Presentation on theme: "FGF and Notch signaling hierarchy in sensory neurogenesis Jacob Voelkel 1, Agostino Molteni 1 Jamison Harvey 2, Jason Adams 2, Rhonda Lassiter 2, Michael."— Presentation transcript:
FGF and Notch signaling hierarchy in sensory neurogenesis Jacob Voelkel 1, Agostino Molteni 1 Jamison Harvey 2, Jason Adams 2, Rhonda Lassiter 2, Michael Stark 2 1 UMKC School of Medicine, 2 Brigham Young University Introduction -Canonical Wnt, Platelet Derived Growth Factor (PDGF), Fibroblast Growth Factor (FGF), and Notch pathways are involved in ophthalmic trigeminal placode (opV) sensory neurogenesis -FGF is necessary for placode cell delamination -Notch inhibition leads to premature neuronal differentiation Methods -FGF signaling was blocked globally with the FGF receptor antagonist SU5402 in 12-14 ss embryos from fertilized chicken eggs (Gallus gallus) -Notch signaling was simultaneously inhibited with the Notch chemical inhibitor DAPT -Embryos were incubated for 24 hr to the 24-28 ss then prepared, cryosectioned, and stained with the opV marker Pax-3 and the proneural marker Islet-1. -Notch signally was blocked with DAPT in 6-9 ss embryos and FGFR4 mRNA expression was evaluated after 4 or 12 hr by in situ hybridization Results Conclusion -FGF activation does not downregulate Notch signaling leading to neurogenesis (A) -Notch downregulation does not lead to upregulation of FGFR4 expressiong and increased FGF signaling leading to neurogenesis (B) -FGF activation and Notch downregulation act in parallel to promote neurogenesis (C) -Notch downregulation disrupts basement membrane integrity References 1.Begbie J, et al. Early steps in the production of sensory neurons by the neurogenic placodes. Mol Cell Neurosci- 2002; vol 21:502-11. 2.Lassiter RN, et al. Sensory neuron differentiation is regulated by notch signaling in the trigeminal placode. Dev Biol- 2010; vol 344:836-48. 3.Lassiter RN, et al. FGF signaling is essential for ophthalmic trigeminal placode cell delamination and differentiation. Dev Dyn- 2009; vol 238:1073- 82. 4.Scaal M, et al. In ovo electroporation of avian somites. Dev Dyn- 2004; vol 229:643-50. 5.Schimmang T. Expression and functions of FGF ligands during early otic development. Int J Dev Biol- 2007; vol 51:473-81. Figure 1. Global suppression of FGF and Notch inhibits delamination and differentiation. Transverse sections through the opV placode region of 24-28 ss embryos Coexpressing Pax3/Islet1 cells are shown in yellow. Figure 3. FGF activation coupled with Notch inhibition disrupts basement membrane integrity. Transverse sections through the opV placode region of 24-28 ss. Arrows indicate areas of disruption in basement membrane integrity. Figure 4. Proposed interactions of FGF and Notch signaling leading to neurogenesis Purpose -To investigate regulatory relationship between FGF and Notch in sensory neurogenesis Future Direction Next step -Determine the role of Notch signaling in disruption of cell-cell and/or cell-extracellular matrix protein interactions Clinical Significance -Notch downregulation leading to basement membrane fragmentation may be a mechanism involved in malignant transformation Figure 2. FGFR4 mRNA is not upregulated by Notch inhibtion after 4 and 12 hr. Assay of FGFR4 mRNA expression in brightfield microscopy.