In the present study, using a MoMLV-based retrovirus vector, we successfully generated a new transgenic chicken line expressing high levels of hEPO. A replication-defective Moloney murine leukemia virus (MoMLV)-based vectors packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected beneath the blastoderm of non-incubated chicken embryos (stage X). One rooster was mated to wild-type hens to produce 748 G1 progeny. PCR analysis of blood samples from these progeny revealed that there were seven G1 transgenic offspring, corresponding to a 0.9% germline transmission rate. Subsequently, Southern blot analysis of the genomic DNA from three G1 transgenic chickens was carried out to verify the stable genomic integration and copy number of the transgene in the genome. Quantitative analyses of the blood samples taken from G1 transgenic chickens resulted in 4,150 ～ 10,823 IU/㎖ (34.6 ～ 90.2 ㎍/㎖) of hEPO in the blood. The biological activity of the recombinant hEPO in transgenic chicken serum was comparable to its commercially available counterpart. Red blood cell numbers were more than three-fold higher in the transgenic chickens compared to the non-transgenic chickens. Successful germline transmission of the transgene was also confirmed in G2 transgenic chicks produced from crossing G1 transgenic roosters with non-transgenic hens. We confirmed that 13 transgenic chicks of 45 G2 progeny, corresponding to a 28.9% germline transmission rate. These results will help establish a useful transgenic chicken model system for studies of embryonic development and for efficient production of transgenic chickens as bioreactors. This work was supported by the Bio-industry Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and by a grant from the Next-Generation BioGreen 21 Program (No. PJ011178), Rural Development Administration, Republic of Korea.

Many transgenic domestic animals have been developed to produce therapeutic proteins in the mammary gland. However, purification of therapeutic proteins from transgenic milk are very important for productivity of recombinant protein. Development of a knock-in vector system is needed to improve production of therapeutic proteins. In this study, we are develop Knock-in vector to express human Erythropoietin protein (hEPO) using Gluthathione S-transferase (GST) fusion system on mouse β-casein exon 3 locus. The knock-in vector consisted of the 5 homologous arm (1.02 kb), GST, PreScission protease site, hEPO cDNA, BGH polyA signal, CMV-EGFP, and 3homologous arm(1.81 kb). The analysis of nucleotide and amino acid sequence revealed that GST-hEPO mRNA is probably translated with the mouse β-casein sequence and the β-casein-GST-hEPO fusion protein is probably secreted by ER-Golgi pathway. After that, the hEPO protein can be cleaved to remove the GST from the fusion protein by PreScission protease during purification of recombinant protein. This knock-in vector may help to create transgenic mouse expressing human Erythropoietin protein via the endogenous expression system of the mouse β-casein gene in the mammary gland.

Effectiveness of transgene transfer into genome is crucially concerned in mass production of the bio-pharmaceuticals using genetically modified transgenic animals as a bioreactor. Recently, the mammary gland has been considered as a potential bioreactor for the mass production of the bio-pharmaceuticals, which appears to be capable of appropriate post-translational modifications of recombinant proteins. The mammary gland tissue specific vector system may be helpful in solving serious physiological disturbance problems which have been a major obstacle in successful production of transgenic animals. In this study, to minimize physiological disturbance caused by constitutive over-expression of the exogenous gene, we constructed new retrovirus vector system designed for mammary gland-specific expression of the hEPO gene. Using piggyBac vector system, we designed to express hEPO gene under the control of mammary gland tissue specific and lactogenic hormonal inducible goat β-casein or mouse Whey Acidic Protein (mWAP) promoter. Inducible expression of the hEPO gene was confirmed using RT-PCR and ELISA in the mouse mammary gland cells treated with lactogenic hormone. We expect the vector system may optimize production efficiency of transgenic animal and reduce the risk of global expression of transgene.

