Volume 509 Number 7500

Editorials

Full support p.259

Germany should follow the United Kingdom’s lead and spell out the benefits of animal research.

doi: 10.1038/509259b

An accident waiting to happen p.259

The release of radioactive material at a US nuclear-waste repository reveals an all-too-common picture of complacency over safety and a gradual downgrading of regulations.

doi: 10.1038/509259a

Hard data p.260

It has been no small feat for the Protein Data Bank to stay relevant for 100,000 structures.

doi: 10.1038/509260a

News

News Features

Under siege p.274

A wave of anti-gay laws and homophobia in Africa is hampering efforts to study and curb the spread of HIV.

doi: 10.1038/509274a

First light p.276

The left-over radiation from the Big Bang has given up what may be its last great secret about the early Universe, but astronomers are determined to mine more from this primordial prize.

doi: 10.1038/509276a

News & Views

Shifting storms p.290

An analysis of historical storm data reveals that the average latitude at which tropical cyclones attain their maximum intensity has undergone a pronounced shift towards the poles over the past three decades. See Letter p.349

doi: 10.1038/509290a

New letters for life's alphabet p.291

The five bases found in nucleic acids define the 'alphabet' used to encode life on Earth. The construction of an organism that stably propagates an unnatural DNA base pair redefines this fundamental feature of life. See Letter p.385

doi: 10.1038/nature13335

Collaborative synthesis p.293

A chemical synthesis has led to the reassignment of the molecular structure of the naturally occurring compound citrinalin B. This, in turn, helps to untangle the biochemical origins of an intriguing family of natural products. See Article p.318

doi: 10.1038/509293a

To care or not to care p.294

The behaviour of adult mice towards pups varies depending on gender and sexual experience. The activity of a population of neurons in the hypothalamus of the brain has now been found to regulate these differing responses. See Article p.325

doi: 10.1038/509294a

Radio waves zap the biomagnetic compass p.296

Weak radio waves in the medium-wave band are sufficient to disrupt geomagnetic orientation in migratory birds, according to a particularly well-controlled study. But the underlying biophysics remains a puzzle. See Letter p.353

doi: 10.1038/nature13334

Geology and climate drive diversification p.297

Data from the Galapagos Islands exemplify how geology and climate can interact to cause episodes of isolation and fusion of the biota across a landscape. Different scales of such cycles dictate varying mechanisms of species generation.

doi: 10.1038/509297a

Reviews

Recent advances in homogeneous nickel catalysis p.299

Some of the most recent and significant developments in homogeneous nickel catalysis are reviewed, including nickel-mediated cross-coupling reactions and carbon–hydrogen bond activation reactions.

doi: 10.1038/nature13274

Nucleotide signalling during inflammation p.310

Extracellular ATP released from cells during inflammatory responses predominantly functions as a signalling molecule through the activation of purinergic P2 receptors and contributes to both beneficial and detrimental inflammatory responses; this review examines P2 receptor signalling via ATP and its effect on the outcome of inflammatory and infectious diseases.

doi: 10.1038/nature13085

Articles

Galanin neurons in the medial preoptic area govern parental behaviour p.325

Sexual experience brings radical changes in how male mice behave with pups—virgin males attack them whereas mature fathers display parental care; here the authors identify a subset of hypothalamic neurons whose ablation leads to parental deficits in both males and females, and whose activation in virgin males suppresses aggression and induces pup grooming.

doi: 10.1038/nature13307

Space–time wiring specificity supports direction selectivity in the retina p.331

Motion detection by the retina is thought to rely largely on the biophysics of starburst amacrine cell dendrites; here machine learning is used with gamified crowdsourcing to draw the wiring diagram involving amacrine and bipolar cells to identify a plausible circuit mechanism for direction selectivity; the model suggests similarities between mammalian and insect vision.

doi: 10.1038/nature13240

c-kit+ cells minimally contribute cardiomyocytes to the heart p.337

Whether or not endogenous c-kit+ cells residing within the heart contribute cardiomyocytes during physiological ageing or after injury remains unknown; here, using an inducible lineage tracing system, the c-kit+ lineage is shown to generate cardiomyocytes at very low levels, and, by contrast, contributes substantially to cardiac endothelial cell generation.

doi: 10.1038/nature13309

Letters

Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird p.353

For the first time under reproducible and fully double-blinded conditions, it is shown that anthropogenic electromagnetic noise below the WHO limits affects a biological system: night-migrating birds lose the ability to use the Earth’s magnetic field for orientation when exposed to anthropogenic electromagnetic noise at strengths routinely produced by commonly used electronic devices.

doi: 10.1038/nature13290

T-cell activation by transitory neo-antigens derived from distinct microbial pathways p.361

T cells discriminate between foreign and host molecules by recognizing distinct microbial molecules, predominantly peptides and lipids. Riboflavin precursors found in many bacteria and yeast also selectively activate mucosal-associated invariant T (MAIT) cells, an abundant population of innate-like T cells in humans. However, the genesis of these small organic molecules and their mode of presentation to MAIT cells by the major histocompatibility complex (MHC)-related protein MR1 (ref. 8) are not well understood. Here we show that MAIT-cell activation requires key genes encoding enzymes that form 5-amino-6-d-ribitylaminouracil (5-A-RU), an early intermediate in bacterial riboflavin synthesis. Although 5-A-RU does not bind MR1 or activate MAIT cells directly, it does form potent MAIT-activating antigens via non-enzymatic reactions with small molecules, such as glyoxal and methylglyoxal, which are derived from other metabolic pathways. The MAIT antigens formed by the reactions between 5-A-RU and glyoxal/methylglyoxal were simple adducts, 5-(2-oxoethylideneamino)-6-d-ribitylaminouracil (5-OE-RU) and 5-(2-oxopropylideneamino)-6-d-ribitylaminouracil (5-OP-RU), respectively, which bound to MR1 as shown by crystal structures of MAIT TCR ternary complexes. Although 5-OP-RU and 5-OE-RU are unstable intermediates, they became trapped by MR1 as reversible covalent Schiff base complexes. Mass spectra supported the capture by MR1 of 5-OP-RU and 5-OE-RU from bacterial cultures that activate MAIT cells, but not from non-activating bacteria, indicating that these MAIT antigens are present in a range of microbes. Thus, MR1 is able to capture, stabilize and present chemically unstable pyrimidine intermediates, which otherwise convert to lumazines, as potent antigens to MAIT cells. These pyrimidine adducts are microbial signatures for MAIT-cell immunosurveillance.

doi: 10.1038/nature13160

A semi-synthetic organism with an expanded genetic alphabet p.385

Triphosphates of hydrophobic nucleotides d5SICS and dNaM are imported into Escherichia coli by an exogenous algal nucleotide triphosphate transporter and then used by an endogenous polymerase to replicate, and faithfully maintain over many generations of growth, a plasmid containing the d5SICS–dNaM unnatural base pair.

doi: 10.1038/nature13314