CELL BIOLOGY OF THE NEURON Polarity ... - Tavernarakis Lab

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Cell Biology of the Neuron: <strong>Polarity</strong>, Plasticity and Regeneration, Crete 2011 Neurotrophins/p75NTR Signaling Specifies Axons during Cortical Development and Adult Neurogenesis Marco Canossa, Emanuela Zuccaro, Matteo Bergami, Beatrice Vignoli, Guillaume Bony, Spartaco Santi, Laura Cancedda Italian Institute of Technology Introduction. How a newly generated neuron initiates polarizing signals that specify a single axon and multiple dendrites is critical for patterning neuronal circuits “in vivo”. Here we report that the pan-neurotrophin receptor (p75NTR) is a polarity regulator that localizes asymmetrically in developing neurons and initiates neurotrophins signals for specification of the future axon. Results. (i) In cultured neurons local exposure to neurotrophins recruits p75NTR and mPar-3 into one undifferentiated neurite, determining a complex essential for axogenesis. (ii) Disruption of p75NTR sub-cellular localization, by knockdown or ectopic expression, prevents from asymmetric accumulation/activation of conserved cell polarity signalling pathways, and neurons fail to initiate axons. (iii) “In vivo” studies revealed that p75NTR governs newborn neurons polarity in the developing cortex and adult hippocampus, which overrides the pattern and assembly of neuronal circuits in these brain areas. Conclusion. Neurotrophins/p75NTR signaling initiate polarity programs resulting in stable signals for axogenesis and neuronal circuits formation. Presented by: Canossa, Marco Poster No 016 Red Session 98
Cell Biology of the Neuron: <strong>Polarity</strong>, Plasticity and Regeneration, Crete 2011 Evidence for a Mechanical Coupling between N- Cadherin Adhesions and F-Actin in Shaping Dendritic Spines Anaël Chazeau, Katalin Czondor, Mikael Garcia, Grégory Giannone, Olivier Thoumine Interdisciplinary Institute for NeuroScience UMR 5297 The dynamic morphology of dendritic spines is controlled by both the actin cytoskeleton and adhesive molecules such as cadherins. We tested here the hypothesis that actin remodeling in dendritic spines could be regulated by Ncadherin adhesion and myosin contractility. We first examined the localization of N-cadherin, actin and myosin in primary hippocampal neurons by STED microscopy. Actin-GFP and N-cadherin-DsRed co-localized mainly at the head of dendritic spines, suggesting a tight association between the two proteins. In contrast, MLC (myosin light chain)-GFP was more localized at the spine base, suggesting a role for myosin II in pulling actin filaments rearward. We then characterized, the basal motility index of dendritic spines using time lapse imaging of actin-GFP, upon treatment to increase myosin II activity, or expression of an N-cadherin mutant. N-Cadherin mutants’ dendritic spines had a higher motility index than N-Cadherin-WT spines, suggesting that the mechanical connection between post-synaptic N-cadherin and actin is stabilizing dendritic spines. Activation of myosin II induced a retraction of actin-GFP spots from the tip to the base of the spine, suggesting a role for myosin II in generating retrograde F-actin flow in dendritic spines. Furthermore, for N-Cadherin mutants the proportion of spines retracting was higher than for N-Cadherin-WT spines. To refine our understanding of actin flow and motility, we are performing single molecule experiments (actin-mEos) using PALM. Taken together, these data show that actin remodeling and flow in dendritic spines is regulated by N-cadherin adhesion and myosin contractility, suggesting a tight mechanical coupling between these three molecules. Presented by: Chazeau, Anaël 99 Poster No 017 Green Session
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Abstracts of papers presented at th
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The meeting was funded in part by E
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These abstracts should not be cited
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CYFIP1, a Neuronal eIF4E‐BP, Link
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POSTER ABSTRACTS Poster # [‐R(ed)
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030‐B Paracrine Pax6 Activity Reg
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058‐R Dynein Light Chain LC8 is a
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088‐R Spectraplakins ‐ Cytoskel
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121‐R Calmyrin1 Binds to SCG10 Pr
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18.00 ‐ 18.15 Non Hyperpolarizing
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10.00 ‐ 10.30 Neurotrophin Regula
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SESSION 10 SYNAPTOGENESIS Chairpers
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da F. Costa, L. 119 D'Adamo, P. 108
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Lewallen, K. 145 Li, Y.‐H. 201 Li
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Teuling, E. 141 Thiebes, K. 87 Thom
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Cell Biology of the Neuron: Polarit
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Dr. Christian Alfano INSERM U636, N
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Prof. Graeme W. Davis University of
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Prof. Zhigang He Harvard Medical Sc
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Dr. Bernhard Lohkamp Karolinska Ins
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Mr. Abhishek Shrikant Sahasrabudhe
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Dr. Med. Andreas Vlachos Goethe‐U
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