Novel Parallelized Electroporation by Electrostatic Manipulation of a Water-in-Oil Droplet as a Microreactor

Electroporation is the most widely used transfection method for delivery of cell-impermeable molecules into cells. We developed a novel gene transfection method, water-in-oil (W/O) droplet electroporation, using dielectric oil and an aqueous droplet containing mammalian cells and transgene DNA. When a liquid droplet suspended between a pair of electrodes in dielectric oil is exposed to a DC electric field, the droplet moves between the pair of electrodes periodically and droplet deformation occurs under the intense DC electric field. During electrostatic manipulation of the droplet, the local intense electric field and instantaneous short circuit via the droplet due to droplet deformation facilitate gene transfection. This method has several advantages over conventional transfection techniques, including co-transfection of multiple transgene DNAs into even as few as 10³ cells, transfection into differentiated neural cells, and the capable establishment of stable cell lines. In addition, there have been improvements in W/O droplet electroporation electrodes for disposable 96-well plates making them suitable for concurrent performance without thermal loading by a DC electric field. This technique will lead to the development of cell transfection methods for novel regenerative medicine and gene therapy.     

Understanding substrate misrecognition of hydrogen peroxide dependent cytochrome P450 from Bacillus subtilis

Cytochrome P450_BSβ, a H₂O₂-dependent cytochrome P450 catalyzing the hydroxylation of long-alkyl-chain fatty acids, lacks the general acid–base residue around the heme, which is indispensable for the efficient generation of the active species using H₂O₂. On the basis of the crystal structure of the palmitic acid bound form of cytochrome P450_BSβ, it was suggested that the role of the general acid–base function was provided by the carboxylate group of fatty acids. The participation of the carboxylate group of the substrate was supported by the fact that cytochrome P450_BSβ can catalyze oxidations of nonnatural substrates such as styrene and ethylbenzene in the presence of a series of short-alkyl-chain carboxylic acids as a dummy molecule of fatty acid. We refer to a series of short-alkyl-chain carboxylic acids as a “decoy molecule”. As shown here, we have clarified the crystal structure of the decoy-molecule-bound form and elucidated that the location of its carboxylate group is virtually the same as that of palmitic acid in the heme cavity, indicating that the carboxylate group of the decoy molecule serves as the general acid–base catalyst. This result further confirms that the role of the acid–base function is satisfied by the carboxylate group of the substrates. In addition, the structure analysis of the substrate-free form has clarified that no remarkable structural change is induced by the binding of the decoy molecule as well as fatty acid. Consequently, whether the carboxylate group is positioned in the active site provides the switching mechanism of the catalytic cycle of cytochrome P450_BSβ.     

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

Humans are unable to synthesize l-ascorbic acid (AsA), yet it is required as a cofactor in many critical biochemical reactions. The majority of human dietary AsA is obtained from plants. In Arabidopsis thaliana, a GDP-mannose pyrophosphorylase (GMPP), VITAMIN C DEFECTIVE1 (VTC1), catalyzes a rate-limiting step in AsA synthesis: the formation of GDP-Man. In this study, we identified two nucleotide sugar pyrophosphorylase-like proteins, KONJAC1 (KJC1) and KJC2, which stimulate the activity of VTC1. The kjc1kjc2 double mutant exhibited severe dwarfism, indicating that KJC proteins are important for growth and development. The kjc1 mutation reduced GMPP activity to 10% of wild-type levels, leading to a 60% reduction in AsA levels. On the contrary, overexpression of KJC1 significantly increased GMPP activity. The kjc1 and kjc1kjc2 mutants also exhibited significantly reduced levels of glucomannan, which is also synthesized from GDP-Man. Recombinant KJC1 and KJC2 enhanced the GMPP activity of recombinant VTC1 in vitro, while KJCs did not show GMPP activity. Yeast two-hybrid assays suggested that the stimulation of GMPP activity occurs via interaction of KJCs with VTC1. These results suggest that KJCs are key factors for the generation of GDP-Man and affect AsA level and glucomannan accumulation through the stimulation of VTC1 GMPP activity.     

