Abstract

During the last years, it has become clear that stem cells in culture display a huge degree of heterogeneity when scored for diverse molecular markers and key factors defining stemness. Live imaging of single progenitor cells in vivo revealed variations at the functional level occurring among neighbor cells within an intact tissue. However, it has not been possible so far to analyze how these heterogeneities shape/affect/define organ growth in vivo. Here we exploit the exquisite spatio/temporal organization of the medaka retina, in which new cells are incorporated at the periphery by constantly active retinal stem cells (RSCs), to uncover long-life decisions of single stem cells in an intact niche. We observe heterogeneities at the cell division level, with different ratios between symmetric and asymmetric divisions along the circumference of the retina. Intriguingly, the decisions made by individual cells during late embryogenesis are maintained up to 2 years after, during the entire post-embryonic life of the fish. Our results demonstrate heterogeneities occurring at the functional level in vivo among stem cells, and indicate that these are not the result of random or cyclic fluctuations but are rather stable during the adult life. We will present the combination of long term genetic labelling and in vivo imaging to trace back the retinal stem cell to their origin in the evaginated optic vesicle and possibly before.