• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.223.2-223.2
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• 2015

Polyurethane acrylate (PUA) has been introduced to utilize as a mold material for sub-100 nm lithography as it provides advantages of stiffness for nanostructure formation, short curing time, flexibility for large area replication and transparency for relevant biomedical applications. Due to the ability to fabricate nanostructures on PUA, there have been many efforts to mimic extracellular matrix (ECM) using PUA especially in a field of tissue engineering. It has been demonstrated that PUA is useful for investigating the nanoscale-topographical effects on cell behavior in vitro such as cell attachment, spreading on a substrate, proliferation, and stem cell fate with various types of nanostructures. In this study, we have conducted surface modification of PUA films with micro/nanostructures on their surfaces using plasma treatment. In general, it is widely known that the plasma treated surface increases cell attachment as well as adsorption of ECM materials such as fibronectin, collagen and gelatin. Effect of plasma treatment on PUA especially with surface of micro/nanostructures needs to be understood further for its biomedical applications. We have evaluated the modified PUA film as a culture platform using adipose derived stem cells. Then, the behavior of stem cells and the level of adsorbed protein have been analyzed.

• BMB Reports
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• 제48권4호
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• pp.223-228
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• 2015

The Drosophila lymph gland is the hematopoietic organ in which stem-like progenitors proliferate and give rise to myeloid-type blood cells. Mechanisms involved in Drosophila hematopoiesis are well established and known to be conserved in the vertebrate system. Recent studies in Drosophila lymph gland have provided novel insights into how external and internal stresses integrate into blood progenitor maintenance mechanisms and the control of blood cell fate decision. In this review, I will introduce a developmental overview of the Drosophila hematopoietic system, and recent understandings of how the system uses developmental signals not only for hematopoiesis but also as sensors for stress and environmental changes to elicit necessary blood responses. [BMB Reports 2015; 48(4): 223-228]

• Biomolecules & Therapeutics
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• 제22권5호
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• pp.371-383
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• 2014

The nematode Caenorhabditis elegans (C. elegans) offers a unique opportunity for biological and basic medical researches due to its genetic tractability and well-defined developmental lineage. It also provides an exceptional model for genetic, molecular, and cellular analysis of human disease-related genes. Recently, C. elegans has been used as an ideal model for the identification and functional analysis of drugs (or small-molecules) in vivo. In this review, we describe conserved oncogenic signaling pathways (Wnt, Notch, and Ras) and their potential roles in the development of cancer stem cells. During C. elegans germline development, these signaling pathways regulate multiple cellular processes such as germline stem cell niche specification, germline stem cell maintenance, and germ cell fate specification. Therefore, the aberrant regulations of these signaling pathways can cause either loss of germline stem cells or overproliferation of a specific cell type, resulting in sterility. This sterility phenotype allows us to identify drugs that can modulate the oncogenic signaling pathways directly or indirectly through a high-throughput screening. Current in vivo or in vitro screening methods are largely focused on the specific core signaling components. However, this phenotype-based screening will identify drugs that possibly target upstream or downstream of core signaling pathways as well as exclude toxic effects. Although phenotype-based drug screening is ideal, the identification of drug targets is a major challenge. We here introduce a new technique, called Drug Affinity Responsive Target Stability (DARTS). This innovative method is able to identify the target of the identified drug. Importantly, signaling pathways and their regulators in C. elegans are highly conserved in most vertebrates, including humans. Therefore, C. elegans will provide a great opportunity to identify therapeutic drugs and their targets, as well as to understand mechanisms underlying the formation of cancer.

