Biomedical subjects

Young Jae Lee

Publications and source records attributed to Young Jae Lee.

11 recordsLinked to original sources

PubMed2006

A murine model for human sepiapterin-reductase deficiency.

Tetrahydrobiopterin (BH(4)) is an essential cofactor for several enzymes, including all three forms of nitric oxide synthases, the three aromatic hydroxylases, and glyceryl-ether mono-oxygenase. A proper level of BH(4) is, therefore, necessary for the metabolism of phenylalanine and the production of nitric oxide, catecholamines, and serotonin. BH(4) deficiency has been shown to be closely associated with diverse neurological psychiatric disorders. Sepiapterin reductase (SPR) is an enzyme that catalyzes the final step of BH(4) biosynthesis. Whereas the number of cases of neuropsychological disorders resulting from deficiencies of other catalytic enzymes involved in BH(4) biosynthesis and metabolism has been increasing, only a handful of cases of SPR deficiency have been reported, and the role of SPR in BH(4) biosynthesis in vivo has been poorly understood. Here, we report that mice deficient in the Spr gene (Spr(-/-)) display disturbed pterin profiles and greatly diminished levels of dopamine, norepinephrine, and serotonin, indicating that SPR is essential for homeostasis of BH(4) and for the normal functions of BH(4)-dependent enzymes. The Spr(-/-) mice exhibit phenylketonuria, dwarfism, and impaired body movement. Oral supplementation of BH(4) and neurotransmitter precursors completely rescued dwarfism and phenylalanine metabolism. The biochemical and behavioral characteristics of Spr(-/-) mice share striking similarities with the symptoms observed in SPR-deficient patients. This Spr mutant strain of mice will be an invaluable resource to elucidate many important issues regarding SPR and BH(4) deficiencies.

Alcohol Oxidoreductases↗

PubMed2006

Generation of activin receptor type IIB isoform-specific hypomorphic alleles.

Activin receptor type IIB (Acvr2b) mediates multiple signals for transforming growth factor-beta (TGF-beta) family members, including Activin, Nodal, Bmp7, Gdf1, Gdf3, Myostatin (Gdf8), and Gdf11. Mouse Acvr2b gene generates four transcriptional isoforms (Acvr2b(1-4)) via alternative splicing of two sequence domains located at the juxtaposition of the transmembrane domain. To investigate whether these splicing domains are essential for signal transduction of the Acvr2b receptor in vivo, we have generated a strain of mutant mice (Acvr2b(4/4)) which produce only the Acvr2b(4) isoform, which lacks both splicing domains. Most homozygous Acvr2b(4(neo)/4(neo)) mice, in which a neomycin-resistant cassette was inserted in Intron 4 displayed a mild form of anterior vertebral transformations. However, the penetrance of the vertebral defect was dramatically decreased when the neomycin-resistant cassette was deleted. These results suggest that the Acvr2b(4) isoform is capable of compensating for the deficiency of the other three isoforms. In the absence of its subfamily receptor Acvr2a, however, the development of Acvr2b(4/4) mice was arrested at the gastrulation stage, recapitulating the Acvr2a(-/-); Acvr2b(+/-) mutant phenotype. In this study, we demonstrate that this phenomenon is most likely due to the reduction in the expressed Acvr2b(4) levels rather than to the functional deficiency of the Acvr2b(4) isoform itself.

Activin Receptors, Type II↗

PubMed2005

Primary bone-derived cells induce osteogenic differentiation without exogenous factors in human embryonic stem cells.

We developed a new and efficient method for osteoblastic differentiation of human embryonic stem cells (hESCs) using primary bone-derived cells (PBDs). Three days after embryoid body (hEB) formation, cells were allowed to adhere to culture surface where PBDs were pre-plated and mitomycin C-treated in DMEM/F12 medium supplemented with 5% knockout serum replacement. As early as 14 days, mineralization and formation of nodule-like structures in cocultured hEBs were prominent by von Kossa and Alizarin S staining, and expressions of osteoblast-specific markers including bone sialoprotein, alkaline phosphates, osteocalcin, collagen 1, and core binding factor alpha1 by RT-PCR. In addition, FACS analysis revealed that over 19% of the differentiated cells expressed osteocalcin. These results suggest that PBDs not only have osteogenic effects releasing osteogenic factors as bone morphogenic protein (BMP) 2 and BMP 4 but also have exerted other effects, whether chemical or physical, for the differentiation of hESCs.

Adult↗

PubMed2004

Enhancement of re-closure capacity by the intra-amniotic injection of human embryonic stem cells in surgically induced spinal open neural tube defects in chick embryos.

