phiC31-integrase-mediated, site-specific integration of transgenes in the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Transgenic silkworms can be useful for investigating the functions of genes in the post-genomic era. However, the common method of using a transposon as an insertion tool may result in the random integration of a foreign gene into the genome and suffer from a strong position effect. To overcome these problems, it is necessary to develop a site-specific integration system. It is known that phiC31 integrase has the capacity to mediate recombination between the target sequences attP and attB. To test the availability of site-specific integration in the silkworm, we first examined the efficiency of recombination between the target sites of the two plasmids in silkworm embryos and found that the frequency of recombination was very high. Then we constructed a host strain that possessed the target sequence attP using the common method. We injected the donor plasmid together with the phiC31 integrase mRNA into the embryos of the host strain and obtained positive lines. Structural analysis of the lines showed that site-specific integration occurred by recombination between the genomic attP site and the attB site of the donor plasmid. We can conclude from the results that phiC31 integrase has the ability to mediate the site-specific integration of transgenes into the silkworm chromosome.     

Kaposi's sarcoma-associated herpesvirus induces the phosphatidylinositol 3-kinase-PKC-zeta-MEK-ERK signaling pathway in target cells early during infection: implications for infectivity

Human herpesvirus 8 (HHV-8) is implicated in the pathogenesis of Kaposi's sarcoma. HHV-8 envelope glycoprotein B (gB) possesses the RGD motif known to interact with integrin molecules, and HHV-8 infectivity was inhibited by RGD peptides, by antibodies against alpha3 and beta1 integrins, and by soluble alpha3beta1 integrin (S. M. Akula, N. P. Pramod, F.-Z. Wang, and B. Chandran, Cell 108:407-419, 2002). Anti-gB antibodies immunoprecipitated the virus alpha3 and beta1 complexes, and virus-binding studies suggest a role for alpha3beta1 in HHV-8 entry. HHV-8 infection induced the integrin-mediated activation of focal adhesion kinase (FAK), implicating a role for integrin and the associated signaling pathways in HHV-8 entry into the target cells. Immediately after infection, target cells exhibited morphological changes and cytoskeletal rearrangements, suggesting the induction of signal pathways. As early as 5 min postinfection, HHV-8 activated the MEK-ERK1/2 pathway. The focal adhesion components phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase C-zeta (PKC-zeta) were recruited as upstream mediators of the HHV-8-induced ERK pathway. Anti-HHV-8 gB-neutralizing antibodies and soluble alpha3beta1 integrin inhibited the virus-induced signaling pathways. Early kinetics of the cellular signaling pathway and its activation by UV-inactivated HHV-8 suggest a role for virus binding and/or entry but not viral gene expression in this induction. Studies with human alpha3 integrin-transfected Chinese hamster ovary cells and FAK-negative mouse DU3 cells suggest that the alpha3beta1 integrin and FAK play roles in the HHV-8 mediated signal induction. Inhibitors specific for PI 3-kinase, PKC-zeta, MEK, and ERK significantly reduced the virus infectivity without affecting virus binding to the target cells. Examination of viral DNA entry suggests a role for PI 3-kinase in HHV-8 entry into the target cells and a role for PKC-zeta, MEK, and ERK at a post-viral entry stage of infection. These findings implicate a critical role for integrin-associated mitogenic signaling in HHV-8's infection of target cells and suggest that, by orchestrating the signal cascade, HHV-8 may create an appropriate intracellular environment to facilitate the infection.     

PhiC31 integrase-mediated cassette exchange in silkworm embryos

To construct an effective site-specific integration system in the silkworm, we examined if phiC31 integrase works in silkworm embryos. As an assay system, we constructed an extrachromosomal cassette exchange reaction system between two attP sites of an acceptor plasmid and two attB sites of a donor plasmid. To evaluate the activity, integrase mRNAs synthesized from three different plasmids were used. We injected a mixture of the acceptor and donor plasmids with the mRNA synthesized in vitro from one of the three plasmids into silkworm embryos at 4-6?h after oviposition and recovered plasmid DNAs from the embryos 3?days after injection. The resultant plasmids were transformed into Escherichia coli and spread on selection medium plates containing the appropriate antibiotics. A colony-forming assay and restriction enzyme digestion of the plasmids purified from the colonies showed that the phiC31 integrase worked very efficiently in the silkworm embryos. Notably, a phiC31 integrase mRNA synthesized from two of the plasmids produced cassette exchange plasmids at a high frequency, suggesting that the mRNA can be used to construct a targeted integration system in silkworms.     

