17-P028 Nanos2 is an intrinsic regulator for maintaining an undifferentiated state of spermatogonial stem cells

Various examples of cellular identity changes have been reported, resulting in the reprogramming of committed cells (transdetermination), or differentiated cells (transdifferentiation). Recently, it has been shown that a differentiated cell can revert to pluripotent state upon expression of defined factors. However, the mechanism(s) involved in cellular plasticity are poorly understood. Understanding these mechanism(s) is important to improve our knowledge of developmental and pathological processes. To answer this question, we have established C. elegans as a powerful invivo model to study cellular reprogramming. We have focused on one transdifferentiation event that happens in a stereotyped manner. One of the six epithelial cells that forms the rectum in young larvae, named ‘‘Y’’, migrates during development and, in absence of cell division, becomes a moto-neuron named ‘‘PDA’’. We are interested in the early events that specifically allow ‘‘Y’’ to change its identity. We have shown that activation of LIN-12/ Notch pathway is necessary just after ‘‘Y’’ birth to give it the competence to transdifferentiate. Furthermore, ligands of the LIN-12/ Notch pathway appear to be expressed in cells close to rectum around ‘‘Y’’ birth, and could represent the signal that activates LIN-12/Notch in ‘‘Y’’. We are assessing the importance of these ligand-expressing cells and if the canonical LIN-12/Notch pathway is involved. We are also developing strategies to identify target genes of the activated LIN-12/Notch pathway. Our study will shed light on the mechanisms involved in reprogramming and will be of interest to a wide audience, from developmental or stem cell biology to regenerative medicine.