Each blot of transgenic lamb was calculated based on standard curve (Table.1). The highest copy number was identified in #12 lamb with 6 copies, followed by #5 lamb with 5 copies. The copy numbers of other transgenic sheep were around 2 to 3. Copy number derived from these two approaches was consistent (Fig. 2A).Analysis of EGFP Expression in Transgenic LambsThe expression of EGFP transgene was analyzed by direct fluorescence observation and Western blotting. At first, we observed embryos injected with EGFP lentivirus in blastula stage under fluorescent microscope (Fig. 3A, left panels). Approximately 80 embryos subjected to injection of lentiviral transgene were presented green fluorescence. Further, we observed green fluorescence in hoof, lip and horn of newborn transgenic lambs (Fig. 3A, middle panels) 
and continuously to maturity (Fig. 3A, right panels), which suggested that the GFP could be expressed persistently in transgenic sheep. Additionally, we anatomized the died lamb (#4 and #12) to investigate the distribution of GFP expression in inner organs (Fig. 4A). Notably, the most intense GFP fluorescence was observed in liver (Fig. 4B) and then in kidney (Fig. 4C), weak GFP fluorescence was observed in lung of #12 lamb (Fig. 4D). To further analyze the GFP expression, we AN 3199 supplier extracted the proteinsDiscussionConcurrent studies documented that lentiviral vectors had been successfully used to generate transgenic mice, rat, pig, cattle, chicken and nonhuman primate [8,14,25,26,27,28]. Different transgenic species generated by lentiviral vectors exhibited variability in gene transfer efficiency, transgene expression and epigenetic status. In this study, we generated 8 transgenic sheep by injection of lentiviral vector containing EGFP reporter into perivitelline space of ovine embryos with 17.4 transgenic efficiency, which was substantially higher than that of cattle produced using same method with rate of 7.5 (3/40) [16]. Previous reports on transgenic mice indicated that lentiviral injection Asiaticoside A site should be performed at one-cell stage of zygotes [22,29]. As the variegation of response on the effect of superovulation treatment among donors, it is difficult to maintain the collected sheep embryos in the same stage. In our studies, approximate 60Generation of Transgenic Sheep by Lentivirusof zygotes gained were on one-cell stage, and the other stayed on two-cell stage. Based on our in vitro study by injection of GFP into IVF embryos at different stages, there is 15755315 no significant difference of transgenic efficacy between one-cell and two-cell stage (76.9 versus 75.4 , data not shown). For the two lambs died postnatal, one (#4) was found with over-bend dorsal keel. The other lamb (#12) displayed the anorexia and diarrhea, which were the major causal that the non-transgenic sheep died from. The ratio of mortality was 25 in transgenic lambs, whereas the mortality of wild type investigated in the same reproductive term was 25 (9/ 36). There is no difference in mortality between transgenic sheep and non-transgenic sheep, which indicated lentiviral transgenesis has no obvious disturbance on development of transgenic sheep. Multiple copies of integration are substantially observed in transgenic animals produced by lentiviral transgenesis [27,30]. Based on our analysis of lentiviral integration, we found that lentiviral transgene was occurred in various tissues of transgenic sheep. Moreover, the southern blotting illustrated that most of the transgenic.Each blot of transgenic lamb was calculated based on standard curve (Table.1). The highest copy number was identified in #12 lamb with 6 copies, followed by #5 lamb with 5 copies. The copy numbers of other transgenic sheep were around 2 to 3. Copy number derived from these two approaches was consistent (Fig. 2A).Analysis of EGFP Expression in Transgenic LambsThe expression of EGFP transgene was analyzed by direct fluorescence observation and Western blotting. At first, we observed embryos injected with EGFP lentivirus in blastula stage under fluorescent microscope (Fig. 3A, left panels). Approximately 80 embryos subjected to injection of lentiviral transgene were presented green fluorescence. Further, we observed green fluorescence in hoof, lip and horn of newborn transgenic lambs (Fig. 3A, middle panels) and continuously to maturity (Fig. 3A, right panels), which suggested that the GFP could be expressed persistently in transgenic sheep. Additionally, we anatomized the died lamb (#4 and #12) to investigate the distribution of GFP expression in inner organs (Fig. 4A). Notably, the 
most intense GFP fluorescence was observed in liver (Fig. 4B) and then in kidney (Fig. 4C), weak GFP fluorescence was observed in lung of #12 lamb (Fig. 4D). To further analyze the GFP expression, we extracted the proteinsDiscussionConcurrent studies documented that lentiviral vectors had been successfully used to generate transgenic mice, rat, pig, cattle, chicken and nonhuman primate [8,14,25,26,27,28]. Different transgenic species generated by lentiviral vectors exhibited variability in gene transfer efficiency, transgene expression and epigenetic status. In this study, we generated 8 transgenic sheep by injection of lentiviral vector containing EGFP reporter into perivitelline space of ovine embryos with 17.4 transgenic efficiency, which was substantially higher than that of cattle produced using same method with rate of 7.5 (3/40) [16]. Previous reports on transgenic mice indicated that lentiviral injection should be performed at one-cell stage of zygotes [22,29]. As the variegation of response on the effect of superovulation treatment among donors, it is difficult to maintain the collected sheep embryos in the same stage. In our studies, approximate 60Generation of Transgenic Sheep by Lentivirusof zygotes gained were on one-cell stage, and the other stayed on two-cell stage. Based on our in vitro study by injection of GFP into IVF embryos at different stages, there is 15755315 no significant difference of transgenic efficacy between one-cell and two-cell stage (76.9 versus 75.4 , data not shown). For the two lambs died postnatal, one (#4) was found with over-bend dorsal keel. The other lamb (#12) displayed the anorexia and diarrhea, which were the major causal that the non-transgenic sheep died from. The ratio of mortality was 25 in transgenic lambs, whereas the mortality of wild type investigated in the same reproductive term was 25 (9/ 36). There is no difference in mortality between transgenic sheep and non-transgenic sheep, which indicated lentiviral transgenesis has no obvious disturbance on development of transgenic sheep. Multiple copies of integration are substantially observed in transgenic animals produced by lentiviral transgenesis [27,30]. Based on our analysis of lentiviral integration, we found that lentiviral transgene was occurred in various tissues of transgenic sheep. Moreover, the southern blotting illustrated that most of the transgenic.
