• BMB Reports
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• 제31권5호
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• pp.453-458
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• 1998

Human thrombopoietin (hTPO) was expressed to high levels in insect cells using the baculovirus expression system. Full-length hTPO cDNA containing a native signal peptide sequence was amplified by PCR from a human fetal liver cDNA library and cloned into the Autographa californica nuclear polyhedrosis virus (AcNPV) expression vector. Immunoblot analysis with antiserum against hTPO indicated that an approximately 55 kDa protein was produced in recombinant AcNPV infected insect cells. Recombinant hTPO was produced 4-fold higher in Trichoplusia ni (Tn5) cells than in Spodoptera frugiperda (Sf9) cells. with most of the hTPO produced in Tn5 cells secreted into the culture medium. Addition of tunicamycin in the culture medium resulted in the reduction of the size of hTPO to 35-38 kDa, and most of the protein remained within the cell. These results suggest that N-glycosylation of hTPO is required for the secretion of the protein into the culture medium in insect cells. hTPO produced in insect cells induced proliferation and maturation of megakaryocyte progenitors, indicating that it is in a biologically active form.

• Journal of Microbiology and Biotechnology
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• 제8권6호
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• pp.553-559
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• 1998

cDNA of human thrombopoietin (hTPO) amplified by polymerase chain reaction from a cDNA library of human fetal liver was cloned. EPO-like domains ($hTPO_{153} \;or\; hTPO_{l63})\; of\; hTPO(hTPO_{332}$) were expressed in Escherichin coli using several kinds of expression systems, such as ompA secretion, thioredoxin fusion, and the $P_L$ and T7 expression systems. To obtain $hTPO_{153}$ in soluble form, $hTPO_{153}$ cDNA was fused in-frame behind the gene encoding ompA signal sequence and thioredoxin protein. When fused with either of the genes, $hTPO_{153}$ was not expressed to the detectable level. However, a high level expression of the EPO-like domain of hTPO was obtained using the PL and T7 expression system. $hTPO_{153} \;or\; hTPO_{l63} cDNA were subcloned into the pLex and pET-28a(＋) vectors under the control of the inducible$ P_L\;T_7$ promoter, respectively. Proteins expressed using pl.ex vector and pET-28a(＋) detected in insoluble forms with an expression level of about 14% and 9% of total cellular proteins, respectively, and the level of expression was rapidly diminished in 2 h after the maximum level of expression was reached.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.105-108
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• 2003

To enhance the performance of a serum-free medium (SFM) for human thrombopoietin (hTPO) production in suspension cultures of recombinant Chinese hamster ovary (rCHO) cells, several low-cost hydrolysates such as yeast hydrolysate (YH), soy hydrolysate, wheat gluten hydrolysate and rice hydrolysate were tested as medium additives. Among various hydrolysates tested, the positive effect of YH on hTPO production was most significant. When 5 g/L YH was added to SFM, the maximum hTPO concentration in batch culture was 40.41 ${\mu}g/mL$, which is 11.5 times higher than that in SFM without YH supplementation. This enhanced hTPO production in YH-supplemented SFM was obtained by the combined effect of enhanced $q_{hTPO}$ and increased culture longevity. In addition YH supplementation did not affect in vivo biological activity of hTPO. Taken together, the results obtained demonstrate the potential of YH as a medium additive for hTPO production in serum-free suspension cultures of rCHO cells.

• 생명과학회지
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• 제17권11호
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• pp.1497-1504
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• 2007

사람의 혈소판조절인자 (TPO)의 분비와 기능을 분석하기 위하여 사람 간 cDNA로부터 TPO cDNA를 분리하여 동물세포에서 재조합체를 생산하였다. 또한, 당쇄의 기능분석을 위하여 6개의 당쇄첨가부위를 Ala으로 치환하여 각각의 돌연변이체 재조합체도 생산하여 이들의 생리활성분석을 위하여 피하주사하여 혈소판의 증가여부를 분석하였으며, 체내 약동학검사를 위하여 꼬리 정맥에 재조합체를 주사하여 24시간까지 혈액을 채취하였다. Wild-type TPO는 효과적으로 분비하였으나, 크로닝에서 분석되어 진 116개 아미노산이 삭제된 돌연변이체는 배양상층으로 분비되지 않았다. N-linked 당쇄첨가 부위는 3번과 4번을 제외하고는 거의 비슷한 발현양상을 나타내었다. 특히 4번당쇄부위는 TPO의 분비에 중요한 역할을 하는 것으로 나타났다. 재조합체 10ng을 피하주사에 의하여 체내 혈소판이 유의적으로 증가하였으며, 5ng을 이용한 약동학 분석결과 1시간에 최대로 증가하였으며 그 이후 급격하게 감소하여 10시간에는 거의 존재하지 않았다. 따라서, 이러한 연구는 고 활성을 가지는 유전자 재조합체 TPO의 생산을 가능하게 하고, 또한 새로운 분자의 TPO를 가능하게 할 것으로 사료된다.

