Induction of tumor angiogenesis by Slit-Robo signaling and inhibition of cancer growth by blocking Robo activity.

Slit is a secreted protein known to function through the Roundabout (Robo) receptor as a chemorepellent in axon guidance and neuronal migration, and as an inhibitor in leukocyte chemotaxis. Here we show Slit2 expression in a large number of solid tumors and Robo1 expression in vascular endothelial cells. Recombinant Slit2 protein attracted endothelial cells and promoted tube formation in a Robo1- and phosphatidylinositol kinase-dependent manner. Neutralization of Robo1 reduced the microvessel density and the tumor mass of human malignant melanoma A375 cells in vivo. These findings demonstrate the angiogenic function of Slit-Robo signaling, reveal a mechanism in mediating the crosstalk between cancer cells and endothelial cells, and indicate the effectiveness of blocking this signaling pathway in treating cancers.

The expression of classical swine fever virus structural protein E2 gene in tobacco chloroplasts for applying chloroplasts as bioreactors.

It has been reported that genes encoding antigens of bacterial and viral pathogens can be expressed in plants and are shown to induce protection antibodies. The structural protein E2 of classical swine fever virus (CSFV), which has been shown to carry critical epitopes, has been expressed in different systems. Here, we report the expression of CFSV E2 gene in tobacco chloroplasts. Mice immunized with leaf extracts elicited specific antibodies. This indicated that the expressed E2 proteins had a certain degree of immunogenicity. To our knowledge, this is the first report showing induction of protective antibody in response to classical swine fever virus (CSFV) by immunization with antigen protein E2 expressed in tobacco chloroplasts, which will open a new way to protection from CSFV by plant chloroplasts as bioreactors.

Stable expression of foot-and-mouth disease virus protein VP1 fused with cholera toxin B subunit in the potato (Solanum tuberosum).

The expression vector, pBI121CTBVP1, containing the fusion of the foot and mouth disease virus (FMDV) VP1 gene and the cholera toxin B subunit (CTB) gene was constructed by fused PCR and transferred into potato (Solanum tuberosum L.) by Agrobacterium-mediated transformation. Transformed plants were obtained by selecting on kanamycin-resistant medium strictly and regenerated. The transgenic plantlets were identified by PCR, Southern-blot and the production of fused protein was confirmed and quantified by Western-blot and ELISA assays. The results showed that the fused genes were expressed stablely under the control of specific-tuber patatin promoter. The expressed fused proteins have a certain degree of immunogenicity.

Recombination and expression of classical swine fever virus (CSFV) structural protein E2 gene in Chlamydomonas reinhardtii chroloplasts.

The expression of classical swine fever virus (CSFV) structural protein E2 in different vectors, which has been shown to carry critical epitopes, has been established. Here, we reported a Chlamydomonas reinhardtii chloroplast expression vector, P64E2, containing classical swine fever virus structural protein E2 gene, which was constructed and transferred to C. reinhardtii by biolistic bombardment method. The transformants were identified by PCR, Southern blotting, Western blotting after selecting on resistant media. ELISA quantification assay showed that the expressed E2 protein accumulated up to 1.5-2% of the total soluble protein. The results of the study on the immunological activity indicated that the protein E2 expressed in C. reinhardtii chloroplasts could elicit animal bodies to produce antibodies against protein E2.

Conserved molecular players for axon guidance and angiogenesis.

Neuronal guidance cues attract or repel axons and/or neurons and play important roles in the pathfinding of neuronal networks and the functioning of nervous system. Prominent among them are the families of ephrins, semaphorins, Slits and netrins and their cognate cell-surface receptors. Due to their biological significance, extensive research has been carried out in the last ten years or so. Angiogenesis is a cellular process of capillary sprouting and configuring of neovasculatures, which shares many developmental, anatomical, physiological and pathophysiological features with the neural counterparts. This review will summarize the emerging evidence indicating the common molecular mechanisms underlying both axon guidance (including neuronal migration) and angiogenesis for exquisite regulation of proper wiring of both systems.

[Advances of genome and secondary metabolism in Streptomyces].

Streptomycetes are Gram-positive, soil-inhabiting bacteria of Actinomycetales. These organisms exhibit complex life cycle and secondary metabolic pathways, and produce many economically important secondary metabolites. This review presented recent progress in Streptomycetes chromosome structure,genomics and the research of secondary metabolic pathway in Streptomyces. As more genomic sequences become available, it wiil be greatly facilitated to elucidate metabolic and regulatory networks and gain the over-production of desired metabolites or create the novel production of commercially important compounds.

A 28-kDa glycoprotein functions as a platelet ligand for P-selectin (CD62P).