유즙 내에 들어있는 유용 단백질을 분리, 정제하였을 때 예상되는 경제적 가치 때문에 우 리는 유즙 내에 들어있는 재조합 hEPO 단백질을 추출하고 정제하려는 많은 시도를 하고 있다. 이러한 노력에도 불구하고 유즙 내에 들어있는 target 단백질의 정제가 매우 어렵고, 그 순도 역시 20%에 지나지 않는다. 우리는 hEPO 유전자를 가지고 있으며 유선에서 hEPO를 분비하는 형질전환 돼지를 생산 보유하고 있다. 그러나, 이들 형질전환 돼지들은 체내에 도입된 유전자의 발현에 의해 야기되는 적혈구 과다증 그리고 혈소판 감소증과 같 은 순환기의 문제가 유발되고 있다. 명백하게, 이러한 종류의 혈액학적 변화는 장기의 정상 적인 기능을 방해하며 형질전환 돼지의 갑작스런 죽음을 초래한다. 그러므로, 앞서 언급한 문제점들을 해결하기 위한 alternative한 방법이 필요하다. 현재 연구에서, 우리는 외인성 hEPO를 발현하는 돼지에서 비정상의 생리학적 증후에 관해서 실험하였으며 hEPO를 생산 하기 위한 alternative choice로서 형질전환 돼지 유래 세포의 배양 system을 제안하였다. 5마리의 F6 hEPO 형질전환 돼지와 4마리와 대조군으로 일반돼지(랜드레이스)를 국립축 산과학원 동물바이오공학과에서 사육 도축하고 순환 장기를 채취하였다. 형질전환 돼지 순 환기 조직(유선, 신장, 폐, 비장)을 계대 배양 후 hEPO mRNA의 발현을 RT-PCR 방법으로 분석하였다. 또한, 면역조직화학 염색법을 통해서 hEPO 형질전환돼지 순환 장기조직에서 발현되는 hEPO의 발현 양상을 분석한 결과로서 유선, 신장 및 폐 조직에서 hEPO의 발현 이 확인되었으나, hEPO 발현 양상이 모든 형질전환동물 조직에서 발현되는 경향을 보이지 는 않았다. 한편, 세포면역화학 분석법에서는 형질전환돼지 유래 세포의 배양 시 hEPO가 발현되고 있는 양상을 확인하였다. 또한, 형질전환 돼지와 일반돼지의 세포 증식률과 증식 속도는 신장 세포에서는 빠른 증식을 나타낸 반면, 폐와 비장 세포에서는 느린 증식률이 확 인되었다. 배양 후 지속적인 세포 증식과 세포의 생존성을 분석하기 위하여 Apoptosis를 TUNEL과 Annexin V를 이용한 방법으로 조사한 결과, 형질전환돼지 유래의 세포와 일반돼 지의 세포 사이에 유의적 차이는 발견하지 못했다. 이들의 결과들로서 본 연구에서는 형질 전환돼지를 생산하여 유용 단백질을 이용하고자 할 경우, 목적으로 하는 세포 뿐 만 아니라 형질전환가축 유래의 다양한 세포를 이용 할 수 있는 가능성을 시사하고 있다.

The production of transgenic animals using somatic cell nuclear transfer (SCNT) has been widely described. A critical problem in the production of transgenic animals is the uncontrolled constitutive expression of the foreign gene which occasionally results in serious physiological disorders in the transgenic animal. In this study, we designed three different expression vectors that express the hEPO gene. hEPO is a hormone produced by the kidney that promotes the formation of red blood cells by the bone marrow. For the in vitro production of transgenic embryos, the different expression vectors were transduced into holstein ear fibroblast cells, respectively, and GFP expressed donor cells were transferred into enucleated oocytes, and then the reconstructed SCNT embryos were developed into pre-implantation stage. From three replicates, GFP expressed 112 transgenic SCNT embryos were produced. When their cleavage rate and blastocyst rate were compared with non-transgenic SCNT embryos, the results were presented into 73.2% vs. 76.9% and 26.8% vs. 30.6%, respectively, there were no differences. Also, total cell number and ICM cell numbers of day 8 blastocysts were statistically not different between the transgenic SCNT groups (120.6±7.9 and 31.4±8.2) and control SCNT group (128.3±4.8 and 35.3±4.0). The GFP expression levels were presented consecutively high during the culture of transgenic SCNT embryos. By analysis of semi-quantitative RT-PCR, the relative expression levels of hEPO mRNA and pluripotent gene were determined. These results demonstrated that the hEPO expressed transgenic bovine embryos can be efficiently produced in vitro by SCNT technique, while their potential of cloned animal production have to be examined in further study.

We report here the production of transgenic chickens that can regulate human erythropoietin (hEPO) gene expression. The glycoprotein hormone hEPO is an essential for viability and growth of the erythrocytic progenitors. Retrovirus vector system used in this study has two features including tetracycline-controllable promoter and woodchuck hepatitis virus posttranscriptional regulator element (WPRE). The former is for to reduce the possibility of physiological disturbance due to constitutional and unregulated expression of hEPO gene in the transgenic chicken. The latter is for maximum expression of the foreign gene when we turn-on the gene expression. A replication-defective Moloney murine leukemia virus (MoMLV)-based vectors packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected beneath the blastoderm of non-incubated chicken embryos (stage X). Out of 325 injected eggs, 28 chicks hatched after 21 days of incubation and 16 hatched chicks were found to express the hEPO gene delivered by the vector. The biological activity of the recombinant hEPO in transgenic chicken serum was comparable to its commercially available counterpart. The recombinant hEPO in transgenic chicken serum had N- and O-linked carbohydrate simillar to that produced from in vitro cultured cells transformed with hEPO gene.