• 한국발생생물학회지:발생과생식
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• 제17권1호
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• pp.9-16
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• 2013

Coactivator-associated arginine methyltransferase 1 (CARM1) is included in the protein arginine methyltransferase (PRMT) family, which methylates histone arginine residues through posttranslational modification. It has been proposed that CARM1 may up-regulate the expression of pluripotency-related genes through the alteration of the chromatin structure. Mouse embryonic stem cells (mESCs) are pluripotent and have the ability to self-renew. The cells are mainly used to study the genetic function of novel genes, because the cells facilitate the transmission of the manipulated genes into target mice. Since the up-regulated methylation levels of histone arginine residue lead to the maintenance of pluripotency in embryos and stem cells, it may be suggested that CARM1 overexpressing mESCs elevate the expression of pluripotency-related genes in reconstituted embryos for transgenic mice and may resist the differentiation into trophectoderm (TE). We constructed a fusion protein by connecting CARM1 and 7X-arginine (R7). As a cell-penetrating peptide (CPP), can translocate CARM1 protein into mESCs. CPP-CARM1 protein was detected in the nuclei of the mESCs after a treatment of 24 hours. Accordingly, the expression of pluripotency-related genes was up-regulated in CPP-CARM1-treated mESCs. In addition, CPP-CARM1-treated mESC-derived embryoid bodies (EBs) showed an elevated expression of pluripotency-related genes and delayed spontaneous differentiation. This result suggests that the treatment of recombinant CPP-CARM1 protein elevates the expression of pluripotency-related genes of mESCs by epigenetic modification, and this protein-delivery system could be used to modify embryonic fate in reconstituted embryos with mESCs.

• Journal of Plant Biotechnology
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• 제33권3호
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• pp.195-207
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• 2006

Stem cells are the primordial, initial cells which usually divide asymmetrically giving rise to on the one hand self-renewals and on the other hand progenitor cells with potential for differentiation. Zygote (fertilized egg), with totipotency, deserves the top-ranking stem cell - he totipotent stem cell (TSC). Both the ICM (inner cell mass) taken from the 6 days-old human blastocyst and ESC (embryonic stem cell) derived from the in vitro cultured ICM have slightly less potency for differentiation than the zygote, and are termed pluripotent stem cells. Stem cells in the tissues and organs of fetus, infant, and adult have highly reduced potency and committed to produce only progenitor cells for particular tissues. These tissue-specific stem cells are called multipotent stem cells. These tissue-specific/committed multipotent stem cells, when placed in altered environment other than their original niche, can yield cells characteristic of the altered environment. These findings are certainly of potential interest from the clinical, therapeutic perspective. The controversial terminology 'somatic stem cell plasticity' coined by the stem cell community seems to have been proved true. Followings are some of the recent knowledges related to the stem cell. Just as the tissues of our body have their own multipotent stem cells, cancerous tumor has undifferentiated cells known as cancer stem cell (CSC). Each time CSC cleaves, it makes two daughter cells with different fate. One is endowed with immortality, the remarkable ability to divide indefinitely, while the other progeny cell divides occasionally but lives forever. In the cancer tumor, CSC is minority being as few as 3-5% of the tumor mass but it is the culprit behind the tumor-malignancy, metastasis, and recurrence of cancer. CSC is like a master print. As long as the original exists, copies can be made and the disease can persist. If the CSC is destroyed, cancer tumor can't grow. In the decades-long cancer therapy, efforts were focused on the reducing of the bulk of cancerous growth. How cancer therapy is changing to destroy the origin of tumor, the CSC. The next generation of treatments should be to recognize and target the root cause of cancerous growth, the CSC, rather than the reducing of the bulk of tumor, Now the strategy is to find a way to identify and isolate the stem cells. The surfaces of normal as well as the cancer stem cells are studded with proteins. In leukaemia stem cell, for example, protein CD 34 is identified. In the new treatment of cancer disease it is needed to look for protein unique to the CSC. Blocking the stem cell's source of nutrients might be another effective strategy. The mystery of sternness of stem cells has begun to be deciphered. ESC can replicate indefinitely and yet retains the potential to turn into any kind of differentiated cells. Polycomb group protein such as Suz 12 repress most of the regulatory genes which, activated, are turned to be developmental genes. These protein molecules keep the ESC in an undifferentiated state. Many of the regulator genes silenced by polycomb proteins are also occupied by such ESC transcription factors as Oct 4, Sox 2, and Nanog. Both polycomb and transcription factor proteins seem to cooperate to keep the ESC in an undifferentiated state, pluripotent, and self-renewable. A normal prion protein (PrP) is found throughout the body from blood to the brain. Prion diseases such as mad cow disease (bovine spongiform encephalopathy) are caused when a normal prion protein misfolds to give rise to PrP$^{SC}$ and assault brain tissue. Why has human body kept such a deadly and enigmatic protein? Although our body has preserved the prion protein, prion diseases are of rare occurrence. Deadly prion diseases have been intensively studied, but normal prion problems are not. Very few facts on the benefit of prion proteins have been known so far. It was found that PrP was hugely expressed on the stem cell surface of bone marrow and on the cells of neural progenitor, PrP seems to have some function in cell maturation and facilitate the division of stem cells and their self-renewal. PrP also might help guide the decision of neural progenitor cell to become a neuron.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1458-1460
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• 2008

