Figure 1. Gene expression profile of retinal progenitor cell progenitor markers under different concentrations of glial cell line-derived neurotrophic factor treatment. Cultured genetically modified (GFP+) RPCs were treated with 2.5, 5, 10, and 20 ng/ml of glial cell line-derived neurotrophic factor (GDNF) for 5 days, then RNA was isolated, and quantitative polymerase chain reaction (qPCR) assay was performed. The progenitor markers in those samples remained at similar levels under different concentrations of GDNF. In each gene column, the five bars from left to right represent cells in epidermal growth factor (EGF) alone (dark red), in EGF+2.5 ng/ml GDNF (dark green), in EGF+5 ng/ml GDNF (blue), in EGF+10 ng/ml GDNF (red), and in EGF+20 ng/ml GDNF (green).