The purpose of this study was to develop an improved zona-free method of goat somatic cell nuclear transfer (SCNT) that has both ease of operation and efficiency. The main steps involved were: (1) optimization of in vitro oocyte maturation, (2) parthenogenetic activation of zona-free oocytes, (3) SCNT of zona-free anaphase II-telophase II (AII-TII) oocytes that subverted the need for long term UV-exposure of the oocytes, and (4) in vitro culture of groups of cloned embryos in wells in a highly efficient continuous serum-free embryo medium to the blastocyst stage before transfer to the recipients. Percentages of transgenic blastocyst production were 22.3 and 33.1% for adult and fetal cell lines, respectively. After transfer of cloned and transgenic blastocysts, 28.6 and 36.4% of the recipients were confirmed pregnant and 75 and 33.3% of the pregnancies resulted in the delivery of viable offspring, respectively. To our knowledge, this is the first report of successful live and survived birth of cloned and transgenic offspring through a whole procedure of in vitro oocyte maturation and embryo development to the blastocyst stage, and in this study the in vitro efficiencies of cloned and transgenic embryo production were higher than the available reports.
Purpose. The aim of this study was to investigate the in vitro gene delivery efficiency of poly[N-(2-aminoethyl)ethylene-imine](PAEEI), a polymer with a linear Polyethyleneimine (LPEI) backbone and with aminoethyl side groups that has two protonatable nitrogen atoms per monomer unit instead of one as in LPEI (an established gene delivery polymer). Method. PAEEI (Mn=4.5 kDa, Mw= 10 kDa) was synthesized by ring-opening polymerization of N-(2-(1’-aziridino)ethyl)formamide followed by hydrolysis of the amide groups. The buffering capacity of the resulting polymer was determined by acid-base titration and consequently the percentage of the protonated nitrogen atoms was calculated. Polyplexes were prepared separately in buffers with different ionic strength including Hepes buffered saline (150 mM NaCl) and Hepes buffered glucose (5% glucose) and their zeta-potential, hydrodynamic diameter and colloidal stability were measured. Transfection activity (and toxicity in Hela cells) of the polyplexes were done in HeLa, CHO and HEK293T cells. Cell incubations with polyplexes were done both in the presence and absence (HeLa cells) of serum. Results. PAEEEI showed two times more buffering capacity than LPEI. PAEEI-based Polyplexes had about the same size and zeta-potential as those of LPEI, with a higher colloidal stability in saline buffer in continuous particle size measurement. Their transfection activity was slightly higher than 22-kDa LPEI polyplexes whereas their toxicity profiles were similar in cell lines studied. The PAEEI polyplexes showed gene expression activity both in the presence and absence of serum. Conclusion. Paying attention to the fact that LPEI molecules with smaller sizes than 22 kDa show less transfection efficiency than LPEI 22, the effect of smaller size of PAEEI (10 kDa) on the gene delivery efficiency was compensated by its higher buffering capacity due to carrying more protonatable nitrogen per monomeric unit comparing with LPEI (22 kDa). Having slightly higher transfection efficiency and better colloidal stability than PEI-based systems, PAEEI is an attractive candidate for future in vivo gene delivery studies.This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.
The presence of a bacterial backbone in conventional eukaryotic expression plasmids may cause undesirable effects by triggering the immune responses in mammals and repression of episomal transgene expression. To avoid these problems, researchers have proposed the use of minicircle DNAs which are episomal vectors that have lost their bacterial backbone using a site-specific recombinase mediated recombination. In the present study, we have constructed a new minicircle DNA vector that carries an enhanced green florescent protein (EGFP) reporter gene using phage ΦC31 integrase-mediated recombination and homing endonuclease ISceI-mediated purification in E. coli. ΦC31 integrase expression was under the control of the araBAD promoter, whereas ISceI endonuclease was controlled by the tac promoter. This vector was transfected into CHO-K1 cells, which showed transient expression of EGFP up to 14 generations. Similar results were obtained upon transient transfection into HEK cells. In addition, PCR results on genomic DNA, demonstrated the EGFP-minicircle was episomal and did not integrate into the host genome. Our constructed parental plasmid expresses EGFP and could be used for the generation of episomal minicircle DNA with intent to carry out transient transfection of interested DNA fragments into the eukaryotic cells for various purposes.
This study has implication on Biotechnology researchers.Background: PhiC31 integrase is a DNA site-specific recombinase integrates DNA into the chromosomes between the two sites of attB and attP. Several pseudo attPs have been identified in mammalian genomes with critical features for long-term expression of transgene. In this manuscript, we report a novel intrinsic pseudo attP site named CHOL1 in the Chinese hamster genome implementing an inverse Polymerase Chain Reaction (IPCR). Objectives: Identification of pseudo attP site(s) of Tenecteplase cDNA integration in the genome of stable transformed CHO cell line. Materials and Methods: First, genome was extracted from a stable transformed CHO cell line expressing Tenecteplase. By creating of minicircle DNA in the last step, sequencing was performed. Results: We obtained one band. BLAST analysis of the respective sequence of inverse PCR band identified a pseudo attP site. Conclusions: Data demonstrated that the phiC31 integrase provides a suitable insertion site in the genome to express the gene of interest.
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