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Park, Jin-Sup,Frost, Jennifer M.,Park, Kyunghyuk,Ohr, Hyonhwa,Park, Guen Tae,Kim, Seohyun,Eom, Hyunjoo,Lee, Ilha,Brooks, Janie S.,Fischer, Robert L.,Choi, Yeonhee National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.8
<P>The DEMETER (DME) DNA glycosylase initiates active DNA demethy-lation via the base-excision repair pathway and is vital for reproduction in Arabidopsis thaliana. DME-mediated DNA demethylation is preferentially targeted to small, AT-rich, and nucleosome-depleted euchromatic transposable elements, influencing expression of adjacent genes and leading to imprinting in the endosperm. In the female gametophyte, DME expression and subsequent genome-wide DNA demethylation are confined to the companion cell of the egg, the central cell. Here, we show that, in the male gametophyte, DME expression is limited to the companion cell of sperm, the vegetative cell, and to a narrow window of time: immediately after separation of the companion cell lineage from the germline. We define transcriptional regulatory elements of DME using reporter genes, showing that a small region, which surprisingly lies within the DME gene, controls its expression in male and female companion cells. DME expression from this minimal promoter is sufficient to rescue seed abortion and the aberrant DNA methylome associated with the null dme-2 mutation. Within this minimal promoter, we found short, conserved enhancer sequences necessary for the transcriptional activities of DME and combined predicted binding motifs with published transcription factor binding coordinates to produce a list of candidate upstream pathway members in the genetic circuitry controlling DNA demethylation in gamete companion cells. These data show how DNA demethylation is regulated to facilitate endosperm gene imprinting and potential transgenerational epigenetic regulation, without subjecting the germline to potentially deleterious transposable element demethylation.</P>
Fluidized Bed Culture System Using Microcarriers for Adherent Cells
Seohyun PARK,Jinwoo LEE,Duk Jae OH 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
Adherent cells are the most common type of animal cells. They are used in many fields such as cell therapy, regenerative medicine, and the production of biological products. Thus the demand for them is also growing significantly. But the typical stationery (two-dimensional, 2-D) cell culture system is not suitable for large-scale culturing of anchorage-dependent cells due to a limited surface area for cell attachment and lack of control for the culture environments. To overcome these issues, we used microcarriers with a high surface-to-volume. Most cell cultures using microcarriers are cultivated in bioreactor systems. However, the impeller of the bioreactor required to maintain homogenous culture conditions causes turbulent flows and high shear forces, which induce negative effects on the cells being cultured. Therefore, we tried to cultivate adherent cells using a non-impeller type 3-D culture system with liquid flows for floating and mixing of beads, fluidized bed. In the fluidized bed cell culture system, the cells well adhered to the microcarriers until the end of the culture, and the cells grew well. The fluidized bed cell culture system can be simply scaled up just by increasing the volume or size of the column so it can be an option for mass culture of adherent cells.
Biological Evaluation of Single-use Bioreactor System, CELBIC System, for Microcarrier Cell Culture
Seohyun PARK,Jinwoo LEE,Duk Jae OH 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.4
A typical stationary (2D) cell culture system is not suitable for large-scale culturing of adherent cells due to a limited surface area for cell attachment. It is also difficult to control the culture environment such as DO and pH. To overcome these issues, we used microcarriers that can significantly increase the area in which cells can attach within the specific culture space, and the CELBIC system, single-use bioreactor system, that can control the culture environment such as DO and pH. The CELBIC system operates by multi-directional rocking movement and can be stirred by the waves of the media. In addition, it is a system that can reduce risks of contamination in the cell culture and burdens such as cleaning and sterilization by using single-use bag. In order to apply to the CELBIC system without an impeller, we performed microcarrier cultures using human embryonic kidney cells (HEK293A) with various microcarriers and experimental conditions in Erlenmeyer flasks. Then we evaluated microcarrier cell cultures at working volume of 500 mL and 1 L in single-use bags using the CELBIC system. The Hillex II microcarrier showed the most stable cell growth and maintained cell adhesion to the microcarrier during cell culture in Erlenmeyer flasks. In the case of single-use bag using the CELBIC system, cells were well attached to the microcarriers, but it was difficult to maintain them after continuous agitation for cell culture. The CELBIC system has many advantages in the mass culture of suspension cells, but it was still difficult to apply to the mass culture of adherent cells. Therefore, it is necessary to further develop processes for continuously maintaining the cells attached to the microcarriers for expansion of adherent cells in the CELBIC system. It is also essential to study for biomaterials that can overcome the disadvantages of microcarriers in the CELBIC system.
Park, Seohyun,Kim, Jong Guk The Korean Society of Environmental Toxicology 2014 환경독성보건학회지 Vol.29 No.-
Objectives This study examined variations in the perceptions of dioxin risk among social groups defined by geographical living location, environmental education, and occupation. Dioxin risk perceptions were analyzed according to values, risk awareness, knowledge, and behavioral preferences. Methods A quasi-experimental survey was designed and conducted on individuals from seven experimental groups in Jeonju city, South Korea, including: people living near incineration facilities; people living far from incineration facilities; governmental experts; non-governmental organization members; office workers in developmental institutes or banks; students who were enrolled in environmental-related classes; and students who were enrolled in business-related classes. Results The results show variations among groups in values, awareness and behavioral preferences. Particular attention should be given to the result that groups with higher connectedness-to-nature values show higher willingness-to-act (WTA) for risk reduction. Result s can be summarized as follows. First, awareness is associated with one's geographical setting. Second, values and WTA behaviors are related to one's environmental-related education and occupation. Third, values are significantly related to WTA behaviors. Conclusions Different cultures, in terms of values or worldview, among groups influence their perceptions of dioxin risk and choices of risk reduction behaviors. It is important to consider values in communicating complicated long-term risk management involving public participation. Further research should be continuously conducted on the effects of multiple dimensions of values on one's WTA for risk reduction behaviors.