The humoral immune response and the productivity of laying hens kept on the ground or in cages

The effects of two different keeping systems on the humoral immune response and productivity were compared for 80 laying hens, divided into four groups. Two groups each of 20 hens were kept on the ground and two were kept in cages. All the birds were immunised subcutaneously with human serum immunoglobulin G (IgG) at a dose of 100(microg per injection. The immunisations were performed twice at 4-week intervals. The lipopeptide Pam(3)Cys-Ser-(Lys)(4) was used as an adjuvant at a dose of 0.25mg per injection in one group from each housing system. In the second group from each housing system, the hens were immunised without any adjuvant (antigen control groups). The mean egg yield was significantly higher in both the antigen control group and the adjuvant group, when laying hens were kept in cages. Total egg weight remained constant in both of the housing systems. Keeping hens in cages resulted in higher mean specific antibody titres and mean immunoglobulin Y concentrations in the egg yolk.     

Exportin 4: a mediator of a novel nuclear export pathway in higher eukaryotes

Transport receptors of the importin beta superfamily account for many of the nuclear import and export events in eukaryotic cells. They mediate translocation through nuclear pore complexes, shuttle between nucleus and cytoplasm and co-operate with the RanGTPase system to regulate their interactions with cargo molecules in a compartment-specific manner. We used affinity chromatography on immobilized RanGTP to isolate further candidate nuclear transport receptors and thereby identified exportin 4 as the most distant member of the importin beta family so far. Exportin 4 appears to be conserved amongst higher eukaryotes, but lacks obvious orthologues in yeast. It mediates nuclear export of eIF-5A (eukaryotic translation initiation factor 5A) and possibly that of other cargoes. The export signal in eIF-5A appears to be complex and to involve the hypusine modification that is unique to eIF-5A. We discuss possible cellular roles for nuclear export of eIF-5A.     

Nuclear export of metazoan replication-dependent histone mRNAs is dependent on RNA length and is mediated by TAP

Replication-dependent histone mRNAs are the only metazoan mRNAs that are not polyadenylated, ending instead in a conserved stem-loop sequence. Histone pre-mRNAs lack introns and are processed in the nucleus by a single cleavage step, which produces the mature 3' end of the mRNA. We have systematically examined the requirements for the nuclear export of a mouse histone mRNA using the Xenopus oocyte system. Histone mRNAs were efficiently exported when injected as mature mRNAs, demonstrating that the process of 3' end cleavage is not required for export factor binding. Export also does not depend on the stem-loop binding protein (SLBP) since mutations of the stem-loop that prevent SLBP binding and competition with a stem-loop RNA did not affect export. Only the length of the region upstream of the stem-loop, but not its sequence, was important for efficient export. Histone mRNA export was blocked by competition with constitutive transport element (CTE) RNA, indicating that the mRNA export receptor TAP is involved in histone mRNA export. Consistent with this observation, depletion of TAP from Drosophila cells by RNAi resulted in the restriction of mature histone mRNAs to the nucleus.     

Multiple pathways contribute to nuclear import of core histones

Nuclear import of the four core histones H2A, H2B, H3 and H4 is one of the main nuclear import activities during S-phase of the cell cycle. However, the molecular machinery facilitating nuclear import of core histones has not been elucidated. Here, we investigated the pathways by which histone import can occur. First, we show that core histone import can be competed by the BIB (β-like import receptor binding) domain of ribosomal protein L23a suggesting that histone import is an importin mediated process. Secondly, affinity chromatography on immobilized core histones revealed that several members of the importin β family of transport receptors are able to interact with core histones. Finally, we demonstrate that at least four known and one novel importin, importin 9, can mediate nuclear import of core histones into the nuclei of permeabilized cells. Our results suggest that multiple pathways of import exist to provide efficient nuclear uptake of these abundant, essential proteins.     

Machine learning improves the precision and robustness of high-content screens: using nonlinear multiparametric methods to analyze screening results

Imaging-based high-content screens often rely on single cell-based evaluation of phenotypes in large data sets of microscopic images. Traditionally, these screens are analyzed by extracting a few image-related parameters and use their ratios (linear single or multiparametric separation) to classify the cells into various phenotypic classes. In this study, the authors show how machine learning-based classification of individual cells outperforms those classical ratio-based techniques. Using fluorescent intensity and morphological and texture features, they evaluated how the performance of data analysis increases with increasing feature numbers. Their findings are based on a case study involving an siRNA screen monitoring nucleoplasmic and nucleolar accumulation of a fluorescently tagged reporter protein. For the analysis, they developed a complete analysis workflow incorporating image segmentation, feature extraction, cell classification, hit detection, and visualization of the results. For the classification task, the authors have established a new graphical framework, the Advanced Cell Classifier, which provides a very accurate high-content screen analysis with minimal user interaction, offering access to a variety of advanced machine learning methods.     

