• Molecules and Cells
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• v.42 no.8
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• pp.589-596
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• 2019

${\beta}Pix$ is a guanine nucleotide exchange factor for the Rho family small GTPases, Rac1 and Cdc42. It is known to regulate focal adhesion dynamics and cell migration. However, the in vivo role of ${\beta}Pix$ is currently not well understood. Here, we report the production and characterization of ${\beta}Pix$-KO mice. Loss of ${\beta}Pix$ results in embryonic lethality accompanied by abnormal developmental features, such as incomplete neural tube closure, impaired axial rotation, and failure of allantois-chorion fusion. We also generated ${\beta}Pix$-KO mouse embryonic fibroblasts (MEFs) to examine ${\beta}Pix$ function in mouse fibroblasts. ${\beta}Pix$-KO MEFs exhibit decreased Rac1 activity, and defects in cell spreading and platelet-derived growth factor (PDGF)-induced ruffle formation and chemotaxis. The average size of focal adhesions is increased in ${\beta}Pix$-KO MEFs. Interestingly, ${\beta}Pix$-KO MEFs showed increased motility in random migration and rapid wound healing with elevated levels of MLC2 phosphorylation. Taken together, our data demonstrate that ${\beta}Pix$ plays essential roles in early embryonic development, cell spreading, and cell migration in fibroblasts.

• Molecules and Cells
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• v.26 no.2
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• pp.171-174
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• 2008

Flavone (2-phenyl chromone) is a well-known plant flavonoid, but its bioactivity has been little explored. Treatment of Caenorhabditis elegans or C. brissage with flavones induced embryonic and larval lethality that was pronounced in early larval stages. This anti-nematodal effect was also observed in the pinewood nematode, B. xylophilus. $LD_{50}$ values were approximately $100{\mu}M$ for both B. xylophilus and C. elegans. Our results indicate that flavone is an active nematicidal compound that should be further investigated with the aim of developing a potent drug against B. xylophilus.

• BMB Reports
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• v.45 no.9
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• pp.496-508
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• 2012

Fas-associated protein with death domain (FADD), an adaptor that bridges death receptor signaling to the caspase cascade, is indispensible for the induction of extrinsic apoptotic cell death. Interest in the non-apoptotic function of FADD has greatly increased due to evidence that FADD-deficient mice or dominant-negative FADD transgenic mice result in embryonic lethality and an immune defect without showing apoptotic features. Numerous studies have suggested that FADD regulates cell cycle progression, proliferation, and autophagy, affecting these phenomena. Recently, programmed necrosis, also called necroptosis, was shown to be a key mechanism that induces embryonic lethality and an immune defect. Supporting these findings, FADD was shown to be involved in various necroptosis models. In this review, we summarize the mechanism of extrinsic apoptosis and necroptosis, and discuss the in vivo and in vitro roles of FADD in necroptosis induced by various stimuli.

• Molecules and Cells
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• v.20 no.2
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• pp.228-234
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• 2005

Caenorhabditis elegans him-6 mutants, which show a high incidence of males and partial embryonic lethality, are defective in the orthologue of human Bloom's syndrome protein (BLM). When strain him-6(e1104) containing a missense him-6 mutation was irradiated with ${\gamma}$-rays during germ cell development or embryogenesis, embryonic lethality was higher than in the wild type, suggesting a critical function of the wild type gene in mitotic and pachytene stage germ cells as well as in early embryos. Even in the absence of ${\gamma}$-irradiation, apoptosis was elevated in the germ cells of the him-6 strain and this increase was dependent on a functional p53 homologue (CEP-1), suggesting that spontaneous DNA damage accumulates due to him-6 deficiency. However, induction of germline apoptosis by ionizing radiation was not significantly affected by the deficiency, indicating that HIM-6 has no role in the induction of apoptosis by exogenous DNA damage. We conclude that the C. elegans BLM orthologue is involved in DNA repair in promeiotic cells undergoing homologous recombination, as well as in actively dividing germline and somatic cells.

• Food Science and Biotechnology
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• v.15 no.3
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• pp.458-461
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• 2006

To determine whether the toxicity of Bacillus cereus would be seen in human cell lines and mice, we screened B. cereus B-38B, B. cereus B-50B, and B. cereus KCCM40935 for genes that coded for 5 enterotoxins using the polymerase chain reaction and cultivated them for 17 hr, by whose time they had grown to $10^7-10^8$ colony-forming units (CFU) per milliliter. Cell-free supernatant was added to make up 1% of the total reaction solution. Human cells from normal lung, lung carcinoma, embryonic kidney, and cervical adenocarcinoma cell lines were grown in culture. The cytotoxicity induced by adding the reaction solution was indicated by cell death rates of 0 to 70%, depending on the bacterial strain involved and the cell line. A lethality of 20% was observed when B. cereus cultures containing $10^7-10^8$ viable cells were administrated orally to mice. Therefore, the culture of B. cereus containing $10^7-10^8$ viable cells seems to have high cytotoxicity on human cell lines and lethality on mice.

