RecET driven chromosomal gene targeting to generate a RecA deficient Escherichia coli strain for Cre mediated production of minicircle DNA

BACKGROUND: Minicircle DNA is the non-replicating product of intramolecular site-specific recombination within a bacterial minicircle producer plasmid. Minicircle DNA can be engineered to contain predominantly human sequences which have a low content of CpG dinucleotides and thus reduced immunotoxicity for humans, whilst the immunogenic bacterial origin and antibiotic resistance marker gene sequences are entirely removed by site-specific recombination. This property makes minicircle DNA an excellent vector for non-viral gene therapy. Large-scale production of minicircle DNA requires a bacterial strain expressing tightly controlled site-specific recombinase, such as Cre recombinase. As recombinant plasmids tend to be more stable in RecA-deficient strains, we aimed to construct a recA(- )bacterial strain for generation of minicircle vector DNA with less chance of unwanted deletions. RESULTS: We describe here the construction of the RecA-deficient minicircle DNA producer Escherichia coli HB101Cre with a chromosomally located Cre recombinase gene under the tight control of the araC regulon. The Cre gene expression cassette was inserted into the chromosomal lacZ gene by creating transient homologous recombination proficiency in the recA(- )strain HB101 using plasmid-born recET genes and homology-mediated chromosomal "pop-in, pop-out" of the plasmid pBAD75Cre containing the Cre gene and a temperature sensitive replication origin. Favourably for the Cre gene placement, at the "pop-out" step, the observed frequency of RecET-led recombination between the proximal regions of homology was 10 times higher than between the distal regions. Using the minicircle producing plasmid pFIXluc containing mutant loxP66 and loxP71 sites, we isolated pure minicircle DNA from the obtained recA(- )producer strain HB101Cre. The minicircle DNA preparation consisted of monomeric and, unexpectedly, also multimeric minicircle DNA forms, all containing the hybrid loxP66/71 site 5'-TACCGTTCGT ATAATGTATG CTATACGAAC GGTA-3', which was previously shown to be an inefficient partner in Cre-mediated recombination. CONCLUSION: Using transient RecET-driven recombination we inserted a single copy of the araC controlled Cre gene into the lacZ gene on the chromosome of E. coli recA(- )strain HB101. The resultant recA(- )minicircle DNA producer strain HB101Cre was used to obtain pure minicircle DNA, consisting of monomeric and multimeric minicircle forms. The obtained recA(- )minicircle DNA producer strain is expected to decrease the risk of undesired deletions within minicircle producer plasmids and, therefore, to improve production of the therapeutic minicircle vectors

Malta : language, literacy and identity in a Mediterranean island society

Available documentation for the early modern period indicates that the Malta harbor towns achieved literacy earlier than the countryside. The Maltese townsmen lived on a trading route, and it was necessary for them to learn the lingua franca, as the language of trade in the Mediterranean. The educated elite were able to acquire fluent speaking knowledge, as well as the ability to write, Tuscan (a dialect then in the process of becoming standard Italian), while continuing to employ their local Maltese ‘dialect’ on numerous occasions. By and large, the erosion of the position of Maltese as the subordinate language was an inevitable by-product of this development. The Maltese language was able to attain the function of a literary language in the nineteenth century but it had no standard orthography until 1931 and was only adopted as Malta’s official language in 1964.peer-reviewe

Transduction of fetal mice with a feline lentiviral vector induces liver tumors which exhibit an E2F activation signature

This article is available open access through the publisher’s website at the link below. Copyright @ 2014 The American Society of Gene & Cell Therapy.Lentiviral vectors are widely used in basic research and clinical applications for gene transfer and long-term expression; however, safety issues have not yet been completely resolved. In this study, we characterized hepatocarcinomas that developed in mice 1 year after in utero administration of a feline-derived lentiviral vector. Mapped viral integration sites differed among tumors and did not coincide with the regions of chromosomal aberrations. Furthermore, gene expression profiling revealed that no known cancer-associated genes were deregulated in the vicinity of viral integrations. Nevertheless, five of the six tumors exhibited highly significant upregulation of E2F target genes, of which a majority are associated with oncogenesis, DNA damage response, and chromosomal instability. We further show in vivo and in vitro that E2F activation occurs early on following transduction of both fetal mice and cultured human hepatocytes. On the basis of the similarities in E2F target gene expression patterns among tumors and the lack of evidence implicating insertional mutagenesis, we propose that transduction of fetal mice with a feline lentiviral vector induces E2F-mediated major cellular processes that drive hepatocytes toward uncontrolled proliferation culminating in tumorigenesis.ISF, DFG, the Kamea Scientific Foundation, the European Research Council, the Lillyan & Alfy Nathan, Barbara Fox Miller, and Wolfson Foundations

Gene and cell therapy for cystic fibrosis: From bench to bedside

Clinical trials in cystic fibrosis (CF) patients established proof-of-principle for transfer of the wild-type cystic fibrosis transmembrane conductance regulator (CFTR) gene to airway epithelial cells. However, the limited efficacy of gene transfer vectors as well as extra- and intracellular barriers have prevented the development of a gene therapy-based treatment for CF. Here, we review the use of new viral and nonviral gene therapy vectors, as well as human artificial chromosomes, to overcome barriers to successful CFTR expression. Pre-clinical studies will surely benefit from novel animal models, such as CF pigs and ferrets. Prenatal gene therapy is a potential alternative to gene transfer to fully developed lungs. However, unresolved issues, including the possibility of adverse effects on pre- and postnatal development, the risk of initiating oncogenic or degenerative processes and germ line transmission require further investigation. Finally, we discuss the therapeutic potential of stem cells for CF lung disease. (C) 2011 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved

Changer les relations dans la société de l'information : les effets des infrastructures de l'information sur les relations entre usagers professionnels

This article focuses on the use of new information networks in the business wold through their threefold impact : - the changes they spawn in the corporate organization ; - their impact on inter-firm relations ; - the limites of the use of electronic communications as a replacement for human interaction. Can this be considered as a whole new set of circumstances or merely a re-organization of existing ones. The article leaves this question open.Cet article met l'accent sur l'usage des nouveaux réseaux d'information dans le monde de l'entreprise à travers un triple impact : - les modifications qu'ils entraînent dans l'organisation des entreprises ; - les conséquences qu'ils ont sur les relations inter-entreprises ; - les limites de l'utilisation de communications électroniques en lieu et place des interactions humaines. S'agit-il d'une véritable nouvelle donne ou d'une réorganisation de l'existant ? L'article laisse cette question ouverte.Steinfield Charles, Caby Laurence, Coutelle Christophe. Changer les relations dans la société de l'information : les effets des infrastructures de l'information sur les relations entre usagers professionnels. In: Réseaux, volume 15, n°84, 1997. Les coûts de transaction. pp. 47-65