Reduced cell number in the hindgut epithelium disrupts hindgut left–right asymmetry in a mutant of pebble,encoding a RhoGEF,in Drosophila embryos

Animals often show left–right (LR) asymmetry in their body structures. In some vertebrates, the mechanisms underlying LR symmetry breaking and the subsequent signals responsible for LR asymmetric development are well understood. However, in invertebrates, the molecular bases of these processes are largely unknown. Therefore, we have been studying the genetic pathway of LR asymmetric development in Drosophila. The embryonic gut is the first organ that shows directional LR asymmetry during Drosophila development. We performed a genetic screen to identify mutations affecting LR asymmetric development of the embryonic gut. From this screen, we isolated pebble (pbl), which encodes a homolog of a mammalian RhoGEF, Ect2. The laterality of the hindgut was randomized in embryos homozygous for a null mutant of pbl. Pbl is a multi-functional protein required for cytokinesis and the epithelial-to-mesenchymal transition in Drosophila. Consistent with Pbl’s role in cytokinesis, we found reduced numbers of cells in the hindgut epithelium in pbl homozygous embryos. The specific expression of pbl in the hindgut epithelium, but not in other tissues, rescued the LR defects and reduced cell number in embryonic pbl homozygotes. Embryos homozygous for string (stg), a mutant that reduces cell number through a different mechanism, also showed LR defects of the hindgut. However, the reduction in cell number in the pbl mutants was not accompanied by defects in the specification of hindgut epithelial tissues or their integrity. Based on these results, we speculate that the reduction in cell number may be one reason for the LR asymmetry defect of the pbl hindgut, although we cannot exclude contributions from other functions of Pbl, including regulation of the actin cytoskeleton through its RhoGEF activity.     

IFN-alpha beta promote priming of antigen-specific CD8+ and CD4+ T lymphocytes by immunostimulatory DNA-based vaccines

Immunostimulatory sequence (ISS) DNA containing unmethylated CpG dinucleotides stimulate NK and APC to secrete proinflammatory cytokines, including IFN-alphabeta and -gamma, TNF-alpha, and IL-6 and -12, and to express costimulatory surface molecules such as CD40, B7-1, and B7-2. Although ISS DNA has little direct effect on T cells by these criteria, immunization of wild-type mice with ISS DNA and OVA results in Ag-specific CTL and Th1-type T helper activity. This investigation examines the mechanisms by which ISS DNA primes CD8(+) and CD4(+) lymphocyte activities. In this report we demonstrate that ISS DNA regulates the expression of costimulatory molecules and TAP via a novel autocrine or paracrine IFN-alphabeta pathway. Coordinated regulation of B7 costimulation and TAP-dependent cross-presentation results in priming of Ag-specific CD8(+) CTL, whereas CD40, B7, and IL-12 costimulation is required for priming of CD4(+) Th cells by ISS-based vaccines.     

Inhibition of catalase activity by oxidative stress and its relationship to salicylic acid accumulation in plants

The decrease in catalase activity and its relationship to change in salicylic acid content were investigated in rice, wheat, and cucumber seedlings exposed to oxidative stresses. A decrease in chlorophyll fluorescence (F/Fm), measured as an indicator of the oxidative stress, and a drop in catalase activity were observed following treatment with NaCl in all plant seedlings tested . Furthermore, such decreases in F/Fm and catalase activity were also observed under low temperature conditions in both rice cultivars, whereas the degrees of decrease were dependent on their low temperature tolerance . Although the content of salicylic acid increased in rice seedlings stressed by NaCl treatment, it was inversely correlated with the decrease in the catalase activity . Such a relationship between the decrease in catalase activity and increase in salicylic acid content was confirmed with paraquat treatment of the rice seedlings . These results suggested that the fall in catalase activity is a phenomenon occurring in many plant species under oxidative stress and is related to the accumulation of salicylic acid in oxidatively-stressed plants.     