To evaluate the re-closure promoting capacity of human embryonic stem (hES) cells injected into the amniotic cavity on spinal open neural tube defects (ONTDs) of chick embryos, neural tubes were opened at Hamburger and Hamilton stage 18 or 19 and the embryos were divided into three groups: a control group (no injection), a vehicle group, and a hES cell group (injection of 20,000 hES cells immediately after neural tube incision). On postoperative days 3, 5, and 7, ONTDs were significantly more re-closed in the hES cell group than in the other two groups. hES cells were present at the area in the process of re-closure, and covered ONTDs, but were not found in the re-closed area, suggesting indirect effects rather than cell replacement on the neural tissue.

Amnion↗

PubMed2004

Generation of dopaminergic neurons in vitro from human embryonic stem cells treated with neurotrophic factors.

The aim of this study was to produce dopaminergic neurons in vitro from human embryonic stem (hES) cells following treatment of various neurotrophic factors. MB03 hES cells were induced by retinoic acid (RA) or basic fibroblast growth factor (bFGF), which were further treated with brain derived neurotrophic factor (BDNF) or transforming growth factor (TGF)-alpha in each induction method during neuron differentiation days. At the final differentiation stage (21 days), all treatment groups revealed very similar levels (bFGF, 76-78%; RA, 70-74%) of mature neurons (anti-NF-200) in two induction methods irrespective of the addition of BDNF or TGF-alpha. In addition, immunostaining and HPLC analyses revealed higher levels of tyrosine hydroxylase (20+/-2.3%) and dopamine (265.5+/-62.8 pg/ml) in the bFGF- and TGF-alpha-treated hES cells than in RA- or BDNF-treated hES cells. These data are one of the first reports on the generation of dopaminergic neurons of hES cells in vitro. Also, our results indicate that TGF-alpha may be successfully used in the bFGF induction protocol and yield higher numbers of dopaminergic neurons from hES cells.

Cell Differentiation↗

PubMed2004

Establishment of human embryonic stem cell lines from frozen-thawed blastocysts using STO cell feeder layers.

BACKGROUND: Recently, human embryonic stem (hES) cells have become very important resources for basic research on cell replacement therapy and other medical applications. The purpose of this study was to test whether pluripotent hES cell lines could be successfully derived from frozen-thawed embryos that were destined to be discarded after 5 years in a routine human IVF-embryo transfer programme and whether an STO cell feeder layer can be used for the culture of hES cells. METHODS: Donated frozen embryos (blastocysts or pronuclear) were thawed, and recovered or in vitro developed blastocysts were immunosurgically treated. All inner cell masses were cultured continuously on an STO cell feeder layer and then presumed hES cell colonies were characterized. RESULTS: Seven and two cell lines were established from frozen-thawed blastocysts (7/20, 35.0%) and pronuclear stage embryos (2/20, 10.0%), respectively. The doubling time of hES cells on the immortal STO cell feeder layer was approximately 36 h, similar to that of cells grown using fresh mouse embryonic fibroblast (MEF) feeder conditions. Subcultured hES cell colonies showed strong positive immunostaining for alkaline phosphatase, stage-specific embryonic antigen-4 (SSEA-4) and tumour rejection antigen 1-60 (TRA1-60) cell surface markers. Also, the hES colonies retained normal karyotypes and Oct-4 expression in prolonged subculture. When in vitro differentiation of hES cells was induced by retinoic acid, three embryonic germ layer cells were identified by RT-PCR or indirect immunocytochemistry. CONCLUSIONS: This study indicates that establishment of hES cells from frozen-thawed blastocysts minimizes the ethical problem associated with the use of human embryos in research and that the STO cell feeder layer can be used for the culture of hES cells.

Alkaline Phosphatase↗

PubMed2004

B-cell translocation gene 2 (Btg2) regulates vertebral patterning by modulating bone morphogenetic protein/smad signaling.

Btg2 is a primary p53 transcriptional target gene which may function as a coactivator-corepressor and/or an adaptor molecule that modulates the activities of its interacting proteins. We have generated Btg2-null mice to elucidate the in vivo function of Btg2. Btg2-null mice are viable and fertile but exhibit posterior homeotic transformations of the axial vertebrae in a dose-dependent manner. Consistent with its role in vertebral patterning, Btg2 is expressed in the presomitic mesoderm, tail bud, and somites during somitogenesis. We further provide biochemical evidence that Btg2 interacts with bone morphogenetic protein (BMP)-activated Smads and enhances the transcriptional activity of BMP signaling. In view of the genetic evidence that reduced BMP signaling causes posteriorization of the vertebral pattern, we propose that the observed vertebral phenotype in Btg2-null mice is due to attenuated BMP signaling.

Alleles↗

PubMed2004

Effects of methanol extract of Uncariae Ramulus et Uncus on ibotenic acid-induced amnesia in the rat.

