Abstract
Purpose::
The RPE is established on embryonic day 3 (E3), but the neural retina and choriocapillaris are not morphologically differentiated until E18. Limited molecular studies suggest extensive remodeling of the RPE in response to this changing environment. A genomic approach was used to investigate the extent of this remodeling.
Methods::
RPE was isolated from E7, E10, E14 and E18 embryos and total RNA extracted for probing the entire chick genome on Affymetrix microarray chips. Statistical parameters using ANOVA were adjusted to yield a theoretical false discovery rate of 5%. STEM software was used to cluster genes into statistically related patterns of expression. Gene ontology clustering, using Affymetrix software was used for functional clustering. The proteinlounge.com database was used as a source of known biological pathways.
Results::
Of the 37,694 probe sets on the microarray, 17,199 were not detected. Of the 20,495 expressed probes, the expression of 8,889 was developmentally regulated. 4814 of these could be clustered into 12 patterns of expression that were statistically significant. The developmental patterns of expression for 21 tight and adherens junction proteins have been reported. Only two showed small variations from the patterns revealed by the microarray. Further, as would be predicted, expression of genes that promote progression through the cell cycle decreased and genes that inhibit progression increased with age. The data indicate extensive remodeling of the extracellular matrix, cell surface receptors, cell-cell junctions, transcellular ion transport and signal transduction pathways throughout development. Notably, the appearance of claudin 20, ZO-3 and cadherin 13 very late in development suggest barrier properties continue to change after functional junctions are formed.
Conclusions::
The data reveal a far more dynamic view of the RPE and its interactions with its environment than would be expected from morphological examination. These data provide a standard whereby culture models of RPE function and regulation may be judged.Supported by NEI grant: RO1 EY8694
Keywords: retinal pigment epithelium • development • cell adhesions/cell junctions