Tissue engineering is an interdisciplinary field that utilizes the principles of engineering and life sciences toward the creation of biological substitutes. Traditionally, major components of tissue engineering are cells, scaffolds, growth factors and recently biomechanical aspects have been given much attention. A large number of studies have reported that mechanical signals are of particular interest in either encouraging or inhibiting cellular responses. In tissue engineering, cell adhesion is a very important step, because quality of adhesion may determine a cell fate in the future. Elasticity of cell-adhesive substrate is found critical in regulating stem cell differentiation. Cells exert different contractile forces for cell migration, depending on substrate mechanics. Though tissue engineering is very interactive with diverse expertise, for a breakthrough, principles of biomechanics in tissue and cell level needs to be fully understood.

• Molecules and Cells
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• 제45권10호
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• pp.695-701
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• 2022

Homeostatic regulation of meristematic stem cells accomplished by maintaining a balance between stem cell self-renewal and differentiation is critical for proper plant growth and development. The quiescent center (QC) regulates root apical meristem homeostasis by maintaining stem cell fate during plant root development. Cell cycle checkpoints, such as anaphase promoting complex/cyclosome/cell cycle switch 52 A2 (APC/C^CCS52A2), strictly control the low proliferation rate of QC cells. Although APC/C^CCS52A2 plays a critical role in maintaining QC cell division, the molecular mechanism that regulates its activity remains largely unknown. Here, we identified SCF^FBS1, a ubiquitin E3 ligase, as a key regulator of QC cell division through the direct proteolysis of CCS52A2. FBS1 activity is positively associated with QC cell division and CCS52A2 proteolysis. FBS1 overexpression or ccs52a2-1 knockout consistently resulted in abnormal root development, characterized by root growth inhibition and low mitotic activity in the meristematic zone. Loss-of-function mutation of FBS1, on the other hand, resulted in low QC cell division, extremely low WOX5 expression, and rapid root growth. The 26S proteasome-mediated degradation of CCS52A2 was facilitated by its direct interaction with FBS1. The FBS1 genetically interacted with APC/C^CCS52A2-ERF115-PSKR1 signaling module for QC division. Thus, our findings establish SCF^FBS1-mediated CCS52A2 proteolysis as the molecular mechanism for controlling QC cell division in plants.

