Volume 549 Number 7671

Editorials

Support Ismail Serageldin p.131

Egypt’s courts must listen to dozens of Nobel prizewinners who have defended the founder of the Alexandria Library.

doi: 10.1038/549131a

News

News Features

News & Views

A fight for scraps of ammonia p.162

Bacteria that can oxidize both ammonia to nitrite and nitrite to nitrate seem to be better adapted to ammonia-limited environments than most cultured microbes that oxidize ammonia to nitrite only, contrary to expectations. See Letter p.269

doi: 10.1038/549162a

A laser model for cosmology p.163

Experiments reveal that the laws governing the immediate aftermath of the Big Bang also apply to the behaviour of coupled lasers. The findings could be used to solve complex computational problems.

doi: 10.1038/549163a

Division hierarchy leads to cell heterogeneity p.164

Cellular diversity can hamper cancer treatment. Analysis of tumour cell-division patterns now reveals how such heterogeneity can arise by a hierarchical pattern of stem-cell divisions yielding a mosaic of different cells. See Article p.227

doi: 10.1038/nature23546

The future of Asia's glaciers p.166

Glaciers in the high mountains of Asia are a crucial water resource, but are at risk from global warming. Modelling suggests that the glaciers will shed mass in direct proportion to the warming to which they are exposed. See Letter p.257

doi: 10.1038/549166a

Plenty of fish in the tree p.167

Polypterid fish were considered to be archaic outliers of the bony-fish grouping. Fossil analysis now places them at the heart of early ray-finned fishes, a radical change that transforms the timing of their evolution. See Letter p.265

doi: 10.1038/549167a

Nanomagnets boost thermoelectric output p.169

The direct conversion of heat into electricity — a reversible process known as the thermoelectric effect — can be greatly enhanced in some materials by embedding them with a small number of magnetic nanoparticles. See Letter p.247

doi: 10.1038/549169a

Review

Perspective

The 4D nucleome project p.219

The 4D Nucleome Network aims to develop and apply approaches to map the structure and dynamics of the human and mouse genomes in space and time with the goal of gaining deeper mechanistic insights into how the nucleus is organized and functions. The project will develop and benchmark experimental and computational approaches for measuring genome conformation and nuclear organization, and investigate how these contribute to gene regulation and other genome functions. Validated experimental technologies will be combined with biophysical approaches to generate quantitative models of spatial genome organization in different biological states, both in cell populations and in single cells.

doi: 10.1038/nature23884

Articles

Letters

Superparamagnetic enhancement of thermoelectric performance p.247

By embedding superparamagnetic nanoparticles in a thermoelectric matrix, phonon and electron transport within the material can be controlled simultaneously at nanometre and mesoscopic length scales, thereby improving the thermoelectric performance of the material.

doi: 10.1038/nature23667

Kinetic analysis of a complete nitrifier reveals an oligotrophic lifestyle p.269

A pure culture of the complete nitrifier Nitrospira inopinata shows a high affinity for ammonia, low maximum rate of ammonia oxidation, high growth yield compared to canonical nitrifiers and genomic potential for alternative metabolisms, probably reflecting an important role in nitrification in oligotrophic environments.

doi: 10.1038/nature23679

m6A modulates haematopoietic stem and progenitor cell specification p.273

N6-methyladenosine (m6A) has been identified as the most abundant modification on eukaryote messenger RNA (mRNA) 1. Although the rapid development of high-throughput sequencing technologies has enabled insight into the biological functions of m6A modification2–13, the function of m6A during vertebrate embryogenesis remains poorly understood. Here we show that m6A determines cell fate during the endothelial-to-haematopoietic transition (EHT) to specify the earliest haematopoietic stem/progenitor cells (HSPCs) during zebrafish embryogenesis. m6Aspecific methylated RNA immunoprecipitation combined with high-throughput sequencing (MeRIP–seq) and m6A individualnucleotide-resolution cross-linking and immunoprecipitation with sequencing (miCLIP–seq) analyses reveal conserved features on zebrafish m6A methylome and preferential distribution of m6A peaks near the stop codon with a consensus RRACH motif. In mettl3-deficient embryos, levels of m6A are significantly decreased and emergence of HSPCs is blocked. Mechanistically, we identify that the delayed YTHDF2-mediated mRNA decay of the arterial endothelial genes notch1a and rhoca contributes to this deleterious effect. The continuous activation of Notch signalling in arterial endothelial cells of mettl3-deficient embryos blocks EHT, thereby repressing the generation of the earliest HSPCs. Furthermore, knockdown of Mettl3 in mice confers a similar phenotype. Collectively, our findings demonstrate the critical function of m6A modification in the fate determination of HSPCs during vertebrate embryogenesis.

doi: 10.1038/nature23883

Polycomb-like proteins link the PRC2 complex to CpG islands p.287

Crystal structures of the Polycomb-like proteins PHF1 and MTF2 with bound DNA and histone peptides show that extended homologous regions of the two proteins form a winged-helix structure that has an unexpected mechanism of binding to unmethylated CpG-containing DNA motifs.

doi: 10.1038/nature23881