A variety of genetically modified (GM) crops have been developed in Korea. In these crops, the resveratrol-enriched transgenic rice plant has moved ahead to generate the dossier for regulatory review process required for commercialization of GM crop. The resveratrol-enriched transgenic rice plant could be released to farmers for cultivation after national regulators have determined that it is safe for the environment and human health. Here we developed a PCR-based DNA marker based on flanking sequences of transgene for the discrimination of zygosity in resveratrol-enriched transgenic rice plant. This DNA marker will be useful for identifying of resveratrol-enriched transgenic rice plant, and can also be use to estimate transgene movement occurred by pollen transfer or seed distribution.

The β-carotene biofortified transgenic soybean was developed recently through Agrobacterium -mediated transformation using the recombinant PAC (Phytoene synthase-2A-Carotene desaturase) gene in Korean soybean (Glycine max L. cv. Kwangan). GM crops prior to use as food or release into the environment required risk assessments to environment and human health in Korea. Generally, transgenic plants containing a copy of T-DNA were used for stable expression of desirable trait gene in risk assessments. Also, information about integration site of T-DNA can be used to test the hypothesis that the inserted DNA does not trigger production of unintended transgenic proteins, or disrupt plant genes, which may cause the transgenic crop to be harmful. As these reasons, we selected four transgenic soybean lines expressing carotenoid biosynthesis genes with a copy of T-DNA by using Southern blot analysis, and analyzed the integration sites of their T-DNA by using flanking sequence analysis. The results showed that, T-DNA of three transgenic soybean lines (7-1-1-1, 9-1-2, 10-10-1) was inserted within intergenic region of the soybean chromosome, while T-DNA of a transgenic soybean line (10-19-1) located exon region of chromosome 13. This data of integration site and flanking sequences is useful for the biosafety assessment and for the identification of the β-carotene biofortified transgenic soybean.

The β-carotene biofortified transgenic soybean was developed recently through Agrobacterium-mediated transformation using the recombinant PAC (Phytoene synthase-2A-Carotene desaturase) gene in Korean soybean (Glycine max L. cv. Kwangan). GM crops prior to use as food or release into the environment required risk assessments to environment and human health in Korea. Generally, transgenic plants containing a copy of T-DNA were used for stable expression of desirable trait gene in risk assessments. Also, information about integration site of T-DNA can be used to test the hypothesis that the inserted DNA does not trigger production of unintended transgenic proteins, or disrupt plant genes, which may cause the transgenic crop to be harmful. As these reasons, we selected four transgenic soybean lines expressing carotenoid biosynthesis genes with a copy of T-DNA by using Southern blot analysis, and analyzed the integration sites of their T-DNA by using flanking sequence analysis. The results showed that, T-DNA of three transgenic soybean lines (7-1-1-1, 9-1-2, 10-10-1) was inserted within intergenic region of the soybean chromosome, while T-DNA of a transgenic soybean line (10-19-1) located exon region of chromosome 13. This data of integration site and flanking sequences is useful for the biosafety assessment and for the identification of the β-carotene biofortified transgenic soybean.

GM벼 OsCK는 벼 유래의 OsCK1 유전자를 벼에 형질전환 하여 벼흰잎마름병 및 벼도열병에 대한 저항성을 높게 한벼로 농촌진흥청에서 개발하였다. 형질전환 벡터의 구성은 양쪽 border (LB, RB) 상간에 2개의 MAR 염기서열이 서로 마주보는 형태로 위치하고 있으며, 제초제 저항성 유전자 PAT는 CaMV 35S promoter에 의하여 발현이 유도되고, 목표 유전자인 choline kinase (OsCK)는 actin promoter에 의하여 발현이 조절되며 left border 기준으로 역방향으로 배치되었다. 도입유전자 확인을 위하여 adaptor ligation PCR을 수행하였는데, MAR 영역에 위치하는 제한효소로 GM벼 genomic DNA를 절단한 후 adaptor를 붙였다. 염기서열 분석을 위하여 T-DNA의 양 말단에서 primer를 제작한 후 sequence 분석을 하였다. 분석한 결과, T-DNA의 right border 인근의 MAR sequence가 벼 genome의 10번 염색체 129971번 염기와 연결되어 있음을 확인하였다. Left 영역의 삽입위치는 이후 실시한 Illumina NGS 시스템을 이용하여 확인할 수 있었으며, GM 벼에는 2개의 T-DNA가 도입되었음을 알 수 있고, 첫 번째 T-DNA는 벼 10번 염색체 BAC클론 OSJNBa0014J14의 128947번째 염기와 129970째 염기에 위치하고 벼 genome 염기 1024 bp가 결실됨을 확인하였다. 이 과정에서 첫 번째 T-DNA left border와 첫 번째 MAR sequence 일부(370 bp)가 결실되었고 right border와 두 번째 MAR 영역 199 bp가 결실되었음도 확인하였다. 두 번째 T-DNA는 right border가 결실된 형태로 첫번째 T-DNA의 35S promoter 중간에 삽입되었음을 확인하였다.

