[Show abstract][Hide abstract] ABSTRACT: The meganuclease I-SceI has been effectively used to facilitate transgenesis in fish eggs for nearly a decade. I-SceI-mediated transgenesis is simply via embryo cytoplasmic microinjection and only involves plasmid vectors containing I-SceI recognition sequences, therefore regarding the transgenesis process and application of resulted transgenic organisms, I-SceI-mediated transgenesis is of minimal bio-safety concerns. However, currently no transgenic mammals derived from I-SceI-mediated transgenesis have been reported. In this work, we found that the native I-SceI molecule was not capable of facilitating transgenesis in mammalian embryos via cytoplasmic microinjection as it did in fish eggs. In contrast, the I-SceI molecule containing mammalian nuclear localization signal (NLS-I-SceI) was shown to be capable of transferring DNA fragments from cytoplasm into nuclear in porcine embryos, and cytoplasmic microinjection with NLS-I-SceI mRNA and circular I-SceI recognition sequence-containing transgene plasmids resulted in transgene expression in both mouse and porcine embryos. Besides, transfer of the cytoplasmically microinjected mouse and porcine embryos into synchronized recipient females both efficiently resulted in transgenic founders with germline transmission competence. These results provided a novel method to facilitate mammalian transgenesis using I-SceI, and using the NLS-I-SceI molecule, a simple, efficient and species-neutral transgenesis technology based on embryo cytoplasmic microinjection with minimal bio-safety concerns can be established for mammalian species. As far as we know, this is the first report for transgenic mammals derived from I-SceI-mediated transgenesis via embryo cytoplasmic microinjection.
[Show abstract][Hide abstract] ABSTRACT: Porcine skin is frequently used as a substitute of human skin to cover large wounds in clinic practice of wound care. In our previous work, we found that transgenic expression of human cytoxicT-lymphocyte associated antigen4-immunoglobulin (hCTLA4Ig) in murine skin graft remarkably prolonged its survival in xenogeneic wounds without extensive immunosuppression in recipients, suggesting that transgenic hCTLA4Ig expression in skin graft may be an effective and safe method to prolong xenogeneic skin graft survival. In this work, using a transgene construct containing hCTLA4Ig coding sequence under the drive of human Keratine 14 (k14) promoter, hCTLA4Ig transgenic pigs were generated by somatic nuclear transfer. The derived transgenic pigs were healthy and exhibited no signs of susceptibility to infection. The hCTLA4Ig transgene was stably transmitted through germline over generations, and thereby a transgenic pig colony was established. In the derived transgenic pigs, hCTLA4Ig expression in skin was shown to be genetically stable over generations, and detected in heart, kidney and corneal as well as in skin. Transgenic hCTLA4Ig protein in pigs exhibited expected biological activity as it suppressed human lymphocyte proliferation in human mixed lymphocyte culture to extents comparable to those of commercially purchased purified hCTLA4Ig protein. In skin grafting from pigs to rats, transgenic porcine skin grafts exhibited remarkably prolonged survival compared to the wild-type skin grafts derived from the same pig strain (13.33 ± 3.64 vs. 6.25 ± 2.49 days, P
Full-text · Article · Sep 2014 · Transgenic Research
[Show abstract][Hide abstract] ABSTRACT: Cytochomosome P450 enzymes (CYP) are heme-containing monooxygenases responsible for oxidative metabolism of many exogenous and endogenous compounds including drugs. The species difference of CYP limits the extent to which data obtained from animals can be translated to humans in pharmacodynamics or pharmacokinetics studies. Transgenic expression of human CYP in animals lacking or with largely reduced endogenous CYP counterparts is recognized as an ideal strategy to correct CYP species difference. CYP3A is the most abundant CYP subfamily both in human and mammals. In this study, we designed a microRNA-based shRNA (miR-shRNA) simultaneously targeting four members of mouse CYP3A subfamily (CYP3A11, CYP3A16, CYP3A41 and CYP3A44), and transgenic mice expressing the designed miR-shRNA were generated by lentiviral transgenesis. Results showed that the CYP3A expression level in transgenic mice was markedly reduced compared to that in wild type or unrelated miR-shRNA transgenic mice, and was inversely correlated to the miR-shRNA expression level. The CYP3A expression levels in transgenic offspring of different generations were also remarkably lower compared to those of controls, and moreover the inhibition rate of CYP3A expression remained comparable over generations. The ratio of the targeted CYP3A transcriptional levels was comparable between knockdown and control mice of the same gender as detected by RT-PCR DGGE analysis. These data suggested that transgenic miR-shRNA suppressed CYP3A expression in a dose-dependent and inheritable manner, and transcriptional levels of the targeted CYP3As were suppressed to a similar extent. The observed knockdown efficacy was further confirmed by enzymatic activity analysis, and data showed that CYP3A activities in transgenic mice were markedly reduced compared to those in wild-type or unrelated miR-shRNA transgenic controls (1.11±0.71 vs 5.85±1.74, 5.9±2.4; P<0.01). This work laid down a foundation to further knock down the remaining murine CYP3As or CYPs of other subfamilies, and a basis to generate CYP knockdown animals of other species.
