FIGURE 1.

RNA‐seq of RPE reveals visual cycle genes are transcriptionally up‐regulated with increasing human age. A, Volcano plot showing up‐regulated SCGs in green and down‐regulated in magenta. Genes in the retinol metabolism KEGG pathway are labelled. B, Pathway enrichment analysis of 341 KEGG pathways identifies retinol metabolism (map00830) to be the most significantly enriched with positively correlated SCGs. Pathways with a BH‐adjusted P < .05 are highlighted in green. Fraction represents the number of SCGs in the pathway over the total number of genes in the pathway. C, KEGG pathway map of retinol metabolism (map00830), with positive SCGs highlighted in green. D, Scatter plots of the expression of 7 retinol metabolism genes from human donors (n = 13) ranging in age from 31 to 93 years. Regression line (black) with 95% confidence interval (grey shading). E, qPCR validation of the positive correlation between age and transcription level of the core visual cycle genes (LRAT, RPE65 and RDH5). Validation carried out in a separate set of 28 human donors aged 45 to 87 years. Regression line (black) with 95% confidence interval (grey shading); regression was weighted by the RNA integrity score of each sample shown by size of circle