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COMMENTS ON PROFESSOR RAMSEYER'S ARTICLE, DO SCHOOL CLIQUES DOMINATE JAPANESE BUREAUCRACIES? EVIDENCE FROM SUPREME COURT APPOINTMENTS On September 11, 2010, I received an e-mail from a graduate of my seminar. [...]

During development, the retinal vasculature grows toward hypoxic areas in an organized fashion. By contrast, in ischemic retinopathies, new blood vessels grow out of the retinal surfaces without ameliorating retinal [...]

The neural fate is generally considered to be the intrinsic direction of embryonic stem (ES) cell differentiation. However, little is known about the intracellular mechanism that leads undifferentiated cells to adopt the neural fate in the absence of extrinsic inductive signals. Here we show that the zinc-finger nuclear protein Zfp521 is essential and sufficient for driving the intrinsic neural differentiation of mouse ES cells. In the absence of the neural differentiation inhibitor BMP4, strong Zfp521 expression is intrinsically induced in differentiating ES cells. Forced expression of Zfp521 enables the neural conversion of ES cells even in the presence of BMP4. Conversely, in differentiation culture, Zfp521-depleted ES cells do not undergo neural conversion but tend to halt at the epiblast state. Zfp521 directly activates early neural genes by working with the co-activator p300. Thus, the transition of ES cell differentiation from the epiblast state into neuroectodermal progenitors specifically depends on the cell-intrinsic expression and activator function of Zfp521., Previous studies, particularly in amphibians, have demonstrated that the initial step of vertebrate neural differentiation from uncommitted embryonic ectodermal cells occurs via a cell-intrinsic mechanism and requires only that inhibitory [...]

Emerging evidence indicates that the tight communication between vascular endothelial cells and mural cells using platelet-derived growth factor (PDGF)-BB is essential for capillary stabilization during the angiogenic process. However, little is known about the related regulator that determines PDGF-BB expression. Using murine models of therapeutic neovascularization, we here show that a typical lymphangiogenic factor, vascular endothelial growth factor (VEGF)-C, is an essential regulator determining PDGF-BB expression for vascular stabilization via a paracrine mode of action. The blockade of VEGF type 3 receptor (VEGFR3) using neutralizing antibody AFL-4 abrogated FGF-2-mediated limb salvage and blood flow recovery in severely ischemic hindlimb. Interestingly, inhibition of VEGFR3 activity not only diminished lymphangiogenesis, but induced marked dilatation of capillary vessels, showing mural cell dissociation. In these mice, VEGF-C and PDGF-B were upregulated in the later phase after induced ischemia, on day 7, when exogenous FGF-2 expression had already declined, and blockade of VEGFR3 or PDGF-BB activities diminished PDGF-B or VEGF-C expression, respectively. These results clearly indicate that VEGF-C is a critical mediator, not only for lymphangiogenesis, but also for capillary stabilization, the essential molecular mechanism of communication between endothelial cells and mural cells during neovascularization. vascular endothelial growth factor-C; platelet-derived growth factor-BB; lymphangiogenesis; capillary stabilization doi: 10.1152/ajpheart.00015.2009.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2007.04.028 Byline: Yasuhiro Takashima (1)(3), Takumi Era (1), Kazuki Nakao (2), Saki Kondo (4), Masato Kasuga (3), Austin G. Smith (5), Shin-Ichi Nishikawa (1) Keywords: STEMCELL Abstract: Mesenchymal stem cells (MSCs) are defined as cells that undergo sustained in vitro growth and are able to give rise to multiple mesenchymal lineages. Although MSCs are already used in regenerative medicine little is known about their in vivo behavior and developmental derivation. Here, we show that the earliest wave of MSC in the embryonic trunk is generated from Sox1.sup.+ neuroepithelium but not from mesoderm. Using lineage marking by direct gfp knock-in and Cre-recombinase mediated lineage tracing, we provide evidence that Sox1.sup.+ neuroepithelium gives rise to MSCs in part through a neural crest intermediate stage. This pathway can be distinguished from the pathway through which Sox1.sup.+ cells give rise to oligodendrocytes by expression of PDGFR[beta] and A2B5. MSC recruitment from this pathway, however, is transient and is replaced by MSCs from unknown sources. We conclude that MSC can be defined as a definite in vivo entity recruited from multiple developmental origins. Author Affiliation: (1) Laboratory for Stem Cell Biology, Riken Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan (2) Laboratory for Animal Resources and Genetic Engineering, Riken Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan (3) Department of Clinical Molecular Medicine, Division of Diabetes and Digestive and Kidney Diseases, Kobe University Graduate School of Medicine, 7-5-1 Kusunokimachi, Chuo-ku, Kobe, 650-0017, Japan (4) Laboratory of Molecular Genetics, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan (5) Institute for Stem Cell Biology, University of Cambridge, Cambridge, CB2, 1QT, UK Article History: Received 14 September 2006; Revised 16 February 2007; Accepted 9 April 2007 Article Note: (miscellaneous) Published: June 28, 2007

