Generation of a Double Reporter mES Cell Line to Simultaneously Trace the Generation of Retinal Progenitors and Photoreceptors.

Three-dimensional retinal culture systems help to understand eye development and the pathology of disorders. There is a need for reporter stem cell lines to allow in vitro studies on retinal progenitors and photoreceptors and their developmental dynamics or properties and to test therapeutic approaches. The isolation of pure progenitor populations or photoreceptor precursors may serve for drug, gene, and cell therapy development. Here, we generated a dual-reporter mouse embryonic stem cell line Crx-GFP;Rax-mCherry enabling the visualization or isolation of photoreceptors and retinal progenitors from retinal organoid settings. From day 4 organoids, we isolated mCherry-positive cells to assess their early retinal progenitor identity with proliferation tests as well as transcriptomic and proteomic profiling. The timing of eye field transcription factor expression at the transcriptomic and protein levels is in accordance with mouse retinogenesis. This new line will be helpful for rapidly investigating biological questions or testing therapeutics before using human induced pluripotent stem cells (iPSCs), which require a much longer time for retinal organoid formation.