Jung-Woong Kim

Control of phase separation behavior of PC/PMMA blends and their application to the gas separation membranes

Gas transport and thermodynamic properties for the blends of polycarbonate (PC) and polymethylmethacrylate (PMMA) were studied. To explore glass transition temperatures of blends and their phase separation temperatures due to a lower critical solution temperature, LCST, a type of phase boundary, transparent blend films that are miscible and do not contain solvent-induced PC crystals were prepared by controlling molecular weights of each component. The average value of interaction energy densities between PC and PMMA obtained from the phase boundaries and the equation of a state theory based on the lattice fluid model was 0.04 cal/cm3. This result confirmed that miscibility of PC and PMMA blends at equilibrium depends upon the molecular weights of components. Gas transport properties of miscible blends and immiscible blends having the same chemical components and composition but a difference in morphology were examined at 35°C and 1 atm for the gases N2 and O2. Permeability and apparent diffusion coefficients were ranked in the order of the immiscible blend having a domain–matrix structure > the immiscible blend having an interconnected structure > the miscible blend. These results might be related to the differences in the local chain motions that depend on the intermolecular mixing level.

Characterization of the interaction energies for polystyrene blends with various methacrylate polymers

The binary interaction energies between styrene and various methacrylates were determined from newly examined phase boundaries with lattice–fluid theory. Because the blends of polystyrene (PS) and poly(cyclohexylmethacrylate) (PCHMA) were only miscible at high molecular weights when the blends were prepared by solution casting from tetrahydrofuran, we examined the miscibility of other blends by changing the molecular weights of PS or methacrylate polymers. On the basis of the phase-separation temperature caused by the lower critical solution temperature, the miscibility of PS with the various methacrylates appeared to be in the order PCHMA > poly(n-propyl-methacrylate) (PnPMA) > poly(ethyl methacrylate) (PEMA) > poly(n-butyl-methacrylate) (PnBMA) > poly(iso-butyl-methacrylate) > poly(methyl methacrylate) (PMMA) > poly(tert-butyl methacrylate), and the branching of butylmethacrylate appeared to decrease the miscibility with PS. The interaction energies between PS with various methacrylates obtained from phase boundaries with lattice–fluid theory reached minimum value corresponding to the styrene/n-propylmethacrylate interaction. They were in the order PnPMA < PEMA < PCHMA < PnBMA < PMMA. The difference in the order of miscibility and interaction energies might be attributed to the terms related to the compressibility. The phase-separation temperatures calculated with the interaction energies obtained here indicated that the PS/PEMA and PS/PnPMA blends at high molecular weights were miscible, whereas the PS/PnBMA blends were immiscible at high molecular weights.

Tip60 regulates myoblast differentiation by enhancing the transcriptional activity of MyoD via their physical interactions

The progression of muscle differentiation is tightly controlled by multiple groups of transcription factors and transcriptional coregulators. MyoD is a transcription factor of the myogenic basic helix–loop–helix family required for the process of muscle cell differentiation. We now show that Tip60 is required for myoblast differentiation via enhancement of the transcriptional activity of MyoD. Knockdown of Tip60 in C2C12 cells leads to a lack of ability to switch from proliferating myoblasts to differentiated myotubes. Ectopic expression of Tip60 increased MyoD‐mediated luciferase activity on the myogenic regulatory gene, myogenin. We also found that Tip60 physically interacts with MyoD using its chromo‐ and Zn‐finger‐containing region, and that these protein interactions were required for the effective transcriptional activation of MyoD. Furthermore, a chromatin immunoprecipitation assay revealed that Tip60 recruits MyoD on the myogenin promoter, and Tip60 also increases the levels of acetylated histones H3 and H4 during myogenic differentiation. Taken together, these findings suggest that Tip60 is an important co‐activator for MyoD‐mediated myogenesis in mouse myoblast C2C12 cells.

