A gene expression profile of the developing human retinal pigment epithelium

The molecular mechanisms associated with human retinal pigment epithelium (RPE) development constitute the basis for cell replacement therapy for the treatment of retinal degenerative diseases. In the current study, gene expression analysis of the human fetal RPE during development was performed and was compared with the human native RPE.

Microdissection of the human RPE at three time points (13 weeks and 16 weeks of gestation and in mature adult eyes) was performed, and total RNA was isolated. Equal amounts of RNA were pooled from two or three independent donor eyes for each time point in each group. Gene expression was analyzed by hybridization to microarray chips. Validation was accomplished by comparing the microarray expression profiles with quantitative real-time reverse transcriptase-polymerase chain reaction (qRT(2)-PCR) analysis of selected genes and by comparing selected expression profiles with predicted profiles based on previous studies.

Of the 45,033 probe sets on the microarray, 30,736 were detected. A total of 3,498 differentially expressed genes could be clustered into eight patterns of expression that were statistically significant. Analysis of the expression patterns of genes coding for key functions (pigment synthesis, visual cycle, phagocytosis, adherens and tight junctions, and transcellular transport) indicated that the human RPE achieves a high degree of maturity during early pregnancy. Compared with 154 signature genes in the RPE, 148 candidate genes were identified in this study, including 53 downregulated genes and 5 upregulated genes. The qRT(2)-PCR results showed similar expression trends to those obtained by microarray analysis at the three time points.

This study demonstrated gene expression profiles in the human RPE during normal development. These findings indicate that the human RPE has different expression patterns than those of other animals. The results of this study may be helpful in furthering the understanding of the developmental processes occurring in humans and of the differentiation of RPE cells derived from human embryonic stem cells and from human induced pluripotent stem cells.