Letters in 2013

Consuming diets rich in plant versus animal products changes the microbes found in the human gut within days, with important implications for our health and evolution.

Observations of local galaxy I Zw 18 imply that the dust mass in star-forming, metal-poor environments is much lower than expected, and, therefore, that the amount of dust in young galaxies of the early Universe, such as redshift-6.6 galaxy Himiko, is probably a factor of about 100 less than previously thought.

A method of selectively activating both allylic carbon–hydrogen bonds and carbon–carbon bonds can furnish sophisticated molecular scaffolds with all-carbon quaternary stereogenic centres that can themselves be derivatized.

The airway mucin Muc5b (but not Muc5ac) is required for mucociliary clearance, defence against bacterial infection in the airways and middle ear, and maintenance of immune homeostasis in the lungs; Muc5b deficiency causes accumulation of apoptotic macrophages, impairment of phagocytosis and reduced production of interleukin-23, leading to infection and inflammation.

Inhibitors of the bile acid transporter ASBT may be useful therapeutics for treating hypercholesterolaemia and type 2 diabetes; here, two X-ray crystal structures of an ASBT homologue from Yersinia frederiksenii are solved.

Using long-term intravital photography to explore the cellular changes after compression-induced traumatic brain injury in a murine model, it is shown that parenchymal and meningeal inflammation as well as cell death can be modulated by topical treatment with purinergic receptor antagonists and glutathione.

The calculated density and seismic structure of the two best-exposed island arc sections (Kohistan and Talkeetna) reveals that the foundering of the lower arc crust produces a sharp seismic discontinuity characteristic of the continental Mohorovičić discontinuity.

The immediate optical afterglow of the γ-ray burst GRB 120308A is highly polarized, showing that γ-ray bursts contain magnetized baryonic jets with large-scale uniform fields that can survive long after the initial explosion.

In mice, chronic stimulation by repetitive sounds, whisker deflection, motor activity or seizures during a postnatal developmental critical period, leads to permanent reductions in brain microvascular density, an effect that impairs oxygen delivery to neurons but can be prevented by blocking nitric oxide signalling.

HMGA2 promotes lung cancer progression in mice and humans; in mouse and human lung cancer cells, HMGA2 competes with mRNAs like TGFBR3 for the let-7 microRNA family, and in human non-small-cell lung cancer tissue, expression levels of HMGA2 and TGFBR3 are correlated, suggesting that HMGA2 functions both as a protein-coding gene and as a non-coding RNA.

A mathematical modelling study assesses the role of peer behaviour and ‘herding’ behaviour in aggregating information through the peer-review process; peer review works best when reviewers exercise intermediate levels of subjectivity.

A full mitochondrial genome from a 400,000-year-old Middle Pleistocene hominin from Spain unexpectedly reveals a close relationship to Denisovans, a sister group to the Neanderthals, raising interesting questions about the origins of Neanderthals and Denisovans.

In a mouse model of pancreatic tumours driven by Kras mutations, the outcome of suppressing autophagy is shown to depend on the status of p53: if p53 is intact, deletion of key autophagy genes blocks the progression of pre-cancerous lesions to aggressive carcinomas; however, in the absence of p53, loss of autophagy accelerates tumorigenesis, accompanied by deregulation of cancer cell metabolism.

Cycles of electron capture and β⁻ decay involving neutron-rich nuclei at a typical depth of about 150 metres are found to cool the outer crust of a neutron star by emitting neutrinos while also thermally decoupling the surface layers from the deeper crust; this mechanism has been studied in other astrophysical environments, but has not hitherto been considered in neutron stars.

Saccharomyces cerevisiae bearing engineered alginate and mannitol catabolic pathways can ferment sugars from brown macroalgae to produce ethanol, potentially allowing the use of brown macroalgae as a viable feedstock for the production of biofuels and renewable chemicals.

This study establishes an important role for the enzyme Tet1 in erasing genomic imprinting in vivo — mice with a knockout of paternal Tet1 give rise to progeny with imprinting defects and associated growth and development defects, which leads to early embryonic lethality; furthermore, analysis of the DNA methylation dynamics in reprogramming primordial germ cells (PGCs) suggests that Tet1 is required at a late stage of the reprogramming process, in the second wave of DNA demethylation in PGCs.

The crystal structure of an archaeal Rce1 protein has been determined; this protein represents a novel type of intramembrane protease, with a distinct architecture and catalytic site.

Drilling by the Integrated Ocean Drilling Program has recovered primitive, modally layered, orthopyroxene-bearing cumulate rocks from the lower plutonic crust formed at a fast-spreading ridge, leading to a better-constrained estimate of the bulk composition of fast-spreading oceanic crust.

Very slow cooling, over several days, of solutions of complementary-DNA-modified nanoparticles through the melting temperature of the system produces nanoparticle assemblies with the Wulff equilibrium crystal structure, thus showing that DNA hybridization can direct nanoparticle assembly along a pathway that mimics atomic crystallization.

The specificity of interferon effectors across an expanded range of viruses is studied, with results indicating that positive-sense single-stranded RNA viruses are more susceptible to interferon-stimulated gene activity than negative-sense RNA or DNA viruses; in addition, the DNA sensor cGAS is shown to have an unappreciated role in RNA virus inhibition.