Sox4-mediated caldesmon expression facilitates differentiation of skeletal myoblasts

Summary Caldesmon (CaD), which was originally identified as an actin-regulatory protein, is involved in the regulation of diverse actin-related signaling processes, including cell migration and proliferation, in various cells. The cellular function of CaD has been studied primarily in the smooth muscle system; nothing is known about its function in skeletal muscle differentiation. In this study, we found that the expression of CaD gradually increased as differentiation of C2C12 myoblasts progressed. Silencing of CaD inhibited cell spreading and migration, resulting in a decrease in myoblast differentiation. Promoter analysis of the caldesmon gene (Cald1) and gel mobility shift assays identified Sox4 as a major trans-acting factor for the regulation of Cald1 expression during myoblast differentiation. Silencing of Sox4 decreased not only CaD protein synthesis but also myoblast fusion in C2C12 cells and myofibril formation in mouse embryonic muscle. Overexpression of CaD in Sox4-silenced C2C12 cells rescued the differentiation process. These results clearly demonstrate that CaD, regulated by Sox4 transcriptional activity, contributes to skeletal muscle differentiation.

SPIN90 depletion and Microtubule Acetylation Mediate Stromal Fibroblast Activation in Breast Cancer Progression

Biomechanical remodeling of stroma by cancer-associated fibroblasts (CAF) in early stages of cancer is critical for cancer progression, and mechanical cues such as extracellular matrix stiffness control cell differentiation and malignant progression. However, the mechanism by which CAF activation occurs in low stiffness stroma in early stages of cancer is unclear. Here, we investigated the molecular mechanism underlying CAF regulation by SPIN90 and microtubule acetylation under conditions of mechanically soft matrices corresponding to normal stromal rigidity. SPIN90 was downregulated in breast cancer stroma but not tumor, and this low stromal expression correlated with decreased survival in breast cancer patients. Spin90 deficiency facilitated recruitment of mDia2 and APC complex to microtubules, resulting in increased microtubule acetylation. This increased acetylation promoted nuclear localization of YAP, which upregulated expression of myofibroblast marker genes on soft matrices. Spin90 depletion enhanced tumor progression, and blockade of microtubule acetylation in CAF significantly inhibited tumor growth in mice. Together, our data demonstrate that loss of SPIN90-mediated microtubule acetylation is a key step in CAF activation in low stiffness stroma. Moreover, correlation among these factors in human breast cancer tissue supports the clinical relevance of SPIN90 and microtubule acetylation in tumor development. Cancer Res; 77(17); 4710-22. ©2017 AACR.

DDR2 controls the epithelial-mesenchymal-transition-related gene expression via c-Myb acetylation upon matrix stiffening

Increasing matrix stiffness caused by the extracellular matrix (ECM) deposition surrounding cancer cells is accompanied by epithelial–mesenchymal transition (EMT). Here, we show that expression levels of EMT marker genes along with discoidin domain receptor 2 (DDR2) can increase upon matrix stiffening. DDR2 silencing by short hairpin RNA downregulated EMT markers. Promoter analysis and chromatin immunoprecipitation revealed that c-Myb and LEF1 may be responsible for DDR2 induction during cell culture on a stiff matrix. Mechanistically, c-Myb acetylation by p300, which is upregulated on the stiff matrix, seems to be necessary for the c-Myb-and-LEF1–mediated DDR2 expression. Finally, we found that the c-Myb–DDR2 axis is crucial for lung cancer cell line proliferation and expression of EMT marker genes in a stiff environment. Thus, our results suggest that DDR2 regulation by p300 expression and/or c-Myb acetylation upon matrix stiffening may be necessary for regulation of EMT and invasiveness of lung cancer cells.

Effect of dietary supplementation of bacteriophage on performance, egg quality and caecal bacterial populations in laying hens

Abstract 1. Bacteriophages (BP) have gained increasing attention as a treatment of bacterial infection for animals. However, the data pertaining to dietary application of BP for laying hens have been limited. 2. This study aimed to investigate the effect of dietary BP on laying performance, egg quality and caecal bacterial populations in laying hens. 3. The dietary BP used in this experiment was a mixture of individual BP targeting Salmonella gallinarum, Salmonella pullorum, Salmonella typhimurium, Salmonella enteritidis, Salmonella derby and Staphylococcus aureus. 4. A total of 360 Hy-Line Brown laying hens of 32 weeks of age were allotted to one of three dietary treatments with 6 replicates in a completely randomised design. The basal diet was prepared, and 0.4 or 0.8 g/kg BP mixture was supplemented to the basal diet. Diets were fed to hens for 8 weeks. 5. Laying performance and egg quality were not affected by dietary treatments. As inclusion levels of BP mixture in diets were increased, the DNA copy numbers for Salmonella spp. in the caecal contents decreased linearly, whereas the DNA copy numbers for Escherichia coli in the caecal contents increased linearly. 6. Results indicate that dietary supplementation of BP mixture decreases the target Salmonella spp. populations but increases Escherichia coli populations in the gastrointestinal tract of laying hens with little impact on laying performance and egg quality.

