Volume 523 Number 7558

Editorials

Gene politics p.5

US lawmakers are asserting their place in the human genetic-modification debate.

doi: 10.1038/523005b

Success in failure p.5

A failed crop trial of genetically modified wheat stil provides crucial lessons for those battling to provide the planet's growing population with a sustainable food supply.

doi: 10.1038/nature.2015.17855

Light detective p.6

Smartphone camera set to come to the aid of sleuths, scientists and wine lovers.

doi: 10.1038/523006a

News

News Features

The robot’s dilemma p.24

Working out how to build ethical robots is one of the thorniest challenges in artificial intelligence.

doi: 10.1038/523024a

News & Views

Hallucigenia's head p.38

The finding of pharyngeal teeth and circumoral mouthparts in fossils of the Cambrian lobopodian animal Hallucigenia sparsa improves our understanding of the deep evolutionary links between moulting animals. See Letter p.75

doi: 10.1038/nature14627

Colourful particles for spectrometry p.39

A smartphone camera, patterned with arrays of filters made from colloidal suspensions of coloured particles, has been transformed into a powerful tool for spectral analysis. See Letter p.67

doi: 10.1038/523039a

The case for pay to quit p.40

A randomized controlled trial of four financial-incentive programmes for smoking cessation finds that reward-based schemes lead to sustained abstinence, but low public acceptability of such schemes threatens their adoption.

doi: 10.1038/523040a

Sink holes and dust jets on comet 67P p.42

Analyses of images taken by the Rosetta spacecraft reveal the complex landscape of a comet in rich detail. Close-up views of the surface indicate that some dust jets are being emitted from active pits undergoing sublimation. See Letter p.63

doi: 10.1038/523042a

Reptile sex determination goes wild p.43

Wild populations of an Australian lizard have sex chromosomes and also exhibit temperature-controlled sexual development, providing insight into how these two sex-determining mechanisms may evolve back and forth. See Letter p.79

doi: 10.1038/523043a

Inversion in the worm p.44

Combinations of spatially and temporally restricted transcription factors are shown to coordinate movement in nematode worms by controlling the formation of synaptic connections to and from motor neurons. See Letter p.83

doi: 10.1038/523044a

Articles

The architecture of the spliceosomal U4/U6.U5 tri-snRNP p.47

This study determines the structure of the spliceosomal tri-snRNP complex (containing three small nuclear RNAs and more than 30 proteins) by single-particle cryo-electron microscopy; the resolution is sufficient to discern the organization of RNA and protein components involved in spliceosome activation, exon alignment and catalysis.

doi: 10.1038/nature14548

Letters

Self-similar energetics in large clusters of galaxies p.59

Massive galaxy clusters are filled with a hot, turbulent and magnetized intra-cluster medium, whose energy is derived from gravitational energy; the energy components of this medium are now shown to be ordered according to a permanent hierarchy, in which the ratio of thermal to turbulent to magnetic energy densities remains virtually unaltered over time.

doi: 10.1038/nature14552

A colloidal quantum dot spectrometer p.67

An efficient, cost effective microspectrometer that consists of a two-dimensional absorptive filter array of 195 different colloidal quantum dots is presented, and its performance demonstrated by measuring shifts in spectral peak positions as small as one nanometre.

doi: 10.1038/nature14576

Hallucigenia’s head and the pharyngeal armature of early ecdysozoans p.75

A re-analysis of the 508-million-year-old stem-group onychophoran Hallucigenia sparsa from the Burgess Shale shows that its anterior gut has structures that indicate evolutionary links with more disparate phyla such as nematodes and kinorhynchs; Hallucigenia now provides concrete evidence of structures that might have existed in the last common ancestor of the Ecdysozoa, previously a matter of conjecture.

doi: 10.1038/nature14573

Spatiotemporal control of a novel synaptic organizer molecule p.83

Neuronal synapses need to be formed at the right time and the right place during nervous system development; here, three gene-regulatory factors (the UNC-30, LIN-14 and UNC-55 DNA-binding proteins) are shown to operate in an intersectional manner to control the expression of a novel synaptic organizer molecule, OIG-1.

doi: 10.1038/nature14545

Cell-intrinsic adaptation of lipid composition to local crowding drives social behaviour p.88

Little is known about how individual cells within a group of cells exposed to the same external signals can produce a specific individual response to their local microenvironment; a quantitative analysis of cell crowding reveals that single cells can autonomously sense local crowding though their ability to spread and activate focal adhesion kinase (FAK), which ultimately results in changes in cellular lipid composition.

doi: 10.1038/nature14429

Mechanical induction of the tumorigenic β-catenin pathway by tumour growth pressure p.92

The tumour microenvironment may contribute to tumorigenesis owing to mechanical forces such as fibrotic stiffness or mechanical pressure caused by the expansion of hyper-proliferative cells. Here we explore the contribution of the mechanical pressure exerted by tumour growth onto non-tumorous adjacent epithelium. In the early stage of mouse colon tumour development in the Notch+Apc+/1638N mouse model, we observed mechanistic pressure stress in the non-tumorous epithelial cells caused by hyper-proliferative adjacent crypts overexpressing active Notch, which is associated with increased Ret and β-catenin signalling. We thus developed a method that allows the delivery of a defined mechanical pressure in vivo, by subcutaneously inserting a magnet close to the mouse colon. The implanted magnet generated a magnetic force on ultra-magnetic liposomes, stabilized in the mesenchymal cells of the connective tissue surrounding colonic crypts after intravenous injection. The magnetically induced pressure quantitatively mimicked the endogenous early tumour growth stress in the order of 1,200 Pa, without affecting tissue stiffness, as monitored by ultrasound strain imaging and shear wave elastography. The exertion of pressure mimicking that of tumour growth led to rapid Ret activation and downstream phosphorylation of β-catenin on Tyr654, imparing its interaction with the E-cadherin in adherens junctions, and which was followed by β-catenin nuclear translocation after 15 days. As a consequence, increased expression of β-catenin-target genes was observed at 1 month, together with crypt enlargement accompanying the formation of early tumorous aberrant crypt foci. Mechanical activation of the tumorigenic β-catenin pathway suggests unexplored modes of tumour propagation based on mechanical signalling pathways in healthy epithelial cells surrounding the tumour, which may contribute to tumour heterogeneity.

doi: 10.1038/nature14329