Cellular responses to photoreceptor death in the rd1 mouse model of retinal degeneration

PURPOSE. Retinal degeneration is a disease that typically involves the loss of photoreceptors. Murine models have been established for such degenerations, and a variety of methods have been used to follow the progression of the disease. In the present study in situ hybridization was used to analyze gene expression responses in the different retinal cell types during the period of cone death in the rd1 mouse model. METHODS. A preliminary microarray analysis led to the selection of 169 candidate genes that might change in level of expression during degeneration. Probes corresponding to these genes were used for in situ hybridization on tissue during the period of cone death. Expression values were assigned to the intensities of in situ hybridization signals and were compared between mutant and wild-type tissue. RESULTS. During the peak of cone death, the in situ hybridization signals were typically higher in the mutant. This signal change was often true of genes with a wild-type pattern of expression in ganglion cells, bipolar cells, and/or Muller glia. In such cases, the upregulation was highest in bipolar cells and/or Muller glia. CONCLUSIONS. All retinal cell types responded during the process of retinal degeneration, as revealed by changes in gene expression. Genes that showed changes in the in situ hybridization signals during the period of cone death were typically higher in the mutant, with many of them expressed in both the ganglion cell layer and the inner nuclear layer.