Our previous study showed that transgenic (TG) pigs harboring human EPO (hEPO) gene have been shown to have reproductive disorders, including low pregnancy rates, irregular estrus cycle and low little size. To investigate these reasons, we assessed estrus behavior (standing response) and plasma 17B-estradiol (E2) level, which partly reflect reproductive function, during the estrus cycles after synchronization and superovulation by hormone treatments. Then, we analysed blood composition and expression of hEPO gene in TG pigs. Pigs were injected with PG600. After 10 days, pigs were fed with Regumate porcine for 6 days. Blood samples were collected from jugular vein. Analysis of blood composition and E2 level were measured by Hemavet 950 and E2 ELISA kit, respectively. And, the expression of hEPO gene in reproductive organs was quantitated by real-time RT-PCR. The percentage of estrus behavior in TG was significantly decreased. Hematocrit (HCT), hemoglobin (Hb) concentration and red blood cell (RBC) number were significantly higher in TG than wild type (WT). On the other hand, high expression of hEPO gene in TG was observed in the mammary gland as well as in the uterus. Moreover, plasma E2 level was significantly higher in TG than WT. These results suggest that nonspecific expression of hEPO gene in the other organs of TG may affect blood composition and plasma E2 level, thereby causing reproductive disorders.

This study was conducted to examine the effect of IRES controlled reporter gene on screening and production of recombinant human erythropoietin (EPO) proteins from cultured CHO cells. The cDNA was cloned for EPO from human liver cDNA. Using site-directed mutagenesis, we generated recombinant human EPO (rhEPO) with two additional N-glycosylations (Novel erythropoiesis-stimulating protein: NESP). Wild type hEPO and NESP were cloned into expression vectors with GFP reporter gene under regulatory control of CMV promoter and IRES so that the vectors could express both rhEPO and GFP. The expression vectors were transfected to cultured CHO-K1 cells. Under microscopy, expression of GFP was visible. Using supernatant of the culture, ELISA assay, immunocytochemistry and in vitro assay using EPO dependant cell line were performed to estimate biological activity to compare the production characteristics (secretion levels, etc.) between rhEPO and NESP. The activity of NESP protein, obtained by mutagenesis, was described and compared with its rhEPO counterpart produced under same conditions. Although NESP had less secretion level in CHO cell line, the biological activity of NESP was greater than that of rhEPO. These results are consistent with previous researches. We also demonstrated that rhEPO and GFP proteins expressed simultaneously from transfected CHO cell line. Therefore we conclude that use of GFP reporter gene under IRES control could be used to screen and produce rhEPO in cultured CHO cells.

This study was conducted to compare the reproduction ability of the wild type boar and recombinant human erythropoietin (hEPO) transgenic boar semen. Ejaculated boar semen was analyzed by flow cytometry, Elisa and IVF methods. In experiment 1, flow cytometric analysis showed that the live sperm ratio of transgenic boar sperm significantly lower (P<0.05) than that of wild type boar after incubation at 20, 22, 24 and 26 hr. In experiment 2, the presence and levels of various cytokines (IL-6, IL-10 and TNF-α) to related animal reproduction in the seminal and blood plasma were examined using specific enzyme immunoassay. There was no significant difference between both groups. In experiment 3, the fertilizing capacity and developmental ability of both boar sperm were compared. The transgenic boar sperm had a significantly low capacity of penetration, sperm-zona binding, embryo development, and blastocyst formation compared to wild type sperm (P<0.05). These results suggest that transgenic boar sperm harboring hEPO gene has low sperm viability than wild type boar, and it is a reason to decrease of fertility and litter size.

The present study were performed to analysis the hematocrit and the red blood cells content into the blood plasma of the transgenic pigs harboring recombinent human erythropoietin gene (rhEPO). Mouse whey acidic protein (mWAP) linked to rhEPO gene was microinjected into pronuclei of porcine one-cell zygotes. After delivered of offspring, PCR analyses identified one mWAP-rhEPO transgenic founder offspring(F/sub 0/). The first generation of transgenic pig (F/sub 0/) harboring mWAP-hEPO appeared to be a male, and the second generation (F₁) pigs were made by natural mating of F/sub 0/ with domestic swine, and male and female transgenic pigs (F₁) were identified by PCR. The blood samples from transgenic and normal pigs were collected for 50 days during lactation and were counted the red blood cell (RBC) numbers and Hematocrit (HCT) content into the blood. The transgenic pigs expressing rhEPO in their blood gave rise to higher RBC numbers and HCT contents than control animals. rhEPO was secreted both in the blood and milk of genetically engineered pigs harboring rhEPO gene. Therefore, this study provides a model regarding the production of transgenic pig carrying hEPO transgene for biomedical research.