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Editors Selection IGR 9-4

Basic Research: Molecular markers for RGCs

Comment by Chris Leung on:

22071 γ-Synuclein as a marker of retinal ganglion cells, Surgucheva I; Weisman AD; Goldberg JL et al., Molecular Vision, 2008; 14: 1540-1548

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Identifying molecular markers specific for retinal ganglion cells (RGCs) is important in glaucoma research. In the study by Surgucheva et al. (1336), they evaluate whether γ-synuclein is a specific marker of RGCs. The synuclein family includes three proteins: α-synuclein, β-synuclein, and γ-synuclein. γ-synuclein is expressed in the brain, spinal cord and the peripheral nervous system. In the retina, γ-synuclein is expressed in the retinal ganglion cells (RGCs) and the axonal fibers, although its cellular function has not been determined. Using immunofluorescent staining, Surgucheva et al. showed that γ-synuclein was colocalized with Brn-3a-positive RGCs in sections of the human retina, primary rat RGCs and immortalized RGC-5 cultures. Brn-3a was localized to RGC nuclei whereas γ-synuclein was diffusely localized in the cytoplasm. While this interesting finding laid the foundation for future investigation of the role of γ-synuclein in normal RGC function, more evidence is needed to support the notion that γ-synuclein is a RGC-specific marker. In the immunofluorescent staining, there were retinal cells stained by Brn-3a, but not by γ-synuclein. Weak immunofluorescence was also detected in the inner plexiform and inner nuclear layers, and in the outer plexiform and outer nuclear layers although it was attributed by cross-reaction of γ-synuclein antibody with α-synuclein. In fact, it has been shown that expression of γ-synuclein can be found in astrocytes and glial cells. Validation with retrograde labeling and immunolabeling with other RGC markers (Thy-1, NF-L, NeuN) would be needed to confirm the specificity of γ-synuclein.

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