A model of globin evolution

Putative globins have been identified in 426 bacterial, 32 Archaeal and 67 eukaryote genomes. Among these sequences are the hitherto unsuspected presence of single domain sensor globins within Bacteria, Fungi, and a Euryarchaeote. Bayesian phylogenetic trees suggest that their occurrence in the latter two groups could be the result of lateral gene transfer from Bacteria. Iterated psiblast searches based on groups of globin sequences indicate that bacterial flavohemoglobins are closer to metazoan globins than to the other two lineages, the 2-over-2 globins and the globin-coupled sensors. Since Bacteria is the only kingdom to have all the subgroups of the three globin lineages, we propose a working model of globin evolution based on the assumption that all three lineages originated and evolved only in Bacteria. Although the 2-over-2 globins and the globin-coupled sensors recognize flavohemoglobins, there is little recognition between them. Thus, in the first stage of globin evolution, we favor a flavohemoglobin-like single domain protein as the ancestral globin. The next stage comprised the splitting off to single domain 2-over-2 and sensor-like globins, followed by the covalent addition of C-terminal domains resulting in the chimeric flavohemoglobins and globin-coupled sensors. The last stage encompassed the lateral gene transfers of some members of the three globin lineages to specific groups of Archaea and Eukaryotes.     

Increased tolerance to salt stress in the phosphate-accumulating <Emphasis Type="Italic">Arabidopsis</Emphasis> mutants <Emphasis Type="Italic">siz1</Emphasis> and <Emphasis Type="Italic">pho2</Emphasis>

High salinity is an environmental factor that inhibits plant growth and development, leading to large losses in crop yields. We report here that mutations in SIZ1 or PHO2, which cause more accumulation of phosphate compared with the wild type, enhance tolerance to salt stress. The siz1 and pho2 mutations reduce the uptake and accumulation of Na⁺. These mutations are also able to suppress the Na⁺ hypersensitivity of the sos3-1 mutant, and genetic analyses suggest that SIZ1 and SOS3 or PHO2 and SOS3 have an additive effect on the response to salt stress. Furthermore, the siz1 mutation cannot suppress the Li⁺ hypersensitivity of the sos3-1 mutant. These results indicate that the phosphate-accumulating mutants siz1 and pho2 reduce the uptake and accumulation of Na⁺, leading to enhanced salt tolerance, and that, genetically, SIZ1 and PHO2 are likely independent of SOS3-dependent salt signaling.     

Engineering of Escherichia coli to facilitate efficient utilization of isomaltose and panose in industrial glucose feedstock

Industrial glucose feedstock prepared by enzymatic digestion of starch typically contains significant amounts of disaccharides such as maltose and isomaltose and trisaccharides such as maltotriose and panose. Maltose and maltosaccharides can be utilized in Escherichia coli fermentation using industrial glucose feedstock because there is an intrinsic assimilation pathway for these sugars. However, saccharides that contain α-1,6 bonds, such as isomaltose and panose, are still present after fermentation because there is no metabolic pathway for these sugars. To facilitate more efficient utilization of glucose feedstock, we introduced glvA, which encodes phospho-α-glucosidase, and glvC, which encodes a subunit of the phosphoenolpyruvate-dependent maltose phosphotransferase system (PTS) of Bacillus subtilis, into E. coli. The heterologous expression of glvA and glvC conferred upon the recombinant the ability to assimilate isomaltose and panose. The recombinant E. coli assimilated not only other disaccharides but also trisaccharides, including alcohol forms of these saccharides, such as isomaltitol. To the best of our knowledge, this is the first report to show the involvement of the microbial PTS in the assimilation of trisaccharides. Furthermore, we demonstrated that an l-lysine-producing E. coli harboring glvA and glvC converted isomaltose and panose to l-lysine efficiently. These findings are expected to be beneficial for industrial fermentation.

