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Role of BDNF in early gustatory neuron development
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Poster abstracts / Int. J. Devl Neuroscience 24 (2006) 495–603
found that PMA and PKC induced a large increase in Notch expression and that the PKCS729A mutant abolished the PMA effect. To examine the role of Notch1 in PMA and PKC effects, we employed the ␥-secretase inhibitor L-685,458. Treatment of the cells with L-685,458 decreased the number of GFAP+ cells whereas it increased the number of -tubulinIII+ cells. Moreover, L-685,458 abolished the effect of PMA on the generation of astrocytes. Our data suggest an important role of PKC in astrocytic differentiation and implicate Notch1 as a possible mediator of this effect. Keywords: Neural progenitor cells; Astrogenesis; PKC; Notch 1 doi:10.1016/j.ijdevneu.2006.09.219 [P160] Origin and migration of oligodendrocytes in the zebrafish hindbrain D. Zannino ∗ , B. Appel Vanderbilt University, USA Uniform myelination requires that oligodendrocytes, the myelinating cell type of vertebrates, are uniformly distributed throughout the central nervous system. The origin and migratory pathways of oligodendrocytes have been well studied in the developing spinal cord. For example, spinal cord oligodendrocytes arise from ventral precursors that also produce motor neurons and then migrate dorsally. However, much less is known about oligodendrocyte development in the brain. We are investigating the origins and migratory behaviours of oligodendrocyte progenitor cells (OPCs) using transgenic zebrafish that express green fluorescent protein under control of olig2 regulatory DNA. Consistent with recently published work describing mouse oligodendrocyte development, our time lapse microscopy revealed that zebrafish OPCs originate in both ventral and dorsal hindbrain and cells subsequently intermix through dorsally and ventrally directed migration. Additionally, OPCs migrate long distances along the anteroposterior axis. Our preliminary analysis indicates that, in contrast to spinal cord, only a subset of hindbrain oligodendrocytes share a common precursor origin with motor neurons. Thus, the molecular mechanisms that specify oligodendrocytes might differ between the spinal cord and hindbrain. Keywords: Oligodendrocyte; Specification; Zebrafish; Hindbrain doi:10.1016/j.ijdevneu.2006.09.220
[P161] Role of BDNF in early gustatory neuron development D. Harlow ∗ , L. Barlow University of Colorado Denver Health Sciences Center, USA Cranial ganglion cells provide gustatory and non-gustatory lingual innervation. We have shown using embryos of an aquatic salamander, the axolotl, that the embryonic origin of ganglion cells predicts mature neuron fate; gustatory neurons derive from epibranchial placodes, while non-gustatory neurons derive from neural crest (Harlow and Barlow, in preperation). Previous studies of brain-derived neurotrophic factor (BDNF) knockout mice revealed that BDNF is necessary for gustatory innervation and ganglion cell survival (Nosrat et al., 1997; Liebl et al., 1997), but the embryonic neuronal populations affected are unknown. Are placodal neurons specifically dependent upon BDNF, and if so when, and from what source? We are using axolotls to answer these questions. We have determined that the receptor for BDNF, trkB, is expressed in the fibers that innervate taste buds, as well as within cells of the VIIth, IXth and Xth cranial ganglia, similar to the pattern observed in mice. We are now performing double label experiments to discern if placodal neurons specifically express trkB, and are thus responsive to BDNF in vivo. Cultured placodal ectoderm will generate sensory neurons de novo (Gross et al., 2003), and when exposed to BDNF in vitro, placodal neurons demonstrate increased axon outgrowth, branching and possibly survival. Moreover, the BDNF effect appears restricted to discrete times in vitro, corresponding to specific developmental events in vivo. Placodal neuron outgrowth is most substantial when explants are exposed to neurotrophin either: (1) during the period placodal neurons would coalesce with neural crest neurons into cranial ganglia in vivo or (2) as these sensory neurons reach their hindbrain target. Thus, our data indicate that placodes give rise to gustatory neurons, which are sensitive to BDNF long before these neurons innervate the tongue and resident taste buds. These data are consistent with reports in mice, where ganglionic sensory neurons are lost in BDNF−/− mice prior to axons reaching the tongue. In sum, these results suggest that gustatory neurons receive neurotrophic support from additional sources early on during embryonic development. Acknowledgements Supported by NIDCD DC003947 to LAB & NIDCD DC007796 to DEH. Keywords: BDNF; Gustatory system; Ganglion neurons; Development doi:10.1016/j.ijdevneu.2006.09.221
