Replication timing properties within the mouse distal chromosome 7 imprinting cluster

Genomic imprinting is characterized by allele-specific expression of genes within chromosomal domains. Here we show, using fluorescence in situ hybridization (FISH) analysis, that the large chromosomal domain of the mouse distal chromosome 7 imprinting cluster, approximately 1 Mb in length between p57Kip2 and H19 genes, replicates asynchronously between the two alleles during S-phase. At the telomeric side of this domain, we found a transition from asynchronous replication at the imprinted p57Kip2 gene to synchronous replication at the Nap2 gene. Two-color FISH suggested that the paternal allele of this whole domain replicates earlier than its maternal allele. Treatment of the cells with a histone deacetylase inhibitor abolished this allele-specific feature accompanied with accelerated replication of the later-replicating allele at a domain level. Allele-specific asynchronous replication was observed even in ES cells. These results suggest that this imprinting cluster consists of a large replication domain which is already found at the early stage in development.     

Analysis of pigmentation in individual cultured plant cells using an image processing system

Anthocyanin accumulation in strawberry (Fragaria ananassa) cells cultured on a solid medium was monitored using an image-processing system that did not require direct sampling or destruction of the cells. Because of the intercellular heterogeneity of secondary metabolite production in plant cell cultures, the maximum metabolite concentration in individual cells is often more than 10 times higher than that of the average concentration. An image-processing based method enabled the growth and the pigmentation behavior of individual cells to be traced. Changes in the time courses of the anthocyanin content of individual cells differed from each other, although the average anthocyanin contents increased gradually with time in a batch culture. However, these various changing patterns in the anthocyanin content of each cell were independent of the cell cycle. In addition, image analysis revealed that the two cells just after cell division were almost identical to each other both in size and anthocyanin content. The proposed method which uses an image-processing system provides a useful tool for analyzing the secondary metabolism in individual cultured plant cells.     

Reciprocal conversion of Gtr1 and Gtr2 nucleotide-binding states by Npr2-Npr3 inactivates TORC1 and induces autophagy

Autophagy is an intracellular degradation process that delivers cytosolic material to lysosomes and vacuoles. To investigate the mechanisms that regulate autophagy, we performed a genome-wide screen using a yeast deletion-mutant collection, and found that Npr2 and Npr3 mutants were defective in autophagy. Their mammalian homologs, NPRL2 and NPRL3, were also involved in regulation of autophagy. Npr2-Npr3 function upstream of Gtr1-Gtr2, homologs of the mammalian RRAG GTPase complex, which is crucial for TORC1 regulation. Both npr2∆ mutants and a GTP-bound Gtr1 mutant suppressed autophagy and increased Tor1 vacuole localization. Furthermore, Gtr2 binds to the TORC1 subunit Kog1. A GDP-bound Gtr1 mutant induced autophagy even under nutrient-rich conditions, and this effect was dependent on the direct binding of Gtr2 to Kog1. These results revealed that 2 molecular mechanisms, Npr2-Npr3-dependent GTP hydrolysis of Gtr1 and direct binding of Gtr2 to Kog1, are involved in TORC1 inactivation and autophagic induction.     

Double Columnar Structure with a Nanogradient Composite for Increased Oxygen Diffusivity and Reduction Activity

The cathodic performances that can be achieved in solid oxide fuel cells (SOFCs), particularly in terms of oxygen diffusion, need to be improved so that high power densities can be produced at intermediate temperatures. Here, to improve the cathodic performance, a double columnar functional interlayer (DCFL) consisting of Sm_0.2Ce_0.8O_2?δ (SDC) and Sm_0.5Sr_0.5CoO_3?δ (SSC) is fabricated between a La_0.9Sr_0.1Ga_0.8Mg_0.2O_3?δ electrolyte film and a SSC cathode film with pulsed laser deposition. The DCFL has a rough surface morphology consisting of nanosized grains (with diameters less than 5 nm), and it is formed of small columns that grow at an angle of ca. 45° from the substrate. Inserting the DCFL causes the electrical conductivity of the cathode to increase significantly, and the power density obtained by using it in a metal‐supported SOFC is increased. Atomic resolution scanning transmission electron microscopy (TEM) images and density functional theory calculations confirm that the samarium atoms in the SDC columns and cobalt atoms in the SSC columns are located at the interfaces between SDC and SSC columns. Therefore, it is possible a SmCoO_3?δ nanogradient is formed, which may cause lattice distortions. The ¹⁸O₂ concentration is actually much higher in the DCFL than in either of SSC or SDC films.     

