Research articles

This paper establishes a role of the extracellular matrix for regulating the BMP morphogen gradient responsible for dorsal–ventral patterning of vertebrate and invertebrate embryos. Type IV collagen binds to the Dpp ligand (the Drosophila form of BMP) and regulates its signalling in the Drosophila embryo and ovary by sequestering Dpp. Human type IV collagen binds the analogous protein in humans.

Shoot branching is regulated by hormones. Branching mutants in several plant species suggests the existence of a plant hormone that is released from the roots and prevents excessive shoot branching. This paper reports on one of two studies that show that a class of chemical compounds called strigolactones found in root exudates are reduced in the branching mutants and that external application of these chemicals inhibits shoot branching in the mutants. It is proposed that strigolactones or related metabolites are the sought after class of hormones.

Shoot branching is regulated by hormones. Branching mutants in several plant species suggests the existence of a plant hormone that is released from the roots and prevents excessive shoot branching. This paper reports on one of two studies that show that a class of chemical compounds called strigolactones found in root exudates are reduced in the branching mutants and that external application of these chemicals inhibits shoot branching in the mutants. It is proposed that strigolactones or related metabolites are the sought after class of hormones.

Mycobacterium tuberculosis virulence is dependent on the secretion system ESX-1. A newly discovered regulator protein termed EspR is described, which positively regulates ESX-1 and is secreted itself, thereby providing a negative feedback regulatory mechanism.

Ghrelin stimulates food uptake by bringing about changes in mitochondrial respiration and proliferation, which are essential for activation of NPY/AgRP neurons. The effects of ghrelin are dependent on the presence of UCP2.

In one of two studies, a technique known as SILAC is used to measure, on a large scale, changes in protein level as a function of expression of endogenous and exogenous miRNAs. It is found that although miRNAs directly repress the translation of hundreds of genes, additional indirect effects result in changes in expression of thousands of genes.

In one of two studies, a technique known as SILAC is used to measure, on a large scale, changes in protein level as a function of expression of endogenous and exogenous miRNAs. It is found that although miRNAs directly repress the translation of hundreds of genes, additional indirect effects result in changes in expression of thousands of genes.

In budding yeast ageing factors are retained in the mother cell, ensuring that the newly formed bud remains young. It is shown that a septin-dependent barrier forms in the nuclear envelope, which prevents pre-existing nuclear pores and other ageing factors from moving into the newly formed bud. These results demonstrate the importance of the nuclear envelope in ageing in yeast cells.

Ligand-gated ion channels can be opened by both full and partial agonists, though in the case of a partial agonist, the maximum response is only a fraction of that evoked by a full agonist. The mechanism underlying this pharmacological observation is investigated and it is shown that cys-loop receptors bound to partial agonists are as efficient at opening as those that are bound to full agonists. Instead, the diminished response results from a reduced ability to adopt an intermediate (agonist bound but pre-open) state.

The crystal structure of Ebola virus glycoprotein is shown in complex with a neutralizing antibody. The structure suggests that the antibody prevents infection by preventing conformational changes of GP2 required for fusion.

Changes in the balance of activity of two distinct neuronal populations in the basolateral amygdala trigger transitions between states of high and low fear in mice. The two populations of neurons tend to participate in different anatomical circuits, suggesting that even within a single brain area, selective activation of specific neuronal circuits can trigger large changes in behavioral state.

A structure of the termination complex shows that release factors that recognize stop codons cause the peptide chain and mRNA to dissociate from the ribosome at the end of translation. A conserved motif in the release factor participates in hydrolysis of the final tRNA-peptide bond.

In budding yeast, the Start checkpoint in the G1 cell cycle phase is a point after which cells are irreversibly committed to cell division. Previous work has identified a linear pathway that triggers the Start transition. In contrast, analyses of single cells reveal that Start represents a positive feedback-dependent sharp switch that coordinates the simultaneous transcription of a large group of cell cycle genes and the budding of a daughter cell.

During mitosis, the two copies of each chromosome pair are held together by cohesin. Three subunits of cohesin form a ring structure and it has been proposed that the sister chromatids are tethered together by being encircled by cohesin rings. This paper provides the most direct evidence to date that cohesin rings topologically entrap two DNA molecules.

The transition from water to land during the late Devonian is marked by the early tetrapods Ichthyostega and Acanthostega, and the tetrapod-like fish Tiktaalik. An analysis of recently discovered material shows that Ventastega curonica might be seen as a simple intermediate between the Tiktaalik and Acanthostega. However, the picture is more complicated than this due to the unexpected morphological diversity of early tetrapods.

In Xenopus, the bone morphogenetic protein (BMP) activity gradient is defined by a 'shuttling-based' mechanism, whereby the BMP ligands are translocated ventrally through their association with the BMP inhibitor Chordin. This shuttling, with feedback repression of the BMP ligand Admp, offers a quantitative explanation to earlier observations, and accounts naturally for the scaling of embryo pattern with its size.