Hepatic oxidoreduction-related genes are upregulated by administration of hydrogen-saturated drinking water

The effects of the administration of molecular hydrogen-saturated drinking water (hydrogen water) on hepatic gene expression were investigated in rats. Using DNA microarrays, 548 upregulated and 695 downregulated genes were detected in the liver after 4 weeks of administration of hydrogen water. Gene Ontology analysis revealed that genes for oxidoreduction-related proteins, including hydroxymethylglutaryl CoA reductase, were significantly enriched in the upregulated genes.     

Miso fermentation

Miso is a fermented food widely consumed in the Orient and is prepared from mold rice, soybeans and salt. About 13 million bushels of soybeans are made into miso each year, the annualproduction amounting to 974,000 metric tons.     

Deposition gene transfection using bioconjugates of DNA and thermoresponsive cationic homopolymer

A poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) homopolymer with both thermoresponsive and cationic characteristics was applied to a vector for use in deposition transfection. PDMAEMA with a molecular weight of 2.5 × 10(5) g mol(-1) was synthesized by photoinduced radical polymerization. Polyplexes approximately 750 nm in size were formed by mixing PDMAEMA with luciferase-encoding plasmid DNA. The polyplexes had a lower critical solution temperature (LCST) of approximately 30 °C. In addition, they exhibited excellent adsorption and durability on a polystyrene surface, as confirmed by a surface chemical compositional analysis. When HeLa cells and primary cells were cultured on a substrate coated with the polyplexes, high transgene expression and cell viability of more than 90% were obtained at low charge ratios (PDMAEMA/plasmid DNA ratio) ranging from 2 to 8. In addition, transgene expression was sustained for over 2 weeks post-transfection whereas decreased expression was observed 5 days post-transfection when the conventional solution-mediated transfection method was used. Thus, high and sustained transgene expression as well as high cell viability can be realized by using small amounts of PDMAEMA as a deposition transfection material.     

Electrostatically constrained alpha-helical peptide inhibits replication of HIV-1 resistant to enfuvirtide

Alpha-helical peptides, such as T-20 (enfuvirtide) and C34, derived from the gp41 carboxyl-terminal heptad repeat (C-HR) of HIV-1, inhibit membrane fusion of HIV-1 and the target cells. Although T-20 effectively suppresses the replication of multi-drug resistant HIV variants both in vitro and in vivo, prolonged therapy with T-20 induces emergence of T-20 resistant variants. In order to suppress the emergence of such resistant variants, we introduced charged and hydrophilic amino acids, glutamic acid (E) and lysine (K), at the solvent accessible site of C34. In particular, the modified peptide, SC34EK, demonstrates remarkably potent inhibition of membrane fusion by the resistant HIV-1 variants as well as wild-type viruses. The activity was specific to HIV-1 and little influenced by serum components. We found a strong correlation between the anti-HIV-1 activities of these peptides and the thermostabilities of the 6-helix bundles that are formed with these peptides. We also obtained the crystal structure of SC34EK in complex with a 36 amino acid sequence (N36) comprising the amino-terminal heptad repeat of HIV-1. The EK substitutions in the sequence of SC34EK were directed toward the solvent and generated an electrostatic potential, which may result in enhanced alpha-helicity of the peptide inhibitor. The 6-helix bundle complex of SC34EK with N36 appears to be structurally similar to that of C34 and N36. Our approach to enhancing alpha-helicity of the peptide inhibitor may enable future design of highly effective and specific HIV-1 inhibitors.     

