Letters in 2012

In the earliest stage of star formation, protostars accrete mass from their surrounding envelopes through circumstellar disks; observations of the protostar L1527 IRS find a large, rotating proto-planetary disk from which the protostellar mass is measured to be 0.19 solar masses, with a protostar-to-envelope mass ratio of about 0.2.

The ultrafast reversibility of changes to the electronic structure and electric polarizability of a dielectric with the electric field of a laser pulse, demonstrated here, offers the potential for petahertz-bandwidth optical signal manipulation.

The spectrum of a quasar at redshift 7.04 reveals absorption from a large column of foreground neutral hydrogen with no corresponding heavy elements; this absorbing gas is either diffuse and intergalactic but has not yet been ionized by starlight at this early epoch, or it is gravitationally bound to a proto-galaxy that has a chemical abundance <1/10,000 the solar level.

Models and field measurements together show that the branching patterns of fine-scale river networks are the result of coupled instabilities in the erosional processes that drive valley incision.

During normal ageing a low rate of division of pre-existing cardiomyocytes, rather than progenitor cells, is responsible for cardiomyocyte genesis; this process is increased fourfold during myocardial infarction.

Adult neural stem and progenitor cells (NSPCs) show high levels of fatty acid synthase (Fasn)-dependent de novo lipogenesis, a process that is controlled by Spot14 to regulate the rate of proliferation; this indicates a functional coupling between the regulation of lipid metabolism and adult NSPC proliferation.

Single-molecule FRET assays used to probe the conformational dynamics of ubiquitin chains reveal that conformational selection is an important mechanism of ubiquitin chain recognition.

Calcium–lipid electrostatic interactions are shown to amplify the tyrosine phosphorylation of CD3ε and CD3ζ in T-cell antigen receptor complex.

The human long non-coding RNA TINCR binds to STAU1 and controls epidermal differentiation by stabilizing key differentiation mRNAs, by means of a TINCR-binding motif found enriched in epidermal differentiation genes.

Observations of trace gases over the south pole of Titan indicate that the moon’s middle-atmospheric circulation extends to an altitude of at least 600 kilometres, which is higher than previously thought and requires active chemistry and dynamics in the upper atmosphere.

Direct measurements of the conduction properties of strongly interacting ultracold fermions reveal the well-known drop of resistance associated with the onset of superfluidity.

Aerotaxy, an aerosol-based growth method, is used to produce gallium arsenide nanowires with a growth rate of about 1 micrometre per second, which is 20 to 1,000 times higher than previously reported for traditional nanowires and allows sensitive and reproducible control of the nanowires’ optical and electronic properties.

It is shown that zinc sulphinate salts can be used to transfer alkyl radicals to heterocycles, allowing for the mild, direct and operationally simple formation of medicinally relevant carbon–carbon bonds while reacting in a complementary fashion to other innate carbon–hydrogen functionalization methods.

Resequencing of genes from individuals of European and African American ancestry indicates that approximately 73% of all protein-coding SNVs and approximately 86% of SNVs predicted to be deleterious arose in the past 5,000–10,000 years, and that European Americans carry an excess of deleterious variants in essential and Mendelian disease genes compared to African Americans.

Observations of the stellar dynamics of the compact lenticular galaxy NGC 1277 show that its central black hole accounts for more than half of the mass of the host galaxy’s bulge, indicating that lenticular galaxies do not follow the usual black-hole mass scaling relations.

A cell-autonomous role for the COUP-TFII transcription factor in prostate cancer cells is identified, in which COUP-TFII inhibits TGF-β signalling by binding to SMAD4; COUP-TFII promotes prostate tumorigenesis and metastasis in a mouse model, and is associated with more aggressive disease in human prostate cancers.

A new mechanism of chromosomal rearrangement is identified through the observation that broken or collapsed DNA replication forks restarted by homologous recombination have a high propensity for U-turns at short inverted repeats; the error-prone nature of this mechanism is suggested to contribute to gross chromosomal rearrangements and copy-number variations present in cancer and other genomic disorders.

GABA-releasing neurons from the ventral tegmental area that project to the nucleus accumbens are shown to block the firing of cholinergic accumbal interneurons, affecting learning in mice.

Cohesin, which tethers sister chromatids together, is found to be cleaved by separase after DNA damage, resulting in cohesin dissociation and allowing for post-replicative repair of DNA double-strand breaks.

Upregulation of gene transcription in stressed cells can lead to clashes between the transcription and repair machineries; here, a stress-activated protein kinase (SAPK), Hog1, is shown to coordinate these two processes in yeast.