Letters in 2012

A general method of cooling polyatomic molecules to ultracold temperatures is reported; the optoelectrical cooling technique removes kinetic energy via a Sisyphus effect, effectively causing the molecules to continually ‘climb’ a hill of potential energy.

In the fission yeast Schizosaccharomyces pombe RNA interference (RNAi) machinery promotes heterochromatin assembly and silencing of centromeric repeats; here it is shown that RNAi participates in silencing other genomic regions, such as sexual differentiation genes and retrotransposons, and this process is regulated by developmental and environmental signals.

Changes in the Walker circulation, an enormous east–west atmospheric circulation over the equatorial Pacific Ocean, are shown to be driven by changes in zonal sea surface temperature gradients rather than by changes in the hydrological cycle, as previously suggested.

A loss-of-function approach in mice is used to show that the methylcytosine dioxygenase Tet1 has a role in regulating meiosis and meiotic gene activation in female germ cells; Tet1 deficiency does not greatly affect genome-wide demethylation but has a more specific effect on the expression of a subset of meiotic genes.

Entanglement of the spin of an electron in a semiconductor quantum dot with a single photon is reported, and verified by means of time-resolved frequency downconversion to a telecommunications wavelength; this process is an essential requirement for future quantum networks.

Mice subjected to an aberrant daily light cycle that still maintain the circadian timing system are shown to exhibit increased depression-like behaviours and disruptions in synaptic plasticity and cognitive function.

Interleukin-1β-induced disruption to endothelial stability and vascular permeability in a human in vitro model is shown to be independent of downstream nuclear factor-κB activation, relying instead on a MYD88–ARNO–ARF6 signalling cascade; inhibiting proteins involved in this pathway is shown to improve outcomes in animal models of inflammatory disease.

Two separate regulatory regions on the Drosophila chromatin remodeller ISWI are defined, AutoN and NegC, which negatively regulate ATP hydrolysis and the coupling of ATP hydrolysis to productive DNA translocation, respectively; epitopes on nucleosomes activate ISWI by inhibiting these negative regulatory domains, ensuring that remodelling occurs only in the appropriate chromatin context.

Evidence is presented that activation of the NLRP3 inflammasome is regulated by the calcium-sensing receptor (CASR).

Recordings from cortical neuron dendrites of head-fixed mice during an object-localization task provide direct evidence that a novel global nonlinearity has a role in integrating sensory and motor information during a behaviour-related computation.

Stabilization of the Earth’s rotation axis by a combination of long-term excess ellipticity and elastic stresses in the broken lithosphere provides an explanation for oscillatory true polar wander events spanning the past few billion years of Earth history.

This study shows that a highly advanced stone tool technology (microlithic) appears earlier than originally thought; this microlithic technology persisted over a vast time span (∼11,000 years), and was part of an even longer-lived (>100,000 years) advanced technology of complex heat treatment.

The sessile tunicate Ciona intestinalis possesses a lineage of cells, originating at the margin of the neural plate, that express several neural crest specification genes and can be reprogrammed into migrating ectomesenchyme by the targeted misexpression of Twist.

Observations of firn structure and meltwater retention on the Greenland ice sheet's percolation zone, a region of the ice sheet that is perennially covered by snow and firn, quantify the capacity of the firn to store future surface meltwater and to delay expansion of the area contributing to sea-level rise.

The image of a fluorescent object hidden behind an opaque layer can be retrieved non-invasively by exploiting the correlation properties of the speckle pattern produced by illuminating the object through the layer using laser light.

Two gold nanostructures with controllable subnanometre separation are used to follow the evolution of plasmonic modes; the distance at which quantum tunnelling sets in is determined, and a quantum limit for plasmonic field confinement is estimated.

The integration of biological and chemocatalytic routes can be used to convert acetone–butanol–ethanol fermentation products efficiently into ketones by palladium-catalysed alkylation, leading to a renewable method for the alternative production of petrol, jet and diesel blend stocks in high yield.

In a mouse model of colorectal cancer, barrier deterioration results in adenoma invasion by microbial products that trigger tumour-elicited inflammation, which in turn drives IL-23-dependent tumour growth.

Atpif1, a mitochondrial ATPase inhibitor, was identified as a zebrafish anemic mutant, pinotage, providing an important link in our understanding of the relationship between mitochondrial homeostasis and haem synthesis and identifying a gene that may have a role in human iron, haem and mitochondrial diseases.

Active materials are hierarchically assembled, starting from extensile microtubule bundles, to form emulsions with unexpected collective biomimetic properties such as autonomous motility.