Axon morphogenesis and local RNA regulation in Drosophila
- understand how post-transcriptional regulatory processes control neuronal plasticity in vivo
- study the regulatory mechanisms underlying neuronal RNP granule transport and dynamic properties
- unravel the functions of mRNA transport and local translation in brain maturation and learning and memory processes
- combine a variety of complementary approaches and perform multi-scale analyses
Our main research goal is to understand how post-transcriptional regulatory processes control neuronal plasticity in vivo. Specifically, we study how neuronal ribonucleoprotein (RNP) granules are regulated in space and time to promote local remodeling of neuronal cells during development, as well as in learning and memory processes. Neuronal RNP granules are dynamic macromolecular complexes that contain RNAs and regulatory proteins, assemble in the cell body, and are transported over long-distances to axons or dendrites. They are implicated in the transport of mRNAs, and in their local translation in response to external cues. Although alterations in the properties of neuronal RNP granules have been associated with different neurodegenerative diseases, surprisingly little is known about the molecular mechanisms underlying their formation and dynamics, as well as their physiological function and regulation.
Figure 1 – Neuronal RNP granules
To understand the role of neuronal RNP granules in neuronal plasticity, as well as their spatio-temporal regulation in response to developmental signals or neuronal activity, one needs to i) dissect the molecular and cellular mechanisms underlying the assembly, transport and remodeling of these granules, and ii) test their functional impact during nervous system development or learning and memory processes. To address these questions, our lab performs multi-scale analyses, and uses Drosophila nervous system as an original in vivo system where advanced genetics, imaging and biochemistry can be combined. We use and develop a range of complementary assays including in vivo live-cell imaging, smFISH, in vivo RIP-seq, high throughput-microscopy, in vitro reconstitution assays. For some of our projects, we collaborate with computer scientists to perform automatic and quantitative image processing, and to develop mathematical models of the biological processes we study (See Morpheme Team ).
Figure 2 – GFP-Imp particle dynamic axonal transport
1- Neuronal RNP granules and axonal remodeling. We have shown that RNP granule components are actively recruited to axons undergoing remodeling in response to developmental cues. Furthermore, they are required for the regrowth of axonal processes that occurs after pruning of immature branches. Our objectives are i) to identify the mechanisms triggering RNP granule axonal recruitment and local translation of transported mRNAs, and ii) to understand their impact on axon regrowth and branching.
Figure 3 – 3D reconstruction of a single axon
2- Regulation of neuronal RNP granule assembly and dynamics. RNP granules are high order assemblages composed of RNAs and proteins dynamically exchanging with the cytoplasm. To identify regulators of the clustering and recycling of RNP granules, we are combining different approaches including biochemical purifications of RNP complexes, high throughput microscopy-based RNAi screens and in vitro reconstitution assays.
Figure 4 – Granules in cell culture
3- Regulation and function of neuronal RNP granules in synaptic plasticity and disease. We aim at understanding how neuronal RNP granules remodel in response to synaptic activity, and how this contributes to the structural changes underlying the establishment and retention of memories. As the progression of several neurodegenerative diseases has been linked to the formation of pathological RNP aggregates, we also study RNP granules assembled by RNA binding proteins involved in such diseases.
Figure 5 – Drosophila Mushroom Body
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- Gama-Carvalho, M, L Garcia-Vaquero, M, R Pinto, F, Besse, F, Weis, J, Voigt, A et al.. Linking amyotrophic lateral sclerosis and spinal muscular atrophy through RNA-transcriptome homeostasis: a genomics perspective. J. Neurochem. 2017;141 (1):12-30. doi: 10.1111/jnc.13945. PubMed PMID:28054357 .
- Bruckert, H, Marchetti, G, Ramialison, M, Besse, F. Drosophila Hrp48 Is Required for Mushroom Body Axon Growth, Branching and Guidance. PLoS ONE. 2015;10 (8):e0136610. doi: 10.1371/journal.pone.0136610. PubMed PMID:26313745 PubMed Central PMC4551846.
- Medioni, C, Ephrussi, A, Besse, F. Live imaging of axonal transport in Drosophila pupal brain explants. Nat Protoc. 2015;10 (4):574-84. doi: 10.1038/nprot.2015.034. PubMed PMID:25763834 .
- Mottini, A, Descombes, X, Besse, F, Pechersky, E. Discrete stochastic model for the generation of axonal trees. Conf Proc IEEE Eng Med Biol Soc. 2014;2014 :6814-7. doi: 10.1109/EMBC.2014.6945193. PubMed PMID:25571561 .
- Marchetti, G, Reichardt, I, Knoblich, JA, Besse, F. The TRIM-NHL protein Brat promotes axon maintenance by repressing src64B expression. J. Neurosci. 2014;34 (41):13855-64. doi: 10.1523/JNEUROSCI.3285-13.2014. PubMed PMID:25297111 PubMed Central PMC6608379.
- Medioni, C, Ramialison, M, Ephrussi, A, Besse, F. Imp promotes axonal remodeling by regulating profilin mRNA during brain development. Curr. Biol. 2014;24 (7):793-800. doi: 10.1016/j.cub.2014.02.038. PubMed PMID:24656828 .
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- Maury, P, Besse, F, Martin, S. Age differences in outdated information processing during news reports reading. Exp Aging Res. 2010;36 (4):371-92. doi: 10.1080/0361073X.2010.511962. PubMed PMID:20845118 .
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- Besse, F, Mertel, S, Kittel, RJ, Wichmann, C, Rasse, TM, Sigrist, SJ et al.. The Ig cell adhesion molecule Basigin controls compartmentalization and vesicle release at Drosophila melanogaster synapses. J. Cell Biol. 2007;177 (5):843-55. doi: 10.1083/jcb.200701111. PubMed PMID:17548512 PubMed Central PMC2064284.
- Martin-Lannerée, S, Lasbleiz, C, Sanial, M, Fouix, S, Besse, F, Tricoire, H et al.. Characterization of the Drosophila myeloid leukemia factor. Genes Cells. 2006;11 (12):1317-35. doi: 10.1111/j.1365-2443.2006.01023.x. PubMed PMID:17121541 .
2009 - HFSP Career Development Award
2008 - ATIP Biologie du Développement (CNRS)
2003 - HFSP, EMBO and FEBS Long-term Fellowships
iBV - Institut de Biologie Valrose
"Centre de Biochimie"
Université Nice Sophia Antipolis
Faculté des Sciences
06108 Nice cedex 2