P-selectin (CD62P) is expressed on activated platelets and on stimulated endothelial cells. It interacts with P-selectin glycoprotein ligand-1 (PSGL-1; CD162) for adhesion of activated platelets on leukocytes and for rolling of leukocytes on stimulated endothelial cells. Recently, resting and activated platelets have been shown to roll on endothelial P-selectin, indicating that platelets express (a) ligand(s) for P-selectin. Here we show that P-selectin specifically precipitated one 28-kDa glycoprotein from the whole cell lysates and the membrane lysates of human platelets in a Ca2+-dependent manner. Further, the purified 28-kDa molecule could inhibit the binding of P-selectin to human resting and activated platelets. In contrast, KPLI (a leukocyte adhesion blocking MoAb to PSGL-1) did not neutralize the binding of P-selectin to human platelets, even though it abolished the binding of P-selectin to human promyeloid HL-60 cells. Our results thus indicate that the 28-kDa glycoprotein may function as an important platelet ligand for P-selectin.

Down-modulation of heat shock protein 70 and up-modulation of Caspase-3 during schisandrin B-induced apoptosis in human hepatoma SMMC-7721 cells.

AIM: To investigate the effect of schisandrin B (Sch B) on proliferation and apoptosis of human hepatoma SMMC-7721 cells in vitro and regulation of Hsp70 and Caspases-3, 7, 9 expression by Sch B. METHODS: Human hepatoma cell line SMMC-7721 was cultured and treated with Sch B at various concentrations. Growth suppression was detected with MTT colorimetric assay. Cell apoptosis was confirmed by DNA ladder detection and flow cytometric analysis. The expression of Hsp70, Caspases-3, 7, 9 were analyzed by Western blot analysis. RESULTS: Sch B inhibited the growth of hepatoma SMMC-7721 cells in a dose-dependent manner, leading to a 50% decrease in cell number (LC50) value of 23.50 mg/L. Treatment with Sch B resulted in degradation of chromosomal DNA into small internucleosomal fragments, evidenced by the formation of a 180-200 bp DNA ladder on agarose gels. FCM analysis showed the peak areas of subdiploid at the increased concentration of Sch B. The results of Western bolt analysis showed that Hsp70 was down-regulated and Caspase-3 was up-regulated, while the activity of Caspases-7, -9 had no significant change. CONCLUSION: Sch B is able to inhibit the proliferation of human hepatoma SMMC-7721 cells and induce apoptosis, which goes through Caspase-3-dependent and Caspase-9-independent pathway accompanied with the down-regulation of Hsp70 protein expression at an early event.

A simple DNA extraction and rapid specific identification technique for single cells and early embryos of two breeds of Bos taurus.

In the process of nuclear transfer (NT), different cytoplasm from a donor cell and a recipient oocyte are mixed. However, it is unclear what effect the donor cytoplasm has upon the dedifferentiation of donor nuclei in enucleated ooplasm and upon subsequent production of live cloned offspring. Mitochondria are component parts of cytoplasm so the detection of mitochondrial DNA is helpful to reveal changes of donor cytoplasm in the NT reconstructed embryos. In this study, the experiments were designed to develop efficient DNA extraction techniques and specific primer pairs for mitochondrial DNA of Holstein and Chinese Yellow breeds in order to identify the changes of donor cytoplasm in early stage embryos. Firstly, by adding Triton X-100 and Taq DNA polymerase reaction buffer to the DNA extraction mixture, DNA was rapidly isolated from single diploid cells, single oocytes, early stage embryos and from single hairs. Secondly, two specific primer pairs for the two breeds were designed to detect the cytoplasmic DNA in a different amount of single cells and in early stage embryos. The results show that two specific fragments were successfully amplified from single somatic cells, single oocytes, parthenogenetic embryos and from NT reconstructed embryos. As a result, the techniques provide a powerful tool for studying the developmental mechanism in NT reconstructed embryos.

Transplastomic Plants Homoplasmic for Foreign Transgenes.

Scientists pay more and more attention to the research on plastid engineering for its following advantages foreign genes can be integrated site-specifically into the plastid genome (plastome) there are no position effects as experienced with random insertion of transgenes in nuclear transformation pollen-mediated dispersion of transgenes can be avoided because chloroplasts are maternally transmitted gene silencing does not occur in plastids and therefore transgene expression is stable in progeny of transplastomic plants and the high ploidy level of the plastome in leaf cells makes high levels of transgene expression feasible. At the same time, however, the highly polyploid plastome makes it difficult to get transplastomic plants homoplasmic for foreign transgenes. In this work, chloroplast transforming vector pTRCH205, which carries two psbA5'-nifH-psbA3'and Prrn-aadA-TpsbA cassettes flanked by plastid DNA sequence to target their insertion between psbA and trnK operons, was constructed. Plastid transformation of Nicotiana tabacum was carried out by the biolistic delivery of transforming plasmid pTRCH205 DNA into leaf cells. Integration of nifH and aadA by two homologous recombination events via the flanking ptDNA sequences, and selective amplification of the transplastomes on MS medium with high concentration of spectinomycin, yielded resistant cell lines. All the independent transplastomic lines were subjected to three additional rounds of regeneration and were subcultured for 6--10 times through stem sections on MS medium containing 500 mg/L spectinomycin, to obtain homoplasmic tissues. The results of PCR assay and Southern blot hybridization, probed with 0.9 kb BglII/SnaBI homologous fragment, indicated that foreign genes had been integrated into the plastomes of transgenic plants, which finally became homoplasmic for foreign transgenes.

