Establishment of germline-competent embryonic stem cell lines from the MSM/Ms strain

MSM/Ms is an inbred mouse strain established from the Japanese wild mouse, Mus musculus molossinus, which has been phylogenetically distinct from common laboratory mouse strains for about 1 million years. The nucleotide substitution rate between MSM/Ms and C57BL/6 is estimated to be 0.96%. MSM/Ms mice display unique characteristics not observed in the commonly used laboratory strains, including an extremely low incidence of tumor development, high locomotor activity, and resistance to high-fat-diet-induced diabetes. Thus, functional genomic analyses using MSM/Ms should provide a powerful tool for the identification of novel phenotypes and gene functions. We report here the derivation of germline-competent embryonic stem (ES) cell lines from MSM/Ms blastocysts, allowing genetic manipulation of the M. m. molossinus genome. Fifteen blastocysts were cultured in ES cell medium and three ES lines, Mol/MSM-1, -2, and -3, were established. They were tested for germline competency by aggregation with ICR morulae and germline chimeras were obtained from all three lines. We also injected Mol/MSM-1 ES cells into blastocysts of ICR or C57BL/6 × BDF1 mice and found that blastocyst injection resulted in a higher production rate of chimeric mice than did aggregation. Furthermore, Mol/MSM-1 subclones electroporated with a gene trap vector were also highly efficient at producing germline chimeras using C57BL/6 × BDF1 blastocyst injection. This Mol/MSM-1 ES line should provide an excellent new tool allowing the genetic manipulation of the MSM/Ms genome.     

Proteomic analysis of Aspergillus nidulans cultured under hypoxic conditions

The fungus Aspergillus nidulans reduces nitrate to ammonium and simultaneously oxidizes ethanol to acetate to generate ATP under hypoxic conditions in a mechanism called ammonia fermentation (Takasaki, K. et al.. J. Biol. Chem. 2004, 279, 12414–12420). To elucidate the mechanism, the fungus was cultured under normoxic and hypoxic (ammonia fermenting) conditions, intracellular proteins were resolved by 2‐DE, and 332 protein spots were identified using MALDI MS after tryptic digestion. Alcohol and aldehyde dehydrogenases that play key roles in oxidizing ethanol were produced at the basal level under hypoxic conditions but were obviously provoked by ethanol under normoxic conditions. Enzymes involved in gluconeogenesis, as well as the tricarboxylic and glyoxylate cycles, were downregulated. These results indicate that the mechanism of fungal energy conservation is altered under hypoxic conditions. The results also showed that proteins in the pentose phosphate pathway as well as the metabolism of both nucleotide and thiamine were upregulated under hypoxic conditions. Levels of xanthine and hypoxanthine, deamination products of guanine and adenine were increased in DNA from hypoxic cells, indicating an association between hypoxia and intracellular DNA base damage. This study is the first proteomic comparison of the hypoxic responses of A. nidulans.     

Enzymatic characterization of scytalone dehydratase Val75Met variant found in melanin biosynthesis dehydratase inhibitor (MBI-D) resistant strains of the rice blast fungus

Carpropamid ((1RS,3SR)-2,2-dichloro-N-[(R)-1-(4-chlorophenyl)ethyl]-1-ethyl-3-methylcyclopropanecarboxamide) is a potent chemical against the rice blast fungus, Pyricularia oryzae. In 2001, isolates of the fungus with reduced sensitivity to this fungicide appeared in Saga Prefecture of Japan and were regarded as a potential threat to rice protection by carpropamid. The cause of the resistance has been identified genetically as a point mutation resulting in the Val75Met change in scytalone dehydratase, the primary target of the fungicide. We constructed an overexpression system of the variant enzyme and characterized the kinetics in the catalysis and the inhibition by carpropamid isomers. The variant enzyme retained a significant level of enzymatic activity. Inhibition of the variant enzyme by carpropamid was more than 200-fold reduced in comparison with that of the wild-type. Based on the results, here we propose possible mechanisms of the carpropamid-resistance of the variant enzyme in retaining the normal enzymatic activity.     