Indoleamines and calcium channels influence morphogenesis in in vitro cultures of Mimosa pudica L.

The present article reports the interplay of indoleamine neurohormones viz. serotonin, melatonin and calcium channels on shoot organogenesis in Mimosa pudica L. In vitro grown nodal segments were cultured on MS medium with B5 vitamins containing Serotonin (SER) and Melatonin (MEL) at 100 µM and indoleamine inhibitors viz. serotonin to melatonin conversion inhibitor p-chlorophenylalanine (p-CPA) at 40 µM, serotonin reuptake inhibitor (Prozac) 20 µM. In another set of experiment, calcium at 5 mM, calcium ionophore ({"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187) 100 µM, and calcium channel blocker varapamil hydrochloride (1 mM) a calcium chelator EGTA (100 µM) were administered to the culture medium. The percentage of shoot multiplication, endogenous MEL and SER were monitored during shoot organogenesis. At 100 µM SER and MEL treatment 60% and 70% explants responded for shoot multiplication respectively. Medium supplemented with either SER or MEL along with calcium (5 mM) 75%–80% explants responded for organogenesis. SER or MEL along with calcium ionophore ({"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187) at 100 µM 70% explants responded for shoot multiplication. p-CPA, prozac, verapamil and EGTA, shoot multiplication was reduced and endogenous pools of SER, MEL decreased by 40–70%. The results clearly demonstrated that indoleamines and calcium channels positively influenced shoot organogenesis in M. pudica L.     

Enhanced ascorbic acid accumulation in transgenic potato confers tolerance to various abiotic stresses

l-Ascorbic acid (Vitamin C, AsA) is an important component of human nutrition. Plants and several animals can synthesize their own ascorbic acid, whereas humans lack the gene essential for ascorbic acid biosynthesis and must acquire from their diet. In the present study, we developed transgenic potato (Solanum tuberosum L. cv. Taedong Valley) over-expressing l-gulono-γ-lactone oxidase (GLOase gene; NCBI Acc. No. NM022220), isolated from rat cells driven by CaMV35S constitutive promoter that showed enhanced AsA accumulation. Molecular analyses of four independent transgenic lines performed by PCR, Southern and RT-PCR revealed the stable integration of the transgene in the progeny. The transformation frequency was ca. 7.5% and the time required for the generation of transgenic plants was 6–7 weeks. Transgenic tubers showed significantly enhanced AsA content (141%) and GLOase activity as compared to untransformed tubers. These transgenics were also found to withstand various abiotic stresses caused by Methyl Viologen (MV), NaCl or mannitol, respectively. The T₁ transgenic plants exposed to salt stress (100 mM NaCl) survived better with increased shoot and root length when compared to untransformed plants. The elevated level of AsA accumulation in transgenics was directly correlated with their ability to withstand abiotic stresses. These results further demonstrated that the overexpression of GLOase gene enhanced basal levels of AsA in potato tubers and also the transgenics showed better survival under various abiotic stresses.     

Homology modeling and QSAR analysis of 1,3,4-thiadiazole and 1,3,4-triazole derivatives as carbonic anhydrase inhibitors

Carbonic anhydrase (CA) inhibitors are very interesting target for designing anticancer (hypoxic) and antiglaucoma drugs. In the present study, a 3D homology modeling of human carbonic anhydrase-IX (hCA-IX) isozyme, based upon the crystal structure of murine CA-XIVA (PDB CODE 1RJ5) was performed, as no experimental 3D structures are available. A homology model of hCA-IX was developed and validated. To explore the responsible physicochemical properties of 1,3,4-thiadiazole and 1,3,4-triazole derivatives for carbonic anhydrase inhibition, a quantitative structure activity relationship (QSAR) study was performed having hCA-II and hCA-IX inhibitory activity respectively. In hCA-II and hCA-IX inhibitory activities, four significant models with good correlations (> or = 0.945 & > or = 0.926) were obtained; two models (models 1 and 3) were selected based on statistical criterion. The QSAR study revealed that in case of hCA-II, overall increase in size and volume of molecule, introduction of electropositive surfaces might increase the inhibitory activity, whereas in case of hCA-IX, decreasing the hydrophobicity and introduction of electron releasing substituents might increase the hCA-IX inhibitory activity.     

