Differential gene expression patterns of the developing and adult mouse cornea compared to the lens and tendon.

The cornea continues to mature after birth to develop a fully functional, refractive and protective barrier tissue. Here we investigated the complex biological events underlying this process by profiling global genome-wide gene expression patterns of the immature postnatal day 10 and 7-week old adult mouse cornea. The lens and tendon were included in the study to increase the specificity of genes identified as upregulated in the corneal samples. Notable similarities in gene expression between the cornea and the tendon were in the mesenchymal extracellular matrix collagen (types I, III, V, VI) and proteoglycan (lumican, decorin and biglycan) genes. Expression similarities in the cornea and lens were limited to certain epithelial genes and the crystallins. Approximately 76 genes were over expressed in the cornea samples that showed basal expression levels in the lens and tendon. Thirty-two of these were novel with no known functions in the cornea. These include genes with a potential role in protection against oxidative stress (Dhcr24, Cdo1, Akr1b7, Prdx6), inflammation (Ltb4dh, Wdr1), ion transport (Pdzk1ip1, Slc12a2, Slc25a17) and transcription (Zfp36l3, Pdzk1ip1). Direct comparison of the cornea of two ages showed selective upregulation of 50 and 12 genes in the P10 and adult cornea, respectively. Of the upregulated P10 genes several encode extracellular matrix collagens and proteoglycans that are stable components of the adult cornea and their high transcriptional activity at P10 indicate a period of actie corneal growth and matrix deposition in the young cornea. Much less is known about the genes selectively over expressed in the adult cornea; some relate to immune response and innervations (Npy), and possibly to electron transport (Cyp24a1, Cyp2f2) and others of yet unknown functions in the cornea (Rgs10, Psmb8, Xlr4). This study detected expression of genes with known functions in the cornea, providing additional validation of the microarray experiments. Importantly, it identified several novel genes whose functions have not been investigated in the cornea.