• Reproductive and Developmental Biology
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• 제32권3호
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• pp.159-166
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• 2008

본 연구는 vesicular stomatitis virus G glycoprotein (VSV-G)으로 피막이 형성되는 replication-defective MoMLV-based vector를 이용한 hTPO 헝질전환 닭의 생산에 관한 연구이다. 실험에 사용한 retrovirus vector의 구조는 hTPO 유전자의 발현 조절을 위해 internal promoter인 hCMV promoter를 이용하였으며 외래 유전자의 발현을 증가시키기 위해 woodchurk hepatitis virus posttranascriptional regulatory element (WPRE) 서열을 도입하였다. 재조합한 vector는 GP2 293 포장세포에 도입하여 virus를 생산하였으며 이 virus를 이용하여 감염시킨 여러 표적세포에서 hTPO의 발현과 생물학적 활성을 확인하였다. 재조합 hTPO의 생물학적 활성은 시판되고 있는 재조합 hTPO에 비해 우월한 것으로 확인되었다. hTPO 형질전환 닭의 생산을 위하여 1,000배 이상 고농도로 농축된 virus를 stage X 단계의 계란의 배반엽 층에 미세주입하여 대리난각 방법으로 배양하였다. 미세주입한 132개의 계란 중 21일 후에 11개의 계란에서 병아리가 부화하였으며 그중 4마리가 형질전환 개체로 확인되었다. 그러나 생산된 4마리 중 3마리가 부화 후 1개월 이내에 원인불명으로 사망하였다. 본 연구의 의의는 상업적 이용 가능성이 있는 생물학적 활성을 가진 사람의 cytokine 단백질의 대량 생산을 위한 생체 반응기로서의 형질전환 닭 개발의 시례를 제공하는데 있다.

• Journal of Microbiology and Biotechnology
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• 제9권3호
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• pp.318-322
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• 1999

A new baculovirus transfer vector (pPGP404) was constructed to increase the expression level of human thrombopoietin (hTPO) in insect cells. In pPGP404, hTPO was cloned next to the AcNPV polyhedrin-gp64 dual promoter and the leader sequence of hTPO was substituted with that of gp64. A recombinant baculovirus, AcPGP404, was constructed by using pPGP404 as a transfer vector. hTPO was expressed in AcPGP404-infected TN5 cells and it was observed that the expression levels of hTPO in TN5 cells increased three-fold ($6.0 {\mu}g/ml^{-1}$) compared to the level expressed under the control of the polyhedrin single promoter. These results indicate that the polyhedrin-gp64 dual promoter system would be useful for expression in large quantities of recombinant proteins in insect cells.

• 한국가금학회지
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• 제36권2호
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• pp.177-186
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• 2009

형질전환 동물에 있어서 외래 유전자의 조절되지 않은 과다 발현은 생리적인 부작용이나 독성을 나타내게 된다. 본 연구에서는 이러한 문제를 해결하기 위하여 외래 유전자 발현 조절 system인 tetracycline-inducible expression system(Tet system)을 도입하였다. 그러나 종래의 Tet system을 이용한 유전자 발현 조절은 system 자체의 구성 요소로 인한 미미한 leaky 현상 때문에 완벽하게 이루어지지 않는다. 본 연구에서는 보다 완벽한 외래 유전자의 발현 조절 system을 구축하기 위하여 rtTA 대신 진일보한 형태의 $rtTA2^SM2$를 도입하고 TRE 부분을 TRE-tight로 대체하였다. 확립된 retrovirus vector system을 이용하여 다양한 표적세포와 형질전환 닭으로부터 혈소판 생산의 일차적인 조절자이며, 조혈간세포의 생존과 증식에 있어서 매우 중요한 역할을 하는 human thrombopoietin(hTPO)를 생산하고자 하였다. In vitro 상의 연구에서, CEF 세포에서 발현되는 hTPO가 가장 높은 발현량과 발현 유도율을 나타내었으며, 상업적으로 판매되고 있는 hTPO나 다른 표적세포에서 생산된 hTPO에 비해 생물학적 활성이 가장 높은 것으로 확인되었다. 고농도로 농축한 재조합 retrovirus를 stage X단계의 계란의 배반엽 층에 미세주입하여 대리 난각 방법으로 배양한 결과, 미세주입한 138개의 계란 중 21일 후에 15개의 계란에서 병아리가 부화하였으며, 그 중 8마리가 형질전환 개체로 확인되었다. 이 형질전환 닭은 사료 1 g 당 0.5 mg의 doxycycline을 첨가하여 2주간 식이하였으며, 그 후 혈액을 채취하여 hTPO 농도를 측정한 결과 200ng/mL로 확인되었다. 또한 형질전환 개체 중 수컷의 정자에서 hTPO 유전자의 존재를 확인함으로써 germLine transmission의 가능성을 입증하였다. 이상의 연구 결과는 사람의 cytokine 단백질의 대량생산을 위한 생체반응기로서의 형질전환 닭의 생산 가능성을 제시한 데 의의가 있다.