Broad Spectrum Antiangiogenic Treatment for Ocular Neovascular Diseases

Pathological neovascularization is a hallmark of late stage neovascular (wet) age-related macular degeneration (AMD) and the leading cause of blindness in people over the age of 50 in the western world. The treatments focus on suppression of choroidal neovascularization (CNV), while current approved therapies are limited to inhibiting vascular endothelial growth factor (VEGF) exclusively. However, this treatment does not address the underlying cause of AMD, and the loss of VEGF''s neuroprotective can be a potential side effect. Therapy which targets the key processes in AMD, the pathological neovascularization, vessel leakage and inflammation could bring a major shift in the approach to disease treatment and prevention. In this study we have demonstrated the efficacy of such broad spectrum antiangiogenic therapy on mouse model of AMD.

Methods and Findings

Lodamin, a polymeric formulation of TNP-470, is a potent broad-spectrum antiangiogenic drug. Lodamin significantly reduced key processes involved in AMD progression as demonstrated in mice and rats. Its suppressive effects on angiogenesis, vascular leakage and inflammation were studied in a wide array of assays including; a Matrigel, delayed-type hypersensitivity (DTH), Miles assay, laser-induced CNV and corneal micropocket assay. Lodamin significantly suppressed the secretion of various pro-inflammatory cytokines in the CNV lesion including monocyte chemotactic protein-1 (MCP-1/Ccl2). Importantly, Lodamin was found to regress established CNV lesions, unlike soluble fms-like tyrosine kinase-1 (sFlk-1). The drug was found to be safe in mice and have little toxicity as demonstrated by electroretinography (ERG) assessing retinal and by histology.

Conclusions

Lodamin, a polymer formulation of TNP-470, was identified as a first in its class, broad-spectrum antiangiogenic drug that can be administered orally or locally to treat corneal and retinal neovascularization. Several unique properties make Lodamin especially beneficial for ophthalmic use. Our results support the concept that broad spectrum antiangiogenic drugs are promising agents for AMD treatment and prevention.     

Evaluation of Skeletal and Cardiac Muscle Function after Chronic Administration of Thymosin β-4 in the Dystrophin Deficient Mouse

Thymosin beta-4 (Tβ4) is a ubiquitous protein with many properties relating to cell proliferation and differentiation that promotes wound healing and modulates inflammatory mediators. We studied the effects of chronic administration of Tβ4 on the skeletal and cardiac muscle of dystrophin deficient mdx mice, the mouse model of Duchenne muscular dystrophy. Female wild type (C57BL10/ScSnJ) and mdx mice, 8–10 weeks old, were treated with 150 µg of Tβ4 twice a week for 6 months. To promote muscle pathology, mice were exercised for 30 minutes twice a week. Skeletal and cardiac muscle function were assessed via grip strength and high frequency echocardiography. Localization of Tβ4 and amount of fibrosis were quantified using immunohistochemistry and Gomori''s tri-chrome staining, respectively. Mdx mice treated with Tβ4 showed a significant increase in skeletal muscle regenerating fibers compared to untreated mdx mice. Tβ4 stained exclusively in the regenerating fibers of mdx mice. Although untreated mdx mice had significantly decreased skeletal muscle strength compared to untreated wild type, there were no significant improvements in mdx mice after treatment. Systolic cardiac function, measured as percent shortening fraction, was decreased in untreated mdx mice compared to untreated wild type and there was no significant difference after treatment in mdx mice. Skeletal and cardiac muscle fibrosis were also significantly increased in untreated mdx mice compared to wild type, but there was no significant improvement in treated mdx mice. In exercised dystrophin deficient mice, chronic administration of Tβ4 increased the number of regenerating fibers in skeletal muscle and could have a potential role in treatment of skeletal muscle disease in Duchenne muscular dystrophy.