Description of the PhD thesis project
The mechanisms underlying morphogenesis and homeostasis of adult organs remain only superficially understood. Somatic stem cells are critical players during developmental growth and for maintaining adult tissue homeostasis. The principal goal of the team is to study tissue-specific stem cells and the signals that orchestrate cell fate specification. We study stem cell behaviour both during physiological tissue development and homeostasis and in tumours, combining in vivo clonal analysis by lineage tracing with time-lapse analysis of 3D organotypic cultures and intravital imaging, whole mount immunofluorescence, transcriptomics and mathematical modelling of clonal dynamics.
Despite recent advances, a lack of robust markers, combined with high cellular heterogeneity, has hampered analysis of the mechanisms driving the hierarchical organisation of mammary epithelial cell lineages. In addition, extensive branching morphogenesis during mammary gland development results in high clonal dispersion, making lineage tracing analysis of fixed tissues very challenging to interpret. Through a combination of novel approaches, the proposed PhD project aims at characterising the behaviour and lineage specification of defined populations of mammary cells in real time during embryogenesis and puberty, two stages characterised by dramatic tissue remodelling.
The PhD student will investigate how embryonic multipotent mammary stem cells (MaSC) become lineage committed during the first morphogenetic events allowing sprouting of embryonic mammary buds. The student will also be involved in the analysis of mutant MaSC, where cell fate choices are skewed toward a specific differentiation program. Transcriptomic analyses of multipotent and unipotent MaSC should permit to define a multipotent signature of embryonic MaSC, whose reactivation in adults has been suggested to be implicated in breast cancer development.
International, interdisciplinary & intersectoral aspects of the project
This project will be performed in tight collaboration with Prof. Benjamin Simons (University of Cambridge, UK) and Prof. Cedric Blanpain (ULB, Brussels, Belgium), ensuring international visibility. The intersectoral dimension comes from collaboration with Carl Zeiss SAS, to optimise time-lapse imaging of embryonic mammary explants using multispectral confocal analysis. The project is interdisciplinary as it involves 4 disciplines: Biology, Mathematics, Imaging and Bioinformatics.
1. Rodilla V, Dasti A, Huyghe M, Lafkas D, Laurent C, Reyal F and Fre S (2015). Luminal Progenitors Restrict Their Lineage Potential During Mammary Gland Development. Plos Biology 13(2): e10020692.
2. Wassef M, Rodilla V, Teissandier A, Zeitouni B, Gruel N, Sadacca B, Irondelle M, Charruel M, Ducos B, Michaud A, Caron M, Marangoni E, Chavrier P, Le Tourneau C, Kamal M, Pasmant E, Vidaud M, Servant N, Reyal F, Meseure D, Vincent-Salomon A, Fre S and Margueron R (2015). Impaired PRC2 activity promotes transcriptional instability and favors breast tumorigenesis. Genes Dev. 2015 Dec 15;29(24):2547-62.
3. Fernandez Sanchez ME, Barbier S, Whitehead J, Béalle G, Michel A, Latorre-Ossa H, Rey C, Fouassier L, Claperon A, Marie H, Lesieur S, Housset C, Gennisson JL, Tanter M, Ménager C, Fre S, Robine S and Farge E (2015). Mechanical induction of the tumorigenic β-catenin pathway by tumour growth pressure. Nature 523(7558):92-5.
4. Lafkas D, Rodilla V, Huyghe M, Mourao L, Kiaris H and Fre S (2013). Notch3 marks clonogenic mammary luminal progenitor cells in vivo. The Journal of cell biology 203(1): 47-56.
5. Fre S, Hannezo E, Sale S, Huyghe M, Lafkas D, Kissel H, Louvi A, Greve J, Louvard D and Artavanis-Tsakonas S (2011). Notch lineages and activity in intestinal stem cells determined by a new set of knock-in mice. PLoS ONE 6(10): e25785.