BackgroundPluripotent embryonic stem cells are considered to be an unlimited cell source for tissue regeneration and cell-based therapy. Investigating the molecular mechanism underlying the regulation of embryonic stem cell expansion is thus important. 14-3-3 proteins are implicated in controlling cell division, signaling transduction and survival by interacting with various regulatory proteins. However, the function of 14-3-3 in embryonic stem cell proliferation remains unclear.Methodology and Principal FindingsIn this study, we show that all seven 14-3-3 isoforms were detected in mouse embryonic stem cells. Retinoid acid suppressed selectively the expression of 14-3-3σ isoform. Knockdown of 14-3-3σ with siRNA reduced embryonic stem cell proliferation, while only 14-3-3σ transfection increased cell growth and partially rescued retinoid acid-induced growth arrest. Since the growth-enhancing action of 14-3-3σ was abrogated by β-catenin knockdown, we investigated the influence of 14-3-3σ overexpression on β-catenin/GSK-3β. 14-3-3σ bound GSK-3β and increased GSK-3β phosphorylation in a PI-3K/Akt-dependent manner. It disrupted β-catenin binding by the multiprotein destruction complex. 14-3-3σ overexpression attenuated β-catenin phosphorylation and rescued the decline of β-catenin induced by retinoid acid. Furthermore, 14-3-3σ enhanced Wnt3a-induced β-catenin level and GSK-3β phosphorylation. DKK, an inhibitor of Wnt signaling, abolished Wnt3a-induced effect but did not interfere GSK-3β/14-3-3σ binding.SignificanceOur findings show for the first time that 14-3-3σ plays an important role in regulating mouse embryonic stem cell proliferation by binding and sequestering phosphorylated GSK-3β and enhancing Wnt-signaled GSK-3β inactivation. 14-3-3σ is a novel target for embryonic stem cell expansion.

BackgroundRho kinases (ROCKs) mediate cell contraction, local adhesion, and cell motility, which are considered to be important in cell differentiation. We postulated that ROCKs are involved in controlling embryonic stem (ES) cell renewal and differentiation.Methodology/Principal FindingsCCE, a murine ES cell, was treated with Y-27632 for 48 to 96 hours and colony formation was evaluated. Y-27632 blocked CCE colony formation and induced CCE to grow as individual cells, regardless of the initial seeding cell density either at 104/cm2 (“high” seeding density) or 2×103/cm2 (“low” density). However, at high seeding density, Y-27632–treated cells exhibited reduction of alkaline phosphatase (AP) staining and Oct3/4 expression. They expressed SOX-1, nestin, and MAP2c, but not βIII-tubulin or NG-2. They did not express endoderm or mesoderm lineage markers. After removal of Y-27632, the cells failed to form colonies or regain undifferentiated state. Silencing of ROCK-1 or ROCK-2 with selective small interference RNA induced CCE morphological changes similar to Y-27632. Silencing of ROCK-1 or ROCK-2 individually was sufficient to cause reduction of AP and Oct3/4, and expression of SOX-1, nestin, and MAP2c; and combined silencing of both ROCKs did not augment the effects exerted by individual ROCK siRNA. Y-27632–treated CCE cells seeded at 2×103 or 6.6×103 cells/cm2 did not lose renewal factors or express differentiation markers. Furthermore, they were able to form AP-positive colonies after removal of Y-27632 and reseeding. Similar to ROCK inhibition by Y-27632, silencing of ROCK-1 or ROCK-2 in cells seeded at 2×103/cm2 did not change renewal factors.Conclusions/SignificanceWe conclude that ROCKs promote ES cell colony formation, maintain them at undifferentiated state, and prevent them from neural differentiation at high seeding density. ROCK inhibition represents a new strategy for preparing large numbers of neural progenitor cells.

BackgroundProtein phosphates 4 (PP4), encoded by the ppp4c gene, is a ubiquitously expressed phosphatase that has been implicated in the regulation of cytokine signaling and lymphocyte survival; recent reports suggest that PP4 may be involved in pre-TCR signaling and B cell development. However, whether PP4 also modulates the functions of peripheral T cells has not been investigated due to the lack of a suitable in vivo model. Treg cells are a specialized subset of CD4 helper T cells that can suppress the proliferation of activated effector T cells. In the absence of this negative regulation, autoimmune syndromes and inflammatory diseases, such as human Crohn’s disease, will arise.ResultsIn this report, we generated mice with T cell-specific ablation of the ppp4c gene (CD4cre:PP4f/f) and a Foxp3-GFP reporter gene to examine the roles of PP4 in Treg development and function. Characterizations of the CD4cre:PP4f/f mice showed that PP4 deficiency induced partial αβ T lymphopenia and T cell hypo-proliferation. Further analyses revealed significant reductions in the numbers of thymic and peripheral Treg cells, as well as in the efficiency of in vitro Treg polarization. In addition, PP4-deficient Treg cells exhibited reduced suppressor functions that were associated with decreased IL-10, CTLA4, GITR and CD103 expression. More interestingly, the CD4cre:PP4f/f mice developed spontaneous rectal prolapse and colitis with symptoms similar to human Crohn’s disease. The pathogenesis of colitis required the presence of commensal bacteria, and was correlated with reduced Treg cells in the gut. Nevertheless, PP4-deficient Treg cells were still capable of suppressing experimental colitis, suggesting that multiple factors contributed to the onset of the spontaneous colitis.ConclusionsWhile the molecular mechanisms remain to be investigated, our results clearly show that PP4 plays a non-redundant role for the differentiation, suppressor activity and gut homeostasis of Treg cells. The onset of spontaneous colitis in the CD4cre:PP4f/f mice further suggests that PP4 is essential for the maintenance of protective gut immunity. The CD4cre:PP4f/f mice thus may serve as a good model for studying the interactions between Treg cells and gut commensal bacteria for the regulation of mucosal immunity.

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Our microRNA (miRNA) expression signatures of oral squamous cell carcinoma (OSCC) revealed that miR-450a was significantly increased in cancer tissues compared with normal epithelium. In this study, we focused on the functional significance of miR-450a in cancer cells and identification of miR-450a-regulated novel targets in OSCC. Overexpression of miR-450a in DOK and SAS cells showed significant inhibition of cell adhesion and induction of cell invasiveness, suggesting that miR-450a functions as an onco-miRNA. We performed genome-wide gene expression analysis to search for miR-450a-regulated molecular targets. Gene expression data and luciferase reporter assays revealed that TMEM182 was directly targeted by miR-450a. The miR-450a-reduced cellular adhesion was blocked by TMEM182 restoration, suggesting that miR-450a exhibits its oncogenic activity through negatively regulating TMEM182 level. Furthermore, miR-450a expression could be induced by the cytokine TNF-α primarily through activating extracellular signal-regulated kinase (ERK) signaling pathway. ERK inhibitor prevented the TNF-α-induced miR-450a expression and enhanced adhesion ability. Taken together, these data indicate that TNF-α/ERK-dependent expression of miR-450a plays an important role in mediating cellular adhesion and invasiveness, and scavenging miR-450a function using antagomir may have therapeutic potential for the treatment of OSCC. (The study was supported by the following grants: MOST 103-2320-B-006-036-MY3 and MOST 105-2325-B-400-001 from the Ministry of Science and Technology of Taiwan, ROC) Citation Format: En-Wei Hsing, Shine-Gwo Shiah, Ching-Chuan Kuo, Jang-Yang Chang. miRNA-450a suppresses adhesion but promotes invasion through targeting of TMEM182 in oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1475. doi:10.1158/1538-7445.AM2017-1475