FP25-4 Anosmin-1 Modulates Astrocyte Development Via FGF Signalling in the Olfactory Bulb of Chick Embryos

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP25-Signaling Originating from Membrane Receptors
Sunday, June 16, 2013: 10:45 AM-11:15 AM
Presentation Start Time: 11:00 AM
Room 133 (Moscone Center)

Poster Board SUN-393
Youli Hu*1, Subathra Poopalasundaram2 and Pierre-Marc Gilles Bouloux3
1UCL Med Schl Royal Free Campus, London, United Kingdom, 2UCL Royal Free Campus, London, United Kingdom, 3Royal Free Campus, UCL, London, United Kingdom
The biological functions of astrocytes include supporting neuronal migration as scaffolding structures, stabilising synapses formation, and providing growth factors and nutrients for neuronal survival. Astrocytes on the CNS/PNS border zone are thought to prevent peripheral axons from crossing into the CNS. The olfactory system is unique within the CNS region as olfactory sensory neurons are born outside of the brain and post-natally, continue to regenerate and project their axons towards the olfactory bulb (OB) where they form synapses with the dendrites of mitral/tufted cells throughout life. FGF signalling and its functional regulator anosmin-1 are associated with abnormal OB morphogenesis, the typical phenotype of Kallmann syndrome (KS). CRE/loxP genetic approach to disrupt telencephalic FGFR1 gene resulted in mice with small OB though normal ontogenesis of olfactory primary and seconday neurons, leading to the hypothesis that the OB precursor cell proliferation and differentiation into the astroglial lineage might be disrupted. We isolated OB from E10 chick embryos and embedded them in collagen. There were no obvious GFAP-positive cells in OB explants cultured for 2h. After three days in vitro (DIV), GFAP-positive cells were seen accumulated along the outmost olfactory nerve layer of the OB, forming the astroglia boundary separating the OB from the culture environment. In the presence of 5nM recombinant ansomin-1, GFAP expression was dramatically reduced. We therefore purified neural precursor cells from E10 chick OB positive for transitin (the avian homologue of nestin), vimentin and FGFR1-3c isoforms, but negative for Pax6 and TuJ-1. In the astrocyte differentiation medium, OB precursor cells start to express GFAP at 4-7 DIV proceeding to differentiate after 7 DIV. GFAP-positive cells exhibit flat and polygonal morphology. Su5402, an inhibitor of FGFR induced GFAP expression and the cells displayed an elongated morphology at 4 DIV, while exposure to 2nM FGF2 kept cells with low GFAP expression even at 7DIV, demonstrating that FGF signalling prevents OB precursor cell differentiation into astrocytes. Addition of exogenous anosmin-1 significantly reduced GFAP-positive cells, a similar effect seen with 2nM FGF2 treatment. By contrast, the combination of anosmin-1 and FGF2 exhibited opposite activities to induce GFAP expression. These anosmin-1/FGF2 treated cells displayed bipolar and elongated morphology and coexisted with other flattened cells. Taken together, these data suggest that anosmin-1 inhibits OB precursor cell differentiation into the astrocyte lineage by activating FGF signalling, but induces astrocyte differentiation with bipolar elongated morphology with FGF2 at higher concentrations. These findings shed further light on the mechanism of action of anosmin-1, and have implications for possible molecular interventions for neuronal regeneration.

Nothing to Disclose: YH, SP, PMGB

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