purpose. Postnatal mouse retinal development involves glial and neuronal differentiation, vascularization, and the onset of vision. In the current study, the gene expression profiles of thousands of genes in the developing postnatal mouse retina were analyzed and compared in a large-scale, unbiased microarray gene expression analysis.

methods. For each of eight different time points during postnatal mouse retinal development, two separate sets of 30 retinas were pooled for RNA isolation, and gene expression was analyzed by hybridization to gene chips in triplicate (Mu74Av2; Affymetrix, Santa Clara, CA). Genes were sorted into clusters based on their expression profiles and intensities. Validation was accomplished by comparing the microarray expression profiles with real-time RT-PCR analysis of selected genes and by comparing selected expression profiles with predicted profiles based on previous studies.

results. The Mu74Av2 chip contains more than 6000 known genes and 6500 estimated sequence tags (ESTs) from the mouse Unigene database. Of these, 2635 known gene sequences and 2794 ESTs were expressed at least threefold above background levels during retinal development. Expressed genes were clustered based on expression profiles allowing potential functions for specific genes during retinal development to be inferred by comparison to developmental events occurring at each time point. Specific data and potential functions for genes with various profiles are discussed. All data can be viewed online at http://www. scripps. edu/cb/friedlander/gene_expression/.

conclusions. Expression analysis of thousands of different genes during normal postnatal mouse retinal development as reported in this study demonstrates that such an approach can be used to correlate gene expression with known functional differentiation, presenting the opportunity to infer functional correlates between gene expression and specific postnatal developmental events.