One gene, RIKEN cDNA 4933409K07 (Figure 1, gene G47), was found to be up-regulated on microarray at all four timepoints examined. This gene showed a unique pattern of expression in the adult rd7 mutant retina. Whereas there was only a barely detectable hint of expression in the inner nuclear layer (INL) in the wild-type retina, this gene showed strong expression in the middle and vitreal thirds of the INL as well as patchy expression in the ganglion cell layer (GCL) and at the scleral edge of the ONL in rd7 (see Table S1). This in situ hybridization pattern is consistent with staining in Müller glia, the principal glial cell type of the mouse retina. One possible interpretation of this unusual expression pattern is that it represents an early reaction of Müller glia to injury in this mutant.