Description of the PhD thesis project
Neurons of the neocortex are generated by
neural stem cells called radial glial cells. The relative abundance of these
cells varies greatly across species. In particular, they are highly amplified
in humans and believed to be critical players in the massive size expansion of
the human brain. These polarized cells extend a long basal fiber that acts as a
scaffold for neuronal migration.
We recently characterized the organization of
the microtubule cytoskeleton in the basal process of mouse and human RG cells
(Coquand et al, 2020, BioRxiv, doi: https://doi.org/10.1101/2020.03.16.993295).
We showed that microtubules in the basal fiber
display a mixed polarity, reminiscent of the mammalian neuronal dendrite, and
identified acentrosomal microtubule organizing centers localized in membrane
swellings of the basal fiber.
In this project, we will identify the factors
controlling the generation and organization of this acentrosomal microtubule
network, and test for the consequences of altered organization on cerebral
development. Using iPS-derived human cerebral organoids, as well as mouse
models, we will test for the function of factors controlling microtubule
severing, minus end capping or acentrosomal nucleation.
We will analyze the consequences on
microtubule organization and polarized transport of secreted molecules. Using
mutant cerebral organoids, we will test how alteration of these processes
affects neural stem cell proliferation, fate, and the development and growth of
the cerebral tissue.
The Baffet lab investigates mouse and human
brain development with a strong focus on neural stem cells. In particular, we
address how cytoskeletal organization and motor proteins, which are severely
altered in many patients with brain malformations, are regulated and control
polarized transport and asymmetric cell division.
Our lab highly relies on in situ live imaging
methods, allowing us to address these questions in real time and within the
International, interdisciplinary & intersectoral aspects of the project
For this project, we will collaborate with
the group of Silvia Cappello (Max Planck, Munich), who has expertise in the
genetics of brain malformations.
In particular, her group has recently
identified mutations in the LGALS3BP gene as a cause of cerebral heterotopia.
Using KO cerebral organoids, they uncovered the role of this secreted factor
for proper cerebral development.
In order to image RG cells at a higher
resolution, we have developed, in collaboration with Catherine Villard,
biophysicist at IPGG, a method for their in vitro culture, coupled to their
alignment on micropatterns of adhesion.
This enables us to mimic their in vivo
elongated morphology, and study the subcellular localization of regulators of
microtubule organization within the basal fiber, with very high resolution.
1. Jacopo A. Carpentieri, Amandine Di Cicco, David Andreau, Laurence Del Maestro, Fatima El Marjou, Laure Coquand, Jean-Baptiste Brault, Nadia Bahi-Buisson, Alexandre D. Baffet (2020) Endosomal trafficking defects alter neural progenitor proliferation and cause microcephaly. BioRxiv doi: https://doi.org/10.1101/2020.08.17.254037
2. Coquand L.*, Victoria G. S.*, Tata A., Brault J.B., Guimiot F., Fraisier V., BAFFET AD (2020) A dendritic-like microtubule network is organized from swellings of the basal fiber in neural progenitors. BioRxiv doi: https://doi.org/10.1101/2020.03.16.993295
3. Vargas-Hurtado D, Brault JB, Piolot T, Leconte L, Da Silva N, Pennetier C, BAFFET A, Marthiens V, Basto R. (2019) Differences in Mitotic Spindle Architecture in Mammalian Neural Stem Cells Influence Mitotic Accuracy during Brain Development. Curr Biol. 29(18):2993‐3005.e9.
4. Brault JB, Khou C, Basset J, Coquand L, Fraisier V, Frenkiel MP, Manuguerra JC, Pardigon N, BAFFET AD. (2016) Comparative Analysis Between Flaviviruses Reveals Specific Neural Stem Cell Tropism for Zika Virus in the Mouse Developing Neocortex. EBioMedicine 10, 71-76.
5. BAFFET AD, Hu D, Vallee R. (2015) Cdk1 activates pre-mitotic nuclear envelope dynein recruitment and apical nuclear migration in neural stem cells. Dev Cell. 33, 1-14.