Melanoblasts (Mbs) are thought to be strictly regulated by cell-cell interactions with epidermal keratinocytes, although the precise molecular mechanism of the regulation has been elusive. Notch signaling, whose activation is mediated by cell-cell interactions, is implicated in a broad range of developmental processes. We demonstrate the vital role of Notch signaling in the maintenance of Mbs, as well as melanocyte stem cells (MSCs). Conditional ablation of Notch signaling in the melanocyte lineage leads to a severe defect in hair pigmentation, followed by intensive hair graying. The defect is caused by a dramatic elimination of Mbs and MSCs. Furthermore, targeted overexpression of Hes1 is sufficient to protect Mbs from the elimination by apoptosis. Thus, these data provide evidence that Notch signaling, acting through Hes1, plays a crucial role in the survival of immature Mbs by preventing initiation of apoptosis.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.12.016 Byline: Atsushi Takebe (a)(c), Takumi Era (a), Mitsuhiro Okada (a)(b), Lars Martin Jakt (a)(b), Yoshikazu Kuroda (c), Shin-Ichi Nishikawa (a) Keywords: ES cell; In vitro differentiation; DNA microarray; PDGFR[alpha]; ARID3b Abstract: An inherent difficulty in using DNA microarray technology on the early mouse embryo is its relatively small size. In this study, we investigated whether use of ES cell differentiation culture, which has no theoretical limit in the number of cells that can be generated, can improve this situation. Seven distinct ES-cell-derived populations were analyzed by DNA microarray and examined for genes whose distribution patterns are similar to those of PDGFR[alpha], a gene implicated in differentiation of mesoderm/mesenchymal lineages. Using software developed in our laboratory, we formed a group of 30 genes which showed the highest similarity to PDGFR[alpha], 18 of these genes were shown to be involved in development of either mesodermal, mesenchymal or neural crest cells. This list also contains several genes whose role in embryogenesis has not yet been fully identified. One such molecule is mARID3b. The mARID3b expression is found in the paraxial mesoderm and cranial mesenchyme. mARID3b-null mouse showed early embryonic lethality, and most phenotypes of this mutant appear to develop from a failure to generate a sufficient number of cranial mesenchymal cells. These results demonstrate the potential use of ES cell differentiation culture in identifying novel genes playing an indispensable role in embryogenesis. Author Affiliation: (a) Laboratory for Stem Cell Biology, RIKEN Center for Development Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (b) The Foundation for Biomedical Research and Innovation, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (c) Division of Gastroenterological Surgery, Graduate School of Medicine, Kobe University, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe, Hyogo 650-0017, Japan Article History: Received 27 June 2005; Revised 18 November 2005; Accepted 6 December 2005

Identification of novel genes that are similar to platelet-derived growth factor receptor, using DNA microarray studies on mouse embryonic cells, to find their role in embryogenesis is presented.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.12.025 Byline: Siu-Shan Mak (a), Mariko Moriyama (a), Eri Nishioka (b), Masatake Osawa (a), Shin-Ichi Nishikawa (a) Keywords: bcl2; bcl2 null; Melanoblast; c-Kit; Hair follicle development; Melanocyte stem cell; Melanocyte survival; Stem cell development; Stem cell factor Abstract: Bcl2 null mice display a characteristic loss of pigmentation demonstrating the importance of Bcl2 in the melanocyte (Mc) lineage. It was recently reported that this abnormal phenotype is due to the failure of melanocyte stem cell (MSC) maintenance and that Bcl2 is selectively important for the survival of MSCs. However, in our analysis of the same mouse, we observe a reduction in melanoblast (Mb) number in both epidermal and follicular populations. More importantly, there is a complete absence of MSCs. SCF downregulation in the epidermis is concomitant with the dramatic reduction in Mb numbers observed in the Bcl2 null, suggesting that Bcl2 is indispensable for the survival of Mbs in the absence of c-Kit signaling. Consistently, abrogation of c-Kit signaling in Bcl2 null mice depletes all Mbs and Mcs, whereas continuous expression of SCF in epidermal keratinocytes rescues the MSCs. Our results demonstrate that Bcl2 has a general role in Mb and Mc survival and is essential for the emergence of MSCs. Moreover, the results indicate that the first wave of Mcs that provide hair pigmentation is derived directly from epidermal Mbs bypassing MSCs. Furthermore, a Bcl2-independent mechanism of action of SCF in the Mc lineage is revealed as SCF c-Kit signaling is functional in the absence of Bcl2. Author Affiliation: (a) RIKEN, Center for Developmental Biology (CDB), Laboratory for Stem Cell Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan (b) Division of Dermatology, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan Article History: Received 29 July 2005; Revised 6 December 2005; Accepted 9 December 2005

Recent findings have shown that embryonic vascular progenitor cells are capable of differentiating into mural and endothelial cells. However, the molecular mechanisms that regulate their differentiation, proliferation, and endothelial sheet formation remain to be elucidated. Here, we show that members of the transforming growth factor (TGF)-[beta] superfamily play important roles during differentiation of vascular progenitor cells derived from mouse embryonic stem cells (ESCs) and from 8.5-days postcoitum embryos. TGF-[beta] and activin inhibited proliferation and sheet formation of endothelial cells. Interestingly, SB-431542, a synthetic molecule that inhibits the kinases of receptors for TGF-[beta] and activin, facilitated proliferation and sheet formation of ESC-derived endothelial cells. Moreover, SB-431542 up-regulated the expression of claudin-5, an endothelial specific component of tight junctions. These results suggest that endogenous TGF-[beta] activin signals play important roles in regulating vascular growth and permeability.