The Effect of Buckyball C(60) Irradiation on the Fluidity of Erythrocyte Membranes.

The erythrocyte membranes were prepared from fresh human blood and 1,6-dipheny1-1,3,5-hexatriene (DPH) was used as a probe to detect their change of fluidity. It was found that after brief irradiation, C(60) remarkably increased the degree of fluorescence polarization of the DPH-labeled erythrocyte membrane, suggesting that C(60) irradiation could greatly reduce the fluidity of erythrocyte membrane. It was also found that the reduction of membrane fluidity was mainly due to the oxidation of sulfhydry groups in the membrane protein and the peroxidation of membrane unsaturated fatty acids.

Production of bacterial blight resistant lines from somatic hybridization between Oryza sativa L. and Oryza meyeriana L.

Novel bacterial blight (BB) resistance gene(s) for rice was (were) introduced into a cultivated japonica rice variety Oryza sativa (cv. 8411), via somatic hybridization using the wild rice Oryza meyeriana as the donor of the resistance gene(s). Twenty-nine progenies of somatically hybridized plants were obtained. Seven somatically hybridized plants and their parents were used for AFLP (amplified fragment length polymorphism) analysis using 8 primer pairs. Results confirmed that these plants were somatic hybrids containing the characteristic bands of both parents. The morphology of the regenerated rice showed characters of both O. sativa and O. meyeriana. Two somatic hybrids showed highest BB resistance and the other 8 plants showed moderate resistance. The new germplasms with highest resistance have been used in the rice breeding program for the improvement of bacterial blight resistance.

[Protein splicing and its application in protein engineering].

Protein splicing, which is an intein mediated posttranslational processing, involves a series of intramolecular cleavage-ligation reactions. Intein is an intervening polypeptide which can catalytic self-cleavage from a pre-protein accompanied by the concomitant joining of the two flanking polypeptides (the extein) through a peptide bond. Protein splicing not only enriches genetic theory of posttranslational processing, but also have wide application prospect.

[Studies of increasing the forward-mutation rate of UV irradiated Streptomyces sp. AP 19-1, an antibiotics producing strain].

UV irradiated spores of Streptomyces sp. AP 19-1 strain that can produce antibiotics were incubated at 27 degrees C, and 33 degrees C which is close to inhibiting growth temperature, respectively. The results showed that there were much more forward mutants, whose level of producing antibiotics is higher than that of original strain, among the offspring of UV irradiated spores grown at 33 degrees C, compared to that grown at 27 degrees C. The percentage of the forward mutants was 25.8 % at 27 degrees C and 58.1% at 33 degrees C. The progeny strains and the original strain were tested by RAPD using total DNA with 17 primers. It was demonstrated that more variations occurred in the chromosomal DNA of the progeny strains grown at 33 degrees C than in that at 27 degrees C. This method facilitates increasing the efficiency of induced mutagenesis in breeding and provides a new way to study the mechanisms of mutation formation in UV irradiated Streptomyces sp. cells.

Recombination and heterologous expression of allophycocyanin gene in the chloroplast of Chlamydomonas reinhardtii.

Heterogeneous expression of multiple genes in the nucleus of transgenic plants requires the introduction of an individual gene and the subsequent backcross to reconstitute multi-subunit proteins or metabolic pathways. In order to accomplish the expression of multiple genes in a single transformation event, we inserted both large and small subunits of allophycocyanin gene (apcA and apcB) into Chlamydomonas reinhardtii chloroplast expression vector, resulting in papc-S. The constructed vector was then introduced into the chloroplast of C. reinhardtii by micro-particle bombardment. Polymerase chain reaction and Southern blot analysis revealed that the two genes had integrated into the chloroplast genome. Western blot and enzyme-linked immunosorbent assay showed that the two genes from the prokaryotic cyanobacteria could be correctly expressed in the chloroplasts of C. reinhardtii. The expressed foreign protein in transformants accounted for about 2%-3% of total soluble proteins. These findings pave the way to the reconstitution of multi-subunit proteins or metabolic pathways in transgenic C. reinhardtii chloroplasts in a single transformation event.