Research articles

The central amygdala relies on inhibitory circuitry to encode fear memories, but how this information is acquired and expressed in these connections is unknown. Two new papers use a combination of cutting-edge technologies to reveal two distinct microcircuits within the central amygdala, one required for fear acquisition and the other critical for conditioned fear responses. Understanding this architecture provides a strong link between activity in a specific circuit and particular behavioural consequences.

The central amygdala relies on inhibitory circuitry to encode fear memories, but how this information is acquired and expressed in these connections is unknown. Two new papers use a combination of cutting-edge technologies to reveal two distinct microcircuits within the central amygdala, one required for fear acquisition and the other critical for conditioned fear responses. Understanding this architecture provides a strong link between activity in a specific circuit and particular behavioural consequences.

Mouse fibroblasts expressing a small subset of transcription factors can be induced to differentiate towards specified lineages without reverting to an embryonic state. Now direct conversion of dermal fibroblasts to multipotent blood progenitors has been achieved in vitro in the human, using just one factor.

Within quantum electrodynamics electric charge is energy dependent, and there is a previous claim that charge is affected by gravity (general relativity) with the implication that the charge is reduced at high energies. But that claim has been very controversial. This author reports an analysis demonstrating that quantum gravity corrections to quantum electrodynamics have a quadratic energy dependence that results in the electric charge vanishing at high energies.

CRISPR/Cas is a microbial immune system that is known to protect bacteria from virus infection. These authors show that the Streptococcus thermophilus CRISPR/Cas system can prevent both plasmid carriage and phage infection through cleavage of invading double-stranded DNA.

Star-forming galaxies trace cosmic history. Recent observational progress has led to the discovery and study of the earliest known galaxies, corresponding to a period when the Universe was only ∼800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen.

Using newly derived genome sequences of 137 marine microbial isolates as well as previously obtained genome and metagenome data, this study presents a functional analysis of picoplankton residing in the ocean's surface layer.

The goal of the 1000 Genomes Project is to provide in-depth information on variation in human genome sequences. In the pilot phase reported here, different strategies for genome-wide sequencing, using high-throughput sequencing platforms, were developed and compared. The resulting data set includes more than 95% of the currently accessible variants found in any individual, and can be used to inform association and functional studies.

SLAC1 is a plant ion channel that controls turgor pressure in the guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals. Here, the X-ray crystal structure of a bacterial homologue of SLAC1 has been solved, and structure-inspired mutagenesis has been used to analyse the conductance properties of the channel. The findings indicate that selectivity among different anions is largely a function of the energetic cost of ion dehydration.

When songbirds sing, neurons in premotor areas fire coordinated bursts precisely timed to the dynamics of the song. The cellular mechanism for such sequence generation is unknown. These authors make the technical breakthrough of recording intracellularly in HVC neurons in singing birds, allowing them to test models of burst generation. They found that membrane potential rapidly depolarizes 5–10 ms before burst onset, consistent with models in which HVC neurons form synaptically connected chains.

DEAD-box helicases use ATP hydrolysis to unwind duplex RNA and facilitate RNA or RNA–protein remodelling. One such helicase is Mss116, which targets a particular group II intron in RNA. Here, single-molecule fluorescence was used to monitor the effect of Mss16 on a minimal construct containing this intron. The data show that Mss16 stimulates the sampling of different folded states of the RNA. Moreover, the helicase promotes RNA folding through discrete ATP-independent and ATP-dependent steps.

The Ndc80 complex is a key component of kinetochore that mediates direct interaction with spindle microtubules. These authors present a cryo-electron microscopy reconstruction of Ndc80 bound to microtubules. They find that Ndc80 uses a novel microtubule recognition mode coupling tubulin binding to self-oligomerization of the complex, and present a mechanistic model for the formation of high-affinity kinetochore–microtubule attachments during cell division.

High-speed atomic force microscopy can be used to record the structure and dynamics of biomolecules simultaneously. These authors use this method to directly observe the dynamics of the motor protein myosin V moving along actin filaments, with unprecedented time resolution. The high-resolution movies provide evidence supporting the 'swinging lever-arm' model of myosin motility, and provide important insights into the mechanism of motor movement.

The F-box protein CORONATINE INSENSITIVE 1 (COI1) mediates jasmonate signalling by promoting hormone-dependent ubiquitylation and degradation of the JASMONATE ZIM DOMAIN (JAZ) family of transcriptional repressors. These authors elucidate the mechanism of jasmonate perception. They present structural and pharmacological data to show that the true jasmonate receptor is a complex of both COI1 and JAZ. In addition, inositol pentakisphosphate functions as a critical component of the hormone receptor complex.

Colour perception arises from the comparison of signals from different cone types, but how these inputs are combined by ganglion cells, which transmit the output of the retina, has been an issue of contention. Using large-scale multi-electrode arrays and fine-grained visual stimulation, these authors map out the locations and types of single-cone inputs to entire populations of ganglion cells, resulting in input–output maps at an unprecedented resolution and scale.

DNA bases that are alkylated or deaminated are removed by DNA glycosylase repair enzymes. In structures of several other DNA glycosylases, the modified base inserts into the active site. These authors solve the structure of glycosylase AlkD, find that the modified base is extruded in an extrahelical position and propose a model for how this solvent-exposed position allows cleavage of N3- and N7-alkylated bases specifically.

The major nutrients nitrate and phosphate have one of the strongest correlations in the sea, with a slope similar to the average nitrogen to phosphorus content of plankton biomass (16:1). Why this global relationship exists, despite the wide range of nitrogen to phosphorus ratios at the organism level, is unknown. Here, an ocean circulation model and observed nutrient distributions have been used to show that the covariation of dissolved nitrate and phosphate is maintained by ocean circulation.

Water security affects human wellbeing both directly and indirectly, through its effects on biodiversity. Here, a global map has been generated that shows threats to both direct and indirect water security from a full range of potential stressors. Technological investments have also been incorporated. The map shows that nearly 80% of the world's population is exposed to high levels of threat to water security. Investment enables rich nations to offset high stressor levels, but less wealthy nations remain vulnerable.

Splicing is carried out by a collection of protein–RNA complexes known as snRNPs. The spliceosome contains equal quantities of the U1, U2, U4, U5 and U6 snRNPs, but the U1 snRNP is made in levels excess to the amounts needed to form spliceosomes, leading to the idea that excess U1s might have splicing independent functions. Here it is shown that the U1 snRNA interacts with some pre mRNAs whose introns have cryptic polyadenylation sites. This interaction prevents premature termination and polyadenylation of the pre mRNA.