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Deciphering the role of the centrosome in tangential migration of cortical interneurons

Research unit

UMR 7104 - Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC)
1 rue Laurent Fries 67404 ILLKIRCH

Group

Name: Mécanismes physiologiques et pathologiques du développement cortical

Group leader: JULIETTE GODIN - godin@igbmc.fr

Group leader's phone: 0032 4 366 59 55

Group organization:
- Chercheurs: 1
- ITA: 1
- Doctorants: 0
- Post-Docs: 1
- Autres: 0

Publications of the team linked to the topic (3 last years):
1) 1) Volvert ML, Prevot PP, Close P, Laguesse S, Pirotte S, Hemphill J, Rogister F, Kruzy N, Sacheli R, Moonen G, Deiters A, Merkenschlager M, Chariot A, Malgrange B, Godin JD, Nguyen L. MicroRNA targeting of CoREST controls polarization of migrating cortical neurons. Cell reports (2014) 7: 1168-1183
2) 2) Godin JD, Thomas N, Laguesse S, Malinouskaya L, Close P, Malaise O, Purnelle A, Raineteau O, Campbell K, Fero M, Moonen G, Malgrange B, Chariot A, Metin C, Besson A, Nguyen L. p27(Kip1) Is a Microtubule-Associated Protein that Promotes Microtubule Polymerization during Neuron Migration. Developmental cell (2012) 23: 729-744
3) 3) Godin JD, Colombo K, Molina-Calavita M, Keryer G, Zala D, Charrin BC, Dietrich P, Volvert ML, Guillemot F, Dragatsis I, Bellaiche Y, Saudou F, Nguyen L, Humbert S. Huntingtin is required for mitotic spindle orientation and mammalian neurogenesis. Neuron (2010) 67: 392-406

About PhD

PhD Director: JULIETTE GODIN - godin@igbmc.fr

Phone: 0032 4 366 59 55

Junior advisor: non

Co-tutely: non

Co-Director: non

About PhD topic :

Title: Deciphering the role of the centrosome in tangential migration of cortical interneurons

Project: Context of the project
The cerebral cortex contains neurons that are distributed within layers and are regionally organized into specialized areas that underlie sophisticated motor, cognitive and perceptual abilities. Cortical lamination follows an “inside-out” sequence of neuronal placement and maturation that arises from the successive birth and orderly migration of projection neurons born in the dorsal telencephalon and GABAergic interneurons originating in the ganglionic eminences. The development of the cortex progresses through several stages, including neuronal proliferation, migration and differentiation. These concurrent steps imply establishment of cell polarity, which largely depends on the dynamic regulation of the centrosome (CTR), the major microtubule organizer. Importantly, mutations in centrosomal proteins have been genetically linked to several brain disorders such as microcephaly, dwarfism, lisencephaly and ciliopathies. Thus, identification of new centrosomal regulators is essential to shed more light on the molecular mechanisms responsible for the generation of fully differentiated cortical neurons.
Cortical interneurons migrate to the cortex along various tangential paths that run across different substrates including progenitor cells, postmitotic neurons as well as radial glia fibers. Interneurons then switch from tangential to multi-directional migration to invade specific cortical layers and integrate into cortical circuit. Tangential migration of interneurons results from successive cycles of nucleokinesis and dynamic branching. Nucleokinesis comprises two alternating phases: the rostral translocation of a cytoplasmic dilatation and the forward migration of the nucleus. During first steps of tangential migration the centrosome is separated from the nucleus and localize within the newly formed cytoplasmic dilatation. Centrosome separation from the nucleus is a prerequisite for proper interneuron migration as this allows assembly of a functional primary cilium, which plays a crucial role in tangential migration and intracortical dispersion by sensing extracellular guidance cues. While a tight control of CTR position is required for interneuron migration, centrosomal proteins have never been involved in tangential migration.

Main objectives
The major goal of the current project is to better characterize the centrosome-regulated cellular and molecular pathways that contribute to cortical interneuron migration in health and disease. We will adopt a candidate-based approach and describe the function of a neurodevelopmental disorders-related centrosomal protein, CEP41, in health and autism conditions. The project aims to 1) investigate whether and how CEP41 controls the migration of interneurons; and 2) analyze the physiological consequences of CEP41 pathologies-associated mutations.

Methodology
To assess CEP41 functions in tangential migration, we will conditionally delete CEP41 from postmitotic interneurons by crossing CEP41 lox mice with Dlx5,6:Cre-GFP mice. We will assess: 1) the distribution of GFP+ interneurons at different developmental stages; 2) the intracortical dispersion of interneurons; 3) the velocity; 4) nucleokinesis; and 5) directionality of migrating cells in cultured brain slices using time-lapse recordings; 6) the morphological changes (cultures of explants combined with time-lapse recordings); and 7) the dynamic behavior of the CTR in migrating neurons (ex vivo electroporation of centrinII-RFP in explants; focal electroporation in slices). To assess the effect of CEP41 mutations (variants associated with autism), we will perform rescue experiments using wt- or mutated CEP41. To identify the molecular mechanisms underlying CEP41 function in tangential migration, this project will benefit from a yeast two-hybrid screen that have been performed in the lab and we will further analyze the most promising CEP41 partners regarding their known function in tangential migration.

Wished skills: Background in neurobiology, and skills in molecular and/or cell biology, imaging
Knowledge of cortical development or cytoskeleton field

Expertises which will be acquired during the training: In vivo mouse techniques (in utero and ex vivo electroporation)
Imaging techniques (time lapse recording- confocal microscopy)
Mouse work
Organotypic brain slices – explants culture – cell culture
Molecular cloning
Biochemistry (immunoprecipitation- Western Blotting)
Expertise in cortical development, neuronal migration, centrosome, cytoskeleton
Training in oral communication (data and journal club – posters)
Develop ability to analyze and synthetize
Teamwork, collaboration