Fig. 1.

Strategy adopted to identify of retinal progenitor cell-enriched transcripts. Cycling cells of the developing retina were FACS-purified based on DNA content, yielding one population enriched in progenitor cells (4N cells) and a second composed of progenitor cells and postmitotic neurons (2N cells). Gene expression was compared directly between the 2N and 4N populations, and also between the 4N population and adult brain (see text for details). Reproducible differences between progenitor cells and the reference used in each case were identified by using the significance analysis of microarrays algorithm (see text for details), and genes that passed this filter were then hierarchically clustered to visualize the data and confirm differential expression.