In the present study, we investigated the effects of Uncariae Ramulus et Uncus (UR) on learning and memory in the Morris water maze task and the central cholinergic system of rats with excitotoxic medial septum (MS) lesion. In the water maze test, the animals were trained to find a platform in a fixed position during 6 days and then received a 60-s probe trial in which the platform was removed from the pool on the 7th day. Ibotenic lesion of the MS showed impaired performance of the maze test and severe cell losses in the septohippocampal cholinergic system (SHC), as indicated by decreased choline acetyltransferase-immunoreactivity and acetylcholinesterase-reactivity in the hippocampus. Daily administrations of UR (100 mg/kg, i.p.) for 21 consecutive days produced significant reversals of ibotenic acid-induced deficit in learning and memory. These treatments also reduced the loss of cholinergic immunoreactivity in the hippocampus induced by ibotenic acid. These results demonstrated that impairments of spatial learning and memory may be attributable to degeneration of SHC neurons and that UR ameliorated learning and memory deficits partly through neuroprotective effects on the central acetylcholine system. Our studies suggest that UR may be useful in the treatment of Alzheimer's disease.

Acetylcholinesterase↗

PubMed2003

Genetically modified human embryonic stem cells relieve symptomatic motor behavior in a rat model of Parkinson's disease.

Embryonic stem (ES) cells have great potential as a cell source for cell replacement therapy. To investigate the possibility of using ES cells as a carrier of therapeutic gene(s), human ES cells (MB03) were co-transfected with cDNAs coding for tyrosine hydroxylase (TH) and GTP cyclohydrolase I (GTPCH I), then bulk-selected in the presence of neomycin and hygromycin-B. Successful transfection was confirmed by Western immunoblotting and RT-PCR. The genetically modified ES cells (bk-THGC) were found to produce a significant amount of L-dopa spontaneously and relieved apomorphine-induced asymmetric motor behavior by approximately 54% when grafted into striatum of 6-OHDA-denervated rat brain. The number of rotations, however, increased up to 176+/-18% in 6 weeks when PBS was used instead (sham-graft). Immunohistochemical stainings revealed that the grafted human ES cells survived and expressed TH for at least 6 weeks while the experiment was continued.

Animals↗

PubMed2003

Allele-specific methylation at the promoter-associated CpG island of mouse Copg2.

We previously reported that the mouse Copg2 (Coatomer Protein Subunit Gamma 2) gene was imprinted in the intraspecific F(1) hybrid mice between C57BL/6 and M. m. molossinus. In this study, methylation status at the promoter-associated CpG island and allele-specific expression pattern of Copg2 were investigated in the interspecific F(1) hybrid (C57BL/6 x M. spretus). We found that Copg2 was biallelically expressed in the interspecific F(1) hybrid, despite the presence of a differentially methylated region (DMR) in the CpG island. Therefore, paternal-specific methylation at the CpG island of Copg2 is not accompanied by allele-specific expression of Copg2 in the F(1) hybrid (C57BL/6 x M. spretus). The results suggest that the imprinted pattern of Copg2 expression is subject to variable epigenetic control systems of different mouse species. In addition, we identified a novel antisense transcript, Copg2AS2, at the Copg2 promoter region. The antisense transcript was expressed monoallelically, indicating that the differential expression of the antisense transcript is correlated with the differential methylation at the CpG island of Copg2.

Alleles↗

PubMed2003

Antimicrobial peptide LL-37 is upregulated in chronic nasal inflammatory disease.

OBJECTIVE: LL-37 is one of the antimicrobial peptides and the only member of the cathelicidin family identified so far in humans. We attempted to find a correlation between LL-37 peptide and inflammation of the nasal mucosa. MATERIAL AND METHODS: Nasal mucosa specimens were obtained from 15 chronic infective rhinitis patients and 6 normal controls. Immunohistochemical staining was used to examine the localization of LL-37 and reverse transcriptase polymerase chain reaction (RT-PCR) was used to determine the levels of LL-37, IL-1beta and IL-8 in tissue. RESULTS: LL-37 peptide was primarily localized in the surface of the epithelia, in the serous and mucous cells of the submucosal glands and in stromal inflammatory cells. The number of LL-37 immunoreactive cells in inflammatory nasal mucosa was significantly increased compared with normal nasal tissue. Using RT-PCR, LL-37 mRNA was detected in 3/6 normal turbinate samples but in all cases with inflammatory nasal tissues. IL-1beta and IL-8 transcripts exhibited a similar pattern to that of LL-37. CONCLUSIONS: We suggest that LL-37 is one of the antimicrobial peptides found in human nasal mucosa and that it participates in the innate immune system of the nasal mucosa.

Adult↗