Poster abstracts / Int. J. Devl Neuroscience 24 (2006) 495–603
found that PMA and PKC induced a large increase in Notch expression and that the PKCS729A mutant abolished the PMA effect. To examine the role of Notch1 in PMA and PKC effects, we employed the ␥-secretase inhibitor L-685,458. Treatment of the cells with L-685,458 decreased the number of GFAP+ cells whereas it increased the number of -tubulinIII+ cells. Moreover, L-685,458 abolished the effect of PMA on the generation of astrocytes. Our data suggest an important role of PKC in astrocytic differentiation and implicate Notch1 as a possible mediator of this effect. Keywords: Neural progenitor cells; Astrogenesis; PKC; Notch 1 doi:10.1016/j.ijdevneu.2006.09.219 [P160] Origin and migration of oligodendrocytes in the zebrafish hindbrain D. Zannino ∗ , B. Appel Vanderbilt University, USA Uniform myelination requires that oligodendrocytes, the myelinating cell type of vertebrates, are uniformly distributed throughout the central nervous system. The origin and migratory pathways of oligodendrocytes have been well studied in the developing spinal cord. For example, spinal cord oligodendrocytes arise from ventral precursors that also produce motor neurons and then migrate dorsally. However, much less is known about oligodendrocyte development in the brain. We are investigating the origins and migratory behaviours of oligodendrocyte progenitor cells (OPCs) using transgenic zebrafish that express green fluorescent protein under control of olig2 regulatory DNA. Consistent with recently published work describing mouse oligodendrocyte development, our time lapse microscopy revealed that zebrafish OPCs originate in both ventral and dorsal hindbrain and cells subsequently intermix through dorsally and ventrally directed migration. Additionally, OPCs migrate long distances along the anteroposterior axis. Our preliminary analysis indicates that, in contrast to spinal cord, only a subset of hindbrain oligodendrocytes share a common precursor origin with motor neurons. Thus, the molecular mechanisms that specify oligodendrocytes might differ between the spinal cord and hindbrain. Keywords: Oligodendrocyte; Specification; Zebrafish; Hindbrain doi:10.1016/j.ijdevneu.2006.09.220
[P161] Role of BDNF in early gustatory neuron development D. Harlow ∗ , L. Barlow University of Colorado Denver Health Sciences Center, USA Cranial ganglion cells provide gustatory and non-gustatory lingual innervation. We have shown using embryos of an aquatic salamander, the axolotl, that the embryonic origin of ganglion cells predicts mature neuron fate; gustatory neurons derive from epibranchial placodes, while non-gustatory neurons derive from neural crest (Harlow and Barlow, in preperation). Previous studies of brain-derived neurotrophic factor (BDNF) knockout mice revealed that BDNF is necessary for gustatory innervation and ganglion cell survival (Nosrat et al., 1997; Liebl et al., 1997), but the embryonic neuronal populations affected are unknown. Are placodal neurons specifically dependent upon BDNF, and if so when, and from what source? We are using axolotls to answer these questions. We have determined that the receptor for BDNF, trkB, is expressed in the fibers that innervate taste buds, as well as within cells of the VIIth, IXth and Xth cranial ganglia, similar to the pattern observed in mice. We are now performing double label experiments to discern if placodal neurons specifically express trkB, and are thus responsive to BDNF in vivo. Cultured placodal ectoderm will generate sensory neurons de novo (Gross et al., 2003), and when exposed to BDNF in vitro, placodal neurons demonstrate increased axon outgrowth, branching and possibly survival. Moreover, the BDNF effect appears restricted to discrete times in vitro, corresponding to specific developmental events in vivo. Placodal neuron outgrowth is most substantial when explants are exposed to neurotrophin either: (1) during the period placodal neurons would coalesce with neural crest neurons into cranial ganglia in vivo or (2) as these sensory neurons reach their hindbrain target. Thus, our data indicate that placodes give rise to gustatory neurons, which are sensitive to BDNF long before these neurons innervate the tongue and resident taste buds. These data are consistent with reports in mice, where ganglionic sensory neurons are lost in BDNF−/− mice prior to axons reaching the tongue. In sum, these results suggest that gustatory neurons receive neurotrophic support from additional sources early on during embryonic development. Acknowledgements Supported by NIDCD DC003947 to LAB & NIDCD DC007796 to DEH. Keywords: BDNF; Gustatory system; Ganglion neurons; Development doi:10.1016/j.ijdevneu.2006.09.221