Letters in 2015

A small-angle X-ray scattering computed tomography method that reduces the amount of data that needs to be collected and analysed to reconstruct the three-dimensional scattering distribution in reciprocal space of a three-dimensional sample in real space is demonstrated by measuring the orientation of collagen fibres within a human tooth.

Fat-resident regulatory T cells (fT_reg cells) accumulate in adipose tissue of mice as a function of age, but not obesity; mice without fT_reg cells are protected against age-associated insulin resistance, but remain susceptible to obesity-associated insulin resistance and metabolic disease, indicating different aetiologies of age-associated versus obesity-associated insulin resistance.

The processes responsible for driving the expansion of the ocean's oxygen minimum zones remain uncertain; here sediment core data from the Gulf of Alaska suggest that reduced oxygen solubility was a result of ocean warming initiating the expansion of the North Pacific oxygen minimum zone, leading to increased marine productivity and carbon export and, in turn, further reductions in dissolved oxygen levels.

Transition disks are natural laboratories for the study of planet formation, with inner clearings explained by the influence of accreting planets, but attempts to observe directly accretion onto protoplanets have proven unsuccessful so far; here the authors detect infrared emission from multiple companions of the LkCa 15 system and Ha emission from the innermost (LkCa 15 b), showing hot (~10,000 K) gas falling deep into the potential well of an accreting protoplanet.

Activation of the sweet and bitter cortical fields in awake mice evokes predetermined behavioural programs, independent of learning and experience, illustrating the hardwired and innate nature of the sense of taste.

A Drosophila chemosensory receptor, expressed in leg sensory neurons, is necessary for behavioural and molecular synchronization of the fly’s circadian clock to low-amplitude temperature cycles; this temperature-sensing pathway functions independently from the known temperature sensors of the fly’s antennae.

The number of long-period variable stars in a stellar population is directly related to their lifetime, which is difficult to predict from first principles; here a time-dependent stellar population model is constructed that includes the effects of long-period variable stars, and is applied to the galaxy M87.

Porous materials find use in applications such as gas separation, drug delivery and energy storage, but have hitherto been solid rather than liquid; now a combination of cage molecules and a crown-ether solvent that cannot enter the cage molecules is used to create a porous liquid that can solubilize methane gas better than non-porous liquids.

High-resolution three-dimensional thermomechanical simulations of Earth's lithosphere indicate that mantle plumes could have initiated the first subduction zones, but only in the hotter early Earth for old oceanic plates.

A causal variant is identified at the LMO1 oncogene locus that drives the genetic association of LMO1 with neuroblastoma susceptibility; the causal SNP disrupts a GATA transcription factor binding site within a tissue-specific super-enhancer element in the first intron of LMO1, thereby affecting LMO1 expression.

In addition to its role in olfaction, Olfr78 is involved in sensing hypoxia.

A low-mass star that is just 12 parsecs away from Earth is shown to be transited by an Earth-sized planet, GJ 1132b, which probably has a rock/iron composition and might support a substantial atmosphere.

Deletion of Twist or Snail, two key transcription factors that induce epithelial-to-mesenchymal transition in a mouse model of pancreatic ductal adenocarcinoma leads to an increase in cell proliferation, and a greater sensitivity to the chemotherapeutic agent gemcitabine, with no effect on invasion or metastasis.

It is widely accepted that contraction of skeletal muscle and the heart involves structural changes in actin-containing thin filaments to allow binding of myosin motors from neighbouring thick filaments, thus driving filament sliding; here, X-ray diffraction of single skeletal muscle cells reveals that this thin-filament mechanism can regulate muscle contraction against low load, but high-load contraction requires a second permissive step involving a structural change in the thick filament.

ASS1, a urea cycle enzyme, promotes cancer cell proliferation by facilitating pyrimidine synthesis via CAD (carbamoyl-phosphate synthase 2, aspartate transcarbamylase, and dihydroorotase complex) activation.

The first stars and their immediate successors should be found today in the central regions (bulges) of galaxies; old, metal-poor stars have now been found in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than that of the Sun without noticeable carbon enhancement, making it possibly the oldest known star in the Galaxy.

Oropetium thomaeum is a resurrection plant that can survive extreme water stress through desiccation to complete dryness, providing a model for drought tolerance; here, whole-genome sequencing and assembly of the Oropetium genome using single-molecule real-time sequencing is reported.

Detection of molecular biomarkers characteristic of beeswax in pottery vessels at archaeological sites reveals that humans have exploited bee products (such as beeswax and honey) at least 9,000 years ago since the beginnings of agriculture.

A large-scale enhancer complementation assay assessing the activating or repressing contributions of over 800 Drosophila transcription factors and cofactors to combinatorial enhancer control reveals a more complex picture than expected, with many factors having diverse regulatory functions that depend on the enhancer context.

The morphogen Decapentaplegic (Dpp) has been implicated in both wing patterning and growth in fruitflies; here, a CRISPR–Cas9 approach is used to rule out the Dpp gradient driving wing growth.