     

Detection of tetanus-induced effects in linearly lined-up micropatterned neuronal networks: application of a multi-electrode array chip combined with agarose microstructures

K-7174, a GATA-specific inhibitor, is a putative anti-inflammatory agent that attenuates effects of inflammatory cytokines in certain cell types. However, molecular mechanisms involved have not been elucidated. We found that, in glomerular podocytes, induction of monocyte chemoattractant protein 1 (MCP-1) and inducible nitric oxide synthase (iNOS) by TNF-alpha was abrogated by K-7174. It was correlated with unexpected induction of unfolded protein response (UPR) evidenced by: (1) induction of endogenous indicators 78 kDa glucose-regulated protein and CCAAT/enhancer-binding protein-homologous protein, and (2) suppression of an exogenous indicator, endoplasmic reticulum stress-repressive alkaline phosphatase. In podocytes, induction of UPR by either tunicamycin, thapsigargin, A23187 or AB5 subtilase cytotoxin completely reproduced the suppressive effect of K-7174. Furthermore, K-7174-elicited UPR abrogated induction of MCP-1 and iNOS not only by TNF-alpha but also by medium conditioned by activated macrophages. These results suggested a novel, UPR-dependent mechanism underlying the anti-inflammatory potential of K-7174.     

Structural divergence of human ghrelin. Identification of multiple ghrelin-derived molecules produced by post-translational processing

Ghrelin, a novel 28-amino acid peptide with an n-octanoyl modification at Ser(3), was isolated from rat stomach and found to be an endogenous ligand for the growth-hormone secretagogue receptor (GHS-R). This octanoyl modification is essential for ghrelin-induced GH release. We report here the purification and identification of human ghrelin from the stomach, as well as structural analysis of the human ghrelin gene and quantitation of changes in plasma ghrelin concentration before and after gastrectomy. Human ghrelin was purified from the stomach by gel filtration and high performance liquid chromatography, using a ghrelin-specific radioimmunoassay and an intracellular calcium influx assay on a stable cell line expressing GHS-R to test the fractions. In the course of purification, we isolated human ghrelin of the expected size, as well as several other ghrelin-derived molecules. Classified into four groups by the type of acylation observed at Ser(3); these peptides were found to be non-acylated, octanoylated (C8:0), decanoylated (C10:0), and possibly decenoylated (C10:1). All peptides found were either 27 or 28 amino acids in length, the former lacking the C-terminal Arg(28), and are derived from the same ghrelin precursor through two alternative pathways. The major active form of human ghrelin is a 28-amino acid peptide octanoylated at Ser(3), as was found for rat ghrelin. Synthetic octanoylated and decanoylated ghrelins produce intracellular calcium increases in GHS-R-expressing cells and stimulate GH release in rats to a similar degree. Both ghrelin and the ghrelin-derived molecules were found to be present in plasma as well as stomach tissue. Plasma levels of immunoreactive ghrelin after total gastrectomy in three patients were reduced to approximately half of their pre-gastrectomy values, after which they gradually increased. This suggests that the stomach is the major source of circulating ghrelin and that other tissues compensate for the loss of ghrelin production after gastrectomy.     

Germ-line mitochondria exhibit suppressed respiratory activity to support their accurate transmission to the next generation

Mitochondria are accurately transmitted to the next generation through a female germ cell in most animals. Mitochondria produce most ATP, accompanied by the generation of reactive oxygen species (ROS). A specialized mechanism should be necessary for inherited mitochondria to escape from impairments of mtDNA by ROS. Inherited mitochondria are named germ-line mitochondria, in contrast with somatic ones. We hypothesized that germ-line mitochondria are distinct from somatic ones. The protein profiles of germ-line and somatic mitochondria were compared, using oocytes at two different stages in Xenopus laevis. Some subunits of ATP synthase were at a low level in germ-line mitochondria, which was confirmed immunologically. Ultrastructural histochemistry using 3,3′-diaminobenzidine (DAB) showed that cytochrome c oxidase (COX) activity of germ-line mitochondria was also at a low level. Mitochondria in one oocyte were segregated into germ-line mitochondria and somatic mitochondria, during growth from stage I to VI oocytes. Respiratory activity represented by ATP synthase expression and COX activity was shown to be low during most of the long gametogenetic period. We propose that germ-line mitochondria that exhibit suppressed respiration alleviate production of ROS and enable transmission of accurate mtDNA from generation to generation.