Regulation of Retinal Progenitor Cell Differentiation by Redox Signaling and Disease Modeling in Zebrafish with CRISPR/Cas9 Based Approaches

Venue: Povo 2 - room B101
Time: 2.00 pm

Speaker:

• Filippo De Bene - Institut de la Vision, Department of Developmental Paris / France

Abstract:
Classically, the majority of research on reactive oxygen species (ROS) such as anion superoxide or H2O2 has focused on their deleterious effect on cell structure and their potential link to several diseases. However in the recent years, data on the importance of ROS in many vital processes from cell proliferation, tissue homeostasis to cell death are emerging. Several reports have shown the role of redox signaling in the proliferation and maintenance of neural stem and progenitor cells under physiological conditions using in vitro model systems. In these cells, the cues that affect proliferation and differentiation of neural stem cells are embedded in developmental and environmental signaling through a highly regulated spatial-temporal expression of specific determinants. Recent studies have shown that neural stem cells maintain high levels of ROS to help regulate normal self-renewal and differentiation. However, it is still not clear how the expression of these earlier transcription factors is regulated. One hypothesis is that stem and progenitor cells may take advantage of redox regulation to coordinate cell cycle with differentiation as a means of holding their stem cell fate in check, while ensuring homeostasis. To address this question, we used the zebrafish developing retina as a powerful model system and its remarkable stem cell niche, also called the ciliary marginal zone. Here we reveal that the fine regulation of hydrogen peroxide (H2O2) levels at the degradation step by its scavenger Catalase is crucial to mediate the switch from retinal progenitor cells (RPCs) proliferation to differentiation. We further show that unbalancing downstream products of the Redox signaling can also alter this switch. We finally show that the local and temporal manipulation of H2O2 levels by catalase overexpression in RPCs was sufficient to trigger their premature differentiation. Therefore the amount of H2O2 in RPCs and their potential to regulate these levels is instructive of their ability to switch from proliferation to differentiation. We propose a novel mechanism linking RPCs’ H2O2 homeostasis and neuronal differentiation via the modulation of lipid peroxidation pathway and the direct control of the key chromatin remodeling enzyme HDAC1. In the final part of this seminar we will present our most recent results in the application of CRISPR/Cas9 based base editors to introduce human disease mimicking point mutations in the zebrafish genome. In particular we will discuss our current results in the study of cancer causing mutations in oncogenes and oncosuppressors.