Of transgenic sheep and transgene can be expressed in almost all transgenic founders and their various tissues. Furthermore, methylation status of transgene and its effect on transgene expression, as well as relationship between integrant numbers and its expression were firstly investigated in lentivirusmediated transgenic sheep.The vector carries self-inactivating long terminal repeat (SIN LTR), internal ribosome entry site (IRES), mammalian selectable marker (puromycin) and woodchuck hepatitis virus posttranscriptional regulatory element (WPRE). EGFP gene is located at downstream of the CMV promoter. To generate pLEX-EGFP lentiviral particles, HEK293T cells were seeded in a 100-mm dish at a density of 60,000 cells/cm2 and co-transfected with pLEX-EGFP (12 mg) along with packaging plasmids (3.5 mg pMD2.G and 6 mg pPAX2) using Lipofectamine 2000 (Invitrogen) at a DNA/Lipofectamine ratio of 1 to 3. After 48 h transfection, the supernatant containing lentivirus particles was filtered through 0.45-mm syringe Linolenic acid methyl ester site filter and concentrated by ultracentrifugation (Beckman) at 50,000 g for 2 hour at 4uC. Precipitation was resuspended in phosphate buffered saline, aliquoted and stored at 280uC. Lentivirus titre was determined by infecting HEK293T cells with serial dilutions of concentrated lentivirus, and thereafter quantitated by counting the GFP fluorescent cells with flow cytometry (Becton, Dickinson and Company) post of 48 h infection as previous described [22]. The titre of pLEX-EGFP was approximately 36109 infectious units (IU) per ml in average.Lentivirus Injection and Embryo TransferTransgenic sheep were generated via injection of lentivirus into perivitelline space of the zygote. In brief, embryos were obtained from Xinjiang Merino Sheep which were approximately 2 years old and weighed at least 50 kg. Superovulation was MedChemExpress SPDP carried out within sheep breeding season from September to November and started on 3 days before oestrus induced by intramuscular injection of follicle stimulating hormone (FSH, Sigma-Aldrich). FSH was injected once per 12 hours lasting for 3 days. Briefly, twice injection of 40 IU FSH was performed on the first day, 30 IU on the second day and 20 IU on the last day. After 12 hour of oestrus, the donors were mated with rams and repeated mating another 12 hours later. At 60 hours, zygotes from mated donors were collected by flushing the umbrella of oviducts with warm phosphate buffered saline containing 2 FBS. Then they were removed from the PBS and cultured in SOF medium with 3 mg/ mL BSA at 38uC in 5 CO2. For lentivirus injection, around 50?00 pl of concentrated lentivirus with 36109 IU/ml titer were injected into perivitelline space of zygotes using a micromanipulator (ECLipse TE2000-U, Nikon). For embryo transfer, recipients were synchronized by the same treatment as donor ewes. Embryos injected at one or two cell stage were transferred to recipient ewes with mid-line laparotomy under general anaesthesia. During surgery, the reproductive tract was exposed and embryos were transferred into the oviduct of recipients using a displacement micropipette. To assess the expression of GFP in vitro, part of injected zygotes were cultured to blastula in SOF medium supplemented with 3 mg/ml BSA at 38uC in 5 CO2 and observed under UV-microscope.Materials and Methods AnimalsAll animals used for this study are Xinjiang Merino Fine Wool Sheep raised in the farm of Sheep Breeding and Reproduction Center. All studies carried out in shee.Of transgenic sheep and transgene can be expressed in almost all transgenic founders and their various tissues. Furthermore, methylation status of transgene and its effect on transgene expression, as well as relationship between integrant numbers and its expression were firstly investigated in lentivirusmediated transgenic sheep.The vector carries self-inactivating long terminal repeat (SIN LTR), internal ribosome entry site (IRES), mammalian selectable marker (puromycin) and woodchuck hepatitis virus posttranscriptional regulatory element (WPRE). EGFP gene is located at downstream of the CMV promoter. To generate pLEX-EGFP lentiviral particles, HEK293T cells were seeded in a 100-mm dish at a density of 60,000 cells/cm2 and co-transfected with pLEX-EGFP (12 mg) along with packaging plasmids (3.5 mg pMD2.G and 6 mg pPAX2) using Lipofectamine 2000 (Invitrogen) at a DNA/Lipofectamine ratio of 1 to 3. After 48 h transfection, the supernatant containing lentivirus particles was filtered through 0.45-mm syringe filter and concentrated by ultracentrifugation (Beckman) at 50,000 g for 2 hour at 4uC. Precipitation was resuspended in phosphate buffered saline, aliquoted and stored at 280uC. Lentivirus titre was determined by infecting HEK293T cells with serial dilutions of concentrated lentivirus, and thereafter quantitated by counting the GFP fluorescent cells with flow cytometry (Becton, Dickinson and Company) post of 48 h infection as previous described [22]. The titre of pLEX-EGFP was approximately 36109 infectious units (IU) per ml in average.Lentivirus Injection and Embryo TransferTransgenic sheep were generated via injection of lentivirus into perivitelline space of the zygote. In brief, embryos were obtained from Xinjiang Merino Sheep which were approximately 2 years old and weighed at least 50 kg. Superovulation was carried out within sheep breeding season from September to November and started on 3 days before oestrus induced by intramuscular injection of follicle stimulating hormone (FSH, Sigma-Aldrich). FSH was injected once per 12 hours lasting for 3 days. Briefly, twice injection of 40 IU FSH was performed on the first day, 30 IU on the second day and 20 IU on the last day. After 12 hour of oestrus, the donors were mated with rams and repeated mating another 12 hours later. At 60 hours, zygotes from mated donors were collected by flushing the umbrella of oviducts with warm phosphate buffered saline containing 2 FBS. Then they were removed from the PBS and cultured in SOF medium with 3 mg/ mL BSA at 38uC in 5 CO2. For lentivirus injection, around 50?00 pl of concentrated lentivirus with 36109 IU/ml titer were injected into perivitelline space of zygotes using a micromanipulator (ECLipse TE2000-U, Nikon). For embryo transfer, recipients were synchronized by the same treatment as donor ewes. Embryos injected at one or two cell stage were transferred to recipient ewes with mid-line laparotomy under general anaesthesia. During surgery, the reproductive tract was exposed and embryos were transferred into the oviduct of recipients using a displacement micropipette. To assess the expression of GFP in vitro, part of injected zygotes were cultured to blastula in SOF medium supplemented with 3 mg/ml BSA at 38uC in 5 CO2 and observed under UV-microscope.Materials and Methods AnimalsAll animals used for this study are Xinjiang Merino Fine Wool Sheep raised in the farm of Sheep Breeding and Reproduction Center. All studies carried out in shee.
