Letters in 2012

YAP has previously been identified as an oncogene that promotes cell growth, but now it is shown to restrict stem cell expansion during regeneration in the mouse intestine, suggesting that it may function as a tumour suppressor in colon cancer.

First-principles calculations on a huge configuration space of four different binary alloy systems reveal that stiffness and heat of formation are negatively and linearly correlated.

Studying six vespertilionid bat species of different sizes to investigate the reason why smaller bats have higher frequency echolocation calls, a model is put forward that the size/frequency range is modulated by the need to maintain a focused, highly directional echolocation beam.

The icy dwarf planet Makemake has projected axes of 1,430 ± 9 and 1,502 ± 45 km and a V-band geometric albedo larger than Pluto’s but smaller than Eris’s, with no global Pluto-like atmosphere.

Spectroscopic measurements now reveal that at low temperatures, the water in hydrophobic hydration shells has greater tetrahedral order and fewer weak hydrogen bonds than the surrounding bulk water; this structure disappears at higher temperatures and around alcohol chains longer than 1 nanometre.

Analysis of data from forest plants worldwide shows that margins between threshold xylem pressures at which plants suffer damage and the lowest xylem pressures experienced are small, with no difference between dry and wet forests, providing insight into why drought-induced forest decline is occurring in both arid and wet forests.

Vacuolar acidity in yeast is shown to decline with age, and preventing this decrease suppresses mitochondrial dysfunction and extends the lifespan of yeast.

Colloidal Janus spheres in a precessing magnetic field are shown to self-assemble into in-motion microtubes dynamically selected on the basis of synchronization rather than static energy minimization.

Iridoids are a large family of bicyclic natural products that possess anticancer, anti-inflammatory, antifungal and antibacterial activities; here the essential cyclization step in their biosynthesis is identified, opening up the possibility of production of naturally occurring and synthetic variants of iridoids for use in pharmacy or agriculture.

Visual responses during wakefulness are dominated by inhibition, and this inhibition shapes visual selectivity by restricting the temporal and spatial extent of neural activity.

High-speed tracking of effortful responses and neuronal activity in rats during a forced swim test identifies medial prefrontal cortex (mPFC) neurons that respond during escape-related swimming but not normal locomotion, and optogenetics shows that mPFC neurons projecting to the brainstem dorsal raphe nucleus, which is implicated in depression, modulate this behavioural response to challenge

DNA damage or replication stress induces the activation of checkpoint kinases, pausing the cell cycle so that DNA repair can take place; checkpoint activation must be regulated to prevent the cell-cycle arrest from persisting after damage is repaired, and now the Slx4–Rtt107 complex is shown to regulate checkpoint kinase activity by directly monitoring DNA-damage signalling.

Critical transitions in experimental and theoretical systems can be anticipated on the basis of specific warning signs, with ‘critical slowing down’ being the best studied; long-term data from a real system, a Chinese lake, now show that a flickering phenomenon can be observed up to 20 years before the critical transition to a eutrophic state.

FusKR, a fucose-sensing two-component system, has been identified in enterohaemorrhagic E. coli, linking fucose utilization and virulence factor gene expression and providing insight into how sensing of a host signal can facilitate bacterial colonization.

A whole-genome and transcriptome analysis of 20 human induced pluripotent stem-cell lines shows that reprogramming does not necessarily add de novo copy number variants to what is already present in the somatic cells from which they originated.

Fast, single-photon detection enables the observation of entanglement between a stationary quantum bit (a single quantum dot spin) and a propagating quantum bit (a single photon), marking a first step towards the implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.

Crystal structures of the Pol II–TFIIB complex in free form and bound by the DNA template and a short RNA product are reported; the latter complex represents an initially transcribing complex, a critical transient state in the pathway from transcription initiation to elongation.

A physically based approach to drought modelling shows that there has been little change in drought from 1950 to 2008, contradicting previous work that suggested an increase in recent years.

A new approach to dating a continuous sea-level record, using speleothem U–Th ages, shows that past variations in global ice volume occurred within centuries of polar climate change, with rates of sea-level rise reaching at least 1 metre per century.

Modelling shows that the misaligned orbits of ‘hot Jupiters’ can follow naturally from disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars.