Gene expression profile of the adult human retinal ganglion cell layer

Purpose: Pathophysiological events in the retinal ganglion cell layer (GCL) are a prominent feature of several optic neuropathies including glaucoma. The purpose of this study was to identify and catalog genes whose expression in the human retina is restricted to the GCL. Methods: Laser capture microdissection (LCM) technology was used to isolate tissue from the perimacular retina of three human donors without retinal or optic nerve disease. RNA was isolated from the (1) retinal GCL and (2) the inner and outer nuclear layers of the same retina, and the gene expression profiles of both fractions were determined using Affymetrix Hu133Plus 2.0 GeneChips. Data were analyzed to identify those genes whose expression is substantially more prevalent in the GCL when compared to the outer retinal layers. Differential expression of selected genes was confirmed by realtime PCR and immunohistochemistry. Results: The results show that mRNA levels of previously described ganglion cell markers, e.g. the neurofilament genes (NEFH, NEF3, or NEFL) and the Brn3a transcription factor (POU4F1), were highly enriched in the isolated GCL fraction. In contrast, transcripts for genes associated with phototransduction (RHO), photoreceptor development (NR2E3), or interphotoreceptor matrix constituents (IMPG1) were nearly absent from the GCL fraction. Using bioinformatics approaches over 80 genes were identified whose expression in the human retina appears to be limited to the GCL. Conclusions: We have successfully used LCM technology to generate gene expression profiles of highly enriched GCL fractions of the normal human retina. These data not only provide clues to the normal function of retinal ganglion cells but also serve as a resource in the development of ganglion cell specific markers or transfection vectors, and the identification of candidate genes for hereditary forms of glaucoma.