Embryonic stem (ES) cells can self-renew and differentiate to various cells depending on the culture condition. Although ES cells are a good model for cell type specification and can be useful for application in clinics in the future, studies on ES cells have many experimental restraints including low transfection efficiency and transgene expression. Here, we observed that transgene expression after transfection was enhanced by treatment with histone deacetylse (HDAC) inhibitors such as trichostatin A, sodium butyrate, and valproic acid. Transfection was performed using conventional transfection reagents with a retroviral vector encoding GFP under the control of CMV promoter as a reporter. Treatment of ES cells with HDAC inhibitors after transfection increased population of GFP positive cells up to 180% compared with untreated control. ES cells showed normal expression of stem cell markers after treatment with HDAC inhibitors. Transgene expression was further enhanced by modifying transfection procedure. GFP positive cells selected after transfection were proved to have the stem cell properties. Our improved protocol for enhanced gene delivery and expression in mouse ES cells without hampering ES cell properties will be useful for study and application of ES cells.

Controllable transgenic expression systems in transgenic animal model are valuable to the development of therapeutic approaches in human medical fields. The aim of this study was to 1) produce a transgenic cloned dog using inducible tetracycline vector system, and 2) investigate whether the transgenic cloned dog could be induced the transgene expression using doxycycline (Doxy). Canine fetal fibroblasts were infected with retroviral vectors designed to express the enhanced green fluorescent protein (eGFP) gene under the control of tetracycline-inducible promoter. For somatic cell nuclear transfer (SCNT), nucleus of an in vivo matured oocyte was removed and an eGFP expressed cell cultured with 1 ㎍/㎖ of Doxy was injected. After electrical fusion and chemical activation, the reconstructed embryos were transferred to a recipient and pregnancy diagnosis was performed by ultrasonography. Experiment I evaluated the mean fluorescence intensity (MFI) of infected cells while the cells were cultured in the presence of 1 ㎍/㎖ of Doxy for 5 days, and then in the absence of Doxy for 7 days using fluorescence-activated cell sorter. Experiment II was designed to produce an eGFP controllable transgenic cloned dog via SCNT. For verification of transgenic dog, experiment III was performed Southern Blot analysis and observation in vivo regulation of eGFP expression in the cloned dog treated with 100 ㎎/㎏ of Doxy every 2 days for 2 weeks under ultraviolet light. In experiment IV, western blot was used to detect eGFP increase and decrease in skin tissues of transgenic dog under the presence or absence of Doxy. In the results of experiment I, the MFI for infected cells was rapidly increased to approximately 42.3 times after 3 day-treatment compared to pre-treatment and quickly decreased 3 days after ceasing the treatment. In experiment II, a total of 203 embryos were transferred to nine recipients and three pregnant delivered three pups (Tet-on eGFP 0, Tet-on eGFP 1, and Tet-on eGFP 2) by C-sec and Tet-on eGFP 2 among them is still alive. All cloned pups were genetically identical to the donor cell. Tet-on eGFP 2 showed an apparent in vivo eGFP expression on her body after Doxy administration in experiment III. The result of Sothern blotting showed that the transgene insertion was detected from the three cloned dogs and all organs of Tet-on eGFP 1. Experiment IV indicated that a robust eGFP expression in skin tissue of Tet-on eGFP 2 rapidly increased after Doxy treatment and gradually decreased to basal level on 9 weeks after ceasing the treatment. In conclusion, we report here for the first time an inducible transgenic system in canine species and it can stably induce the transgene expression at intended time. This study has demonstrated the capacity to generate transgenic model dog which could regulate the transgene and it would contribute to human medical research fields.