Samuel Tozer
I was recently recruited as a CNRS researcher at IBENS in Xavier Morin’s team. I have throughout my carrier always been interested in the signals that regulate embryonic development. During my thesis at UPMC (now Sorbonne Université) in the group of Delphine Duprez, I worked on the early phases of muscle organization in the chick limb bud. I Then decided to carry out a post-doc in the lab of James Briscoe in London to work on neural patterning. I showed how BMPs diffusing from the roof plate are integrated and instruct different dorsal interneuron subtype identities. I also developed a growing interest for the mechanisms controlling lineage decisions over the course of neural differentiation. Thus, I decided to join Xavier Morin’s team at IBENS to develop a project on the regulation of division mode during early nervous system development in the chick embryo.
Generating the right number of neural cells relies on the right « consumption » of the initial stock of progenitors. This stock must first be amplified through symmetric divisions. Asymmetric divisions then allow the generation of differentiated cells while maintaining the stock of progenitors, the system ending with terminal symmetric divisions that generate two differentiated cells. During my post-doc in Xavier Morin’s lab, I highlighted the importance of Mindbomb1 (Mib1), an effector of Notch signaling, in the regulation of the mode of division. Mib1 symmetric or asymmetric distribution in mitosis (via its anchoring to the Golgi apparatus and/or the young centrosome) generates a bias in Notch signaling among sister cells and therefore controls their commitment to differentiation.
I now intend to explore more closely the sub-cellular dynamics of neural differentiation regulators. We have first generated a Mib1-GFP mouse ES cell line by GFP knock-in and established a differentiation protocol to generate ES cell-derived neuroepithelial rosettes. This system will give us the unique opportunity to monitor the endogenous distribution of a fate determinant during vertebrate neurogenesis. In parallel, I will keep taking advantage of the chick embryo in order to characterize the nature of the inter-cellular interactions allowing the neuroepithelium to grow and differentiate in a harmonious manner.
