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c-Raf regulates cell survival and retinal ganglion cell morphogenesis during neurogenesis
B Pimentel1, C Sanz, I Varela-Nieto
1Department of Cell and Developmental Biology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), E-28006 Madrid, Spain.
Abstract:
The signaling cascade Ras/Raf/mitogen-activated protein kinases modulates cell proliferation, differentiation, and survival, all key cellular processes during neural development. To better define the in vivo role of Raf during chick retinal neurogenesis, we interfered with Raf-dependent signaling during days 4.5 to 7.5 of embryonic development by expressing a dominant negative mutant of c-Raf (DeltaRaf), which blocks Ras-dependent Raf activation, and by overexpressing wild-type c-Raf. DeltaRaf expression induced an increase in cell death by apoptosis, whereas it did not affect overall cell proliferation and differentiation. In parallel, the number of Islet-1/2-positive and TUJ1-positive retinal ganglion cells were diminished in their definitive layer, whereas there was an increase in the number of mislocated Islet-1/2-positive cells. This disturbed morphogenesis correlated with a disruption of the optic fiber layer. Conversely, c-Raf overexpression caused moderate opposite effects on apoptosis. These results frame in vivo early neurogenesis processes in which c-Raf is essential.
Insights
Chick retinal neurogenesis relies on c-Raf signaling. Disrupting c-Raf (Raf-dependent kinase) increased cell death and mislocated retinal ganglion cells, highlighting its essential role.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Signaling
Background:
- The Ras/Raf/mitogen-activated protein kinase cascade is crucial for cell proliferation, differentiation, and survival.
- These processes are fundamental during neural development, including retinal neurogenesis.
Purpose of the Study:
- To investigate the in vivo function of c-Raf during chick retinal neurogenesis.
- To elucidate the role of Raf-dependent signaling in early retinal development.
Main Methods:
- Expression of a dominant-negative c-Raf mutant (DeltaRaf) to inhibit Ras-dependent Raf activation.
- Overexpression of wild-type c-Raf in chick embryos during critical neurogenesis periods (days 4.5-7.5).
- Analysis of cell death (apoptosis), proliferation, differentiation, cell positioning, and optic fiber layer formation.
Main Results:
- DeltaRaf expression led to increased apoptosis but did not alter overall proliferation or differentiation.
- A decrease in correctly located Islet-1/2 and TUJ1-positive retinal ganglion cells was observed, with an increase in mislocated cells.
- Morphogenesis was disrupted, evidenced by a compromised optic fiber layer.
- Conversely, c-Raf overexpression showed moderate opposing effects on apoptosis.
Conclusions:
- c-Raf plays an essential role in chick retinal neurogenesis.
- Proper c-Raf signaling is critical for regulating cell survival, cell positioning, and the formation of the optic fiber layer during early retinal development.