Ninein is expressed in the cytoplasm of angiogenic tip-cells and regulates tubular morphogenesis of endothelial cells.
OBJECTIVE
Angiogenesis is an integral part of many physiological processes but may also aggravate pathological conditions such as cancer. Development of effective angiogenesis inhibitors requires a thorough understanding of the molecular mechanisms regulating vessel formation. The aim of this project was to identify proteins that regulate tubular morphogenesis of endothelial cells.


RESULTS
Phosphotyrosine-dependent affinity-purification and mass spectrometry showed tyrosine phosphorylation of ninein during tubular morphogenesis of endothelial cells. Ninein was recently identified as a centrosomal microtubule-anchoring protein. Our results show that ninein is localized in the cytoplasm in endothelial cells, and that it is highly expressed in the vasculature in normal and pathological human tissues. Using embryoid bodies as a model of vascular development, we found that ninein is abundantly expressed in the cytoplasm of endothelial cells during sprouting angiogenesis, in particular in the sprouting tip-cell. In accordance, siRNA-dependent silencing of ninein in endothelial cells inhibited tubular morphogenesis.


CONCLUSIONS
In this study, we show that ninein is expressed in developing vessels and in endothelial tip cells, and that ninein is critical for formation of the vascular tube. These data strongly implicate ninein as an important new regulator of angiogenesis.
Matsumoto
Taro
T
Department of Genetics and Pathology, Rudbeck Laboratory, S-751 85 Uppsala, Sweden.
Schiller
Petter
P
Dieterich
Lothar C
LC
Bahram
Fuad
F
Iribe
Yuji
Y
Hellman
Ulf
U
Wikner
Charlotte
C
Chan
Gordon
G
Claesson-Welsh
Lena
L
Dimberg
Anna
A
D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002478:Cells, Cultured; D003593:Cytoplasm / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D051379:Mice; D008955:Models, Cardiovascular; D018919:Neovascularization, Physiologic / Q000187:drug effects; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013552:Swine; D014162:Transfection
D003598:Cytoskeletal Proteins; C512806:NIN protein, human; C099035:Nin protein, mouse; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D016222:Fibroblast Growth Factor 2