Histone deacetylase 1 (HDAC1) regulates retinal development through a PAX6-dependent pathway

Cell fate determination is tightly controlled by the expression of transcription factors and gene regulatory networks. PAX6 is a transcription factor containing a DNA-binding paired-box domain and homeobox domain that plays a key role in the development of the eye, brain, and pancreas. Here, we showed that histone deacetyltransferase 1 (HDAC1) is a novel binding partner of PAX6 in newborn mouse retinas. We also showed that HDAC1 specifically binds to the paired and transactivation domains of PAX6, and these physical interactions were required for effective repression of PAX6 transcriptional activity during retinal development. Furthermore, HDAC1 preferentially regulates the transcriptional activity of PAX6 when it binds to paired-domain (P6CON and chimeric pCON/P3) PAX6 responsive elements compared to homeodomain (pP3) PAX6 responsive elements. The repressive effect of HDAC1 on the transcriptional activity of PAX6 was reversed by knockdown of HDAC1 or treatment with an HDAC inhibitor, TSA. Taken together, these results show that HDAC1 binds PAX6 and that protein-protein interaction leads to transcriptional repression of PAX6 target genes during mouse retinal development.

Transcriptional regulatory network of SOX4 during myoblast differentiation

The construction of transcriptional regulatory networks of transcription factors (TFs) has become more important and attractive to understand the alterations of binding protein-dependent transcriptional activity that governs the changes in spatiotemporal expression of TF target genes required in various cellular processes. Therefore, identification of new inner modules including target genes and protein interactions involved in unveiled TF-based transcription networks is currently in the research spotlight. In this study, we reveal a possible SOX4-centered transcriptional network by the identification of novel binding partners and target genes of the TF SOX4 using various screening techniques. Lamin B2, barrier to autointegration factor 1, and apolipoprotein C-III were identified as novel interacting partners of SOX4 by yeast two-hybrid screening, and the genes encoding lysosomal-associated membrane protein 1, ubiquitin-conjugating enzyme E2S, and Map2k2 were identified as putative target genes of SOX4. Differently from the computational networks of TFs, we revealed a SOX4-centered physical network during myoblast differentiation. These results will provide opportunities to better understand the SOX4-centered transcriptional regulation network and TF-based specific gene expression in various cellular environments.

Effect of stocking density and sex on growth performance, meat quality, and intestinal barrier function in broiler chickens

ABSTRACT The objective of the current experiment was to investigate the effect of stocking density and sex on growth performance, meat quality, and intestinal barrier function in broiler chickens. The experiment was conducted in a completely randomized design with a 2 × 4 factorial arrangement consisting of sex and four different stocking densities in battery cages. A total of 540 1‐d‐old Ross 308 broiler chickens were allotted to one of eight treatments with five replicates. Within each sex, birds were raised at four different stocking densities of 15.2, 20.2, 25.3, or 30.4 birds/m2 from 1 to 28 d of age. Different stocking densities were achieved by raising a different number of birds per battery cage with identical floor size (0.76 m × 0.78 m). At the end of the experiment, two birds per replicate were euthanized by CO2 asphyxiation to collect tissue samples for further analyses. Results indicated that no interactions between sex and stocking density were observed for all measurements except for serum lipopolysaccharide (LPS) concentrations. Increasing stocking density decreased (linear, P < 0.01) body weight gain and feed intake, but had no negative effects on meat quality. Trans‐epithelial electrical resistance values, a measure of intestinal permeability, were decreased (linear, P < 0.01) with increasing stocking density, regardless of sex. Accordingly, serum LPS concentrations were increased (linear, P < 0.01) with increasing stocking density. However, increasing stocking density increased serum LPS concentrations in male broiler chickens, but had no effects on female broiler chickens, showing an interaction (P < 0.01). The expression of zonula occludens‐1 (ZO‐1) and junctional adhesion molecule B (JAM‐2) was decreased (linear, P < 0.05) with increasing stocking density. In conclusion, increasing stocking density decreases broiler performance regardless of sex and this negative effect is likely associated with decreased intestinal barrier function.