Related Experiment Videos
Endothelial apoptosis in Braf-deficient mice
L Wojnowski1, A M Zimmer, T W Beck
1Section on Genetics, National Institute of Mental Health/National Human Genome Research Institute, Bethesda, Maryland 20892, USA.
Abstract:
Tyrosine kinase growth factor receptors and Ras/Raf/MEK/MAPK signalling have been implicated in the suppression as well as augmentation of programmed cell death. In addition, a Ras-independent role for Raf as a suppressor of programmed cell death has been suggested by the recent finding that Craf1 interacts with members of the Bcl-2 family at mitochondrial membranes. However, genetic studies of C. elegans and Drosophila, as well as the targeted mutagenesis of the murine Araf gene, have failed to support such a role. Here we show that mice with a targeted disruption in the Braf gene die of vascular defects during mid-gestation. Braf -/- embryos, unlike Araf -/- or Craf1 -/- embryos (L.W. et al., unpublished), show an increased number of endothelial precursor cells, dramatically enlarged blood vessels and apoptotic death of differentiated endothelial cells. These results establish Braf as a critical signalling factor in the formation of the vascular system and provide the first genetic evidence for an essential role of Raf gene in the regulation of programmed cell death.
Insights
The Braf gene is crucial for vascular system development and regulating programmed cell death. Braf-deficient mice exhibit severe vascular defects and increased endothelial cell apoptosis, highlighting Braf
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Tyrosine kinase receptors and Ras/Raf/MEK/MAPK signaling pathways influence programmed cell death.
- Raf proteins, including Craf1, may suppress cell death independently of Ras, potentially through interactions with Bcl-2 family proteins at mitochondria.
- Previous genetic studies in model organisms and mice lacking Araf or Craf1 have not definitively established a role for Raf in cell death suppression.
Purpose of the Study:
- To investigate the role of the Braf gene in embryonic development and programmed cell death.
- To determine if Braf plays a critical role in vascular system formation.
- To provide genetic evidence for the function of Raf genes in regulating apoptosis.
Main Methods:
- Targeted gene disruption in mice to create Braf knockout (Braf-/-) embryos.
- Comparative analysis of Braf-/- embryos with Araf-/- and Craf1-/- embryos.
- Histological examination of embryonic vasculature and assessment of cell death.
Main Results:
- Mice with a targeted disruption in the Braf gene (Braf-/-) exhibit embryonic lethality due to vascular defects during mid-gestation.
- Braf-/- embryos display an increased number of endothelial precursor cells and significantly enlarged blood vessels.
- Apoptotic death of differentiated endothelial cells is observed in Braf-/- embryos.
Conclusions:
- Braf is an essential signaling factor for the proper formation of the vascular system.
- These findings provide the first genetic evidence for a critical role of a Raf gene (Braf) in the regulation of programmed cell death.
- The study underscores the importance of Braf in endothelial cell survival and vascular development.