Constraining the connectivity of neuronal networks cultured on microelectrode arrays with microfluidic techniques: a step towards neuron-based functional chips

In vitro culture of small neuronal networks with pre-defined topological features is particularly desirable when the electrical activity of such assemblies can be monitored for long periods of time. Indeed, it is hoped that such networks, with pre-determined connectivity, will provide unique insights into the structure/function relationship of biological neural networks and their properties of self-organization. However, the experimental techniques that have been developed so far for that purpose have either failed to provide very long-term pattern definition and retention, or they have not shown potential for integration into more complex microfluidic devices. To address this problem, three-dimensional microfluidic systems in poly(dimethylsiloxane) (PDMS) were fabricated and used in conjunction with both custom-made and commercially available planar microelectrode arrays (pMEAs). Various types of primary neuronal cell cultures were established inside these systems. Extracellular electrical signals were successfully recorded from all types of cells placed inside the patterns, and this bioelectrical activity was present for several weeks. The advantage of this approach is that it can be further integrated with microfluidic devices and pMEAs to yield, for example, complex neuron-based biosensors or chips for pharmacological screening.     

Evidence for a Role of the Transcriptional Regulator Maid in Tumorigenesis and Aging

Maid is a helix-loop-helix protein that is involved in cell proliferation. In order to further elucidate its physiological functions, we studied Maid activity in two small fish model systems. We found that Maid expression was greatest in zebrafish liver and that it increased following partial hepatectomy. Maid levels were also high in hepatic preneoplastic foci induced by treatment of zebrafish with diethylnitrosamine (DEN), but low in hepatocellular carcinomas (HCC), mixed tumors, and cholangiocarcinomas developing in these animals. In DEN-treated transgenic medaka overexpressing Maid, hepatic BrdU uptake and proliferation were reduced. After successive breedings, Maid transgenic medaka exhibited decreased movement and a higher incidence of abnormal spine curvature, possibly due to the senescence of spinal cord cells. Taken together, our results suggest that Maid levels can influence the progression of liver cancer. In conclusion, we found that Maid is important regulator of hepatocarconogenesis and aging.     

Osteopontin Deficiency Accelerates Spontaneous Colitis in Mice with Disrupted Gut Microbiota and Macrophage Phagocytic Activity

Background

Osteopontin (OPN) is a multifunctional protein expressed in a variety of tissues and cells. Recent studies revealed increased OPN expression in the inflamed intestinal tissues of patients with inflammatory bowel disease (IBD). The role of OPN in the pathophysiology of IBD, however, remains unclear.

Aims

To investigate the role of OPN in the development of intestinal inflammation using a murine model of IBD, interleukin-10 knock out (IL-10 KO) mice.

Methods

We compared the development of colitis between IL-10 KO and OPN/IL-10 double KO (DKO) mice. OPN expression in the colonic tissues of IL-10 KO mice was examined by fluorescence in situ hybridization (FISH) analysis. Enteric microbiota were compared between IL-10 KO and OPN/IL-10 DKO mice by terminal restriction fragment length polymorphism analysis. The effect of OPN on macrophage phagocytic function was evaluated by phagocytosis assay.

Results

OPN/IL-10 DKO mice had an accelerated onset of colitis compared to IL-10 KO mice. FISH analysis revealed enhanced OPN synthesis in the colonic epithelial cells of IL-10 KO mice. OPN/IL-10 DKO mice had a distinctly different enteric bacterial profile with a significantly lower abundance of Clostridium subcluster XIVa and a greater abundance of Clostridium cluster XVIII compared to IL-10 KO mice. Intracellular OPN deletion in macrophages impaired phagocytosis of fluorescence particle-conjugated Escherichia coli in vitro. Exogenous OPN enhanced phagocytosis by OPN-deleted macrophages when administered at doses of 1 to 100 ng/ml, but not 1000 ng/ml.

