A phylogenetic reconstruction of the diversification of birds across space and time provides a novel resource for evolutionary studies. But the methods used to construct this tree, and what insights can be inferred from it, are a source of debate. Two evolutionary biologists provide opinions on how to draw the lines. See Letter p.444

doi: 10.1038/nature11642

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Climate scienceHistorical drought trends revisited p.338

A new assessment of drought trends over the past 60 years finds little evidence of an expansion of the area affected by droughts, contradicting several previous estimates. See Letter p.435

doi: 10.1038/491338a

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Active matterSpontaneous flows and self-propelled drops p.340

The construction of in vitro assemblies of biological components that exhibit properties of living matter may shed light on the physical aspects of the dynamic reorganization that continuously occurs inside cells. See Letter p.431

doi: 10.1038/nature11750

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Animal behaviourPersonality in the wild p.341

Behavioural traits can influence an individual animal's fitness, and trait combinations can change over its lifetime, according to a study of wild trout during a key period in their development.

doi: 10.1038/491341a

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CancerComplexion matters p.342

Sun exposure indisputably increases the risk of skin cancer. Mouse studies suggest that, in red-haired individuals, genetic factors also contribute through a mechanism that acts independently of exposure to sunlight. See Letter p.449

doi: 10.1038/nature11641

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Quantum physicsPutting a spin on photon entanglement p.343

Entanglement between a photon and a stationary particle is a key resource for quantum communication. The effect has now been observed for a photon and a single electron spin in a semiconductor nanostructure. See Letters p.421 & p.426

doi: 10.1038/491343a

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Vascular biologyNitric oxide caught in traffic p.344

Nitric oxide is a vital signalling molecule that controls blood flow and pressure. Unexpectedly, a redox switch in the protein haemoglobin α within endothelial cells regulates this molecule's diffusion in blood vessels. See Letter p.473

doi: 10.1038/nature11640

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Articles

Analyses of pig genomes provide insight into porcine demography and evolution p.393

doi: 10.1038/nature11622

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Pancreatic cancer genomes reveal aberrations in axon guidance pathway genes p.399

Pancreatic cancer is a highly lethal malignancy with few effective therapies. We performed exome sequencing and copy number analysis to define genomic aberrations in a prospectively accrued clinical cohort (n = 142) of early (stage I and II) sporadic pancreatic ductal adenocarcinoma. Detailed analysis of 99 informative tumours identified substantial heterogeneity with 2,016 non-silent mutations and 1,628 copy-number variations. We define 16 significantly mutated genes, reaffirming known mutations (KRAS, TP53, CDKN2A, SMAD4, MLL3, TGFBR2, ARID1A and SF3B1), and uncover novel mutated genes including additional genes involved in chromatin modification (EPC1 and ARID2), DNA damage repair (ATM) and other mechanisms (ZIM2, MAP2K4, NALCN, SLC16A4 and MAGEA6). Integrative analysis with in vitro functional data and animal models provided supportive evidence for potential roles for these genetic aberrations in carcinogenesis. Pathway-based analysis of recurrently mutated genes recapitulated clustering in core signalling pathways in pancreatic ductal adenocarcinoma, and identified new mutated genes in each pathway. We also identified frequent and diverse somatic aberrations in genes described traditionally as embryonic regulators of axon guidance, particularly SLIT/ROBO signalling, which was also evident in murine Sleeping Beauty transposon-mediated somatic mutagenesis models of pancreatic cancer, providing further supportive evidence for the potential involvement of axon guidance genes in pancreatic carcinogenesis.

doi: 10.1038/nature11547

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Broad and potent neutralization of HIV-1 by a gp41-specific human antibody p.406

Characterization of human monoclonal antibodies is providing considerable insight into mechanisms of broad HIV-1 neutralization. Here we report an HIV-1 gp41 membrane-proximal external region (MPER)-specific antibody, named 10E8, which neutralizes ∼98% of tested viruses. An analysis of sera from 78 healthy HIV-1-infected donors demonstrated that 27% contained MPER-specific antibodies and 8% contained 10E8-like specificities. In contrast to other neutralizing MPER antibodies, 10E8 did not bind phospholipids, was not autoreactive, and bound cell-surface envelope. The structure of 10E8 in complex with the complete MPER revealed a site of vulnerability comprising a narrow stretch of highly conserved gp41-hydrophobic residues and a critical arginine or lysine just before the transmembrane region. Analysis of resistant HIV-1 variants confirmed the importance of these residues for neutralization. The highly conserved MPER is a target of potent, non-self-reactive neutralizing antibodies, suggesting that HIV-1 vaccines should aim to induce antibodies to this region of HIV-1 envelope glycoprotein.

doi: 10.1038/nature11544

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The Mu transpososome structure sheds light on DDE recombinase evolution p.413

Studies of bacteriophage Mu transposition paved the way for understanding retroviral integration and V(D)J recombination as well as many other DNA transposition reactions. Here we report the structure of the Mu transpososome—Mu transposase (MuA) in complex with bacteriophage DNA ends and target DNA—determined from data that extend anisotropically to 5.2 Å, 5.2 Å and 3.7 Å resolution, in conjunction with previously determined structures of individual domains. The highly intertwined structure illustrates why chemical activity depends on formation of the synaptic complex, and reveals that individual domains have different roles when bound to different sites. The structure also provides explanations for the increased stability of the final product complex and for its preferential recognition by the ATP-dependent unfoldase ClpX. Although MuA and many other recombinases share a structurally conserved ‘DDE’ catalytic domain, comparisons among the limited set of available complex structures indicate that some conserved features, such as catalysis in trans and target DNA bending, arose through convergent evolution because they are important for function.

doi: 10.1038/nature11602

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