Myrmecophilous aphids produce cuticular hydrocarbons that resemble those of their tending ants

Aphid-tending ants protect aphids from natural enemies and collect honeydew secreted by the aphids. However, ants also often prey on the aphids they attend. Aphids, therefore, like social parasites of ants, may well have evolved chemical mimicry as an anti-predation strategy. In this study, we aimed to determine whether the aphid Stomaphis yanonis actively produces cuticular hydrocarbons (CHCs) that resemble those of the tending ant Lasius fuji. In the wild, ants put their CHCs on the aphids that they are tending, so in this study we analyzed “ant-free” aphids. Mature aphids that exuviated in the absence of ant attendance had almost all of the hydrocarbon components that the ants’ CHCs had. Moreover, hydrocarbons artificially applied to the aphids’ body surface were lost by exuviation. Taken together, these findings indicate that mature aphids actively produced ant-like CHCs, and they constitute the first documentation of a chemical resemblance between aphids and ants in a specific aphid–ant association.     

Biliary excretion of excess iron in mice requires hepatocyte iron import by Slc39a14

Iron is essential for erythropoiesis and other biological processes, but is toxic in excess. Dietary absorption of iron is a highly regulated process and is a major determinant of body iron levels. Iron excretion, however, is considered a passive, unregulated process, and the underlying pathways are unknown. Here we investigated the role of metal transporters SLC39A14 and SLC30A10 in biliary iron excretion. While SLC39A14 imports manganese into the liver and other organs under physiological conditions, it imports iron under conditions of iron excess. SLC30A10 exports manganese from hepatocytes into the bile. We hypothesized that biliary excretion of excess iron would be impaired by SLC39A14 and SLC30A10 deficiency. We therefore analyzed biliary iron excretion in Slc39a14-and Slc30a10-deficient mice raised on iron-sufficient and -rich diets. Bile was collected surgically from the mice, then analyzed with nonheme iron assays, mass spectrometry, ELISAs, and an electrophoretic assay for iron-loaded ferritin. Our results support a model in which biliary excretion of excess iron requires iron import into hepatocytes by SLC39A14, followed by iron export into the bile predominantly as ferritin, with iron export occurring independently of SLC30A10. To our knowledge, this is the first report of a molecular determinant of mammalian iron excretion and can serve as basis for future investigations into mechanisms of iron excretion and relevance to iron homeostasis.     

Intra-airway administration of small interfering RNA targeting plasminogen activator inhibitor-1 attenuates allergic asthma in mice

Recent studies suggest that plasminogen activator inhibitor-1 (PAI-1), a major inhibitor of the fibrinolytic system, may promote the development of asthma. To further investigate the significance of PAI-1 in the pathogenesis of asthma and determine the possibility that PAI-1 could be a therapeutic target for asthma, this study was conducted. First, PAI-1 levels in induced sputum (IS) from asthmatic subjects and healthy controls were measured. In asthmatic subjects, IS PAI-1 levels were elevated, compared with that of healthy controls, and were significantly higher in patients with long-duration asthma compared with short-duration asthma. PAI-1 levels were also found to correlate with IS transforming growth factor-β levels. Then, acute and chronic asthma models induced by ovalbumin were established in PAI-1-deficient mice and wild-type mice that received intra-airway administrations of small interfering RNA against PAI-1 (PAI-1-siRNA). We could demonstrate that eosinophilic airway inflammation and airway hyperresponsiveness were reduced in an acute asthma model, and airway remodeling was suppressed in a chronic asthma model in both PAI-1-deficient mice and wild-type mice that received intra-airway administration of PAI-1-siRNA. These results indicate that PAI-1 is strongly involved in the pathogenesis of asthma, and intra-airway administration of PAI-1-siRNA may be able to become a new therapeutic approach for asthma.