• Reproductive and Developmental Biology
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• 제32권1호
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• pp.45-49
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• 2008

We have previously produced transgenic (TG) mice expressing the human lactoferrin (hLF), interleukin-10 (hIL-10), and thrombopoietin (hTPO) proteins in the milk. In this study, we examined whether simple crossbreeding between two kids of a single transgenic mouse can produce double transgenics co-expressing two human proteins.. The hLF male, and the hIL-10 male were crossbred with the hIL-10 and hTPO females, and the hTPO female, respectively. PCR analysis for genotyping showed 32%, 23% and 24% double transgenic rates for hLF/hIL-10, hLF/hTPO, and hIL-10/hTPO transgenes, respectively. We analyzed the expression levels of the human proteins from double transgenic mice and compared those with their single transgenic siblings. All double transgenic co-expressed two human proteins at comparable levels to singles', unless hTPO was not co-expressed: for hLF, 1.1 mg/ml in hLF/hIL-10, whereas 0.5 mg/ml in hLF/hTPO; for hIL-10, 4.1 mg/ml in hIL-10/hLF, whereas 1.4 mg/ml in hIL-10/hTPO. Ihe downregulation of hTPO to half level of singles' was observed in double transgenic mice. The possible reason why hTPO co-expressed might lead to down-regulation of another human protein was discussed. These results suggested that double transgenic generated by crossbreeding between two singles' could be useful system for bioreactor.

• Journal of Microbiology and Biotechnology
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• 제13권5호
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• pp.759-766
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• 2003

Recombinant Chinese hamster ovary (rCHO) cell lines expressing a high level of human thrombopoietin (hTPO) or its analog, TPO33r, were obtained by transfecting expression vectors into dihydrofolate reductase-deficient (dhfr) CHO cells and subsequent gene amplification in media containing stepwise increments in methotrexate (MTX) level such as 20, 80, and 320 nM. The parental clones with a hTPO expression level $>0.40\;{\mu}g/ml$ (27 out of 1,200 clones) and the parental clones with a TPO33r expression level $>0.20\;{\mu}g/ml$ (36 out of 400 clones) were subjected to 20 nM MTX. The clones that displayed an increased expression level at 20 nM MTX were subjected to stepwise increasing levels of MTX such as 80 and 320 nM. When subjected to 320 nM MTX, most clones did not display an increased expression level, since the detrimental effect of gene amplification on growth reduction outweighed its beneficial effect of specific TPO productivity ($q_{TPO}$) enhancement at 320 nM MTX. Accordingly, the highest producer subclones ($1-434-80^{*}$ for hTPO and $2-3-80^{*}$ for TPO33r), whose $q_{TPO}$ was 2- to 3-fold higher than that of their parental clones selected at 80 nM MTX, were isolated by limiting dilution method and were established as rCHO cel1 lines. The $q_{TPO}$ of $1-434-80^{*}\;and\;2-3-80^{*}\;was\;5.89{\pm}074\;and\;1.02{\pm}0.23\;{\mu}g/10^6$ cells/day, respectively. Southern and Northern blot analyses showed that the enhanced $q_{TPO}$ of established rCHO cell lines resulted mainly from the increased TPO gene copy number and subsequent increased TPO mRNA level. The hTPO and TPO33r produced from the established rCHO cell lines were biologically active in vivo, as demonstrated by their ability to elevate platelet counts in treated mice.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2001년도 춘계학술발표대회
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• pp.60-60
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• 2001

Human thrombopoietin (hTPO) is a cytokine that plays a central role in megakaryopoiesis by influencing on the development and maturation of megakaryocyte and platelet production. To induce hTPO production in the mammary gland, expression vector was constructed by combining the promoter of bovine beta-casein gene, cDNA of hTPO and neomycine resistance gene for transfection into fibroblasts. Bovine fibroblast cells derived from female ear skin were transfercted with the expression vector using Lipofectamine (Life Technology, NY). Transected cells resistant to G4l8 treatment (600 $\mu\textrm{g}$/$m\ell$) were recovered and colony formation was initiated at 13 days. The colonies with about 1 cm diameter were picked and analysed by PCR. Single transfected cells were individually transferred to enucleated oocytes. After electrofusion, the reconstructed embryos were exposed to calcium ionophore (5uM) for 5 min followed by treatment with 6-DMAP (2.5 mM) for 4h. The nuclear transfer embryos were cultured in CRlaa medium at 38.5C, 5% $CO_2$ for 7 days. Twenty three of 29 (79.3%) colonies were proved to be hTPO transfectants by PCR. The colonies were further passaged and used to produce transgenic embryos using nuclear transfer. Cleavage and developmental rates of reconstructed embryos to the blastocyst stage were 65.1% and 39.4%, respectively Of 22 blastocysts that developed from reconstructed embryos with the transfected cell, 20 embryos (90.9%) were positive for hTPO by using PCR analysis. The results suggest that somatic cell nuclear transfer is efficient for production of transgenic embryos.