[Show abstract][Hide abstract] ABSTRACT: Xenogeneic skin, especially porcine skin, has already been used to cover large wounds in clinic practice of wound care. Our previous data showed that transgenic expression of human cytoxic T-lymphocyte associated antigen4-immunoglobulin (hCTLA4Ig) in murine skin graft remarkably prolonged its survival in xenogeneic burn wounds without extensive immunosuppression in recipients, suggesting that transgenic hCTLA4Ig expression in skin graft may be an effective and safe method to prolong its survival in xenogeneic wounds for coverage. Lentiviral transgenesis provides an extremely efficient and cost-effective method to produce transgenic animals. However, tissue-targeted transgenic expression of biologically functional protein by lentiviral transgenesis is rarely reported. In this work, a recombinant lentiviral vector (LV), named FKCW in this article, was constructed by inserting a skin-specific hCTLA4Ig expression cassette consisting of keratin 14 (K14) promoter, hCTLA4Ig coding sequence and an intronic fragment. Its efficacy for transgenesis and skin-specific expression of bio-active hCTLA4Ig protein was tested using mice as models. The LV FKCW was readily to be packaged and concentrated to high titres (1.287-6.254 × 10(9) TU/ml) by conventional lentivirus package system. Using eggs collected from only five mated females having been subjected to conventional super-ovulation treatment, 8 hCTLA4Ig transgenic founder mice were generated with the concentrated FKCW vector, and transgenic founder per injected and transferred egg was 6.3%, which was nearly 9-fold higher than that for DNA micro-injection with a similar transgene construct in our previous work. The lentiviral transgenic hCTLA4Ig exhibited strictly skin-specific expression at a level comparable to or even slightly higher than that of transgenic hCTLA4Ig delivered by micro-injection in a similar cassette. Lentiviral transgenic hCTLA4Ig protein remarkably suppressed human lymphocyte proliferation in vitro to a degree comparable to that of commercially purchased purified hCTLA4Ig protein with defined activity at similar concentrations. Besides, lentiviral hCTLA4Ig transgenic mouse skin grafted into rat burn wounds exhibited remarkably extended survival compared to wild-type skin of the same strain (13.8 ± 3.8 vs. 6.8 ± 3.0 days), indicating that lentiviral transgenic hCTLA4Ig did inhibit immune rejection against xenogeneic skin graft in vivo. These results laid down the foundation to further efficiently generate transgenic pigs skin-specifically expressing bio-active hCTLA4Ig by lentiviral transgenesis, and provided a demonstration that transgenic animals with tissue-targeted expression of biologically functional protein can be efficiently produced using LV.
No preview · Article · Oct 2011 · Transgenic Research
[Show abstract][Hide abstract] ABSTRACT: Lentiviral transgenesis is now recognized as an extremely efficient and cost-effective method to produce transgenic animals. Transgenes delivered by lentiviral vectors exhibited inheritable expression in many species including those which are refractory to genetic modification such as non-human primates. However, epigenetic modification was frequently observed in lentiviral integrants, and transgene expression found to be inversely correlated with methylation density. Recent data showed that about one-third lentiviral integrants exhibited hypermethylation and low expression, but did not demonstrate whether those integrants with high expression could remain constant expression and hypomethylated during long term germline transmission. In this study, using lentiviral eGFP transgenic mice as the experimental animals, lentiviral eGFP expression levels and its integrant numbers in genome were quantitatively analyzed by fluorescent quantitative polymerase-chain reaction (FQ-PCR), using the house-keeping gene ribosomal protein S18 (Rps18) and the single copy gene fatty acid binding protein of the intestine (Fabpi) as the internal controls respectively. The methylation densities of the integrants were quantitatively analyzed by bisulfite sequencing. We found that the lentiviral integrants with high expression exhibited a relative constant expression level per integrant over at least seven generations. Besides, the individuals containing these integrants exhibited eGFP expression levels which were positively and almost linearly correlated with the integrant numbers in their genomes, suggesting that no remarkable position effect on transgene expression of the integrants analyzed was observed. In addition, over seven generations the methylation density of these integrants did not increase, but rather decreased remarkably, indicating that these high expressing integrants were not subjected to de novo methylation during at least seven generations of germline transmission. Taken together, these data suggested that transgenic lines with long term stable expression and no position effect can be established by lentiviral transgenesis.
No preview · Article · Oct 2010 · Transgenic Research