Essential role of B-Raf in ERK activation during extraembryonic development.
The kinases of the Raf family have been intensively studied as activators of the mitogen-activated protein kinase kinase/extra-cellular signal-regulated kinase (ERK) module in regulated and deregulated proliferation. Genetic evidence that Raf is required for ERK activation in vivo has been obtained in lower organisms, which express only one Raf kinase, but was hitherto lacking in mammals, which express more than one Raf kinase. Ablation of the two best studied Raf kinases, B-Raf and Raf-1, is lethal at midgestation in mice, hampering the detailed study of the essential functions of these proteins. Here, we have combined conventional and conditional gene ablation to show that B-Raf is essential for ERK activation and for vascular development in the placenta. B-Raf-deficient placentae show complete absence of phosphorylated ERK and strongly reduced HIF-1alpha and VEGF levels, whereas all these parameters are normal in Raf-1-deficient placentae. In addition, neither ERK phosphorylation nor development are affected in B-raf-deficient embryos that are born alive obtained by epiblast-restricted gene inactivation. The data demonstrate that B-Raf plays a nonredundant role in ERK activation during extraembyronic mammalian development in vivo.
Galabova-Kovacs
Gergana
G
Max F. Perutz Laboratories, Vienna Biocenter, Dr. Bohr Gasse 9, 1030 Vienna, Austria.
Matzen
Dana
D
Piazzolla
Daniela
D
Meissl
Katrin
K
Plyushch
Tatiana
T
Chen
Adele P
AP
Silva
Alcino
A
Baccarini
Manuela
M
D000483:Alleles; D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D005091:Exons; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005821:Genetic Techniques; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D019394:Ki-67 Antigen / Q000096:biosynthesis; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D009389:Neovascularization, Pathologic; D010641:Phenotype; D010766:Phosphorylation; D010920:Placenta / Q000378:metabolism; D016133:Polymerase Chain Reaction; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019394:Ki-67 Antigen; D042461:Vascular Endothelial Growth Factor A; D008156:Luciferases; D048493:Proto-Oncogene Proteins B-raf; D048049:Extracellular Signal-Regulated MAP Kinases