Letters in 2014

Usually materials design focuses on attractive interactions, but here a hydrogel is described whose properties are dominated by electrostatic repulsion between negatively charged titanate nanosheets embedded within it; the material, inspired by articular cartilage, deforms easily when sheared parallel to the sheets but resists compressive forces applied orthogonally.

Quantized conductance in the transport of neutral atoms is observed in an optically produced channel — either a quantum point contact or a quantum wire — between two atom reservoirs; the lowest non-zero conductance value is the universal conductance quantum, the reciprocal of Planck’s constant.

Laboratory measurements of iron opacity made under conditions similar to those inside the Sun reveal much higher opacity than predicted, helping to resolve inconsistencies within stellar models of the internal temperatures of stars.

Collective behaviour in animal groups can improve individual perception and decision-making, but the neural mechanisms involved have been hard to access in classic models for these phenomena; here it is shown that Drosophila’s olfactory responses are enhanced in groups of flies, through mechanosensory neuron-dependent touch interactions.

Up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis; here, in a systematic and nationwide study of 1,133 children with severe, undiagnosed developmental disorders, and their parents, exome sequencing and array-based detection of chromosomal rearrangements reveals novel genes causing developmental disorders, increasing the proportion of children that can now be diagnosed to 31%.

The integrative analysis of epigenetic footprints along consecutive stages of neural progenitors derived from human ES cells reveals regulatory mechanisms that orchestrate stage-specific differentiation.

Lineage-tracing experiments identify a rare, undifferentiated population of quiescent cells in the mouse distal lung that are activated through a Notch signalling pathway to repair the epithelium after bleomycin- or influenza-mediated injury; inappropriate Notch signalling may be a major contributor to failed regeneration within the lungs of patients with chronic lung disease.

A newly developed method, NAD captureSeq, has been used to show that bacteria cap the 5′-ends of some RNAs to protect against degradation, much as happens with eukaryotic messenger RNAs, although with a different modification: nicotinamide adenine dinucleotide.

A human tRNA synthetase connects resveratrol to stress signalling.

The structure and function of CetZ, a protein related to both tubulin and FtsZ (the bacterial homologue of tubulin) from the archaeon Haloferax volcanii, is reported and its involvement in the control of cell shape uncovered; it appears that this family of proteins was involved in the control of cell shape long before the evolution of eukaryotes.

Group 2 innate lymphoid cells are shown to have a critical role in energy homeostasis by producing methionine-enkephalin peptides in response to interleukin 33, thus promoting the beiging of white adipose tissue; increased numbers of beige (also known as brown-like or brite) fat cells in white adipose tissue leads to increased energy expenditure and decreased adiposity.

The structural polymorphism of intrinsically disordered protein 4E-BP2 allows it to regulate translation initiation through post-translational modification-mediated folding, exemplifying a new and potentially general mechanism of biological regulation mediated by intrinsically disordered proteins.

The orexin system regulates sleep and arousal in humans, with orexin receptor antagonists becoming promising therapeutics for insomnia; now, the X-ray crystal structure of the human OX₂ receptor in the presence of the insomnia drug suvorexant is solved.

Hubble Space Telescope observations of the stellar cluster NGC 1651, which is approximately two billion years old, show that the colour–brightness distribution of stars old enough to have left the main sequence can be explained only by a single-age population, despite having a feature usually interpreted to indicate an age spread of more than 300 million years.

Cationic substances, including some drugs, can activate mast cells in an IgE-independent manner, leading to histamine release, inflammation and airway contraction; here, the G-protein-coupled receptor MrgprB2, the orthologue of human MRGPRX2, is shown to be the sole mast cell receptor for these substances in mice.

A protein degradation pathway is found at the inner nuclear membrane that is distinct from, but complementary to, endoplasmic-reticulum-associated protein degradation, and which is mediated by the Asi protein complex; a genome-wide library screening of yeast identifies more than 20 substrates of this pathway, which is shown to target mislocalized integral membrane proteins for degradation.

The dynamics of two correlated electrons can be reconstructed from the quantum interference of low-lying doubly excited states in helium, as observed in attosecond transient-absorption spectra, and can be controlled by tuning the interaction with a visible laser field of variable intensity.

Population recordings reveal that neurons in the mouse superior colliculus are grouped according to their preferred orientations or movement axes for visual line stimuli, similar to the columnar arrangement in visual cortex of higher mammals; this functional architecture suggests that the superior colliculus samples the visual world unevenly for stimulus orientations.

The production of hydrogen gas from the Precambrian continental lithosphere has been underestimated; taking into account hydrogen from serpentinization and radiolysis may double estimates previously based on marine systems alone.

Endophilin-A2 (endoA2) is shown to mediate clathrin-independent endocytosis of Shiga and cholera toxins, and to function in parallel with dynamin and actin in the pulling-force-driven scission of Shiga-toxin-induced tubular structures.