• BMB Reports
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• v.49 no.5
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• pp.247-248
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• 2016

Necroptosis is a well-known form of caspase-independent cell death. Necroptosis can be triggered by various extrinsic stimuli, including death ligands in the presence of receptorinteracting protein kinase 3 (RIPK3), a key mediator of necroptosis induction. Our recent studies have revealed that C-terminus HSC-70 interacting protein (CHIP), an E3 ligase, can function as an inhibitor of necroptosis. CHIP^−/− mouse embryonic fibroblast showed higher sensitivity to necrotic stimuli than wild-type mouse embryonic fibroblast cells. Deleterious effects of CHIP knockout MEFs were retrieved by RIPK3 depletion. We found that CHIP negatively regulated RIPK3 and RIPK1 by ubiquitylation- and lysosome- dependent degradation. In addition, CHIP^−/− mice showed postnatal lethality with intestinal defects that could be rescued by crossing with RIPK3^−/− mice. These results suggest that CHIP is a negative regulator of RIPK1 and RIPK3, thus inhibiting necroptosis.

• Molecules and Cells
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• v.19 no.3
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• pp.452-457
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• 2005

The adaptor protein (AP) complexes are involved in membrane transport of many proteins. There are 3 AP complexes in C. elegans unlike mammals that have four. To study the biological functions of the AP-3 complexes of C. elegans, we sought homologues of the mouse and human genes that encode subunits of the AP-3 complexes by screening C. elegans genomic and EST sequences. We identified single copies of homologues of the ${\mu}3$, ${\sigma}3$, ${\beta}3$ and ${\delta}$ genes. The medium chain of AP-3 is encoded by a single gene in C. elegans but two different genes in mammals. Since there are no known mutations in these genes in C. elegans, we performed RNAi to assess their functions in development. RNAi of each of the genes caused embryonic and larval lethal phenotypes. APM-3 is expressed in most cells, particularly strongly in spermatheca and vulva. We conclude that the products of the C. elegans ${\mu}3$, ${\sigma}3$, ${\beta}3$ and d genes are essential for embryogenesis and larval development.

• Molecules and Cells
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• v.38 no.3
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• pp.251-258
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• 2015

Germline mutations in the breast cancer type 2 susceptibility gene (BRCA2) are linked to familial breast cancer and the progressive bone marrow failure syndrome Fanconi anaemia. Established Brca2 mouse knockout models show embryonic lethality, but those with a truncating mutation at the C-terminus survive to birth and develop thymic lymphoma at an early age. To overcome early lethality and investigate the function of BRCA2, we used T cell-specific conditional Brca2 knockout mice, which were previously shown to develop thymic lymphoma at a low penetrance. In the current study we showed that the number of peripheral T cells, particularly na$\ddot{i}$ve pools, drastically declined with age. This decline was primarily ascribed to improper peripheral maintenance. Furthermore, heterozygous mice with one wild-type Brca2 allele manifested reduced T cell numbers, suggesting that Brca2 haploinsufficiency might also result in T cell loss. Our study reveals molecular events occurring in Brca2-deficient T cells and suggests that both heterozygous and homozygous Brca2 mutation may lead to dysfunction in T cell populations.

• Molecules and Cells
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• v.27 no.3
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• pp.345-350
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• 2009

We previously reported that flavone induces embryonic lethality in Caenorhabditis elegans, which appeared to be the result of cell cycle arrest during early embryogenesis. To test this possibility, here we examined whether flavone inhibits the activity of a key cell cycle regulator, CDC-25.1 in C. elegans. A gain-of-function cdc-25.1 mutant, rr31, which exhibits extra cell divisions in intestinal cells, was used to test the inhibitory effects of flavone on CDC-25 activity. Flavone inhibited the extra cell divisions of intestinal cells in rr31, and modifications of flavone reduced the inhibitory effects. The inhibitory effects of flavone on CDC-25.1 were partly, if not completely, due to transcriptional repression.

• Molecules and Cells
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• v.24 no.3
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• pp.409-415
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• 2007

The retinoblastoma (Rb) gene is one of the most important genes in cell cycle regulation and tumorigenesis. Homozygosity for a germ-line Rb mutation results in embryonic lethality and evokes developmental defects associated with inappropriate S-phase entry and high levels of apoptosis. Although Rb has been extensively studied, more target genes need to be identified and characterized to unravel the precise mechanism of Rb function. In order to identify Rb-regulated genes, we analyzed the gene expression profile of Rb-deficient mouse embryo fibroblasts (MEFs), and identified an unknown gene, RbEST47, that is transcriptionally upregulated in Rb-deficient MEFs. This gene is conserved from fruitfly to human. It is expressed in brain, lung, kidney, and testis, and is located on mouse chromosome 2. This region is syntenic to human chromosome 9q34.3, which frequently exhibits loss of heterozygosity in neoplastic diseases. RbEST47 was considerably down-regulated in immortalized cells, and showed cell cycle-dependent expression, suggesting important roles in S and/or G2.