Binding of netrin-4 to laminin short arms regulates basement membrane assembly

Netrins were first identified as neural guidance molecules, acting through receptors that are members of the DCC and UNC-5 family. All netrins share structural homology to the laminin N-terminal domains and the laminin epidermal growth factor-like domains of laminin short arms. Laminins use these domains to self-assemble into complex networks. Here we demonstrate that netrin-4 is a component of basement membranes and is integrated into the laminin polymer via interactions with the laminin gamma1 andgamma3 short arms. The binding is mediated through the laminin N-terminal domain of netrin-4. In contrast to netrin-4, other members of the netrin family do not bind to these laminin short arms. Moreover, a truncated form of netrin-4 completely inhibits laminin-111 self-assembly in vitro, and full-length netrin-4 can partially disrupt laminin self-interactions. When added to explant cultures, netrin-4 retards salivary gland branching morphogenesis.     

Epidermal Notch signalling: differentiation, cancer and adhesion

The Notch pathway plays an important role in regulating epidermal differentiation. Notch ligands, receptors and effectors are expressed in a complex and dynamic pattern in embryonic and adult skin. Genetic ablation or activation of the pathway reveals that Notch signalling promotes differentiation of the hair follicle, sebaceous gland and interfollicular epidermal lineages and that Notch acts as an epidermal tumour suppressor. Notch signalling interacts with a range of other pathways to fulfil these functions and acts via RBP-Jkappa dependent and independent mechanisms. The effects on differentiation can be cell autonomous and non-autonomous, and Notch contributes to stem cell clustering via modulation of cell adhesion.     

Expanding the genetic code of Drosophila melanogaster

Genetic code expansion for unnatural amino acid mutagenesis has, until recently, been limited to cell culture. We demonstrate the site-specific incorporation of unnatural amino acids into proteins in Drosophila melanogaster at different developmental stages, in specific tissues and in a subset of cells within a tissue. This approach provides a foundation for probing and controlling processes in this established metazoan model organism with a new level of molecular precision.     

Malaria parasite colonisation of the mosquito midgut--placing the Plasmodium ookinete centre stage

Vector-borne diseases constitute an enormous burden on public health across the world. However, despite the importance of interactions between infectious pathogens and their respective vector for disease transmission, the biology of the pathogen in the insect is often less well understood than the forms that cause human infections. Even with the global impact of Plasmodium parasites, the causative agents of malarial disease, no vaccine exists to prevent infection and resistance to all frontline drugs is emerging. Malaria parasite migration through the mosquito host constitutes a major population bottleneck of the lifecycle and therefore represents a powerful, although as yet relatively untapped, target for therapeutic intervention. The understanding of parasite-mosquito interactions has increased in recent years with developments in genome-wide approaches, genomics and proteomics. Each development has shed significant light on the biology of the malaria parasite during the mosquito phase of the lifecycle. Less well understood, however, is the process of midgut colonisation and oocyst formation, the precursor to parasite re-infection from the next mosquito bite. Here, we review the current understanding of cellular and molecular events underlying midgut colonisation centred on the role of the motile ookinete. Further insight into the major interactions between the parasite and the mosquito will help support the broader goal to identify targets for transmission-blocking therapies against malarial disease.     

The use of stable isotope ratios in whitebait otolith carbonate to identify the source of prey for Western Australian penguins

A methodology has been developed and used to investigate a direct link between juvenile whitebait (Hyperlophus vittatus), the key prey species sampled from the stomachs of Little Penguins (Eudyptula minor), and the specific nursery area of that prey. A unique application of existing methodology initially involved the measurement of the stable isotopes of oxygen (δ¹⁸O:δ¹⁶O) and carbon (δ¹³C:δ¹²C) in sagittal otolith carbonate, using standard mass spectrometric techniques. The results indicated that the inshore distribution of juvenile (0+ year old) whitebait between Cockburn Sound and Koombana Bay, Western Australia consisted of a number of separate assemblages. Measured differences in stable oxygen isotope ratios were attributed to variations in freshwater input to the embayments that provided the whitebait habitats. In contrast, the measured stable carbon isotope ratios probably resulted from the different isotopic compositions of the food webs in the various habitats. Secondly, a comparison of the average value of carbon and oxygen isotope signatures of pooled otoliths from samples of whitebait from a number of different nearshore coastal sites (assemblages), with that of whitebait obtained from the stomachs of penguins at their main breeding site (Penguin Island) indicated that the values from the penguins resemble most closely those of the average otolith values obtained from whitebait from only one site (Becher Point). Assuming that the whitebait sampled were representative of the whitebait in the nearshore habitats and the diets of the penguins, then these results imply that at the time of sampling the penguins were feeding on whitebait from only one site.     

Unusual redox behaviour of cytochrome b-561 from bovine chromaffin granule membranes

(1) Redox titrations of cytochrome b-561 have been performed with the purified cytochrome and with intact and detergent-solubilized chromaffin-granule membranes. (2) The midpoint redox potential of the cytochrome is 100–130 mV; this depends upon the composition of the buffer, but is independent of pH in the range 5.5–7.5; partial proteolysis of the cytochrome raises the midpoint potential to 160 mV. (3) The Nernst plots of titration data have slopes of 75–115 mV, and are in some cases sigmoid in shape. This may be explained by negative cooperativity during redox transitions in oligomeric cytochrome b-561. (4) Measurements of the haem and cytochrome content of chromaffin granule membrane suggest a haem content of 1 mol/mol protein. (5) Chemical crosslinking of cytochrome b-561 suggests that it may exist as an oligomer of 4–6 polypeptide chains within the chromaffin granule membrane. Aggregation of purified cytochrome b-561 was shown by gel filtration studies and by immunological methods in SDS-polyacrylamide gels. Studies of the molecular weight of the aggregates suggest that the monomer has a molecular weight close to 22 000, but migrates anomalously slowly during electrophoresis.     

Behavioural phase polyphenism in the Australian plague locust (Chortoicetes terminifera)

Swarming and the expression of phase polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust (Chortoicetes terminifera) regularly forms migratory bands and swarms, but is claimed not to express phase polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual''s lifetime in response to a change in population density.