Loss of retinal progenitor cells leads to an increase in the retinal stem cell population in vivo

Retinal stem cells [with the potential to produce either neural retinal progenitors or retinal pigment epithelial (RPE) progenitors] exist in the mammalian eye throughout life, and indeed the greatest absolute increase in the stem population occurs postnatally. The stem cells proliferate embryonically and thus may help to build the retina initially, but in postnatal mammals they clearly do not proliferate to regenerate the retina in response to injury. Using Chx10(orJ/orJ) and Mitf(mi/mi) mice, with small eye phenotypes due to the reduction of the neural retinal progenitor population and the retinal pigmented epithelial progenitor population, respectively, we now report that the retinal stem cell population, when assayed from the ciliary margin, increases 3-8-fold in both mutants. These findings suggest that the mammalian retinal stem cell population may be capable of responding to genetically induced signals from the progenitor populations.