Oligonucleotide-mediated gene modification and its promise for animal agriculture

DNA oligonucleotides and plasmids perform equally as donors for targeted gene conversion

Site-specific gene modifications in cells are initiated by the introduction of exogenous DNA. We used a recently established cell assay to compare the ability of DNA donors to induce a single point mutation that converts a target gene encoding blue fluorescent protein (BFP) into expressing green fluorescent protein (GFP). In a chromosomal assay with cells stably expressing BFP, we showed that fluorescently labeled single-stranded oligonucleotides and a donor plasmid cotranscribing a red fluorescent protein provide similar efficiencies in triggering BFP-GFP conversions. In transient cotransfections, an isogenic donor plasmid comprising a nonfunctional GFP gene yielded a greater efficiency for the conversion of the BFP target gene than a nonisogenic donor, and all plasmid donors were superior to oligonucleotides.

Genetic modification through oligonucleotide-mediated mutagenesis. A GMO regulatory challenge?

In the European Union, the definition of a GMO is technology-based. This means that a novel organism will be regulated under the GMO regulatory framework only if it has been developed with the use of defined techniques. This approach is now challenged with the emergence of new techniques. In this paper, we describe regulatory and safety issues associated with the use of oligonucleotide-mediated mutagenesis to develop novel organisms. We present scientific arguments for not having organisms developed through this technique fall within the scope of the EU regulation on GMOs. We conclude that any political decision on this issue should be taken on the basis of a broad reflection at EU level, while avoiding discrepancies at international level.

Selection of antisense oligonucleotides for reversal of multidrug resistance in breast carcinoma cells

BACKGROUND

Multidrug resistance (MDR) is a major obstacle in cancer treatment. In the present study, six regions of the mdr1 gene associated with transcription control or translation initiation were selected as targets. Six antisense oligonucleotides (ASODN; AS1-AS6) complementary to the corresponding sequence of the mdr1 gene were synthesized to investigate whether or not blocking the transcription control sites with ASODN could reverse MDR and which ASODN had the best efficiency for reversing MDR in breast carcinoma cells.

METHODS

Forty-eight hours after transfection, mdr1 mRNA and P-glycoprotein (Pgp) were determined by RT-PCR, flow cytometry and Rhodamine 123 (Rh123) retention assay. The chemosensitivity of the treated cells was evaluated by MTT assay.

RESULTS

A significant reduction in expression of mdr1 mRNA and Pgp was found in four groups (AS1, AS3, AS5 and AS6), accompanying a dysfunction of Pgp. The lowest levels of mdr1 index and Pgp expression were observed in the AS6 group. MTT assay showed that a significant reduction of drug resistance was found in the four groups, especially in the AS6 group, which showed an 8.4-fold reduction in drug resistance for adriamycin and a 10.5-fold reduction in drug resistance for vinblastine.

DISCUSSION

These data suggest that the MDR phenotype of breast carcinoma cells could be reversed by ASODN complementary to the transcription control site or translation initiation region. AS6, which is complementary to the translation initiation codon (ATG) of mdr1 cDNA, has the best reversal efficiency.