• Molecules and Cells
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• 제46권7호
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• pp.441-450
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• 2023

β-Catenin (Ctnnb1) has been shown to play critical roles in the development and maintenance of epithelial cells, including the retinal pigment epithelium (RPE). Ctnnb1 is not only a component of intercellular junctions in the epithelium, it also functions as a transcriptional regulator in the Wnt signaling pathway. To identify which of its functional modalities is critically involved in mouse RPE development and maintenance, we varied Ctnnb1 gene content and activity in mouse RPE lineage cells and tested their impacts on mouse eye development. We found that a Ctnnb1 double mutant (Ctnnb1^dm), which exhibits impaired transcriptional activity, could not replace Ctnnb1 in the RPE, whereas Ctnnb1^Y654E, which has reduced affinity for the junctions, could do so. Expression of the constitutively active Ctnnb1^∆ex3 mutant also suppressed the development of RPE, instead facilitating a ciliary cell fate. However, the post-mitotic or mature RPE was insensitive to the loss, inactivation, or constitutive activation of Ctnnb1. Collectively, our results suggest that Ctnnb1 should be maintained within an optimal range to specify RPE through transcriptional regulation of Wnt target genes in the optic neuroepithelium.

• 생체재료학회지
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• 제22권4호
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• pp.337-345
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• 2018

Background: Human mesenchymal stem cells (hMSCs) are, due to their pluripotency, useful sources of cells for stem cell therapy and tissue regeneration. The phenotypes of hMSCs are strongly influenced by their microenvironment, in particular the extracellular matrix (ECM), the composition and structure of which are important in regulating stem cell fate. In reciprocal manner, the properties of ECM are remodeled by the hMSCs, but the mechanism involved in ECM remodeling by hMSCs under topographical stimulus is unclear. In this study, we therefore examined the effect of nanotopography on the expression of ECM proteins by hMSCs by analyzing the quantity and structure of the ECM on a nanogrooved surface. Methods: To develop the nanoengineered, hMSC-derived ECM, we fabricated the nanogrooves on a coverglass using a UV-curable polyurethane acrylate (PUA). Then, hMSCs were cultivated on the nanogrooves, and the cells at the full confluency were decellularized. To analyze the effect of nanotopography on the hMSCs, the hMSCs were re-seeded on the nanoengineered, hMSC-derived ECM. Results: hMSCs cultured within the nano-engineered hMSC-derived ECM sheet showed a different pattern of expression of ECM proteins from those cultured on ECM-free, nanogrooved surface. Moreover, hMSCs on the nano-engineered ECM sheet had a shorter vinculin length and were less well-aligned than those on the other surface. In addition, the expression pattern of ECM-related genes by hMSCs on the nanoengineered ECM sheet was altered. Interestingly, the expression of genes for osteogenesis-related ECM proteins was downregulated, while that of genes for chondrogenesis-related ECM proteins was upregulated, on the nanoengineered ECM sheet. Conclusions: The nanoengineered ECM influenced the phenotypic features of hMSCs, and that hMSCs can remodel their ECM microenvironment in the presence of a nanostructured ECM to guide differentiation into a specific lineage.

• Molecules and Cells
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• 제43권12호
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• pp.1011-1022
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• 2020

Cell type specification is a delicate biological event in which every step is under tight regulation. From a molecular point of view, cell fate commitment begins with chromatin alteration, which kickstarts lineage-determining factors to initiate a series of genes required for cell specification. Several important neuronal differentiation factors have been identified from ectopic over-expression studies. However, there is scarce information on which DNA regions are modified during induced pluripotent stem cell (iPSC) to neuronal progenitor cell (NPC) differentiation, the cis regulatory factors that attach to these accessible regions, or the genes that are initially expressed. In this study, we identified the DNA accessible regions of iPSCs and NPCs via the Assay for Transposase-Accessible Chromatin sequencing (ATAC-seq). We identified which chromatin regions were modified after neuronal differentiation and found that the enhancer regions had more active histone modification changes than the promoters. Through motif enrichment analysis, we found that NEUROD1 controls iPSC differentiation to NPC by binding to the accessible regions of enhancers in cooperation with other factors such as the Hox proteins. Finally, by using Hi-C data, we categorized the genes that directly interacted with the enhancers under the control of NEUROD1 during iPSC to NPC differentiation.