BESSE

Florence BESSE

Axon morphogenesis and local RNA regulation in Drosophila

Main interests

  • 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

Scientific Questions

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

Our Strategy

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

 

Research Aims

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

Researchers

DE GRAEVE Fabienne
MEDIONI Caroline

PreDocs

FORMICOLA Nadia
PUSHPALATHA Kavya Vinayan
VIJAYAKUMAR Jeshlee

Engineers & Technicians

PALIN Lucile

 

Recent publications

  1. De Graeve, F, Besse, F. Neuronal RNP granules: from physiological to pathological assemblies. Biol. Chem. 2018;399 (7):623-635. doi: 10.1515/hsz-2018-0141. PubMed PMID:29641413 .
  2. Dang, LT, Tondl, M, Chiu, MHH, Revote, J, Paten, B, Tano, V et al.. TrawlerWeb: an online de novo motif discovery tool for next-generation sequencing datasets. BMC Genomics. 2018;19 (1):238. doi: 10.1186/s12864-018-4630-0. PubMed PMID:29621972 PubMed Central PMC5887194.
  3. Khayachi, A, Gwizdek, C, Poupon, G, Alcor, D, Chafai, M, Cassé, F et al.. Sumoylation regulates FMRP-mediated dendritic spine elimination and maturation. Nat Commun. 2018;9 (1):757. doi: 10.1038/s41467-018-03222-y. PubMed PMID:29472612 PubMed Central PMC5823917.
  4. Medioni, C, Besse, F. The Secret Life of RNA: Lessons from Emerging Methodologies. Methods Mol. Biol. 2018;1649 :1-28. doi: 10.1007/978-1-4939-7213-5_1. PubMed PMID:29130187 .
  5. 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 .
  6. 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.
  7. 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 .
  8. 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 .
  9. 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 .
  10. 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 .
  11. Medioni, C, Mowry, K, Besse, F. Principles and roles of mRNA localization in animal development. Development. 2012;139 (18):3263-76. doi: 10.1242/dev.078626. PubMed PMID:22912410 PubMed Central PMC3424039.
  12. 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 .
  13. Besse, F, López de Quinto, S, Marchand, V, Trucco, A, Ephrussi, A. Drosophila PTB promotes formation of high-order RNP particles and represses oskar translation. Genes Dev. 2009;23 (2):195-207. doi: 10.1101/gad.505709. PubMed PMID:19131435 PubMed Central PMC2648539.
  14. Besse, F, Ephrussi, A. Translational control of localized mRNAs: restricting protein synthesis in space and time. Nat. Rev. Mol. Cell Biol. 2008;9 (12):971-80. doi: 10.1038/nrm2548. PubMed PMID:19023284 .
  15. 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.
  16. 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 .
  17. Narbonne-Reveau, K, Besse, F, Lamour-Isnard, C, Busson, D, Pret, AM. fused regulates germline cyst mitosis and differentiation during Drosophila oogenesis. Mech. Dev. 2006;123 (3):197-209. doi: 10.1016/j.mod.2006.01.001. PubMed PMID:16516445 .
  18. Besse, F, Busson, D, Pret, AM. Hedgehog signaling controls Soma-Germen interactions during Drosophila ovarian morphogenesis. Dev. Dyn. 2005;234 (2):422-31. doi: 10.1002/dvdy.20537. PubMed PMID:16145667 .
  19. Narbonne, K, Besse, F, Brissard-Zahraoui, J, Pret, AM, Busson, D. polyhomeotic is required for somatic cell proliferation and differentiation during ovarian follicle formation in Drosophila. Development. 2004;131 (6):1389-400. doi: 10.1242/dev.01003. PubMed PMID:14993188 .
  20. Besse, F, Pret, AM. Apoptosis-mediated cell death within the ovarian polar cell lineage of Drosophila melanogaster. Development. 2003;130 (5):1017-27. . PubMed PMID:12538526 .
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1 PostDoc – 3 years – Start October 2018

POST-DOC POSITION AVAILABLE:
Regulation of neuronal RNA granules and function in long-term memory

A three-year post-doctoral position is available in the group of Florence Besse
(http://ibv.unice.fr/research-team/besse/) at the Institute of Biology Valrose (iBV-UMR7277, Nice, France).

Project description

Long-term molecular and structural changes occurring at synapses in response to neuronal activation provide the mechanistic bases for the establishment and retention of memories, and are altered in both developmental and age-related memory disorders. Such changes rely on local experience-induced translation of quiescent mRNAs packaged together with regulatory proteins into neuronal RNA granules transported and stored at synapses. How RNA granules are remodeled in response to neuronal activity to relieve translation repression of mRNAs is unclear. Furthermore, the importance of such a remodeling in the establishment of long-term memories remains to be demonstrated in vivo.
The successful candidate will address these questions in Drosophila, by dissecting the cellular and molecular mechanisms underlying the remodeling of conserved neuronal RNP granules in response to activity. She/he will also participate in characterizing how such a remodeling impacts on the establishment of long-term memory traces assessed via learning and memory behavior assays (in collaboration with K. Keleman’s lab).

Qualifications and Experience

Candidates should have a PhD in cell biology, molecular biology, genetics, or neurobiology.
Experience with fly genetics, behavior assays and/or transcriptomics will be considered advantageous.
English is the working language in the lab and in the Institute.

Funding

The position is funded for 3 years, and the starting date is October 2018

Applications

Interested candidates are encouraged to send a CV, a description of research interests and accomplishments, and names and contact information of 2 referees to Florence Besse: besse@unice.fr.

Selected references:

- De Graeve F. and Besse F. (2018). Biol.chem doi: 10.1515/hsz-2018-0141
- Medioni C., Ephrussi A. and Besse F. (2015). Nat. Protoc. doi: 10.1038/nprot.2015.034.
- Marchetti G. et al., (2014). J. Neurosci. doi: 10.1523/JNEUROSCI.3285-13.2014.
- Medioni C. et al., (2014). Cur Biol. doi: 10.1016/j.cub.2014.02.038.

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
Parc Valrose
06108 Nice cedex 2