Project title: Dynamics of PRC1 chromatin factors during neuronal differentiation and reprogramming.

Type of rotation: M1 (2 months) or M2 (6 months)

Supervisor: Vincent Bertrand

Concept and Objectives

Understanding how cells maintain their differentiated identity has important implications for both cancer biology and regenerative medicine. During development, a high diversity of neurons is generated and subsequently maintained throughout the life of the animal. Our team studies the mechanisms that specify and maintain the identity of neurons using the invertebrate model C. elegans (1,2,3,4,5). C. elegans is a good model to study neuronal cell fate specification and maintenance as its nervous system is simple and well characterized. In addition, C. elegans is transparent and the development and maintenance of its nervous system can be easily followed by in vivo time-lapse imaging. Using a genetic screen, we have identified a role for chromatin factors of the PRC1 family in the specification and maintenance of neuronal cell fate (4). We now want to characterize the dynamics of PRC1 chromatin factors during this process and to test the effect of PRC1 factors on neuron fate reprogramming. Using lines where the endogenous PRC1 factors have been tagged with a fluorescent protein by CRISPR, we have recently observed that PRC1 factors are distributed in a non-homogenous manner inside the nucleus, forming localized dots of higher concentration. During this master project (M1 or M2), the student will analyze the dynamics of PRC1 dots during neuronal specification and maintenance by in vivo time-lapse imaging, and characterize the nature of these dots. In addition, differentiated neurons are usually resistant to reprogramming into other neuron types. As we have observed that PRC1 factors are involved in neuronal type identity maintenance, we now want to test whether PRC1 factors also act as a barrier against reprogramming. The student will analyze whether removing PRC1 function facilitates neuronal fate changes induced by reprogramming transcription factors.

References

1)         Barrière A. and Bertrand V. (2020). Neuronal specification in C. elegans: combining lineage inheritance with intercellular signaling. J. Neurogenetics 34, 273-81. (review)

2)         Kaur S., Mélénec P., Murgan S., Bordet G., Recouvreux P., Lenne P.F. and Bertrand V. (2020). Wnt ligands regulate the asymmetric divisions of neuronal progenitors in C. elegans embryos. Development 147, dev183186.

3)         Filippopoulou K., Couillault C., and Bertrand V. (2021). Multiple neural bHLHs ensure the precision of a neuronal specification event in Caenorhabditis elegans. Biol. Open 10, bio058976.

4)         Bordet G., Couillault C., Soulavie F., Filippopoulou K. and Bertrand V. (2022). PRC1 chromatin factors strengthen the consistency of neuronal cell fate specification and maintenance in C. elegans. PLoS Genetics 18, e1010209.       

5)         Toudji-Zouaz A., Bertrand V. and Barrière A. (2021). Imaging of native transcription and transcriptional dynamics in vivo using a tagged Argonaute protein. Nucleic Acids Res. gkab469.