Validation of the plasma half-life of 11alpha-deuterium cortisol as a sensitive index for the analysis of human 11beta-HSD2 activity in vivo

This study is concerned with validating the measurement of the plasma half-life of 11alpha-(2)H cortisol in an attempt to accurately assess the in vivo activity of 11beta-HSD2 in man. Oral administration of 5mg of cortisol-(13)C(4),(2)H(1) to a human subject after repeated ingestions of 130mg/day of glycyrrhetinic acid for 5 days resulted in a decrease in the rate constant of the cortisol-(13)C(4),(2)H(1) to cortisone-(13)C(4) conversion, a direct index reflecting 11beta-HSD2 activity. The reduced 11beta-HSD2 activity led to an increase in the elimination half-life of cortisol-(13)C(4),(2)H(1), indicating that the loss of 11alpha-(2)H is a sensitive in vivo means of assessing 11beta-HSD2 activity. A simultaneous oral administration of 3mg each of [1,2,4,19-(13)C(4),11alpha-(2)H]cortisol (cortisol-(13)C(4),(2)H(1)) and 11alpha-(2)H cortisol to another human subject confirmed the bioequivalency of the two labeled cortisols. The information obtained from the kinetic analysis of the 11beta-HSD2-catalyzed conversion of cortisol-(13)C(4),(2)H(1) to cortisone-(13)C(4) indicated that the elimination half-life of 11alpha-(2)H cortisol was a sensitive index of renal 11beta-HSD2 activity. The use of 11alpha-(2)H cortisol as a tracer appears to offer a significant advance in evaluating human 11beta-HSD2 activity in vivo.     

Entamoeba histolytica: the serine-rich gene polymorphism-based genetic variability of clinical isolates from Georgia

It is generally accepted that a majority of individuals infected by Entamoeba histolytica do not develop symptomatic disease. However, the parasite and the host factors contributing to the development of the disease, remain undetermined. It is also unclear why certain individuals develop extra-intestinal amebiasis without exhibiting apparent intestinal symptoms. An outbreak of amebic liver abscess in Tbilisi, Georgia in 1998-1999 suggested that the causative E. histolytica strain had an unusual propensity for extra-intestinal spread. To correlate the genetic differences with pathogenic potential of the parasite, we have examined the SREHP gene polymorphisms among Georgian E. histolytica isolates. Comparison of polymorphic patterns revealed the presence of several different genotypes of E. histolytica, thus preventing an association of a single genotype with hepatic disease, but supporting the previous finding of extensive genetic diversity among E. histolytica isolates from the same geographic origin.     

Species cohesion of an extremophyte (Carex angustisquama,Cyperaceae) in solfatara fields maintained under interspecific natural hybridization

Background and AimsHybridization is the main driver of plant diversification, and gene flow via hybridization has multifaceted effects on plant evolution. Carex angustisquama is an extremophyte that grows on soils heavily acidified by volcanism. Despite its habitat distinct from that of other species, this species is known to form interspecific hybrids, implying interspecific gene flow. It is crucial to verify the extent and direction of interspecific gene flow between C. angustisquama and closely related species to understand the evolutionary process of an extremophyte in solfatara fields.MethodsIn this study, expressed sequence tag–simple sequence repeat markers were utilized to infer the extent and direction of interspecific gene flow between C. angustisquama and closely related species.Key ResultsBayesian clustering and simulation analyses revealed that all individuals of the three hybrid species were classified into the first hybrid generation or first backcross to C. angustisquama; therefore, current interspecific gene flow is limited. Moreover, in the Bayesian inference of historical gene flow based on multispecies samples, the model that assumed no interspecific gene flow was the most strongly supported across all species pairs, including phylogenetically close but ecologically distinctive species pairs.ConclusionsOur results revealed that interspecific gene flow between C. angustisquama and its related species has been limited both currently and historically. Moreover, our results of Bayesian inference of historical gene flow indicated that extrinsic, rather than intrinsic, factors probably act as isolating barriers between Carex species, with hybrid breakdown via microhabitat segregation being the probable potential barrier. Overall, our findings provide insights into the evolutionary process of an extremophyte in solfatara fields and offer an important example of the mechanisms of diversification of the speciose genus Carex.