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Interdependent fibroblast growth factor and activin A signaling promotes the expression of endodermal genes in differentiating mouse embryonic stem cells expressing Src Homology 2-domain inactive Shb
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
2008 (English)In: Differentiation, ISSN 0301-4681, E-ISSN 1432-0436, Vol. 76, no 5, 443-453 p.Article in journal (Refereed) Published
Abstract [en]

The mechanisms controlling endodermal development during stem cell differentiation have been only partly elucidated, although previous studies have suggested the participation of fibroblast growth factor (FGF) and activin A in these processes. Shb is a Src homology 2 (SH2) domain-containing adapter protein that has been implicated in FGF receptor 1 (FGFR1) signaling. To study the putative crosstalk between activin A and Shb-dependent FGF signaling in the differentiation of endoderm from embryonic stem (ES) cells, embryoid bodies (EBs) derived from mouse ES cells overexpressing wild-type Shb or Shb with a mutated SH2 domain (R522K-Shb) were cultured in the presence of activin A. We show that expression of R522K-Shb results in up-regulation of FGFR1 and FGF2 in EBs. Addition of activin A to the cultures enhances the expression of endodermal genes primarily in EBs expressing mutant Shb. Inhibition of FGF signaling by the addition of the FGFR1 inhibitor SU5402 completely counteracts the synergistic effects of R522K-Shb and activin A. In conclusion, the present results suggest that expression of R522K-Shb enhances certain signaling pathways downstream of FGF and that an interplay between FGF and activin A participates in ES cell differentiation to endoderm.

Place, publisher, year, edition, pages
2008. Vol. 76, no 5, 443-453 p.
Keyword [en]
ES cells, Shb, endoderm, activin A, FGF, liver, pancreas
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97229DOI: 10.1111/j.1432-0436.2007.00249.xISI: 000256117500001OAI: oai:DiVA.org:uu-97229DiVA: diva2:172070
Available from: 2008-05-09 Created: 2008-05-09 Last updated: 2017-12-14Bibliographically approved
In thesis
1. The role of Shb in ES cell differentiation, angiogenesis and tumor growth
Open this publication in new window or tab >>The role of Shb in ES cell differentiation, angiogenesis and tumor growth
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Shb is a ubiquitously expressed adaptor protein with the ability to bind several tyrosine kinase receptors and intracellular signaling proteins. Previous studies have implied a wide spectrum of Shb-mediated cellular responses, which motivated me to further investigate the role of Shb in differentiation and angiogenesis. Embryonic stem (ES) cells differentiate into endoderm and mesoderm from a bipotent mesendodermal cell population. Interregulatory signals between these germlayers are required for further specification. ES cells overexpressing Shb with an inactive SH2 domain (R522K-Shb) altered the expression of endodermal genes as a consequence of upregulated FGF expression. This response was enhanced by addition of activin A, suggesting a synergistic mechanism operative between FGF and activin A signaling in endoderm specification. To investigate a role for Shb in mesodermal specification, Shb knockout ES cells were established. These cells showed a reduced ability to form blood vessels after VEGF stimulation and delayed downregulation of genes associated with mesendoderm, indicating a reduced capacity for these cells to enter later stages.

To assess a role for Shb in tumor cell apoptosis, Shb expression was silenced in angiosarcoma endothelial cells. FAK-phosphorylation was reduced in Shb knockdown cells and this made them more susceptible to apoptotic stimuli both in vitro and in vivo.

Shb knockout microvasculature in mouse kidney, liver, and heart showed irregular endothelial linings with cytoplasmic projections toward the lumen, a feature that was also related to increased vascular permeability. VEGF treatment failed to stimulate vascular permeability in Shb knockout mice.

In order to elucidate whether these features relate to reduced angiogenesis, tumor growth was examined. Tumors grown in knockout mice showed reduced growth capacity and lower vessel density. In conclusion, Shb is a multifunctional adaptor protein that may be involved in several cellular responses both during embryonic development and adult life.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 355
Keyword
Cell biology, Shb, tyrosine kinase signaling, ES, endoderm, mesoderm, apoptosis, microvasculature, tumor growth, Cellbiologi
Identifiers
urn:nbn:se:uu:diva-8746 (URN)978-91-554-7205-4 (ISBN)
Public defence
2008-05-31, Auditorium minus, Gustavianum, Akademigatan 3, Uppsala, 13:00
Opponent
Supervisors
Available from: 2008-05-09 Created: 2008-05-09Bibliographically approved

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Åkerblom, BjörnWelsh, Michael

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