Reviews & Analysis

Seven small planets whose surfaces could harbour liquid water have been spotted around a nearby dwarf star. If such a configuration is common in planetary systems, our Galaxy could be teeming with Earth-like planets. See Letter p.456

Statistical analysis has revealed a simple rule for the occurrence of warm periods during the Quaternary, whereas on much longer timescales geological data have confirmed that the Solar System is chaotic. See Article p.427 & Letter p.468

Ageing is associated with an increased risk of cardiovascular disease caused by the rupture of inflamed cholesterol plaques in arteries. It emerges that this might be partly due to genetic mutations that cause cancerous changes in white blood cells.

The biosynthesis of a coenzyme in the microbial production of methane has been determined — completing the biosynthetic pathways for the family of compounds that includes chlorophyll, haem and vitamin B₁₂. See Article p.78

Immune cells known as T cells can destroy tumour cells, but their clinical use requires complex preparation and the cells can lose effectiveness over time. A new approach might improve the efficiency of T-cell therapy. See Letter p.113

T cells of the immune system often fail to target cancer cells because they enter a dysfunctional state known as exhaustion. Molecular analysis of T-cell exhaustion provides insights into the clinical use of these cells.

During the last ice age, huge numbers of icebergs were episodically discharged from an ice sheet that covered North America. Numerical modelling suggests that these events resulted from a conceptually simple feedback cycle. See Letter p.332

Oxygen is essential to most life in the ocean. An analysis shows that oxygen levels have declined by 2% in the global ocean over the past five decades, probably causing habitat loss for many fish and invertebrate species. See Letter p.335

Chemists have long aspired to synthesize two-dimensional polymers that are fully conjugated — an attribute that imparts potentially useful properties. Just such a material has been prepared using a solid-state polymerization reaction.

Many organ surfaces are covered by a protective epithelial-cell layer. It emerges that such layers are maintained by cell stretching that triggers cell division mediated by the force-sensitive ion-channel protein Piezo1. See Letter p.118

It emerges that blood-cancer-targeting drugs that block a tumour-survival pathway also activate a mutation-causing enzyme in mice and in human cells. This might have implications for the clinical use of these drugs. See Letter p.489

WIMPs, or weakly interacting massive particles, are the leading candidates for dark matter, the 'missing' mass in the Universe. An experiment has obtained no evidence for such particles, despite an impressive increase in sensitivity.

The ocean's uptake of carbon dioxide increased during the 2000s. Models reveal that this was driven primarily by weak circulation in the upper ocean, solving a mystery of ocean science. See Letter p.215

The existence of medium-sized black holes has long been debated. Such an object has now been discovered in the centre of a dense cluster of stars, potentially enhancing our understanding of all black holes. See Letter p.203

Technological advances have allowed scientists to sequence the complex quinoa genome. This highlights the ongoing expansion of genomics beyond major crops to other plants that have relevance for global food security. See Article p.307

The enzyme S6K1 phosphorylates the enzyme glutamyl-prolyl tRNA synthetase to modulate metabolic activity and lifespan, revealing an atypical role for this synthetase as a target of a key metabolic signalling pathway. See Letter p.357

One effect of weight-loss surgery is a change in food preferences. An analysis in rats shows that this is caused by altered nutrient signals in the intestine. These activate the vagus nerve to increase signalling in the brain by the neurotransmitter dopamine.

A systematic analysis of bipolar cells, which act as a central signalling conduit in the retina, reveals that the neurons' diverse responses to light are generated largely by feedback from neighbouring amacrine cells. See Article p.439

A theory proposed in 2015 suggested that relatively flat surfaces in mountain ranges were formed by the reorganization of river networks. A fresh analysis rebuts this idea, reigniting discussion of a long-standing problem in Earth science.