Gle1 does double duty

During nuclear export, Gle1 (the nuclear-pore-associated mRNA export factor) activates the DEAD-box protein Dbp5 to remodel exported mRNA-protein complexes on the cytoplasmic face of the nuclear pore complex. In this issue, Bolger et al. (2008) now report additional roles for Gle1 in translation initiation and termination.     

Turtles in trouble. Conservation ecology and priorities for Australian freshwater turtles

The Australian freshwater turtle fauna is dominated by species in the family Chelidae. The extant fauna comprises a series of distinct lineages, each of considerable antiquity, relicts of a more extensive and perhaps diverse fauna that existed when wetter climes prevailed. Several phylogenetically distinctive species are restricted to single, often small, drainage basins, which presents challenges for their conservation. Specific threats include water resource development, which alters the magnitude, frequency, and timing of flows and converts lentic to lotic habitat via dams and weirs, fragmentation of habitat, sedimentation, nutrification, and a reduction in the frequency and extent of floodplain flooding. Drainage of wetlands and altered land use are of particular concern for some species that are now very restricted in range and critically endangered. The introduced European red fox is a devastatingly efficient predator of turtle nests and can have a major impact on recruitment. In the north, species such as the northern snake-necked turtle are heavily depredated by feral pigs. Other invasive animals and aquatic weeds dramatically alter freshwater habitats, with consequential impacts on freshwater turtles. Novel pathogens such as viruses have brought at least one species to the brink of extinction. Species that routinely migrate across land are impacted by structural simplification of habitat, reduction in availability of terrestrial refugia, fencing (including conservation fencing), and in some areas, by high levels of road mortality. We report on the listing process and challenges for listing freshwater turtles under the Australian Environment Protection and Biodiversity Conservation Act, summarize the state of knowledge relevant to listing decisions, identify the key threatening processes impacting turtles, and identify key knowledge gaps that impede the setting of priorities. We also focus on how to best incorporate First Nations Knowledge into decisions on listing and discuss opportunities to engage Indigenous communities in on-ground work to achieve conservation outcomes.     

Concordant congenital malformations in twins with inherited translocation: t(9p-;13q+)

Summary Several members of a family with a translocation between the short arm of chromosome 9 and the long arm of chromosome 13 (9p-;13q+) are presented. Although the translocation found in various members of the family looked alike and appeared to be balanced, the clinical features were different. The like-sex twins displayed some features of 9p monosomy syndrome, whereas their mother and maternal grandmother, who apparently had the same translocation, showed only a few features of 9p- syndrome in addition to mild mental retardation. We suggest that a minute deletion of the short arm of chromosome 9 may cause features of 9p- syndrome and that the clinical features of this syndrome in older individuals may be too mild for the clinical diagnosis to be possible.     

Nuclear import of the stem-loop binding protein and localization during the cell cycle

A key factor involved in the processing of histone pre-mRNAs in the nucleus and translation of mature histone mRNAs in the cytoplasm is the stem-loop binding protein (SLBP). In this work, we have investigated SLBP nuclear transport and subcellular localization during the cell cycle. SLBP is predominantly nuclear under steady-state conditions and localizes to the cytoplasm during S phase when histone mRNAs accumulate. Consistently, SLBP mutants that are defective in histone mRNA binding remain nuclear. As assayed in heterokaryons, export of SLBP from the nucleus is dependent on histone mRNA binding, demonstrating that SLBP on its own does not possess any nuclear export signals. We find that SLBP interacts with the import receptors Impalpha/Impbeta and Transportin-SR2. Moreover, complexes formed between SLBP and the two import receptors are disrupted by RanGTP. We have further shown that SLBP is imported by both receptors in vitro. Three sequences in SLBP required for Impalpha/Impbeta binding were identified. Simultaneous mutation of all three sequences was necessary to abolish SLBP nuclear localization in vivo. In contrast, we were unable to identify an in vivo role for Transportin-SR2 in SLBP nuclear localization. Thus, only the Impalpha/Impbeta pathway contributes to SLBP nuclear import in HeLa cells.