Lineage-independent determination of cell type in the embryonic mouse retina.

We previously used a retroviral vector to mark clones in the postnatal rodent retina and showed that at least two types of neurons and Müller glia can arise from a common progenitor. Here we describe the use of exo utero surgery to introduce a marker retrovirus into the proliferative zone of the retinas of embryonic day 13 and 14 mice. Analysis of marked clones in the resulting adult retinas shows that almost all progenitor cells that continued mitosis were multipotential and that a single progenitor can generate most retinal cell types. The size of marked clones indicates that retinal cells do not employ a stem cell mode of division, but instead, both daughter cells of a progenitor can continue to divide. These results suggest that cell type determination in the rodent retina is independent of lineage. We propose a model for the generation of retinal cell types in which the cessation of mitosis and cell type determination are independent events, controlled by environmental interactions.