Donchan Choi

Seoul National University, Sŏul, Seoul, South Korea

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Publications (4)7.05 Total impact

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    ABSTRACT: To examine whether an ultrashort feedback mechanism of gonadotropin-releasing hormone (GnRH) operates at the level of gene transcription, we studied the effects of GnRH analogs on GnRH promoter activity and GnRH mRNA level in hypothalamic GT1–1 neuronal cells. Treatment of GT1–1 cells with buserelin, a GnRH agonist, or native GnRH for 24 h significantly decreased GnRH promoter activity and its mRNA level, whereas that with GnRH antagonists, antide or [D-Phe2,D-Ala6]-GnRH, showed no effect. The inhibitory effects of buserelin on GnRH gene transcription and GnRH mRNA level were dose-related, and a significant inhibition was observed in cells treated with buserelin at concentrations higher than 0.1 μM. Time-course experiments showed that significant decreases in GnRH promoter-driven luciferase activity and GnRH mRNA level were observed within 12 h and sustained up to 48 h. Moreover, treatment with GnRH agonist for 12 h significantly decreased the transcription rate of the mouse GnRH gene, as revealed by nuclear run-on transcription assay. The promoter analysis with the 5′-deletional constructs demonstrated that cis-acting elements important for GnRH autoregulation by GnRH agonist reside within −854 bp upstream from the transcription start site. These data clearly demonstrate that GnRH can exert autocrine regulation at the level of GnRH gene transcription.
    Full-text · Article · Nov 1997 · Molecular Brain Research
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    ABSTRACT: Galectin-1 is a member of beta-galactoside-binding lectins expressed in a variety of mammalian tissues. We report here that galectin-1 mRNA is abundantly expressed in the mouse reproductive organs such as the uterus and ovary. Uterine expression of galectin-1 mRNA is specifically regulated in the embryonic implantation process. Its expression increased at a high level on the fifth day post coitum (dpc 5) when embryos hatched into the endometrial epithelial cells. In the absence of embryos, however, galectin-1 expression in the mouse uterus decreased on dpc 5. In the delayed implantation mice, galectin-1 mRNA levels was augmented by the termination of the delay of implantation. Ovarian steroids progesterone and estrogen differentially regulated galectin-1 mRNA level in uterine tissues. Treatment with RU486, a progesterone receptor antagonist, blocked progesterone-induced galectin-1 mRNA level in uterine tissues of ovariectomized mouse. ICI182780, a pure estrogen receptor antagonist, clearly blocked the estrogen effect. Taken together, galectin-1 gene expression in the uterine tissues was regulated by ovarian steroids and this regulation correlated with the implantation process.
    Preview · Article · Oct 1997 · Molecular Reproduction and Development
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    Chanseob Shim · Donchan Choi · Hyuk Bang Kwon · Kyungjin Kim
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    ABSTRACT: Laminin may be involved in uterine re-organization and embryo attachment to the uterine wall during the peri-implantation period. In the present study using a competitive reverse transcription-polymerase chain reaction (RT-PCR), the precise expression patterns of laminin chain (A, B1, and B2)-specific mRNAs were examined in mouse uterine tissues during the peri-implantation period. Although Northern blot hybridization failed to detect laminin A chain mRNA in mouse uterus, RT-PCR analysis showed that laminin A chain mRNA was present even at the lower level compared with B1 and B2 chain mRNA levels. Competitive RT-PCR revealed that approximately 3 x 10(6), 3.6 x 10(7), and 4 x 10(8) copies of A, B1, and B2 chain mRNA transcripts were present in 1 microgram of total RNA isolated from the uterus. During pregnancy, the A chain mRNA level was significantly increased only from day 6 after post-hCG when embryo attachment and decidualization started. Elevated level of A chain mRNA was sustained thereafter. Laminin A chain mRNA synthesized at this period was mainly originated from stroma decidual cells. The discrete elevation of laminin A chain mRNA level was also observed after estrogen stimulation in the delayed implantation model. Estrogenic stimulation to ovariectomized, progesterone-treated pregnant mice resulted in about a three-fold increase of laminin A chain mRNA levels. In contrast to A chain mRNA, both B1 and B2 chain mRNA levels were insignificantly altered during the peri-implantation period and delayed implantation by an estrogenic stimulation. Taken together, our results for the first time demonstrate that: (1) laminin A chain mRNA as well as B chain mRNAs is expressed in mouse uterus, (2) its mRNA level is significantly increased along with implantation process, and (3) ovarian steroids, especially estrogen, are likely to be involved in the regulation of laminin gene expression in the uterus.
    Preview · Article · Oct 1997 · Molecular Reproduction and Development
  • Chanseob Shim · Dongho Geum · Donchan Choi · Kyungjin Kim
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    ABSTRACT: To precisely analyze the role of ovarian steroids in the regulation of laminin chain gene expression in mouse uterine tissues, the ovariectomized mouse model was used. Ovariectomized mice received a single injection of steroid hormones and total RNA was isolated from whole uterine tissues. Messenger RNA levels of each laminin chain (A, B1, and B2) were determined by competitive RT‐PCR procedures. Estradiol decreased mRNA levels of laminin B1 chain about two‐fold, and B2 chain rather moderately. Estradiol‐induced inhibition of laminin B1 and B2 chain mRNA levels were completely blocked by pretreatment with estrogen receptor antagonist tamoxifen. Estriol, a short acting estrogen which cannot induce hyperplastic responses of rodent uterine tissues, also showed an inhibitory effect on B1 and B2 chain mRNA levels, while estrone, an inactive estrogen, failed to influence either B chain mRNA levels. Effects of steroids on A chain mRNA level were quite different from those on B chains. Laminin A chain mRNA level was slightly increased by estradiol treatment, but negatively affected by progesterone. Progesterone treatment greatly increased both B chain mRNA levels, but slightly decreased A chain mRNA level compared to the control. The effect of progesterone on laminin chain‐specific mRNA levels was further increased by co‐injection of estradiol in a time‐dependent manner. Progesterone‐induced B1 and B2 chain mRNA transcription was inhibited by RU486, a synthetic anti‐progesterone/anti‐glucocorticoid. The present study demonstrates for the first time that steroids are able to regulate laminin gene expression in mouse uterine tissues, indicating that steroid‐regulated laminin gene expression is involved in uterine growth and probably differentiation.
    No preview · Article · Jan 1997 · Korean journal of biological sciences