Shb promotes blood vessel formation in embryoid bodies by augmenting vascular endothelial growth factor receptor-2 and platelet-derived growth factor receptor-beta signaling.
The mechanisms controlling blood vessel formation during early embryonal development have only partly been elucidated. Shb is an adaptor protein previously implicated in the angiogenic response to vascular endothelial growth factor (VEGF). To elucidate a possible role of Shb in embryonic vascular development, wild-type and SH2 domain mutated (R522K) Shb were overexpressed in murine embryonic stem (ES) cells. Embryoid bodies (EBs) differentiating from Shb-overexpressing ES cells in vitro were stained for CD31 or VEGFR-2 to visualize the formation of vascular structures. We found that Shb promotes the outgrowth of blood vessels in EBs both in the absence and presence of growth factors. This response may be the consequence of an increased number of VEGFR-2 positive cells at an early stage of EB development, a finding corroborated by both immunostaining and real-time RT-PCR. In addition, Shb overexpression upregulated the expression of PDGFR-beta, CD31, CD41 and Tal1. Cells co-expressing VEGFR-2 and PDGFR-beta were commonly observed when Shb was overexpressed and inhibition of PDGF-BB signaling reduced the amount of VEGFR-2 mRNA under these conditions. EBs expressing the Shb R522K-mutant did not form vascular structures. Microarray analysis of VEGFR-2/CD31 positive cells after 6 days of differentiation revealed numerous changes of expression of genes relating to an endothelial/hematopoietic phenotype in response to Shb overexpression. The findings suggest that Shb may play a crucial role during early ES cell differentiation to vascular structures by transducing VEGFR-2 and PDGFR-beta signals.
Rolny
Charlotte
C
Department of Medical Cell Biology, Box 571, BMC, Husargatan 3, 751 23 Uppsala, Sweden.
Lu
Lingge
L
Agren
Nina
N
Nilsson
Ingrid
I
Roe
Cheryl
C
Webb
Gene C
GC
Welsh
Michael
M
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001808:Blood Vessels / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D046149:Embryo Culture Techniques; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D051379:Mice; D009154:Mutation / Q000235:genetics; D018919:Neovascularization, Physiologic / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D040201:Platelet Membrane Glycoprotein IIb / Q000235:genetics / Q000378:metabolism; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000378:metabolism*
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D040201:Platelet Membrane Glycoprotein IIb; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D020797:Receptor, Platelet-Derived Growth Factor beta; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors; D040301:Vascular Endothelial Growth Factor Receptor-2; C085634:Shb protein, mouse; C489366:Tal1 protein, mouse