the 'best and worst' locations in the UK for domestic small-scale wind turbines.

'15-year high' for rhino poaching

Rhino poaching around the world is set to reach a 15-year high as demand for the animals' horns grows, conservation groups warn.

Ban criticises G8 climate efforts

UN Secretary General Ban Ki-moon criticises G8 nations for not going far enough to combat climate change.

A glimpse of ancient dying stars

Snapshots of the most distant supernovae known to astronomy, which exploded 11 billion years ago, have been revealed.

EBI2 mediates B cell segregation between the outer and centre follicle

EBI2 mediates B cell segregation between the outer and centre follicle

Nature advance online publication 13 July 2009. doi:10.1038/nature08226

Authors: João P. Pereira, Lisa M. Kelly, Ying Xu & Jason G. Cyster

B cell follicles are specialized microenvironments that support events necessary for humoral immunity. After antigen encounter, activated B cells initially seek T-cell help at the follicle–T-zone boundary and then move to interfollicular and T-zone distal (outer) regions of the follicle. Subsequently, some cells move to the follicle centre, become germinal centre B cells and undergo antibody affinity maturation. Although germinal centres within follicles were described in 1885 (ref. 12), the molecular cues mediating segregation of B cells between the outer and centre follicle have remained undefined. Here we present a role for the orphan G-protein-coupled receptor, Epstein-Barr virus induced molecule-2 (EBI2, also known as GPR183), in this process. EBI2 is expressed in mature B cells and increases in expression early after activation, before being downregulated in germinal centre B cells. EBI2 deficiency in mice led to a reduction in the early antibody response to a T-dependent antigen. EBI2-deficient B cells failed to move to the outer follicle at day 2 of activation, and instead were found in the follicle centre, whereas EBI2 overexpression was sufficient to promote B cell localization to the outer follicle. In mixed bone marrow chimaeras, EBI2-deficient B cells phenocopied germinal centre B cells in preferentially localizing to the follicle centre. When downregulation of EBI2 in wild-type B cells was antagonized, participation in the germinal centre reaction was impaired. These studies identify an important role for EBI2 in promoting B cell localization in the outer follicle, and show that differential expression of this receptor helps position B cells appropriately for mounting T-dependent antibody responses.

Switch in FGF signalling initiates glial differentiation in the Drosophila eye

Switch in FGF signalling initiates glial differentiation in the Drosophila eye

Nature advance online publication 13 July 2009. doi:10.1038/nature08167

Authors: Sigrídur Rut Franzdóttir, Daniel Engelen, Yeliz Yuva-Aydemir, Imke Schmidt, Annukka Aho & Christian Klämbt

The formation of a complex nervous system requires the intricate interaction of neurons and glial cells. Glial cells generally migrate over long distances before they initiate their differentiation, which leads to wrapping and insulation of axonal processes. The molecular pathways coordinating the switch from glial migration to glial differentiation are largely unknown. Here we demonstrate that, within the Drosophila eye imaginal disc, fibroblast growth factor (FGF) signalling coordinates glial proliferation, migration and subsequent axonal wrapping. Glial differentiation in the Drosophila eye disc requires a succession from glia–glia interaction to glia–neuron interaction. The neuronal component of the fly eye develops in the peripheral nervous system within the eye–antennal imaginal disc, whereas glial cells originate from a pool of central-nervous-system-derived progenitors and migrate onto the eye imaginal disc. Initially, glial-derived Pyramus, an FGF8-like ligand, modulates glial cell number and motility. A switch to neuronally expressed Thisbe, a second FGF8-like ligand, then induces glial differentiation. This switch is accompanied by an alteration in the intracellular signalling pathway through which the FGF receptor channels information into the cell. Our findings reveal how a switch from glia–glia interactions to glia–neuron interactions can trigger formation of glial membrane around axonal trajectories. These results disclose an evolutionarily conserved control mechanism of axonal wrapping, indicating that Drosophila might serve as a model to understand glial disorders in humans.

Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires

Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires

Nature advance online publication 13 July 2009. doi:10.1038/nature08176

Authors: Per Ahlberg, Kate Trinajstic, Zerina Johanson & John Long

Recent finds demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata), making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be identical in males and females, with males presumed to have an additional cartilaginous element or series forming a clasper. Here we report the discovery of a completely ossified pelvic clasper in Incisoscutum ritchiei (WAM 03.3.28) which shows that this interpretation was incorrect: the basipterygium described previously is in fact unique to females. The male clasper is a slender rod attached to a square basal plate that articulates directly with the pelvis. It carries a small cap of dermal bone covered in denticles and small hooks that may be homologous with the much larger dermal component of the ptyctodont clasper.

Proteome-wide cellular protein concentrations of the human pathogen Leptospira interrogans

Proteome-wide cellular protein concentrations of the human pathogen Leptospira interrogans

Nature advance online publication 15 July 2009. doi:10.1038/nature08184

Authors: Johan Malmström, Martin Beck, Alexander Schmidt, Vinzenz Lange, Eric W. Deutsch & Ruedi Aebersold

Mass-spectrometry-based methods for relative proteome quantification have broadly affected life science research. However, important research directions, particularly those involving mathematical modelling and simulation of biological processes, also critically depend on absolutely quantitative data—that is, knowledge of the concentration of the expressed proteins as a function of cellular state. Until now, absolute protein concentration measurements of a considerable fraction of the proteome (73%) have only been derived from genetically altered Saccharomyces cerevisiae cells, a technique that is not directly portable from yeast to other species. Here we present a mass-spectrometry-based strategy to determine the absolute quantity, that is, the average number of protein copies per cell in a cell population, for a large fraction of the proteome in genetically unperturbed cells. Applying the technology to the human pathogen Leptospira interrogans, a spirochete responsible for leptospirosis, we generated an absolute protein abundance scale for 83% of the mass-spectrometry-detectable proteome, from cells at different states. Taking advantage of the unique cellular dimensions of L. interrogans, we used cryo-electron tomography morphological measurements to verify, at the single-cell level, the average absolute abundance values of selected proteins determined by mass spectrometry on a population of cells. Because the strategy is relatively fast and applicable to any cell type, we expect that it will become a cornerstone of quantitative biology and systems biology.

Dawn of the animals: Solving Darwin's dilemma

A series of extraordinary discoveries over the past decade has transformed our ideas about the evolution of early animals, and of the world they lived in