Conclusions

OPN deficiency accelerated the spontaneous development of colitis in mice with disrupted gut microbiota and macrophage phagocytic activity.     

Characterization of RyDEN (C19orf66) as an Interferon-Stimulated Cellular Inhibitor against Dengue Virus Replication

Dengue virus (DENV) is one of the most important arthropod-borne pathogens that cause life-threatening diseases in humans. However, no vaccine or specific antiviral is available for dengue. As seen in other RNA viruses, the innate immune system plays a key role in controlling DENV infection and disease outcome. Although the interferon (IFN) response, which is central to host protective immunity, has been reported to limit DENV replication, the molecular details of how DENV infection is modulated by IFN treatment are elusive. In this study, by employing a gain-of-function screen using a type I IFN-treated cell-derived cDNA library, we identified a previously uncharacterized gene, C19orf66, as an IFN-stimulated gene (ISG) that inhibits DENV replication, which we named Repressor of yield of DENV (RyDEN). Overexpression and gene knockdown experiments revealed that expression of RyDEN confers resistance to all serotypes of DENV in human cells. RyDEN expression also limited the replication of hepatitis C virus, Kunjin virus, Chikungunya virus, herpes simplex virus type 1, and human adenovirus. Importantly, RyDEN was considered to be a crucial effector molecule in the IFN-mediated anti-DENV response. When affinity purification-mass spectrometry analysis was performed, RyDEN was revealed to form a complex with cellular mRNA-binding proteins, poly(A)-binding protein cytoplasmic 1 (PABPC1), and La motif-related protein 1 (LARP1). Interestingly, PABPC1 and LARP1 were found to be positive modulators of DENV replication. Since RyDEN influenced intracellular events on DENV replication and, suppression of protein synthesis from DENV-based reporter construct RNA was also observed in RyDEN-expressing cells, our data suggest that RyDEN is likely to interfere with the translation of DENV via interaction with viral RNA and cellular mRNA-binding proteins, resulting in the inhibition of virus replication in infected cells.     

A Novel Assay System for Anti-Human Immunodeficiency Virus Type 1 (HIV-1) Activity Using a Subclone of a Monocytic Cell Line,U937

A subclonal cl.1–14 cell was established from a monocytic cell line U937 by a limiting dilution method. The anti-HIV-1 activity of some antiviral compounds was evaluated in HIV-1-infected cl.1–14 cells. The results demonstrated that although AZT was a potent inhibitor of HIV-1 replication in cl.1–14 cells, its 50% effective concentration (EC₅₀) values was 80 times higher than that in HIV-1 infected MT-4 cells; the EC₅₀ of AZT was 0.16 μM and 0.002 μM in cl.1–14 and MT-4 cells, respectively. In contrast, the anti-HIV-1 activity of ddA, ddI and ddC in cl.1–14 cells was comparable to that in MT-4 cells. The antiviral activity of nevirapine, dextran sulfate, curdlan sulfate and T22 did not differ significantly between the cl. 1–14 and MT-4 cells. The antiviral activity of several compounds in the HIV-1-infected cl.1–14 cells was similar to that in the HIV-1jr -fl -infected human peripheral macrophages. Our results suggest that cl.1–14 cell cultures are very useful for estimating antiviral activity and more advantageous than the use of peripheral blood macrophages.     

RBM10 regulates alternative splicing

RBM10, originally called S1-1, is a nuclear RNA-binding protein with domains characteristic of RNA processing proteins. It has been reported that RBM10 constitutes spliceosome complexes and that RBM5, a close homologue of RBM10, regulates alternative splicing of apoptosis-related genes, Fas and cFLIP. In this study, we examined whether RBM10 has a regulatory function in splicing similar to RBM5, and determined that it indeed regulates alternative splicing of Fas and Bcl-x genes. RBM10 promotes exon skipping of Fas pre-mRNA as well as selection of an internal 5′-splice site in Bcl-x pre-mRNA. We propose a consensus RBM10-binding sequence at 5′-splice sites of target exons and a mechanistic model of RBM10 action in the alternative splicing.