Volume 493 Issue 7431


Culture shock p.133

Health-benefit claims for Europe’s foods must at last be substantiated by science.

doi: 10.1038/493133b

No easy answer p.133

Demands to analyse Connecticut school shooter’s DNA are misguided and could lead to dangerous stigmatization, or worse.

doi: 10.1038/493133a

Realities of risk p.134

We should focus on dangers that we can control, and particularly on those of our own creation.

doi: 10.1038/493134a


News Features

Dyscalculia: Number games p.150

Brian Butterworth is on a crusade to understand the number deficit called dyscalculia — and to help those who have it.

doi: 10.1038/493150a

News & Views

Quantum physicsTime crystals p.166

Physicists have come up with the mind-boggling concept of a time crystal. This intriguing proposal, which is based on the notion of broken time-translation symmetry, might open up a whole new field of research.

doi: 10.1038/493166a

Animal behaviourOlder but less wise p.167

Most fish living in marine reserves are older, bigger and more fecund than those outside their borders, but they are also slower to flee a threat. The potential for 'spillover' of such fish into fisheries may boost support for reserves.

doi: 10.1038/493167a

Developmental biologyLed by the nose p.169

Hagfish embryos show developmental features that contradict the idea that these jawless fish are the most primitive living vertebrates. The findings also help to trace the evolution of vertebrate cranial structure. See Article p.175

doi: 10.1038/nature11766

PhotonicsPhased array on a fingertip p.170

An array of more than 4,000 optical antennas working in unison has been demonstrated on a millimetre-scale silicon chip. The result highlights the remarkable capabilities of optical integration in silicon. See Letter p.195

doi: 10.1038/493170a

Structural biologyInsulin meets its receptor p.171

The hormone insulin has a central role in human physiology, yet the answer to a fundamental biochemical question — how it binds to its cell-surface receptor — has remained elusive, until now. See Letter p.241

doi: 10.1038/493171a

Polymer chemistryWasted loops quantified p.172

A method for dissecting the polymeric networks of gels enables the number of loops — strands that connect to themselves — within them to be counted. This allows network morphologies to be correlated with gel properties.

doi: 10.1038/493172a

Earth scienceHow glaciers grow p.173

A state-of-the-art numerical model shows that the advance of glaciers in a cooling climate depends strongly on the pre-existing landscape, and that glacial erosion paves the way for greater glacial extent in the future. See Letter p.206

doi: 10.1038/493173a


Craniofacial development of hagfishes and the evolution of vertebrates p.175

Cyclostomes, the living jawless vertebrates including hagfishes and lampreys, represent the most basal lineage of vertebrates. Although the monophyly of cyclostomes has been supported by recent molecular analyses, the phenotypic traits of hagfishes, especially the lack of some vertebrate-defining features and the reported endodermal origin of the adenohypophysis, have been interpreted as hagfishes exhibiting a more ancestral state than those of all other vertebrates. Furthermore, the adult anatomy of hagfishes cannot be compared easily with that of lampreys. Here we describe the craniofacial development of a series of staged hagfish embryos, which shows that their adenohypophysis arises ectodermally, consistent with the molecular phylogenetic data. This finding also allowed us to identify a pan-cyclostome pattern, one not shared by jawed vertebrates. Comparative analyses indicated that many of the hagfish-specific traits can be explained by changes secondarily introduced into the hagfish lineage. We also propose a possibility that the pan-cyclostome pattern may reflect the ancestral programme for the craniofacial development of all living vertebrates.

doi: 10.1038/nature11794

Crystallographic snapshot of cellulose synthesis and membrane translocation p.181

Cellulose, the most abundant biological macromolecule, is an extracellular, linear polymer of glucose molecules. It represents an essential component of plant cell walls but is also found in algae and bacteria. In bacteria, cellulose production frequently correlates with the formation of biofilms, a sessile, multicellular growth form. Cellulose synthesis and transport across the inner bacterial membrane is mediated by a complex of the membrane-integrated catalytic BcsA subunit and the membrane-anchored, periplasmic BcsB protein. Here we present the crystal structure of a complex of BcsA and BcsB from Rhodobacter sphaeroides containing a translocating polysaccharide. The structure of the BcsA–BcsB translocation intermediate reveals the architecture of the cellulose synthase, demonstrates how BcsA forms a cellulose-conducting channel, and suggests a model for the coupling of cellulose synthesis and translocation in which the nascent polysaccharide is extended by one glucose molecule at a time.

doi: 10.1038/nature11744


Flows of gas through a protoplanetary gap p.191

Observations of the young star HD 142527, whose disk is separated into inner and outer regions by a gap suggestive of the formation of a gaseous giant planet, show that accretion onto the star is maintained by a flow of gas across the gap, in agreement with dynamical models of planet formation.

doi: 10.1038/nature11769

Large-scale nanophotonic phased array p.195

A large-scale silicon nanophotonic phased array with more than 4,000 antennas is demonstrated using a state-of-the-art complementary metal-oxide–semiconductor (CMOS) process, enabling arbitrary holograms with tunability, which brings phased arrays to many new technological territories.

doi: 10.1038/nature11727

Topological colloids p.200

Topologically distinct colloidal particles introduced into a nematic liquid crystal align and generate topology-constrained three-dimensional director fields and defects in the liquid crystal fluid that can be manipulated with a variety of methods, opening up a new area of exploration in the field of soft matter.

doi: 10.1038/nature11710

Analysis of 6,515 exomes reveals the recent origin of most human protein-coding variants p.216

Resequencing of genes from individuals of European and African American ancestry indicates that approximately 73% of all protein-coding SNVs and approximately 86% of SNVs predicted to be deleterious arose in the past 5,000–10,000 years, and that European Americans carry an excess of deleterious variants in essential and Mendelian disease genes compared to African Americans.

doi: 10.1038/nature11690

How insulin engages its primary binding site on the insulin receptor p.241

The three-dimensional structure of the insulin–insulin receptor complex has proved elusive, confounded by the complexity of producing the receptor protein; here is the first glimpse of the interaction between insulin and its primary binding site on the insulin receptor, a view based on four crystal structures of insulin bound to truncated insulin receptor complexes.

doi: 10.1038/nature11781

Recombination-restarted replication makes inverted chromosome fusions at inverted repeats p.246

A new mechanism of chromosomal rearrangement is identified through the observation that broken or collapsed DNA replication forks restarted by homologous recombination have a high propensity for U-turns at short inverted repeats; the error-prone nature of this mechanism is suggested to contribute to gross chromosomal rearrangements and copy-number variations present in cancer and other genomic disorders.

doi: 10.1038/nature11676